Subject: [netlmm] Comments on draft-ietf-netlmm-proxymip6-07.txt

From: "George Tsirtsis" <[email-masked]>
Date: Tue, 20 Nov 2007 09:35:33 +0000

Hi Sri, et.al.,

I am happy to see that a lot of things have been clarified and the document
is indeed in much better shape than before.

I have the following high level observation and some more specific comments
below starting with "GT>"

I think there is still lack of clarity wrt what is considered a "PMIP
session" and when a new one is created or not. With the multitude of
parameters now used to determine handoff vs multihoming this is getting a
bit complicated (HI, IF-ID, IF-Type etc). In the detailed comments below I
observe that only some of the possible combination of the values and
parameters are explicitly discussed and the rest is left undefined. I think
as a minimum the full matrix of combinations should be examined and defined.
Even then, however, I fear that since a lot of these parameters are expected
to be set by external to PMIP entities (Authentication, L2 signaling,
external databases etc) the result might still not be as clear as it would
be desirable, but I do not think anything can be done about that.
Also, in terms of the writting style of Section 5.4, the section is a series
of bullet points with no apparent structure or hierarchy. I have commented
extensively in that section and I think some restructuring is needed to at
least indicate hierarchy between the bullets when one point depends or is a
further limitation on the previous point.

Regards
George

--------------------------------------------------------------------------------------------------------------------
                           Proxy Mobile IPv6
                   draft-ietf-netlmm-proxymip6-07.txt

...
1.  Introduction

   IP mobility for IPv6 hosts is specified in Mobile IPv6 [RFC-3775].
   Mobile IPv6 requires client functionality in the IPv6 stack of a
   mobile node.  Exchange of signaling messages between the mobile node
   and home agent enables the creation and maintenance of a binding
   between the mobile node's home address and its care-of-address.
   Mobility as specified in [RFC-3775] is host centric as it requires
   the IP host to manage its own mobility by signaling the Home Agent,
   which is located in the network.

   Network-based mobility is another approach to solving the IP mobility
   challenge.  It is possible to support mobility for IPv6 nodes without
   host involvement by extending Mobile IPv6 [RFC-3775] signaling
   messages and reusing the home agent.  This approach to supporting
   mobility does not require the mobile node to be involved in the
   exchange of signaling messages between itself and the Home Agent.  A
   proxy mobility agent in the network performs the signaling with the
   home agent and does the mobility management on behalf of the mobile
   node attached to the network.  Because of the use and extension of
   Mobile IPv6 signaling and home agent functionality, this protocol is
   referred to as Proxy Mobile IPv6 (PMIPv6).

   Network deployments which are designed to support mobility would be
   agnostic to the capability in the IPv6 stack of the nodes which it
   serves.  IP mobility for nodes which have mobile IP client
   functionality in the IPv6 stack as well as those hosts which do not,
   would be supported by enabling Proxy Mobile IPv6 protocol
   functionality in the network.

GT> The above should either be removed or a sentence indicating that "The
details of MIPv6 – PMIPv6 interactions are out of scope" should be added.

The advantages of developing a network
   based mobility protocol based on Mobile IPv6 are:

   o  Reuse of home agent functionality and the messages/format used in
      mobility signaling.  Mobile IPv6 is a mature protocol with several
      implementations that have undergone interoperability testing.

   o  A common home agent would serve as the mobility agent for all
      types of IPv6 nodes.

GT> Add "although the MIPv6 - PMIPv6 interactions are out of scope of this
specification"

   o  Addresses a deployment need.

   o  May be better suited on certain types of resource-constrained
      links or because of service provider specific policies.

   The problem statement and the need for a network based mobility
   protocol solution has been documented in [RFC-4830].  Proxy Mobile
   IPv6 is a solution that addresses these issues and requirements.
   This document builds on Mobile IPv6 [RFC-3775] in specifying a
   network-based mobility management protocol.

GT> Last sentence is repetitive, could be removed.

...
2.2.  Terminology

   All the general mobility related terms used in this document are to
   be interpreted as defined in the Mobile IPv6 base specification [RFC-
   3775].

   This document adopts the terms, Local Mobility Anchor (LMA) and
   Mobile Access Gateway (MAG) from the NETLMM Goals document [RFC-
   4831].  This document also provides the following context specific
   explanation to the following terms used in this document.

   Proxy Mobile IPv6 Domain (PMIPv6-Domain)

      Proxy Mobile IPv6 domain refers to the network where the mobility
      management of a mobile node is handled using the Proxy Mobile IPv6
      protocol as defined in this specification.  The Proxy Mobile IPv6
      domain includes local mobility anchors and mobile access gateways
      between which security associations can be setup and authorization
      for sending Proxy Binding Updates on behalf of the mobile nodes
      can be ensured.

   Local Mobility Anchor (LMA)

      Local Mobility Anchor is the home agent for the mobile node in the
      Proxy Mobile IPv6 domain.  It is the topological anchor point for
      the mobile node's home network prefix and is the entity that
      manages the mobile node's binding state.  It is important to
      understand that the local mobility anchor has the functional
      capabilities of a home agent as defined in Mobile IPv6 base
      specification [RFC-3775] with the additional capabilities required
      for supporting Proxy Mobile IPv6 protocol as defined in this
      specification.

GT> Although this is described here I do not see a corresponding normative
MUST statement in section 5 (LMA Operation). I added one there.

   Mobile Access Gateway (MAG)

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      Mobile Access Gateway is a function that manages the mobility
      related signaling for a mobile node that is attached to its access
      link.  It is responsible for tracking the mobile node's movements
      on the access link and for signaling the mobile node's local
      mobility anchor.

   Mobile Node (MN)

      Throughout this document, the term mobile node is used to refer to
      an IP host whose mobility is managed by the network.  The mobile
      node may be operating in IPv6 mode, IPv4 mode or in IPv4/IPv6 dual
      mode.  The mobile node is not required to participate in any
      mobility related signaling for achieving mobility for an IP
      address that is obtained in that Proxy Mobile IPv6 domain.  This
      document further uses explicit text when referring to a mobile
      node that is involved in mobility related signaling as per the
      Mobile IPv6 specification [RFC-3775].

   LMA Address (LMAA)

      The address that is configured on the interface of the local
      mobility anchor and is the transport endpoint of the bi-
      directional tunnel established between the local mobility anchor
      and the mobile access gateway.  This is the address to where the
      mobile access gateway sends the Proxy Binding Update messages.
      When supporting IPv4 traversal, i.e., when the network between the
      local mobility anchor and the mobile access gateway is an IPv4
      network, this address will be an IPv4 address and will be referred
      to as IPv4-LMAA, as specified in [ID-IPV4-PMIP6].

   Proxy Care-of Address (Proxy-CoA)

      Proxy-CoA is the address configured on the interface of the mobile
      access gateway and is the transport endpoint of the tunnel between
      the local mobility anchor and the mobile access gateway.  The
      local mobility anchor views this address as the Care-of Address of
      the mobile node and registers it in the Binding Cache entry for
      that mobile node.  When the transport network between the mobile
      access gateway and the local mobility anchor is an IPv4 network
      and if the care-of address that is registered at the local
      mobility anchor is an IPv4 address, the term, IPv4-Proxy-CoA is
      used, as specified in [ID-IPV4-PMIP6].

   Mobile Node's Home Address (MN-HoA)

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      MN-HoA is the home address of a mobile node in a Proxy Mobile IPv6
      domain.  It is an address from its home network prefix obtained by
      a mobile node in a Proxy Mobile IPv6 domain.  The mobile node can
      continue to use this address as long as it is attached to the
      network that is in the scope of that Proxy Mobile IPv6 domain.

   Mobile Node's Home Network Prefix (MN-HNP)

      This is the on-link IPv6 prefix that is always present in the
      Router Advertisements that the mobile node receives when it is
      attached to any of the access links in that Proxy Mobile IPv6
      domain.  This home network prefix is topologically anchored at the
      mobile node's local mobility anchor.  The mobile node configures
      its interface with an address from this prefix.  If the mobile
      node connects to the Proxy Mobile IPv6 domain through multiple
      interfaces, simultaneously, there will be multiple and unique home
      network prefixes assigned for that mobile node.

GT> The last sentence is confusing. I assume it should be possible to assign
multiple HNPs to the same MN over the same PMIP session (probably the
subject of NEMO-PMIP work). The sentence above attempts to capture something
about multihoming but it does not do it too well. Maybe it should be
clarified that
"each interface assigned a different HNP is treated as a different PMIP
session." If this is too much detail for the definitions or not exactly what
is meant, the last two sentences could IMO be removed, and the concepts
discussed in more detail later.

   Mobile Node's Home Link

      This is the link on which the mobile node obtained its initial
      Layer-3 address configuration for one of its interfaces after it
      moved into that Proxy Mobile IPv6 domain.  This is the link that
      conceptually follows the mobile node.  The network will ensure the
      mobile node always sees this link with respect to the layer-3
      network configuration, on any access link that it attaches to in
      that Proxy Mobile IPv6 domain.

   Multihomed Mobile Node

      A mobile node that connects to the Proxy Mobile IPv6 domain
      through more than one interface and uses the interfaces
      simultaneously is referred to as a multihomed mobile node.

   Mobile Node Identifier (MN-Identifier)

      The identity of a mobile node in the Proxy Mobile IPv6 domain.
      This is the stable identifier of a mobile node that the mobility
      entities in a Proxy Mobile IPv6 domain can always acquire and
      using which a mobile node can predictably be identified.  This is
      ^^^^^
GT> //using/use

      typically an identifier such as NAI or other identifier such as a
      MAC address.

   Mobile Node Interface Identifier (MN-Interface-Identifier)

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      The interface identifier that identifies a given interface of a
      mobile node.  For those interfaces that have a layer-2 identifier,
      the interface identifier can be based on that layer-2 identifier.
      The interface identifier in some cases is generated by the mobile
      node and conveyed to the access router or the mobile access
      gateway.  In some cases, there might not be any interface
      identifier associated with the mobile node's interface.

   Proxy Binding Update (PBU)

      A binding registration request message sent by a mobile access
      gateway to a mobile node's local mobility anchor for establishing
      a binding between the mobile node's MN-HNP and the Proxy-CoA.

