Subject: Re: [DMM] I-D Action: draft-ietf-dmm-requirements-07.txt

From: h chan <[email-masked]>
Date: Thu, 26 Sep 2013 05:34:40 +0000

Sri,

Thanks for the comments. We are replying under different sections in separate emails. More emails will follow.
-----------------------------------------------
We accept your comment on the abstract and have changed the abstract to the following in version 08. Please check.

Abstract

   This document defines the requirements for Distributed Mobility
   Management (DMM).  The hierarchical structure in traditional wireless
   networks has led primarily to centralized deployment models.  As some
   wireless networks are evolving away from the hierarchical structure,
   such as in moving the content delivery servers closer to the users, a
   distributed model for mobility management can be useful to them.

The following have contributed to the revisions in draft 08: Pierrick, Dapeng, and Jouni

From: [email-masked]<mailto:[email-masked]> [mailto:[email-masked]] On Behalf Of Sri Gundavelli (sgundave)
Sent: Sunday, August 25, 2013 10:04 PM
To: [email-masked]<mailto:[email-masked]>
Subject: Re: [DMM] I-D Action: draft-ietf-dmm-requirements-07.txt

Please see inline for some comments.

Regards
Sri

Abstract

   This document defines the requirements for Distributed Mobility

   Management (DMM) in IPv6 deployments.  The hierarchical structure in

   traditional wireless networks has led to deployment models which are

   in practice centralized.  Mobility management with logically

   centralized mobility anchoring in current mobile networks is prone to

   suboptimal routing and raises scalability issues.  Such centralized

   functions can lead to single points of failure and inevitably

   introduce longer delays and higher signaling loads for network

   operations related to mobility management.  The objective is to

   enhance mobility management in order to meet the primary goals in

   network evolution, i.e., improve scalability, avoid single points of

   failure, enable transparent mobility support to upper layers only

   when needed, and so on.  Distributed mobility management must be

   secure and may co-exist with existing network deployments and end

   hosts.

[Sri] We don't need to argue against centralized model to justify distributed model. In the absence of proper data to compare on both the approaches, we cannot have such text.  The pros and cons extend to both the models. Please simply state distributed model can be useful in certain deployments and hence there is interest for this work.

1.  Introduction

   In the past decade a fair number of mobility protocols have been

   standardized [RFC6275] [RFC5944] [RFC5380] [RFC6301] [RFC5213].

   Although the protocols differ in terms of functions and associated

   message formats, we can identify a few key common features:

   o  a centralized mobility anchor providing global reachability and an

      always-on experience to the user;

   o  extensions to the base protocols to optimize handover performance

      while users roam across wireless cells; and

   o  extensions to enable the use of heterogeneous wireless interfaces

      for multi-mode terminals (e.g. smartphones).

[Sri] Currently defined mobility protocols support handovers and multiple access technologies  ? Not sure, how these two "common features" make the case for DMM  If the point is about centralized anchor's, you don't need the other two points.

   The presence of the centralized mobility anchor allows a mobile node

   to remain reachable after it has moved to a different network.  The

   anchor point, among other tasks, ensures connectivity by forwarding

   packets destined to, or sent from, the mobile node.  In practice,

   most of the deployed architectures today have a small number of

   centralized anchors managing the traffic of millions of mobile nodes.

   Compared with a distributed approach, a centralized approach is

   likely to have several issues or limitations affecting performance

   and scalability, which require costly network engineering to resolve.

[Sri] All 3G/4G systems are based on this model and they are running fine. Again, we don't need to argue against centralized model to justify distributed model. Please simply state distributed model can be useful in certain deployments and hence the motivation for this work.

   To optimize handovers from the perspective of mobile nodes, the base

   protocols have been extended to efficiently handle packet forwarding

   between the previous and new points of attachment.  These extensions

   are necessary when applications have stringent requirements in terms

   of delay.  Notions of localization and distribution of local agents

   have been introduced to reduce signaling overhead at the centralized

   routing anchor point [Paper-Distributed.Centralized.Mobility].

   Unfortunately, today we witness difficulties in getting such

   protocols deployed, resulting in sub-optimal choices for the network

   Operators.