   Proxy Binding Acknowledgement (PBA)

      A binding registration reply message sent by a local mobility
      anchor in response to a Proxy Binding Update request message that
      it received from a mobile access gateway.

3.  Proxy Mobile IPv6 Protocol Overview

GT> This section would benefit from stated assumptions WRT the existence and
interaction between link layer triggers (attach/detach), address allocation
procedures (stateless autoconf, DHCP etc) and PMIPv6 protocols. For example,
is it required that MAGs can detect attach/detach at L2? Can address
allocation signaling be used to trigger PMIP, etc?

   This specification describes a network-based mobility management
   protocol.  It is called Proxy Mobile IPv6 and is based on Mobile IPv6
   [RFC-3775].

   Proxy Mobile IPv6 protocol is intended for providing network-based
   mobility management support to a mobile node, without requiring the
   participation of the mobile node in any mobility related signaling.
   The mobility entities in the network will track the mobile node's
   movements and will initiate the mobility signaling and setup the
   required routing state.

   The core functional entities in the NETLMM infrastructure are the
   Local Mobility Anchor (LMA) and the Mobile Access Gateway (MAG).  The
   local mobility anchor is responsible for maintaining the mobile
   node's reachability state and is the topological anchor point for the
   mobile node's home network prefix.  The mobile access gateway is the
   entity that performs the mobility management on behalf of a mobile
   node and it resides on the access link where the mobile node is
   anchored.  The mobile access gateway is responsible for detecting the
   mobile node's movements on its access link and for sending binding
   registrations to the mobile node's local mobility anchor.  The
   architecture of a Proxy Mobile IPv6 domain is shown in Figure 1.

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               +----+                +----+
               |LMA1|                |LMA2|
               +----+                +----+
        LMAA1 -> |                      | <-- LMAA2
                 |                      |
                 \\                    //\\
                  \\                  //  \\
                   \\                //    \\
                +---\\------------- //------\\----+
               (     \\  IPv4/IPv6 //        \\    )
               (      \\  Network //          \\   )
                +------\\--------//------------\\-+
                        \\      //              \\
                         \\    //                \\
                          \\  //                  \\
              Proxy-CoA1--> |                      | <-- Proxy-CoA2
                         +----+                 +----+
                         |MAG1|-----{MN2}       |MAG2|
                         +----+    |            +----+
                           |       |               |
              MN-HoA1 -->  |     MN-HoA2           | <-- MN-HoA3
                         {MN1}                   {MN3}

                    Figure 1: Proxy Mobile IPv6 Domain

   Once a mobile node enters a Proxy Mobile IPv6 domain and attaches to
   an access link, the mobile access gateway on that access link, after
   identifying the mobile node and acquiring its identity, will
   determine if the mobile node is authorized for the network-based
   mobility management service.

   If the network determines that the network-based mobility management
   service needs to be offered to that mobile node, the network will
   ensure that the mobile node using any of the address configuration
   mechanisms permitted by the network will be able to obtain the
   address configuration on the connected interface and move anywhere in
   that Proxy Mobile IPv6 domain.  The obtained address configuration
   includes the address(es) from its home network prefix, the default-
   router address on the link and other related configuration
   parameters.  From the perspective of the mobile node, the entire
   Proxy Mobile IPv6 domain appears as a single link, the network
   ensures that the mobile node believes it is always on the same link
   where it obtained its initial address configuration, even after

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   changing its point of attachment in that network.

   The mobile node may be operating in an IPv4-only mode, IPv6-only mode
   or in dual IPv4/IPv6 mode.  Based on what is enabled in the network
   for that mobile node, the mobile node will be able to obtain an IPv4,
   IPv6 or dual IPv4/IPv6 addresses and move anywhere in that Proxy
   Mobile IPv6 domain.  However, the specific details related to the
   IPv4 addressing or IPv4 transport support are specified in the
   companion document [ID-IPV4-PMIP6].

   If the mobile node connects to the Proxy Mobile IPv6 domain, through
   multiple interfaces and over multiple access networks, the network
   will allocate an unique home network prefix for each of the connected
                ^^^^
GT> //an/a

   interfaces and the mobile node will be able to configure an
   address(es) on those interfaces from the respective home network
   prefixes.

   If the mobile node performs a handover from one interface
   to another in the same Proxy Mobile IPv6 domain, then the local
   mobility anchor will assign the same prefix to the new interface.

GT> This needs further clarification. If the different interfaces have
already been assigned different HNPs, then is this statement correct? I
think not. I think the document is lacking a clear statement of what is
considered handover vs multihoming. This is discussed in 5.4 in some more
detail so maybe the discussion can be removed from here?

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    +-----+                +-----+                +-----+
    | MN  |                | MAG |                | LMA |
    +-----+                +-----+                +-----+
       |                      |                      |
   MN Attached                |                      |
       |                      |                      |
       |               MN Attached Event             |
       |        (Acquire MN-Id and Profile)          |
       |                      |                      |
       |                      |----- PBU ----------->|
       |                      |                      |
       |                      |                  Accept PBU
       |                      |  (Allocate MN-HNP, Setup BCE and Tunnel)
       |                      |                      |
       |                      |<--------- PBA -------|
       |                      |                      |
       |                 Accept PBA                  |
       |          (Setup Tunnel and Routing)         |
       |                      |                      |
       |                      |==== Bi-Dir Tunnel ===|
       |                      |                      |
       |--- Rtr Sol --------->|                      |
       |                      |                      |
       |<------- Rtr Adv -----|                      |
       |                      |                      |
    IP Address                |                      |
   Configuration              |                      |
       |                      |                      |

          Figure 2: Mobile Node Attachment - Signaling Call Flow

   Figure 2 shows the signaling call flow when the mobile node enters
   the Proxy Mobile IPv6 domain.

   For updating the local mobility anchor about the current location of
   the mobile node, the mobile access gateway sends a Proxy Binding
   Update message to the mobile node's local mobility anchor.  Upon
   accepting this Proxy Binding Update message, the local mobility
   anchor sends a Proxy Binding Acknowledgement message including the
   mobile node's home network prefix.  It also creates the Binding Cache
   entry and establishes a bi-directional tunnel to the mobile access
   gateway.

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   The mobile access gateway on receiving the Proxy Binding
   Acknowledgement message sets up a bi-directional tunnel to the local
   mobility anchor and sets up the data path for the mobile node's
   traffic.  At this point the mobile access gateway will have all the
   required information for emulating the mobile node's home link.  It
   sends Router Advertisement messages to the mobile node on the access
   link advertising the mobile node's home network prefix as the hosted
   on-link-prefix.

   The mobile node on receiving these Router Advertisement messages on
   the access link will attempt to configure its interface either using
   stateful or stateless address configuration modes, based on the modes
   that are permitted on that access link.  At the end of a successful
   address configuration procedure, the mobile node will end up with an
   address from its home network prefix.

   Once the address configuration is complete, the mobile node has a
   valid address from its home network prefix at the current point of
   attachment.  The serving mobile access gateway and the local mobility
   anchor also have proper routing states for handling the traffic sent
   to and from the mobile node using an address from its home network
   prefix.

   The local mobility anchor, being the topological anchor point for the
   mobile node's home network prefix, receives any packets that are sent
   by any correspondent node to the mobile node.  The local mobility
   anchor forwards these received packets to the mobile access gateway
   through the bi-directional tunnel.  The mobile access gateway on
   other end of the tunnel, after receiving the packet, removes the
   outer header and forwards the packet on the access link to the mobile
   node.

   The mobile access gateway typically acts as a default router on the
   access link.  Any packet that the mobile node sends to any
   correspondent node will be received by the mobile access gateway and
   will be sent to its local mobility anchor through the bi-directional
   tunnel.  The local mobility anchor on the other end of the tunnel,
   after receiving the packet, removes the outer header and routes the
   packet to the destination.

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    +-----+          +-----+          +-----+          +-----+
    | MN  |          |p-MAG|          | LMA |          |n-MAG|
    +-----+          +-----+          +-----+          +-----+
       |                |                |                |
       |                |==Bi-Dir Tunnel=|                |
   MN Detached          |                |                |
       |         MN Detached Event       |                |
       |                |                |                |
       |                |-- DeReg PBU -->|                |
       |                |                |                |
       |                |            Accept PBU           |
       |                |   (Start MinDelayBeforeBCEDelete Timer)
       |                |                |                |
       |                |<-------- PBA --|                |
       |                |                |                |
   MN Attached          |                |                |
       |                |                |       MN Attached Event
       |                |                |   (Acquire MN-Id and Profile)
                               ....
                                    Registration steps as in fig 2.
                               ....
       |                |                |==Bi-Dir Tunnel=|
       |--- Rtr Sol ------------------------------------->|
       |                |                |                |
       |<------------------------------------ Rtr Adv ----|
       |                |                |                |
   MN retains HoA/HNP
       |                |                |                |

            Figure 3: Mobile Node Handoff - Signaling Call Flow

   Figure 3 shows the signaling call flow for the mobile node's handoff
   from previously attached mobile access gateway (p-MAG) to the newly
   attached mobile access gateway (n-MAG).

   After obtaining the initial address configuration in the Proxy Mobile
   IPv6 domain, if the mobile node changes its point of attachment, the
   mobile access gateway on the new access link will signal the local
   mobility anchor for updating the binding and routing state.  The
   mobile node will continue to receive the Router Advertisements
   containing its home network prefix, making it believe it is still on
   the same link and can use the same address configuration on the new
   access link.

GT> This section does not seem to fully describe the figures included in it.
E.g., what is the MinDelayBeforeBCEDelete timer? While the timer description
might be a detail, some hints towards the idea of delaying the old tunnel
release etc may be useful.

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4.  Proxy Mobile IPv6 Protocol Security

   The signaling messages, Proxy Binding Update and Proxy Binding
   Acknowledgement, exchanged between the mobile access gateway and the
   local mobility anchor MUST be protected using end-to-end security
   association(s) offering integrity and data origin authentication.  A
   security association with the mobile node for which the signaling
   message is issued is not required for protection of these messages.

GT> While no SA is required between the MN and the LMA, is there no
expectation of trust between MN and MAG? Without such trust (although MN-MAG
interface is outside the scope of the PMIP protocol) the protocol is clearly
broken. Indeed at the end of this section it is recognized that the MAG must
only send PBUs for authorized (i.e., trusted) MNs.

   The mobile access gateway and the local mobility anchor MUST
   implement IPsec for protecting the Proxy Mobile IPv6 signaling
   messages [RFC-4301].  IPsec is the default security mechanism for
   securing the signaling messages.  However in certain deployments of
   this protocol, other security mechanisms MAY be applied and the
   signaling messages must be protected using the semantics provided by
   that respective mechanism.

   IPsec ESP [RFC-4303] in transport mode with mandatory integrity
   protection SHOULD be used for protecting the signaling messages.
   Confidentiality protection of these messages is not required.

   IKEv2 [RFC-4306] SHOULD be used to setup security associations
   between the mobile access gateway and the local mobility anchor to
   protect the Proxy Binding Update and Proxy Binding Acknowledgement
   messages.  The mobile access gateway and the local mobility anchor
   can use any of the authentication mechanisms, as specified in IKEv2,
   for mutual authentication.

   The Mobile IPv6 specification [RFC-3775] requires the home agent to
   prevent a mobile node from creating security associations or creating
   binding cache entries for another mobile node's home address.  In the
   protocol described in this document, the mobile node is not involved
   in creating security associations for protecting the signaling
   messages or sending binding updates.  Therefore, this is not a
   concern.

GT> I think the sentence "this is not a concern" may be a bad choice of
words. The fact that the MN is not directly involved in authorizing
rerouting of its own traffic is of course a big concern. I suggest these
words are deleted and replaced with "Therefore, the local mobility anchor
MUST allow…"

   However, the local mobility anchor MUST allow only
   authorized mobile access gateways to create binding cache entries on
   behalf of the mobile nodes.  The actual mechanism by which the local
   mobility anchor verifies if a specific mobile access gateway is
   authorized to send Proxy Binding Updates on behalf of a mobile node
   is outside the scope of this document.  One possible way this could
   be achieved is by sending a query to the policy store, such as AAA.

GT> The last sentence is too vague to be useful. I would either remove it or
rephrase to indicate that it may be possible to authenticate the MN during
access specific link layer attach procedures.

4.1.  Peer Authorization Database Entries

GT> Sections 4.1/4.2 seem to be using IPSEC/IKEv2 terms without pointing to
them... some referencing could be useful.

   This section describes PAD entries on the mobile access gateway and
   the local mobility anchor.  The PAD entries are only example
   configurations.  Note that the PAD is a logical concept and a
   particular mobile access gateway or a local mobility anchor

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   implementation can implement the PAD in any implementation specific
   manner.  The PAD state may also be distributed across various
   databases in a specific implementation.

       mobile access gateway PAD:
         - IF remote_identity = lma_identity_1
              Then authenticate (shared secret/certificate/EAP)
              and authorize CHILD_SA for remote address lma_addres_1

       local mobility anchor PAD:
         - IF remote_identity = mag_identity_1
              Then authenticate (shared secret/certificate/EAP)
              and authorize CHILD_SAs for remote address mag_address_1

                           Figure 4: PAD Entries

   The list of authentication mechanisms in the above examples is not
   exhaustive.  There could be other credentials used for authentication
   stored in the PAD.

4.2.  Security Policy Database Entries

   This section describes the security policy entries on the mobile
   access gateway and the local mobility anchor required to protect the
   Proxy Mobile IPv6 signaling messages.  The SPD entries are only
   example configurations.  A particular mobile access gateway or a
   local mobility anchor implementation could configure different SPD
   entries as long as they provide the required security.

   In the examples shown below, the identity of the mobile access
   gateway is assumed to be mag_1, the address of the mobile access
   gateway is assumed to be mag_address_1, and the address of the local
   mobility anchor is assumed to be lma_address_1.

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      mobile access gateway SPD-S:
        - IF local_address = mag_address_1 &
             remote_address = lma_address_1 &
             proto = MH & local_mh_type = BU & remote_mh_type = BA
          Then use SA ESP transport mode
          Initiate using IDi = mag_1 to address lma_address_1

      local mobility anchor SPD-S:
        - IF local_address = lma_address_1 &
             remote_address = mag_address_1 &
             proto = MH & local_mh_type = BA & remote_mh_type = BU
          Then use SA ESP transport mode

                           Figure 5: SPD Entries

5.  Local Mobility Anchor Operation

   For supporting the Proxy Mobile IPv6 protocol specified in this
   document, the home agent function, specified in [RFC-3775] requires
   certain functional modifications and enhancements.

   The home agent
   with these modifications and enhanced capabilities for supporting
   Proxy Mobile IPv6 protocol is referred to as the local mobility
   anchor.

GT> to implement one of my earlier comments this could be rephrased as
follows: "The Proxy Mobile IPv6 local mobility anchor MUST support the home
agent functions defined in [RFC-3775] and the extensions defined in this
specification.

   This section describes the operational details of the local mobility
   anchor.

5.1.  Extensions to Binding Cache Entry Data Structure

   Every local mobility anchor MUST maintain a Binding Cache entry for
   each currently registered mobile node.  Binding Cache entry is a
   conceptual data structure, described in Section 9.1 [RFC-3775].

   For supporting this specification, the Binding Cache Entry data
   structure needs to be extended with the following additional fields.

GT> Not clear which of the following are optional/mandatory

   o  A flag indicating whether or not this Binding Cache entry is
      created due to a proxy registration.  This flag is enabled for
      Binding Cache entries that are proxy registrations and is turned
      off for all other entries that are created due to the
      registrations directly sent by the mobile node.

   o  The identifier of the registered mobile node, MN-Identifier.  This
      identifier is obtained from the Mobile Node Identifier Option
      [RFC-4283] present in the received Proxy Binding Update request.

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   o  The interface identifier of the mobile node's connected interface
      on the access link.  This identifier can be acquired from the
      Mobile Node Interface Identifier option (with P Flag set to 0),
      present in the received Proxy Binding Update request.  If the
      option was not present in the request, this value MUST be set to
      ALL_ZERO.

GT> What value is stored if P=1? In general the case of P=1 seems
underspecified.

   o  The Link-local address of the mobile node on the interface
      attached to the access link.  This is obtained from the Link-local
      Address option, present in the Proxy Binding Update request.

   o  The IPv6 home network prefix of the registered mobile node.  The
      home network prefix of the mobile node may have been statically
      configured in the mobile node's policy profile, or, it may have
      been dynamically allocated by the local mobility anchor.  The IPv6
      home network prefix also includes the corresponding prefix length.

   o  The interface identifier of the bi-directional tunnel established
      between the local mobility anchor and the mobile access gateway
      where the mobile node is currently anchored.  The tunnel interface
      identifier is acquired during the tunnel creation.

   o  The access technology through which the mobile node is currently
      connected.  This is obtained from the Access Technology Type
      option, present in the Proxy Binding Update message.

   o  The 64-bit timestamp value of the most recently accepted Proxy
      Binding Update request sent for this mobile node.  This is
      obtained from the Timestamp option, present in the request.

   Typically, the MN-Identifier is the key for locating a Binding Cache
   entry.  However, when supporting multihoming there MAY be more than
   one Binding Cache entry with the same MN-Identifier and in such cases
   the entry can be located using any of the following key combinations:

   o  MN-Identifier, MN-HNP

   o  MN-Identifier, Proxy-CoA

   o  MN-Identifier, MN-Interface-Identifier

   o  MN-Identifier, Access Technology Type (When MN-Interface-
      Identifier is not present)

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5.2.  Supported Home Network Prefix Models

   This specification supports Per-MN-Prefix model and does not support
   Shared-Prefix model.  As per the Per-MN-Prefix model, there will be
   an unique home network prefix assigned to each mobile node and no
   other node shares an address from that prefix.

   The mobile node's home network prefix is always hosted on the access
   link where the mobile node is anchored.  Conceptually, the entire
   home network prefix follows the mobile node as it moves within the
   Proxy Mobile IPv6 domain.  The local mobility anchor is not required
   to perform any proxy ND operations [RFC-4861] for defending the
   mobile node's home address on the home link.  However, from the
   routing perspective, the home network prefix is topologically
   anchored on the local mobility anchor.

GT> Given multihoming considerations this is not "per-MN" but "per-MN and
per something more... interface/access_type?

5.3.  Signaling Considerations

   Processing Binding Registrations

   Upon receiving a Proxy Binding Update request (a Binding Update
   Request with the 'P' flag set) from a mobile access gateway on behalf
   of a mobile node, the local mobility anchor MUST process the request
   as defined in Section 10.3 [RFC-3775], with one exception that this
   request is a Proxy Binding Update request and hence the following
   additional considerations must be applied.

   o  The local mobility anchor MUST observe the rules described in
      Section 9.2 [RFC-3775] when processing Mobility Headers in the
      received Proxy Binding Update request.

   o  The local mobility anchor MUST identify the mobile node from the
      identifier present in the Mobile Node Identifier option [RFC-4283]
      of the Proxy Binding Update request.  If the Mobile Node
      Identifier option is not present in the Proxy Binding Update
      request, the local mobility anchor MUST reject the request and
      send a Proxy Binding Acknowledgement message with Status field set
      to MISSING_MN_IDENTIFIER_OPTION (Missing mobile node identifier).

   o  If the local mobility anchor cannot identify the mobile node, from
      the Mobile Node Identifier option [RFC-4283] present in the
      request, it MUST reject the Proxy Binding Update request and send
      a Proxy Binding Acknowledgement message with Status field set to
      133 (Not home agent for this mobile node).

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   o  If the local mobility anchor determines that the mobile node is
      not authorized for the network-based mobility management service,
      it MUST reject the request and send a Proxy Binding
      Acknowledgement message with Status field set to
      PROXY_REG_NOT_ENABLED (Proxy Registration not enabled).

   o  The local mobility anchor MUST ignore the check, specified in
      Section 10.3.1 [RFC-3775], related to the presence of Home Address
      destination option in the Proxy Binding Update request.

   o  The local mobility anchor MUST authenticate the Proxy Binding
      Update request as described in Section 4.0.  When IPsec is used
      for message authentication, the SPI in the IPsec header [RFC-4306]
      of the received packet for locating the security association
      needed for authenticating the Proxy Binding Update request.

GT> Something is missing in this sentence? Is the following what you
mean?