[Sri] I assume this is about hierarchical models / Chaining ? What are these "difficulties in getting such protocols deployed" ?

   Moreover, the availability of multiple-interface host and the

   possibility of using several network interfaces simultaneously have

   motivated the development of even more protocol extensions to add

   more capabilities to the mobility management protocol.  In the end,

   deployment is further complicated with the multitude of extensions.

[Sri] Not sure I follow. Mobile IP protocols are in general access agnostic. Not sure, what are the extensions that we have added on access-basis.

   As an effective transport method for multimedia data delivery, IP

   multicast support, including optimizations, have been introduced but

   by "patching-up" procedure after completing the design of reference

   mobility protocol, leading to network inefficiency and non-optimal

   routing.

[Sri] Multicast related extensions have nothing to do with multi-access support/host's capability to support multiple interfaces. Can you clarify ? This text is not clear.

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   Mobile users are, more than ever, consuming Internet content; such

   traffic imposes new requirements on mobile core networks for data

   traffic delivery.  The presence of content providers closer to

   Internet Service Providers (ISP) network requires taking into account

   local Content Delivery Networks (CDNs) while providing mobility

   services.  Moreover, when the traffic demand exceeds available

   capacity, service providers need to implement new strategies such as

   selective traffic offload (e.g. 3GPP work items LIPA/SIPTO

   [TS.23.401]) through alternative access networks (e.g.  WLAN) [Paper-

   Mobile.Data.Offloading].

[Sri] Please add reference to IETF SIPTO doc, RFC6909, before 23.401 :)

A gateway selection mechanism also takes

   the user proximity into account within EPC [TS.29303].  These

   mechanisms were not pursued in the past owing to charging and billing

   reasons.   Assigning a gateway anchor node from a visited network in

   roaming scenario has until recently been done and are limited to

   voice services only.  Charging and billing require solutions beyond

   the mobility protocol.

   Both traffic offloading and CDN mechanisms could benefit from the

   development of mobile architectures with fewer levels of routing

   hierarchy introduced into the data path by the mobility management

   system.  This trend towards so-called "flat networks" works best for

   direct communications among peers in the same geographical area.

   Distributed mobility management in a truly flat mobile architecture

   would anchor the traffic closer to the point of attachment of the

   user.

   Today's mobile networks present service providers with new

   challenges.  Mobility patterns indicate that mobile nodes often

   remain attached to the same point of attachment for considerable

   periods of time [Paper-Locating.User].  Specific IP mobility

   management support is not required for applications that launch and

   complete their sessions while the mobile node is connected to the

   same point of attachment.

 However, currently, IP mobility support is

   designed for always-on operation, maintaining all parameters of the

   context for each mobile subscriber for as long as they are connected

   to the network.  This can result in a waste of resources and unnecessary costs for the service provider.

[Sri]  Is the intent of this is text is about routing based approaches ?

If a mobile is attached to the network, it does have some state at the anchor. Also, if we consider the home link in mobility models, there is no state for the mobile node when it is at home. In case of DMM, or with the current models, if the gateway selection is based on the MN's location and when there is no node mobility, there should not be any state at the anchor. CDMA

 Infrequent node mobility

   coupled with application intelligence suggest that mobility support

   could be provided selectively, thus reducing the amount of context

   maintained in the network.

   The distributed mobility management (DMM) charter addresses two

   complementary aspects of mobility management procedures: the

   distribution of mobility anchors towards a more flat network and the

   dynamic activation/deactivation of mobility protocol support as an

   enabler to distributed mobility management.

[Sri] Not sure, I follow this point on Dynamic activation/de-activation. Can you clarify.

The former aims at

   positioning mobility anchors (e.g., HA, LMA) closer to the user;

   ideally, mobility agents could be collocated with the first-hop

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   router.  The latter, facilitated by the distribution of mobility

   anchors, aims at identifying when mobility support must be activated

   and identifying sessions that do not require mobility management

   support -- thus reducing the amount of state information that must be

   maintained in various mobility agents of the mobile network.  The key

   idea is that dynamic mobility management relaxes some of the

   constraints of previously-standardized mobility management solutions

   and, by doing so, it can avoid the unnecessary establishment of

   mechanisms to forward traffic from an old to a new mobility anchor.