"When IPsec is used for message authentication, the SPI in the IPsec header
[RFC-4306] of the received packet is needed for locating the security
association, for authenticating the Proxy Binding Update request."

   o  The local mobility anchor MUST apply the required policy checks,
      as explained in Section 4.0, to verify the sender is a trusted
      mobile access gateway, authorized to send Proxy Binding Update
      requests on behalf of this mobile node.

   o  If the local mobility anchor determines that the requesting node
      is not authorized to send Proxy Binding Update requests
      *for the specific MN*, it MUST
      ^^^^^^^^^^^^^^^^^^^^^
      reject the request and send a Proxy Binding Acknowledgement
      message with Status field set to MAG_NOT_AUTHORIZED_FOR_PROXY_REG
      (Not authorized to send proxy registrations).

GT> Is this about authorizing the MAG or is it about authorizing that the
MAG can send PBUs on behalf of a specific MN? The previous bullet indicates
the later but this bullet is unclear. I assume it refers to the latter too
in which case it could be clarified by the text added above.

   o  If the Home Network Prefix option is not present in the Proxy
      Binding Update request, the local mobility anchor MUST reject the
      request and send a Proxy Binding Acknowledgement message with
      Status field set to MISSING_HOME_NETWORK_PREFIX_OPTION (Missing
      mobile node's home network prefix option).

   o  If the Access Technology Type option is not present in the Proxy
      Binding Update request, the local mobility anchor MUST reject the
      request and send a Proxy Binding Acknowledgement message with
      Status field set to MISSING_ACCESS_TECH_TYPE_OPTION (Missing
      mobile node's access technology type).

   o  The local mobility anchor MUST apply the considerations specified
      in Section 5.5, for processing the Sequence Number field and the
      Timestamp option, in the Proxy Binding Update request.

   o  The local mobility anchor MUST use the identifier from the Mobile
      Node Identifier Option [RFC-4283] present in the Proxy Binding
      Update request and MUST apply multihoming considerations specified
      in Section 5.4 for performing the Binding Cache entry existence
      test or for identifying the mobility session.  If the entry does

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      not exist, the local mobility anchor MUST consider this request as
      an initial binding registration request.  If the entry exists, the
      local mobility anchor MUST consider this request as an binding re-
      registration request.  However, from the perspective of the mobile
      access gateway that sent the request, this binding re-registration
      request may be an initial Binding Update request after the mobile
      node's attachment to that mobile access gateway.

   Initial Binding Registration:

   o  If the Home Network Prefix option present in the Proxy Binding
      Update request has the value 0::/0, the local mobility anchor MUST

GT> A MUST does not make sense here. IMO this is a SHOULD since the LMA may
not be able to do that as the following bullet indicates.

      allocate a prefix for the mobile node and send a Proxy Binding
      Acknowledgement message including the Home Network Prefix option
      containing the allocated prefix value.  The specific details on
      how the local mobility anchor allocates the home network prefix is
      outside the scope of this document.

GT> How the HNP is allocated is fully defined in this spec already. Is this
meant to say that where the LMA gets the HNP (e.g., local pool, DHCP, AAA
etc) is out of scope? Maybe it should be rephrased along these lines?

      The local mobility anchor
      MUST ensure the allocated prefix is not in use by any other mobile
      node.

GT> I guess it should make sure it is not in use by any other *node* in
general...not just *mobile node*.

   o  If the local mobility anchor is unable to allocate a home network
      prefix for the mobile node, it MUST reject the request and send a
      Proxy Binding Acknowledgement message with Status field set to 130
      (Insufficient resources).

   o  If the Home Network Prefix option present in the request has a
      specific prefix hint, the local mobility anchor before accepting
      that request, MUST ensure the prefix is owned by the local
      mobility anchor and further the mobile node is authorized to use
      that prefix.  If the mobile node is not authorized to use that
      prefix, the local mobility anchor MUST reject the request and send
      a Proxy Binding Acknowledgement message with Status field set to
      NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX (Mobile node not authorized
      to use that prefix).

   o  Upon accepting the request, the local mobility anchor MUST create
      a Binding Cache entry for the mobile node.  It must set the fields
      in the Binding Cache entry to the accepted values for that
      binding.  If there is a Link-local Address option present in the
      request, the address must be copied to the link-local address
      field in the Binding Cache entry.

   o  Upon accepting the Proxy Binding Update request, the local
      mobility anchor MUST establish a bi-directional tunnel to the
      mobile access gateway, as described in [RFC-2473].  Considerations
      from Section 5.6 must be applied.

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   Binding Re-Registration:

GT> The following does not make very clear what is the conditions for
considering a PBU as a reregistration.

   o  If the requesting prefix in the Home Network Prefix option is a
      non 0::/0 value and is different from what is present in the
      currently active Binding Cache entry for that mobile node, the
      local mobility anchor MUST reject the request and send a Proxy
      Binding Acknowledgement message with Status field set to 129
      (Administratively Prohibited).

   o  If there is a Link-local Address option present in the request
      with a value other than ALL_ZERO (not set), and upon accepting the
      binding re-registration request, the local mobility anchor MUST
      update the link-local address field in the Binding Cache entry to
      the address value received in the request.

   o  Upon accepting a Proxy Binding Update request for extending the
      lifetime of a currently active binding for a mobile node, the
      local mobility anchor MUST update the existing Binding Cache entry
      for this mobile node.  Unless there exists an established bi-
      directional tunnel to the mobile access gateway with the same
      transport and encapsulation mode, the local mobility anchor MUST
      create a tunnel to the mobile access gateway, as described in
      [RFC-2473] and also delete the existing tunnel route to the
      previous mobile access gateway.  It MUST also send a Proxy Binding
      Acknowledgement message to the mobile access gateway with the
      Status field set to 0 (Proxy Binding Update Accepted).

   Binding De-Registration:

   o  If the prefix in the Home Network Prefix option is a non 0::/0
      value and is different from what is present in the currently
      active Binding Cache entry for that mobile node, the local
      mobility anchor MUST reject the request and send a Proxy Binding
      Acknowledgement message with Status field set to 129
      (Administratively Prohibited).

GT> Shouldn't this start with: "If the received Proxy Binding Update request
with the lifetime value of zero and if the prefix..."?

   o  If the received Proxy Binding Update request with the lifetime
      value of zero, has a Source Address in the IPv6 header different
      from what is present in the Proxy-CoA address field in the Binding
      Cache entry existing for that mobile node, the local mobility
      anchor MUST ignore the request.

   o  Upon accepting the Proxy Binding Update request for a mobile node,
      with the lifetime value of zero, the local mobility anchor MUST
      wait for MinDelayBeforeBCEDelete amount of time, before it deletes
      the mobile node's Binding Cache entry.  Within this wait period,
      if the local mobility anchor receives a Proxy Binding Update

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      request message for the same mobile node with the lifetime value
      of greater than zero, and if that request is accepted, then the
      Binding Cache entry MUST NOT be deleted, but must be updated with
      the newly accepted registration values.  The local mobility anchor
      MUST send the Proxy Binding Acknowledgement message, immediately
      upon accepting the request.  However, within this wait period, if
      the local mobility anchor does not receive any valid binding
      registration request for that mobile node, then at the end of this
      wait period, it MUST delete the mobile node's Binding Cache entry
      and remove the routing state created for that mobile node.  In
      addition, during this MinDelayBeforeBCEDelete wait period, the
      local mobility anchor MUST continue to route the mobile node's
      data traffic.

   Constructing the Proxy Binding Acknowledgement Message:

   o  The local mobility anchor when sending the Proxy Binding
      Acknowledgement message to the mobile access gateway MUST
      construct the message as specified below.

               IPv6 header (src=LMAA, dst=Proxy-CoA)
                    Mobility header
                        -BA /*P flag is set*/
                       Mobility Options
                          - Home Network Prefix Option
                          - Link-local Address Option (optional)
                          - Timestamp Option (optional)
                          - Mobile Node Identifier Option
                          - Access Technology Type option (Mandatory)
                          - Mobile Node Interface Identifier option
                            (Optional)

GT> This is confusing. Either only mark options that are optional (implying
that the rest are mandatory) or mark all of the options as either optional
or mandatory.

            Figure 6: Proxy Binding Acknowledgement message format

   o  The Source Address field in the IPv6 header of the message SHOULD
      be set to the destination address of the received Proxy Binding
      Update request.

GT> Why is this a SHOULD??

   o  The Destination Address field in the IPv6 header of the message
      SHOULD be set to the source address of the received Proxy Binding
      Update request.

GT> Why is this a SHOULD??

   o  The Home Network Prefix option MUST be present in the Proxy
      Binding Acknowledgement message.  If the option was not present in

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      the request and if the Status field value is set to
      MISSING_HOME_NETWORK_PREFIX_OPTION, the value MUST be set to
      ALL_ZERO.

   o  The Access Technology Type option MUST be present.  The access
      technology type value in the option MUST be copied from the Access
      Technology Type option in the received Proxy Binding Update
      request.  If the option was not present in the request and if the
      Status field value is set to MISSING_ACCESS_TECH_TYPE_OPTION, the
      value MUST be set to 0.

   o  The Mobile Node Interface Identifier option MAY be present, if the
      same option was present in the corresponding Proxy Binding Update
      request message.

GT> Why is this a "MAY be present, if", while the link local address option
below is "MUST be present, if and only if"

   o  If the Status field is set to a value greater than or equal to
      128, i.e., if the binding request was rejected, then the prefix
      value in the Home Network Prefix option MUST be set to the prefix
      value from the received Home Network Prefix option.  For all other
      cases, the prefix value MUST be set to the allocated prefix value
      for that mobile node.

   o  The Link-local Address option MUST be present in the Proxy Binding
      Acknowledgement message if and only if the same option was present
      in the corresponding Proxy Binding Update request message.

   o  If the Status field is set to a value greater than or equal to
      128, i.e., if the binding request was rejected, then the link-
      local address value in the Link-local Address option MUST be set
      to the value from the received Link-local Address option.

   o  If there is an existing Binding Cache entry for the mobile node
      with the link-local address value of ALL_ZERO (value not set), or
      if there was no existing Binding Cache entry, then the link-local
      address MUST be copied from the Link-local Address option in the
      received Proxy Binding Update request.  For all other cases, it
      MUST be copied from the mobile node's Binding Cache entry.

GT> How is the MN If-ID used by the MAG when present in the BA??

   o  Considerations from Section 5.5 must be applied for constructing
      the Timestamp option.

   o  The identifier in the Mobile Node Identifier option [RFC-4283]
      MUST be copied from the received Proxy Binding Update request.  If
      the Status field value is set to MISSING_MN_IDENTIFIER_OPTION, the
      Mobile Node Identifier Option MUST NOT be present in the Proxy
      Binding Acknowledgement message.

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   o  The message MUST be protected by using IPsec, using the security
      association existing between the local mobility anchor and the
      mobile access gateway.

   o  The Type 2 Routing header MUST NOT be present in the IPv6 header
      of the packet.

5.4.  Multihoming Support

   When a mobile node connects to a Proxy Mobile IPv6 domain through
   multiple interfaces simultaneously, the local mobility anchor MUST
   allocate a unique home network prefix for each of the connected
   interfaces.

   The local mobility anchor MUST manage each of the allocated home
   network prefixes as part of a separate mobility session, each with a
   separate Binding Cache entry.

   The local mobility anchor MUST allow for an handover between two
                                           ^^^^
GT> //an/a

   different interfaces of the mobile node.  In such a case, the home
   network prefix that is associated with a specific interface
   identifier of a mobile node will be updated with the new interface
   identifier.

GT> This is still very unclear. On one hand a different HNP must be
allocated to each interface but then HNPs can be moved from one interface to
another. For the same MN or only different MNs? How is it determined when to
do what?

   The local mobility anchor MUST apply the following multihoming
   considerations when processing a received Proxy Binding Update
   request message.

   Processing De-Registration Message:

   o  If the received Proxy Binding Update message has lifetime value of
      zero, the local mobility anchor MUST verify if there is an
      existing Binding Cache entry for the mobile node, identified by
      the MN-Identifier and with the Proxy-CoA address matching the
      source address in the IPv6 header of the received packet.  If
      there exists a Binding Cache entry, the local mobility anchor MUST
      consider the message as a request for de-registering that specific
      mobility session.  If there does not exist a Binding Cache entry,
      the message MUST be ignored.

   Mobile Node Interface Identifier Option not present in the request:

   o  The local mobility anchor MUST verify if there is an existing
      Binding Cache entry for the mobile node, identified by the MN-
      Identifier and with the interface identifier value set to ALL_ZERO

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      .

   o  If there does not exist a Binding Cache entry, the local mobility
      anchor upon accepting the request MUST assign a new home network
      prefix and create a new Binding Cache entry.

   o  If there exists a Binding Cache entry and if the Handoff Indicator
      flag in the Access Technology Type option present in the received
      Proxy Binding Update message is set to value 1 (Attachment over a
      new interface), the local mobility anchor upon accepting the
      request MUST assign a new home network prefix and create a new
      Binding Cache entry.

   o  If there exists a Binding Cache entry and if the Handoff Indicator
      flag in the Access Technology Type option present in the received
      Proxy Binding Update message is set to either value 2 (Handoff
      between interfaces) or 3 (Handoff between mobile access gateways
      for the same mobile node's interface), the local mobility anchor
      upon accepting the request MUST update the existing Binding Cache
      entry and assign the home network prefix present in the Binding
      Cache entry.

   o  If there exists a Binding Cache entry and if the Handoff Indicator
      flag in the Access Technology Type option present in the received
      Proxy Binding Update message is set to value 4 (Handoff state
      unknown), the local mobility anchor SHOULD wait till the existing
      Binding Cache entry is de-registered by the previously serving
      mobile access gateway,

GT> Should we not add the following: "and the MinDelayBeforeBCEDelete
expires,"

      before it assigns the same home network
      prefix or updates the existing Binding Cache entry.  However, if
      there is no de-registration message that is received within a
      given amount of time, the local mobility anchor upon accepting the
      request MUST assign a new home network prefix and create a new
      Binding Cache entry.

     The local mobility anchor MAY also choose to
      assign a new home network prefix and without waiting for a de-
      registration message.

   o  Either upon creating a new Binding Cache entry or from matching an
      existing Binding Cache entry, after applying the above
      considerations, the interface identifier field in the Binding
      Cache entry MUST be set to the value present in the received
      Mobile Node Interface Identifier Option

GT> The above set of bullets has a heading indicating that "MNID is not
present" so how si the Binding Cache entry set to the value of the MNID
Option??

and the access technology
      type MUST be copied from the Access Technology type option present
      in the received Proxy Binding Update message.  If the Mobile Node
      Interface Identifier Option is not present, the interface
      identifier field in the Binding Cache entry MUST be set to
      ALL_ZERO.

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   Mobile Node Interface Identifier Option present in the request:

   o  The local mobility anchor MUST verify if there is an existing
      Binding Cache entry for the mobile node, identified by the MN-
      Identifier and with the interface identifier value matching the
      identifier value present in the received Mobile Node Interface
      Identifier Option.

   o  If there exists a Binding Cache entry, the local mobility anchor
      upon accepting the request MUST update the existing Binding Cache
      entry and assign the home network prefix present in the Binding
      Cache entry.

GT> In the following bullets it is not always clear which Binding Cache
entry does not exist. It is not clear if each bullet is a sub-bullet of the
previous one or an self contain bullet. I have attempted to clarify the text
when possible but I might have also misunderstood the intent.

   o  If there does not exist a Binding Cache entry and if the Handoff
      Indicator flag in the Access Technology Type option present in the
      received Proxy Binding Update message is set to value 1
      (Attachment over a new interface), the local mobility anchor upon
      accepting the request MUST assign a new home network prefix and
      create a new Binding Cache entry.

   o  If there does not exist a Binding Cache entry

GT> Add: "matching the MN-Identifier and the interface identifier received,"

and if the Handoff
      Indicator flag in the Access Technology Type option present in the
      received Proxy Binding Update message is set to value 2 (Handoff
      between interfaces), the local mobility anchor MUST verify if
      there exists one and only one Binding Cache entry for the mobile
      node, identified by the MN-Identifier and with any interface
      identifier value.  If there exists such an entry, the local
      mobility anchor upon accepting the request MUST update the
      existing Binding Cache entry and assign the home network prefix
      present in the Binding Cache entry.

GT> What happens if there are more than one entries already in the Binding
Cache?

   o  If there does not exist a Binding Cache entry

GT> Add: "matching the MN-Identifier receive and with any interface
identifier,"

      and if the Handoff
      Indicator flag in the Access Technology Type option present in the
      received Proxy Binding Update message is set to value 2 (Handoff
      between interfaces), the local mobility anchor MUST verify if
      there exists a Binding Cache entry for the mobile node, identified
      by the MN-Identifier and with the home network prefix value
      matching the prefix value in the received Home Network Prefix
      option.  If there exists a Binding Cache entry, the local mobility
      anchor upon accepting the request MUST assign the same prefix,
      else it MUST assign a new home network prefix and create a new
      Binding Cache entry.

   o  If there does not exist a Binding Cache entry and if the Handoff

GT> What type of Binding Cache entry is expected to exist in this case if no
entries match the MNID + any IID, and MNID + HNP described in the last two
bullets??

      Indicator flag in the Access Technology Type option present in the
      received Proxy Binding Update message is set to value 4 (Handoff
      state unknown), the local mobility anchor SHOULD wait till the
      existing Binding Cache entry is de-registered by the previously

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      serving mobile access gateway.  However, if there is no de-
      registration message that is received within a given time, the
      local mobility anchor upon accepting the request MUST assign a new
      home network prefix and create a new Binding Cache entry.  The
      local mobility anchor MAY also choose to assign a new home network
      prefix and without waiting for a de-registration message.

   o  Either upon creating a new Binding Cache entry or from matching an
      existing Binding Cache entry, after applying the above
      considerations, the interface identifier field in the Binding
      Cache entry MUST be set to the value present in the received
      Mobile Node Interface Identifier Option and the access technology
      type MUST be copied from the Access Technology type option present
      in the received Proxy Binding Update message.  If the Mobile Node
      Interface Identifier Option is not present, the interface
      identifier field in the Binding Cache entry MUST be set to
      ALL_ZERO.

GT> I believe there are many other cases here that are not fully defined:
If I understand correctly the following parameters received in a PBU, are
compared to parameters in the Binding Cache, to determine what HNP should be
allocated and what entry should be created/updated/deleted in the Binding
Cache..
- HNP (same, different)
- Interface ID (not present, same, different)
- Access Type (same, different)
- HI (new if, handoff between different ifs, handoff with same if, unknown)
I do not believe the above set of bullets covers all possible combinations.
What is to be assumed for the ones not yet covered?

5.5.  Timestamp Option for Message Ordering

...
   o  An implementation MUST support Sequence Number based scheme, as
      per [RFC-3775].

GT> Is the reference to 3775 correct here since in PMIP the SNs are not sent
by the MN is a BU? Or maybe it should be clarified that the treatment of SNs
in the LMA is a s per 3775?

...
6.4.  Supported Address Configuration Models

GT> Not sure this section adds anything

   A mobile node in the Proxy Mobile IPv6 domain can configure one or
   more IPv6 addresses on its interface using Stateless or Stateful
   address autoconfiguration procedures.  The Router Advertisement
   messages sent on the access link specify the address configuration
   methods permitted on that access link for that mobile node.  However,
   the advertised flags with respect to the address configuration will
   be consistent for a mobile node, on any of the access links in that
   Proxy Mobile IPv6 domain.  Typically, these configuration settings
   will be based on the domain wide policy or based on a policy specific
   to each mobile node.

   When stateless address autoconfiguration is supported on the link,
   the mobile node can generate one or more IPv6 addresses by combining
   the network prefix advertised on the access link with an interface
   identifier, using the techniques described in Stateless
   Autoconfiguration specification [RFC-4862] or as per Privacy
   extension specification [RFC-4941].

   When stateful address autoconfiguration is supported on the link, the
   mobile node can obtain the address configuration from the DHCPv6
   server using DHCPv6 client protocol, as specified in DHCPv6
   specification [RFC-3315].

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   Additionally, other address configuration mechanisms specific to the
   access link between the mobile node and the mobile access gateway may
   also be used for pushing the address configuration to the mobile
   node.