[Sri] The DMM model should not exclude the case of centralized anchor and distributed data plane. This is sub-case of DMM.

   This document compares distributed mobility management with

   centralized mobility management in Section 3.  The problems that can

   be addressed with DMM are summarized in Section 4.  The mandatory

   requirements as well as the optional requirements are given in

   Section 5.  Finally, security considerations are discussed in Section

   6.

   The problem statement and the use cases [I-D.yokota-dmm-scenario] can

   be found in [Paper-Distributed.Mobility.Review].

2.  Conventions used in this document

2.1.  Terminology

   All the general mobility-related terms and their acronyms used in

   this document are to be interpreted as defined in the Mobile IPv6

   base specification [RFC6275], in the Proxy mobile IPv6 specification

   [RFC5213], and in Mobility Related Terminology [RFC3753].  These

   terms include the following: mobile node (MN), correspondent node

   (CN), and home agent (HA) as per [RFC6275]; local mobility anchor

   (LMA) and mobile access gateway (MAG) as per [RFC5213], and context

   as per [RFC3753].

   In addition, this draft introduces the following term.

   Mobility context

      is the collection of information required to provide mobility

      management support for a given mobile node.

[Sri] There needs to be some definition of "centrally deployed mobility anchor". This term is used through-out the document. What is central, what is local ? Even in the so called, "centralized anchor models", a gateway can be enabled locally. Ex: LMA/MAG, PGW/SGW functions can exist on the same node.

3.  Centralized versus distributed mobility management

   Mobility management functions may be implemented at different layers

   of the protocol stack.  At the IP (network) layer, they may reside in

   the network or in the mobile node.  In particular, a network-based

   solution resides in the network only.  It therefore enables mobility

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   for existing hosts and network applications which are already in

   deployment but lack mobility support.

[Sri] Above text is bit confusing to me, specially the last sentence. Mobility management can be based on client-based, or network-based.

   At the IP layer, a mobility management protocol supporting session

   continuity is typically based on the principle of distinguishing

   between identifier and routing address and maintaining a mapping

   between the two.

[Sri] Replace, "Session continuity" with "IP mobility" or "IP address continuity".

In Mobile IP, the home address serves as an

   identifier of the device whereas the care-of-address (CoA) takes the

   role of the routing address.  The binding between these two is

   maintained at the home agent (mobility anchor).  If packets can be

   continuously delivered to a mobile node at its home address, then all

   sessions using that home address are unaffected even though the

   routing address (CoA) changes.

[Sri] We should leave it at, "IP address mobility".

   The next two subsections explain centralized and distributed mobility

   management functions in the network.

3.1.  Centralized mobility management

   In centralized mobility management, the mapping information between

   the persistent node identifier and the locator IP address of a mobile

   node (MN) is kept at a single mobility anchor.  At the same time,

   packets destined to the MN are routed via this anchor.

[Sri] Can we use the MIP terminology, home address/Care-of address terminology, as supposed to LISP terminology ?

  In other

   words, such mobility management systems are centralized in both the

   control plane and the data plane (mobile node IP traffic).

   Many existing mobility management deployments make use of centralized

   mobility anchoring in a hierarchical network architecture, as shown

   in Figure 1.  Examples of such centralized mobility anchors are the

   home agent (HA) and local mobility anchor (LMA) in Mobile IPv6

   [RFC6275] and Proxy Mobile IPv6 [RFC5213], respectively.  Current

   cellular networks such as the Third Generation Partnership Project

   (3GPP) GPRS networks, CDMA networks, and 3GPP Evolved Packet System

   (EPS) networks employ centralized mobility management too.  In

   particular, the Gateway GPRS Support Node (GGSN), Serving GPRS

   Support Node (SGSN) and Radio Network Controller (RNC) in the 3GPP

   GPRS hierarchical network, and the Packet Data Network Gateway (P-GW)

   and Serving Gateway (S-GW) in the 3GPP EPS network all act as anchors

   in a hierarchy.

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         3G GPRS                 3GPP EPS                MIP/PMIP

         +------+                +------+                +------+

         | GGSN |                | P-GW |                |HA/LMA|

         +------+                +------+                +------+

            /\                      /\                      /\

           /  \                    /  \                    /  \

          /    \                  /    \                  /    \

         /      \                /      \                /      \

        /        \              /        \              /        \

       /          \            /          \            /          \

      /            \          /            \          /            \

  +------+      +------+  +------+      +------+  +------+      +------+

  | SGSN |      | SGSN |  | S-GW |      | S-GW |  |MN/MAG|      |MN/MAG|

  +------+      +------+  +------+      +------+  +------+      +------+

     /\            /\

    /  \          /  \

   /    \        /    \

+---+  +---+  +---+  +---+

|RNC|  |RNC|  |RNC|  |RNC|

+---+  +---+  +---+  +---+

   Figure 1.  Centralized mobility management.

3.2.  Distributed mobility management

   Mobility management functions may also be distributed to multiple

   networks as shown in Figure 2, so that a mobile node in any of these

   networks may be served by a nearby mobility function (MF).

                    +------+  +------+  +------+  +------+

                    |  MF  |  |  MF  |  |  MF  |  |  MF  |

                    +------+  +------+  +------+  +------+

                                           |

                                         +----+

                                         | MN |

                                         +----+

   Figure 2.  Distributed mobility management.

   Mobility management may be partially or fully distributed.  In the

   former case only the data plane is distributed.  Fully distributed

   mobility management implies that both the data plane and the control

   plane are distributed.  Such concepts of data and control plane

   separation are not yet described in the IETF developed mobility

   protocols so far but are described in detail in [I-D.yokota-dmm-

   scenario].  While mobility management can be distributed, it is not

   necessary for other functions such as subscription management,

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   subscription database, and network access authentication to be

   similarly distributed.

[Sri] The case of centralized CP and distributed DP is covered in IETF docs,

http://datatracker.ietf.org/doc/draft-wakikawa-netext-pmip-cp-up-separation/

This is a variant of the DMM models.

   A distributed mobility management scheme for flat IP-based mobile

   network architecture consisting of access nodes is proposed in

   [Paper-Distributed.Dynamic.Mobility].  Its benefits over centralized

   mobility management are shown through simulations in [Paper-

   Distributed.Centralized.Mobility].  Moreover, the (re)use and

   extension of existing protocols in the design of both fully

   distributed mobility management [Paper-Migrating.Home.Agents] [Paper-

   Distributed.Mobility.SAE] and partially distributed mobility

   management [Paper-Distributed.Mobility.PMIP] [Paper-

   Distributed.Mobility.MIP] have been reported in the literature.

   Therefore, before designing new mobility management protocols for a

   future flat IP architecture, it is recommended to first consider

   whether existing mobility management protocols can be extended to

   serve a flat IP architecture.

[Sri] Lot of unnecessary text in this document. Not sure, we need all of this text.

4.  Problem Statement

   The problems that can be addressed with DMM are summarized in the

   following:

   PS1:  Non-optimal routes

         Routing via a centralized anchor often results in a longer

         route.

[Sri] "longer route" ?  I assume this is about routing/tx delay. Please re-word.

The problem is manifested, for example, when accessing

         a local server or servers of a Content Delivery Network (CDN),

         or when receiving locally available IP multicast or sending IP

         multicast packets.

[Sri] Does RFC 6705, or RFC 6909 does not address this issue ? May be the CDN example is incorrect.

   PS2:  Divergence from other evolutionary trends in network

         architectures such as distribution of content delivery.

         Centralized mobility management can become non-optimal with a

         flat network architecture.

[Sri] How is this making the case of DMM ? We want the MN to access content locally in the access network and we want localized routing. We have that in the form of 6705 and 6909. The other approach is give localized IP addresses and have the content locally accessed. There are simply two many considerations and points may be valid, but when we bring all those assumptions. We are bringing these points in a less logical manner without stating the assumptions.

   PS3:  Low scalability of centralized tunnel management and mobility

         context maintenance

         Setting up tunnels through a central anchor and maintaining

         mobility context for each MN usually requires more concentrated

         resources in a centralized design, thus reducing scalability.

         Distributing the tunnel maintenance function and the mobility

         context maintenance function among different network entities

         with proper signaling protocol design can increase scalability.