6.5.  Access Authentication & Mobile Node Identification

   When a mobile node attaches to an access link connected to the mobile
   access gateway, the deployed access security protocols on that link
   SHOULD ensure that the network-based mobility management service is
   offered only after authenticating and authorizing the mobile node for
   that service.  The exact specifics on how this is achieved or the
   interactions between the mobile access gateway and the access
   security service is outside the scope of this document.  This
   specification goes with the stated assumption of having an
   established trust between the mobile node and mobile access gateway,
   before the protocol operation begins.

GT> Maybe the stated assumption should be stated more clearly. i.e., "This
specification assumes that the mobile access gateway can verify the fact
that a given MN-ID belongs to an attached MN before the protocol operation
begins"

6.6.  Acquiring Mobile Node's Identifier

GT> Section 6 is about MAG Operations, but this subsection contains
normative "MUST" statements about all network entities involved (presumably
including the LMA). Since I think this is already covered in the LMA
Operations section the MUST could be limited to the MAG here.

   All the network entities in a Proxy Mobile IPv6 domain MUST be able
   to identify a mobile node, using its MN-Identifier.  This identifier
   MUST be stable across the Proxy Mobile IPv6 domain and the entities
   must be able to use this identifier in the signaling messages.
   Typically, this identifier is obtained as part of the access
   authentication or through other means as specified below.

   o  The identifier of the mobile node that the mobile access gateway
      obtains typically as part of the access authentication or from the
      notified network attachment event, can be a temporary identifier
      and this identifier may also change at each re-authentication.
      However, the mobile access gateway MUST be able to use this
      identifier and obtain the mobile node's MN-Identifier from the
      policy store, such as from the RADIUS attribute, Chargeable-User-
      Identifier [RFC-4372].

GT> This implies that two different IDs exist, one that is retrieved during
access authentication and another that is derived from a policy store. What
is this have to do with PMIPv6?

   o  The MN-Identifier that the policy store delivers to the mobile
      access gateway may not be the true identifier of the mobile node.
      However, the mobility access gateway MUST be able to use this
      identifier in the signaling messages exchanged with the local
      mobility anchor.

GT> The above two bullets seem to assume a policy store exists. Other parts
of the document only mention a policy store as an example. IMO, the more we
say about MN-IDs in this spec the worse it gets.  I think the following
bullet is all that is needed here. I would just remove the other two bullets
or even the section as redundant.

   o  The mobile access gateway MUST be able identify the mobile node by
      its MN-Identifier and it MUST be able to associate this identity
      to the sender of any IPv4 or IPv6 packets on the access link.

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6.7.  Home Network Emulation

   One of the key functions of a mobile access gateway is to emulate the
   mobile node's home network on the access link.  It must ensure, the
   mobile node believes it is still connected to its home link or on the
   link where it obtained its initial address configuration after it
   moved into that Proxy Mobile IPv6 domain.

   For emulating the mobile node's home link on the access link, the
   mobile access gateway must be able to send Router Advertisements
   advertising the mobile node's home network prefix and other address
   configuration parameters consistent with its home link properties.
   Typically, these configuration settings will be based on the domain
   wide policy or based on a policy specific to each mobile node.

   Typically, the mobile access gateway learns the mobile node's home
   network prefix information from the received Proxy Binding
   Acknowledgement message or it may be obtained from the mobile node's
   policy profile.  However, the mobile access gateway SHOULD send the
   Router Advertisements advertising the mobile node's home network
   prefix only after successfully completing the binding registration
   with the mobile node's local mobility anchor.

   When advertising the home network prefix in the Router Advertisement
   messages, the mobile access gateway MAY set the prefix lifetime value
   for the advertised prefix to any chosen value at its own discretion.
   An implementation MAY choose to tie the prefix lifetime to the mobile
   node's binding lifetime.  The prefix lifetime can also be an optional
   configuration parameter in the mobile node's policy profile.

GT> The above allows the lifetime advertised to the MN to be larger than the
lifetime value in the PBA. Why is that? I think "the MAG SHOULD advertise a
value equal or lower than the one received in the PBA".

6.8.  Link-Local and Global Address Uniqueness

   A mobile node in the Proxy Mobile IPv6 domain, as it moves from one
   mobile access gateway to the other, will continue to detect its home
   network and thus making it believe it is still on the same link.
   Every time the mobile node attaches to a new link, the event related
   to the interface state change will trigger the mobile node to perform
   DAD operation on the link-local and global addresses.  However, if
   the mobile node is DNAv6 enabled, as specified in [ID-DNAV6], it may
   not detect the link change due to DNAv6 optimizations and may not
   trigger the duplicate address detection (DAD) procedure for
   establishing the link-local address uniqueness on that new link.
   Further, if the mobile node uses an interface identifier that is not
   based on EUI-64 identifier, such as specified in IPv6 Stateless
   Autoconfiguration specification [RFC-4862], there is a very low
   possibility of a link-local address collision between the two
   neighbors on that access link.

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   For solving this problem, this specification allows the mobile access
   gateway to upload the mobile node's link-local address to the local
   mobility anchor using the Link-local Address option, exchanged in the
   binding registration messages.  The mobile access gateway can learn
   the mobile node's link-local address, by snooping the DAD messages
   sent by the mobile node for establishing the link-local address
   uniqueness on the access link.  Subsequently, at each handoff, the
   mobile access gateway can obtain this address from the local mobility
   anchor to ensure link-local address uniqueness and may change its own

GT> In the BA processing (section 6.9.1) this is a MUST; so maybe remove the
"may" above?

   link-local address, if it detects a collision.

   Alternatively, one of the workarounds for this issue is to set the
   DNAv6 configuration parameter, DNASameLinkDADFlag to TRUE and that
   will force the mobile node to redo DAD operation on the global and
   link-local addresses every time the interface detects a handover,
   even when DNAv6 does not detect a link change.

   However, this issue will not impact point-to-point links based on a
   PPP session.  Each time the mobile node moves and attaches to a new
   mobile access gateway, either the PPP session [RFC-1661] is
   reestablished or the PPP session may be moved as part of context
   transfer procedures between the old and the new mobile access
   gateway.

   When the mobile node tries to establish a PPP session with the mobile
   access gateway, the PPP goes through the Network layer Protocol phase
   and the IPv6 Control Protocol, IPV6CP [RFC-5072] gets triggered.
   Both the PPP peers negotiate a unique identifier using Interface-
   Identifier option in IPV6CP and the negotiated identifier is used for
   generating a unique link-local address on that link.  Now, if the
   mobile node moves to a new mobile access gateway, the PPP session
   gets torn down with the old mobile access gateway and a new PPP
   session gets established with the new mobile access gateway, and the
   mobile node obtains a new link-local address.  So, even if the mobile
   node is DNAv6 capable, the mobile node always configures a new link-
   local address whenever it moves to a new link.

   If the PPP session state is moved to the new mobile access gateway as
   part of context transfer procedures that are in place, there will not
   be any change to the interface identifiers of the two nodes on that
   point-to-point change.  The whole link is moved to the new mobile
   access gateway and there will not be any need for establishing link-
   local address uniqueness on that link.

   The issue of address collision is not relevant to the mobile node's
   global address.  Since there is an unique home network prefix
   assigned for each mobile node, the uniqueness for the mobile node's
   global address is assured on the access link.

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6.9.  Signaling Considerations

6.9.1.  Binding Registrations

   Mobile Node Attachment and Initial Binding Registration:

   o  After detecting a new mobile node on its access link, the mobile
      access gateway must identify the mobile node and acquire its MN-
      Identifier.  If it determines that the network-based mobility
      management service needs to be offered to the mobile node, it MUST
      send a Proxy Binding Update message to the local mobility anchor.

   o  The Proxy Binding Update message MUST have the Mobile Node

GT> //have/include

      Identifier option [RFC-4283], identifying the mobile node, the
      Home Network Prefix option, either the Timestamp option or a valid
      sequence number and optionally the Link-local Address option.
      When Timestamp option is added to the message, the mobile access
      gateway MAY set the Sequence Number field to a value of a
      monotonically increasing counter and the local mobility anchor
      will ignore this field, but will return the same value in the
      Proxy Binding Acknowledgement message.  This will be useful for
      matching the reply to the request message.

GT> Why is this optional? And how are BU/BA messages matched if the SN is
not incremented as suggested here? Change the MAY to SHOULD? Or MUST?

   o  The Home Address option MUST NOT be present in the Destination
      Option extension header of the Proxy Binding Update message.

   o  The Access Technology Type option MUST be present in the Proxy
      Binding Update message.  The access technology Type field in the
      option MUST be set to the access technology using which the mobile
      node is currently attached to the mobile access gateway.

   o  The Handoff Indicator flag in the Access Technology Type option
      MUST be set to value 1 (Attachment over a new interface), if the
      mobile access gateway predictably knows that the mobile node's
      attachment to the network using the current interface is due to
      neither a handover between two interfaces of the mobile node nor a
      handover of the mobility session for the same interface of the
      mobile node between two mobile access gateways.  This essentially
      serves as a request to the local mobility anchor to allocate a new
      home network prefix for this mobility session and not update any
      existing Binding Cache entry created for the same mobile node
      connected to the Proxy Mobile IPv6 domain through a different
      interface.

   o  The Handoff Indicator flag in the Access Technology Type option
      MUST be set to value 2 (Handoff between interfaces), if the mobile
      access gateway definitively knows the mobile node's current
      attachment is due to a handoff of the mobility session between two

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      interfaces of the mobile node.

   o  The Handoff Indicator flag in the Access Technology Type option
      MUST be set to value 3 (Handoff between mobile access gateways for
      the same interface), if the mobile access gateway definitively
      knows the mobile node's current attachment is due to a handoff of
      the mobility session between two interfaces of the mobile node.

GT> This is not between two interfaces, it is a handoff between two MAGs
using the same interface.

   o  The Handoff Indicator flag in the Access Technology Type option
      MUST be set to value 4 (Handoff State Unknown), if the mobile
      access gateway cannot predictably know if the mobile node's
      session is due to a handoff.

   o  The Mobile Node Interface Identifier option carrying the
      identifier of the currently attached interface MUST be present in
      the Proxy Binding Update message, if the mobile access gateway
      knows the interface identifier of the mobile node's currently
      attached interface.  The "P" Flag in the option MUST be set to 0,
      indicating that the carried identifier is the currently attached
      interface identifier.  If the interface identifier is now known,

GT> remove the word "now"?

      this identifier MUST NOT be present.

   o  If the mobile access gateway learns the mobile node's home network
      prefix either from its policy store or from other means, the
      mobile access gateway MAY choose to specify the same in the Home
      Network Prefix option for requesting the local mobility anchor to
      allocate that prefix.  If the specified value is 0::/0, then the
      local mobility anchor will consider this as a request for prefix
      allocation.