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   PS4:  Single point of failure and attack

         Centralized anchoring designs may be more vulnerable to single

         points of failures and attacks than a distributed system.  The

         impact of a successful attack on a system with centralized

         mobility management can be far greater as well.

   PS5:  Unnecessarily reserving resources to provide mobility support

         to nodes that do not need such support

         IP mobility support is not always required, and not every

         parameter of mobility context is always used.  For example,

         some applications do not need a stable IP address during a

         handover to maintain session continuity.  Sometimes, the entire

         application session runs while the terminal does not change the

         point of attachment.  Besides, some sessions, e.g.  SIP-based

         sessions, can handle mobility at the application layer and

         hence do not need IP mobility support; it is then more

         efficient to deactivate IP mobility support for such sessions.

[Sri]  Mobility systems today do support the aspect of service for the subscriber, as "Simple IP", or "Mobile IP". A PDSN can assign a local IP address and it does not have to be the home address. Network does have this intelligence, but what is missing is the client's ability to pick the correct type of IP address, among different IP addresses. The network is also the missing the aspect of marking those addresses with proper properties. The currently active drafts in IETF are to address this issue. We should talk about these missing semantics.

draft-bhandari-dhc-class-based-prefix-05<http://datatracker.ietf.org/doc/draft-bhandari-dhc-class-based-prefix/>

draft-korhonen-6man-prefix-properties-02<http://datatracker.ietf.org/doc/draft-korhonen-6man-prefix-properties/>

   PS6:  (Related problem) Mobility signaling overhead with peer-to-peer

         communication

         Wasting resources when mobility signaling (e.g., maintenance of

         the tunnel, keep alive signaling, etc.) is not turned off for

         peer-to-peer communication.  Peer-to-peer communications have

         particular traffic patterns that often do not benefit from

         mobility support from the network.  Thus, the associated

         mobility support signaling (e.g., maintenance of the tunnel,

         keep alive signaling, etc.) wastes network resources for no

         application gain.  In such a case, it is better to enable

         mobility support selectively.

[Sri] How is PS6 different from PS5 ? We talk about application's ability to pick the address with or without mobility properties in PS5. So, the traffic patterns can be localized based on the application requirements. But, even if we take the argument that mobility is not required, operator needs visibility into these flows and so they can charge.  Again, we have 6705 and 6909 for adjusting to those traffic patterns. So, this P without those considerations is incomplete.

   PS7:  (Related problem) Deployment with multiple mobility solutions

         There are already many variants and extensions of MIP.

         Deployment of new mobility management solutions can be

         challenging, and debugging difficult, when they must co-exist

         with solutions already in the field.

   PS8:  Duplicate multicast traffic

         IP multicast distribution over architectures using IP mobility

         solutions (e.g.  RFC6224) may lead to convergence of duplicated

         multicast subscriptions towards the downstream tunnel entity

         (e.g.  MAG in PMIPv6).  Concretely, when multicast subscription

         for individual mobile nodes is coupled with mobility tunnels

         (e.g.  PMIPv6 tunnel), duplicate multicast subscription(s) is

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         prone to be received through different upstream paths.  This

         problem may also exist or be more severe in a distributed

         mobility environment.

[Sri] Is this for MN's from different LMA's attached to the same MAG ?

5.  Requirements

   After comparing distributed mobility management against centralized

   deployment in Section 3, this section identifies the following

   requirements:

5.1.  Distributed processing

   REQ1:  Distributed processing

          IP mobility, network access and routing solutions provided by

          DMM MUST enable distributed processing for mobility management

          so that traffic does not need to traverse centrally deployed

          mobility anchors and thereby avoid non-optimal routes.

          Motivation: This requirement is motivated by current trends in

          network evolution: (a) it is cost- and resource-effective to

          cache and distribute content by combining distributed mobility

          anchors with caching systems (e.g., CDN); (b) the

          significantly larger number of mobile nodes and flows call for

          improved scalability; (c) single points of failure are avoided

          in a distributed system; (d) threats against centrally

          deployed anchors, e.g., home agent and local mobility anchor,

          are mitigated in a distributed system.

   This requirement addresses the problems PS1, PS2, PS3, and PS4

   described in Section 4.  (Existing route optimization is only a host-

   based solution.  On the other hand, localized routing with PMIPv6

   addresses only a part of the problem where both the MN and the CN are

   located in the PMIP domain and attached to a MAG, and is not

   applicable when the CN is outside the PMIP domain.)

[Sri] I'm still stuck on the CDN example driving this requirement.

5.2.  Transparency to Upper Layers when needed

   REQ2:  Transparency to Upper Layers when needed

          DMM solutions MUST provide transparent mobility support above

          the IP layer when needed.  Such transparency is needed, for

          example, when, upon change of point of attachment to the

          network, an application flow cannot cope with a change in the

          IP address.  However, it is not always necessary to maintain a

          stable home IP address or prefix for every application or at

          all times for a mobile node.

[Sri] Please reflect the two key aspects of this requirement:

*        Network can assign IP addresses with different properties; It carries those properties

*        Applications have different requirements and will pick the address with the correct property.

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          Motivation: The motivation of this requirement is to enable

          more efficient use of network resources and more efficient

          routing by not maintaining context at the mobility anchor when

          there is no such need.

   This requirement addresses the problem PS5 as well as the related

   problem PS6 stated in Section 4.

5.3.  IPv6 deployment

   REQ3:  IPv6 deployment

          DMM solutions SHOULD target IPv6 as the primary deployment

          environment and SHOULD NOT be tailored specifically to support

          IPv4, in particular in situations where private IPv4 addresses

          and/or NATs are used.

          Motivation: This requirement conforms to the general

          orientation of IETF work.  DMM deployment is foreseen in mid-

          to long-term horizon, when IPv6 is expected to be far more

          common than today.

   This requirement avoids the unnecessarily complexity in solving the

   problems in Section 4 for IPv4, which will not be able to use some of

   the IPv6-specific features.

5.4.  Existing mobility protocols

   REQ4:  Existing mobility protocols

          A DMM solution SHOULD first consider reusing and extending

          IETF-standardized protocols before specifying new protocols.

          Motivation: Reuse of existing IETF work is more efficient and

          less error-prone.

   This requirement attempts to avoid the need of new protocols

   development and therefore their potential problems of being time-

   consuming and error-prone.

5.5.  Co-existence

   REQ5:  Co-existence with deployed networks and hosts

          The DMM solution MUST be able to co-exist with existing

          network deployments and end hosts.  For example, depending on

          the environment in which DMM is deployed, DMM solutions may

          need to be compatible with other deployed mobility protocols

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          or may need to co-exist with a network or mobile hosts/routers

          that do not support DMM protocols.  The mobile node may also

          move between different access networks, where some of them may

          support neither DMM nor another mobility protocol.

          Furthermore, a DMM solution SHOULD work across different

          networks, possibly operated as separate administrative

          domains, when allowed by the trust relationship between them.

          Motivation: (a) to preserve backwards compatibility so that

          existing networks and hosts are not affected and continue to

          function as usual, and (b) enable inter-domain operation if

          desired.

   This requirement addresses the related problem PS7 described in

   Section 4.

5.6.  Security considerations

   REQ6:  Security considerations

          A DMM solution MUST not introduce new security risks or

          amplify existing security risks against which the existing

          security mechanisms/protocols cannot offer sufficient

          protection.

          Motivation: Various attacks such as impersonation, denial of

          service, man-in-the-middle attacks, and so on, may be launched

          in a DMM deployment.  For instance, an illegitimate node may

          attempt to access a network providing DMM.  Another example is

          that a malicious node can forge a number of signaling messages

          thus redirecting traffic from its legitimate path.

          Consequently, the specific node is under a denial of service

          attack, whereas other nodes do not receive their traffic.

          Accordingly, security mechanisms/protocols providing access

          control, integrity, authentication, authorization,

          confidentiality, etc. can be used to protect the DMM entities

          as they are already used to protect against existing networks

          and existing mobility protocols defined in IETF.  In addition,

          end-to-end security measures between communicating nodes may

          already be used when deploying existing mobility protocols

          where the signaling messages travel over the Internet.  For

          instance, EAP-based authentication can be used for network

          access security, while IPsec can be used for end-to-end

          security.  When the existing security mechanisms/protocols are

          applied to protect the DMM entities, the security risks that

          may be introduced by DMM MUST be considered to be eliminated.