   Receiving Binding Registration Reply:

   o  The mobile access gateway MUST observe the rules described in
      Section 9.2 [RFC-3775] when processing Mobility Headers in the
      received Proxy Binding Acknowledgement message (a Binding
      Acknowledgement message with the 'P' flag set).

   o  The message MUST be authenticated as described in Section 4.0.
      When IPsec is used for message authentication, the SPI in the
      IPsec header [RFC-4306] of the received packet MUST be used for
      locating the security association needed for authenticating the
      message.

   o  The mobile access gateway MUST apply the considerations specified
      in Section 5.5 for processing the Sequence Number field and the
      Timestamp option, in the message.

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   o  The mobile access gateway MUST ignore any checks, specified in
      [RFC-3775] related to the presence of Type 2 Routing header in the
      Proxy Binding Acknowledgement message.

   o  If the Timestamp option is present in the received Proxy Binding
      Acknowledgement message and with the Status field value set to any
      value other than TIMESTAMP_MISMATCH (Invalid Timestamp), the
      mobile access gateway MAY use the timestamp value for matching the
      response to the request message that it sent recently.  For all
      other cases, it MAY use the sequence number in combination with
      the identifier present in the Mobile Node Identifier option for
      matching the response to the request.

   o  If the received Proxy Binding Acknowledgement message has the
      Status field value set to PROXY_REG_NOT_ENABLED (Proxy
      registration not enabled for the mobile node), the mobile access
      gateway SHOULD NOT send binding registration requests again for
      that mobile node.  It must also deny the mobility service to that
      mobile node.

   o  If the received Proxy Binding Acknowledgement message has the
      Status field value set to TIMESTAMP_LOWER_THAN_PREV_ACCEPTED
      (Timestamp lower than previously accepted timestamp), the mobile
      access gateway SHOULD try to register again to reassert the mobile
      node's presence to the mobility anchor.  The mobile access gateway
      is not specifically required to synchronize its clock upon
      receiving this error code.

   o  If the received Proxy Binding Acknowledgement message has the
      Status field value set to TIMESTAMP_MISMATCH (Invalid Timestamp),
      the mobile access gateway SHOULD try to register again only after
      it has synchronized its clock to a common time source that is used
      by all the mobility entities in that domain for their clock
      synchronization.  The mobile access gateway SHOULD NOT synchronize
      its clock to the local mobility anchor's system clock, based on
      the timestamp present in the received message.

   o  If the received Proxy Binding Acknowledgement message has the
      Status field value set to NOT_AUTHORIZED_FOR_HOME_NETWORK_PREFIX
      (Not authorized for that prefix), the mobile access gateway SHOULD
      try to request for that prefix in the binding registration
      request, only after it learned the validity of that prefix.

   o  If the received Proxy Binding Acknowledgement message has the
      Status field value set to any value greater than or equal to 128
      (i.e., if the binding is rejected), the mobile access gateway MUST
      NOT advertise the mobile node's home network prefix in the Router
      Advertisements sent on that access link and there by denying

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      mobility service to the mobile node.

   o  If the received Proxy Binding Acknowledgement message has the
      Status field value set to 0 (Proxy Binding Update accepted) and if
      there is no existing Binding Update List entry for that mobile
      node, the mobile access gateway MUST create a Binding Update List
      entry and must setup the routing state, as explained in section
      6.10.  But, if there is an existing Binding Update List entry for
      that mobile node, the entry MUST be updated reflecting the
      accepted binding registration.

   o  If the received Proxy Binding Acknowledgement message has the
      address in the Link-local Address option set to a value that
      matches its own link-local address on that access interface where
      the mobile node is anchored, the mobile access gateway MUST change
      its link-local address on that interface.

   Extending Binding Lifetime:

   o  For extending the lifetime of a currently registered mobile node
      (i.e., if there exists a Binding Update List entry for that mobile
      node), the mobile access gateway MUST send a Proxy Binding Update
      message to the local mobility anchor.  The prefix value in the
      Home Network Prefix option present in the request SHOULD be set to
      the currently registered home network prefix and the value in the
      Link-local Address option MAY be set to ALL_ZERO or to the link-
      local address of the mobile node.

   Mobile Node Detachment and Binding De-Registration:

   o  At any point, if the mobile access gateway detects that the mobile
      node has moved away from its access link, it SHOULD send a Proxy
      Binding Update message to the local mobility anchor with the
      lifetime value set to zero.

   o  Either upon receipt of a Proxy Binding Acknowledgement message
      from the local mobility anchor or after a certain timeout waiting
      for the reply, the mobile access gateway MUST remove the Binding
      Cache entry for that mobile node from its Binding Update List and
      withdraw the mobile node's home network prefix as the hosted on-
      link prefix on that access link.

   Constructing the Proxy Binding Update Message:

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   o  The mobile access gateway when sending the Proxy Binding Update
      request to the local mobility anchor MUST construct the message as
      specified below.

               IPv6 header (src=Proxy-CoA, dst=LMAA)
                    Mobility header
                        -BU /*P & A flags are set*/
                       Mobility Options
                          - Home Network Prefix option
                          - Link-local Address option (Optional)
                          - Timestamp Option (optional)
                          - Mobile Node Identifier option
                          - Access Technology Type option (Mandatory)
                          - Mobile Node Interface Identifier option
                            (Optional)

                Figure 8: Proxy Binding Update message format

GT> This is confusing. Either only mark options that are optional (implying
that the rest are mandatory) or mark all of the options as either optional
or mandatory.

   o  The Source Address field in the IPv6 header of the message SHOULD
      be set to the address of the mobile access gateway.

   o  The Destination Address field in the IPv6 header of the message
      SHOULD be set to the local mobility anchor address.

   o  The Home Network Prefix option MUST be present.  The prefix value
      MAY be set 0::/0 or to a specific prefix value.

   o  The Link-local Address option MAY be present.  The value MAY be
      set to ALL_ZERO or the mobile node's link-local address.

   o  The Access Technology Type option MUST be present.  The value MUST
      be set to the type of the access technology using which the mobile
      node is currently attached to the mobile access gateway.

   o  The Mobile Node Interface Identifier option MAY be present.

   o  Considerations from Section 5.5 must be applied for constructing
      the Timestamp option.

   o  The Mobile Node Identifier option [RFC-4283] MUST be present, the
      identifier field in the option MUST be set to mobile node's
      identifier, MN-Identifier.

   o  The message MUST be protected by using IPsec, using the security
      association existing between the local mobility anchor and the
      mobile access gateway.

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...
6.11.  Supporting DHCPv6 based Address Configuration on the Access Link

   This section explains how Stateful Address Configuration using DHCPv6
   can be enabled on the access link attached to a mobile access gateway
   and how a mobile node attached to that link can obtain an address
   from its home network prefix using DHCPv6.

   o  The DHCPv6 relay agent [RFC-3315] service needs to be enabled on
      each of the access links in the Proxy Mobile IPv6 domain.

GT> Does that mean that the MAG must also be a DHCP Relay Agent, if DHCP is
turned on? Should this be stated more clearly?

      Further, as specified in Section 20 [RFC-3315], the relay agent
      should be configured to use a list of destination addresses, which
      MAY include unicast addresses, the All_DHCP_Servers multicast
      address, or other addresses selected by the network administrator.

   o  The DHCPv6 server in the Proxy Mobile IPv6 domain can be
      configured with a list of prefix pools (P1, P2, ..., Pn).  Each
      one of these prefix pools corresponds to a home network prefix
      that a local mobility anchor allocates to a mobile node in that
      domain.  However, the DHCPv6 server will not know the relation
      between a given address pool and a mobile node to which the
      corresponding prefix is allocated.  It just views these pools as
      prefixes hosted on different links in that domain.

GT> Is anything assumed about the location of the DHCPv6 Server? Can be
collocated with MAG/LMA or it must be separate for some reason?

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   o  When a mobile node sends a DHCPv6 request message, the DHCP relay
      agent function on the access link will set the link-address field
      in the DHCP message to an address in the mobile node's home
      network prefix, so as to provide a prefix hint to the DHCP Server
      for the address pool selection.  The DHCP server on receiving the
      request from the mobile node, will allocate an address from the
      prefix pool present in the link-address field of the request.

   o  Once the mobile node obtains an address and moves to a different
      link and sends a DHCP request, the DHCP relay agent on the new
      link will set the prefix hint in the DHCP messages to the mobile
      node's home network prefix.  The DHCP server will identify the
      client from the Client-DUID option and present in the request and
      will allocate the same address as before.

   o  The DHCP based address configuration is not recommended for
      deployments where the local mobility anchor and the mobile access
      gateways are located in different administrative domains.  For
      this configuration to work, all the mobile access gateways in the
      Proxy Mobile IPv6 domain should be able to ensure that the DHCP
      requests from a given mobile node anchored on any of the access
      links in that domain, will always be handled by the same DHCP
      server.

   o  The DHCP server should be configured to offer low address lease
      times.  A lease time that is too large prevents the DHCP server
      from reclaiming the address even after the local mobility anchor
      deletes the mobile node's binding cache entry.

6.12.  Home Network Prefix Renumbering

   If the mobile node's home network prefix gets renumbered or becomes
   invalid during the middle of a mobility session, the mobile access
   gateway MUST withdraw the prefix by sending a Router Advertisement on
   the access link with zero prefix lifetime for the mobile node's home
   network prefix.  Also, the local mobility anchor and the mobile
   access gateway MUST delete the routing state for that prefix.
   However, the specific details on how the local mobility anchor
   notifies the mobile access gateway about the mobile node's home
   network prefix renumbering are outside the scope of this document.

GT> This is a strange MUST for the implementation when no mechanism exists
for the LMA to communicate such information to the MAG.
...
7.2.  Roaming in the Proxy Mobile IPv6 Domain

   After obtaining the address configuration in the Proxy Mobile IPv6
   domain, as the mobile node moves and changes its point of attachment
   from one mobile access gateway to the other, it can still continue to
   use the same address configuration.  As long as the attached access
   network is in the scope of that Proxy Mobile IPv6 domain, the mobile
   node will always detect the same link, where it obtained its initial
   address configuration.  If the mobile node performs DHCP operation,
   it will always obtain the same address as before.

   However, the mobile node will always detect a new default-router on
   each connected link, but still advertising the mobile node's home
   network prefix as the on-link prefix and with the other configuration
   parameters consistent with its home link properties.

GT> Not sure that the text reflects the subject matter indicated by the
title. The text does not say what happens when the MN moves between
administrative PMIPv6 domains (i.e., when it is roaming). Or is the title
wrong??

7.3.  IPv6 Host Protocol Parameters

   This specification does not require any changes to the mobile node's
   IP stack.  It assumes the mobile node to be a normal IPv4/IPv6 node,
   with its protocol operation consistent with the respective
   specifications.

   However, for achieving protocol efficiency and for faster hand-offs,
   implementations may choose to adjust the following IPv6 operating
   parameters on the mobile node be adjusted to the below recommended
   values.

   Lower Default-Router List Cache Time-out:

   As per the base IPv6 specification [RFC-4861], each IPv6 host is
   required to maintain certain host data structures including a
   Default-Router list.  This is the list of on-link routers that have
   sent Router Advertisement messages and are eligible to be default

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   routers on that link.  The Router Lifetime field in the received
   Router Advertisement defines the life of this entry.

   In case of Proxy Mobile IPv6, when a mobile node moves from one link
   to another, the source address of the received Router Advertisement
   messages advertising the mobile node's home network prefix will be
   from a different link-local address and thus making the mobile node
   believe that there is a new default-router on the link.  It is
   important that the mobile node uses the newly learnt default-router
   and not the previously known default-router.  The mobile node must
   update its default-router list with the new default router entry and
   must age out the previously learnt default router entry from its
   cache, just as specified in Section 6.3.5 [RFC-4861].  This action
   will help in minimizing packet losses during a hand off switch.

   On detecting a reachability problem, the mobile node will certainly
   detect the default-router loss by performing the Neighbor
   Unreachability Detection procedure, but it is important that the
   mobile node times out the previous default router entry at the
   earliest.  If a given IPv6 host implementation has the provision to
   adjust these flush timers, still conforming to the base IPv6 ND
   specification, it is desirable to keep the flush-timers to suit the
   above consideration.

   In access network where SEND [RFC-3971] is not deployed, the mobile
   access gateway may withdraw the previous default-router entry, by
   sending a Router Advertisement using the link-local address that of
   the previous mobile access gateway and with the Router Lifetime field
   set to value 0, then this will force the flush of the Previous
   Default-Router entry from the mobile node's cache.  This certainly
   requires context-transfer mechanisms in place for notifying the link-
   local address of the default-router on the previous link to the
   mobile access gateway on the new link.

   There are other solutions possible for this problem, including the
   assignment of a fixed link-local address for all the mobility
   entities in a Proxy Mobile IPv6 domain and where SEND [RFC-3971] is
   not deployed.  In such scenario, the mobile node is not required to
   update the default-router entry.  However, this is an implementation
   choice and has no bearing on the protocol interoperability.
   Implementations are free to adopt the best approach that suits their
   target deployments.

GT> This section defines a number of optimizations that can be performed by
the MN when in a PMIPv6 domain. It is not clear how an MN detects that it is
in the PMIPv6 domain or what impact these "optimizations" are applied if the
MN is not attached to a PMIPv6 domain.
_______________________________________________
netlmm mailing list
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https://www1.ietf.org/mailman/listinfo/netlmm

---

From: "Sri Gundavelli" <[email-masked]>
Date: Sat, 24 Nov 2007 10:39:58 -0800

Hi George,
 
Thanks for the LC comments. Please see inline.
 
Sri

  _____  

From: George Tsirtsis [mailto:[email-masked]] 
Sent: Tuesday, November 20, 2007 1:36 AM
To: [email-masked]
Subject: [netlmm] Comments on draft-ietf-netlmm-proxymip6-07.txt

Hi Sri, et.al.,

 
[Sri] Ok. We will identify and address if we are missing any parameter
combination.

[Sri] Ok. We will clarify this. 

Regards
George

----------------------------------------------------------------------------
----------------------------------------
                           Proxy Mobile IPv6 
                   draft-ietf-netlmm-proxymip6-07.txt

...
1.  Introduction

GT> The above should either be removed or a sentence indicating that "The
details of MIPv6 - PMIPv6 interactions are out of scope" should be added.

[Sri] Hmm... The text is not venturing into CMIP-PMIP interaction scenario.
Its just stating the network assumptptions on the host capability.

[Sri] :). The text is just about the HA reuse. If others have no comment, we
can add this explicit caution note.

[Sri] Ok. We will reword it. 

 ...
2.2.  Terminology

[Sri] Ok. 

   Mobile Node (MN)

   LMA Address (LMAA)

[Sri] Ok. Will reword it.

   Mobile Node's Home Link

   Multihomed Mobile Node

[Sri] Ok. Will slightly reword it.

[Sri] Good point. Triggers are very much technology specific, I'm not sure,
if we will be able to generalise them and capture them here.

               +----+                +----+ 
               |LMA1|                |LMA2|
               +----+                +----+
        LMAA1 -> |                      | <-- LMAA2
                 |                      |
                 \\                    //\\ 
                  \\                  //  \\
                   \\                //    \\

 

[Sri]  Ok. Will clarify it.

    +-----+                +-----+                +-----+
    | MN  |                | MAG |                | LMA |
    +-----+                +-----+                +-----+
       |                      |                      | 
   MN Attached                |                      |
       |                      |                      |
       |               MN Attached Event             |

[Sri] Might be too much for introduction. Will try to add an hint.

only send PBUs for authorized ( i.e., trusted) MNs.

[Sri] Offcourse not. The signaling messages between the LMA and MAG are to
not required to be protocted using the MN-LMA SA. This does not imply there
is no trust between MN and the MAG. Will review this and if it appears to
suggest what you thought, will reword it.

MUST allow." 

[Sri] Ok

[Sri] General hint towards the possible approaches, dont see the harm.

4.1 .  Peer Authorization Database Entries

[Sri] Sure.

                           Figure 4: PAD Entries

                           Figure 5: SPD Entries

   The home agent

[Sri] Sure

[Sri]  These fields in the conceptual data structure. What field is
populated in what scenario is the protocol detail.  It just talks about the
extensions,

[Sri]  The idea was to use the prev interface identifier option. Will remove
this bit, as the MAG can always use the HNP to achieve the same.

   o  MN-Identifier, MN-HNP

[Sri] Agree.

GT> Something is missing in this sentence? Is the following what you mean?

[Sri] Sounds better.

[Sri] The prev point touches on how the LMA can determine if the MAG is
authorized to send PBU's and the later point specifies the action it takes
when the MAG fails the authorization. We feel both the points are required.

[Sri] Ok 

[Sri] Ok

 [Sri] Sure. Typically, the aggregated prefix is owned by the LMA. But, we
can be explicit here.

   Binding Re-Registration:

[Sri] Its specified in the flow.

   Binding De-Registration:

[Sri] Ok 

[Sri] It should have been there. Will fix it.

[Sri] Given the networks with mid boxes, thought its better to leave some
room for different configurations. But, thinking of it, not sure how the LMA
can learn the dest field address to use, otherwise. 

[Sri] The link-local address option in cases of handoff is sent from the
LMA. In case of IID, its not really required at the MAG.

[Sri] It just needs to ignore it.  We will add this point.

5.4.  Multihoming Support

[Sri] Ok.

[Sri] Will rephrase this slightly that the HI is the indicator.

      .

[Sri] Not for this case. 

[Sri] Will fix it. 

[Sri] Its a processing flow and its ordered list. Will clarify it.

[Sri] Ok

and if the Handoff

[Sri] For the same non-zero IID, there cant be more than one entry. 

[Sri] Ok

 and if the Handoff

[Sri]  Then there is no BCE match found.

[Sri] Ok. Will review this for completeness.

...

[Sri] The HA or the LMA processing logic is consistent w.r.t seq numbers in
BU's or PBU's. 

...

[Sri] MAG implementations would know what options to enable on the MN-AR
link. Its a dynamically created link and this guidance is required.

[Sri] Hmm... The MAG is expected to acquire the MN-Id of the attached mob
ile node. The details are covered in 6.6. 

[Sri True, but it must send and receive MN-IID that the other entities
including LMA can identify a given mobile. The acquiring of MN-Id happens on
the MAG and so some text around that. Otherwise, we need to duplicate all
this in the LMA section as well.

[Sri] MN-Id is essential for the protocol operation. The MAG must be able to
obtain this. Given that the access authentication protocols do not always
provide the real identifier or even a temp identifier that it can send it to
the LMA in protocol messages, this talks about how it learn the MN-ID, using
CUI ..etc. There was a dicussion thread on this.

[Sri] Will comment on this in response to Gerardo's comments.

[Sri] It wont have an impact either way. Some networks may want to minimize
the RA traffic, may choose to have large prefix lifetime, while still doing
periodic BU lifetime exchanges.

                                                     

[Sri] ok.

                                            
GT> //have/include

[Sri] Ok

[Sri]  When TS is used, SN its optional. 

[Sri] Yes 

                                                           

[Sri] Will reword it.

[Sri] It should have been there. Will fix it.

...

[Sri] If this feature needs to be supported, the relay agent needs to be
enabled on the MAG and that is clearly stated. Will review it and clarify,
it required.

[Sri] No such assumption. This is as per 3315. 

[Sri] It can send a revocation message. MPA or MPD as per 3775, wont fit
here.

GT> Not sure that the text reflects the subject matter indicated by the
title. The text does not say what happens when the MN moves between
administrative PMIPv6 domains ( i.e., when it is roaming). Or is the title
wrong??

[Sri] Ok. Will make it explicit that the roaming is within a PMIP domain 

[Sri] The section presents on the protocol operation from the view of the
mobile node and some hints on how the protocol can benifit from certain
optimizations and certainly when its known the MN is operating in a PMIP
domain.

Thanks for the review.

Sri