          Else the security protection would be degraded in the DMM

          solution versus in existing mobility protocols.

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   This requirement prevents a DMM solution from introducing

   uncontrollable problems of potentially insecure mobility management

   protocols which make deployment infeasible because platforms

   conforming to the protocols are at risk for data loss and numerous

   other dangers, including financial harm to the users.

5.7.  Multicast

   REQ7:  Multicast considerations

          DMM SHOULD consider multicast early so that solutions can be

          developed not only to provide IP mobility support when it is

          needed, but also to avoid network inefficiency issues in

          multicast traffic delivery (such as duplicate multicast

          subscriptions towards the downstream tunnel entities).  The

          multicast solutions should therefore avoid restricting the

          management of all IP multicast traffic to a single host

          through a dedicated (tunnel) interface on multicast-capable

          access routers.

          Motivation: Existing multicast deployment have been introduced

          after completing the design of the reference mobility

          protocol, then optimization and extensions have been followed

          by "patching-up" procedure, thus leading to network

          inefficiency and non-optimal routing.  The multicast solutions

          should therefore be required to consider efficiency nature in

          multicast traffic delivery.

   This requirement addresses the problems PS1 and PS8 described in

   Section 4.

6.  Security Considerations

   Please refer to the discussion under Security requirement in Section

   5.6.

7.  IANA Considerations

   None

8.  Co-authors and Contributors

   This problem statement document is a joint effort among the numerous

   participants.  Each individual has made significant contributions to

   this work and have been listed as co-authors.

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9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate

              Requirement Levels", BCP 14, RFC 2119, March 1997.

9.2.  Informative References

   [I-D.yokota-dmm-scenario]

              Yokota, H., Seite, P., Demaria, E., and Z. Cao, "Use case

              scenarios  for Distributed Mobility Management",

              draft-yokota-dmm-scenario-00 (work in progress),

              October 2010.

   [Paper-Distributed.Centralized.Mobility]

              Bertin, P., Bonjour, S., and J-M. Bonnin, "A Distributed

              or Centralized Mobility",  Proceedings of Global

              Communications Conference  (GlobeCom), December 2009.

   [Paper-Distributed.Dynamic.Mobility]

              Bertin, P., Bonjour, S., and J-M. Bonnin, "A Distributed

              Dynamic Mobility Management Scheme  Designed for Flat IP

              Architectures",  Proceedings of 3rd International

              Conference  on New Technologies, Mobility and Security

              (NTMS), 2008.

   [Paper-Distributed.Mobility.MIP]

              Chan, H., "Distributed Mobility Management with Mobile

              IP",  Proceedings of  IEEE International Communication

              Conference (ICC)  Workshop on Telecommunications:  from

              Research to Standards, June 2012.

   [Paper-Distributed.Mobility.PMIP]

              Chan, H., "Proxy Mobile IP  with Distributed Mobility

              Anchors",  Proceedings of GlobeCom Workshop  on Seamless

              Wireless Mobility, December 2010.

   [Paper-Distributed.Mobility.Review]

              Chan, H., Yokota, H., Xie, J., Seite, P., and D. Liu,

              "Distributed and Dynamic Mobility Management  in Mobile

              Internet: Current Approaches and Issues, Journal of

              Communications, vol. 6, no. 1, pp. 4-15, Feb 2011.",

               Proceedings of GlobeCom Workshop  on Seamless Wireless

              Mobility, February 2011.

   [Paper-Distributed.Mobility.SAE]

              Fisher, M., Anderson, F., Kopsel, A., Schafer, G., and M.

Chan (Ed.), et al.      Expires February 3, 2014               [Page 15]

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              Schlager, "A Distributed IP Mobility Approach for 3G SAE",

               Proceedings of the 19th International Symposium  on

              Personal, Indoor and Mobile Radio Communications (PIMRC),

              2008.

   [Paper-Locating.User]

              Kirby, G., "Locating the User",  Communication

              International, 1995.

   [Paper-Migrating.Home.Agents]

              Wakikawa, R., Valadon, G., and J. Murai, "Migrating Home

              Agents  Towards Internet-scale Mobility Deployments",

               Proceedings of the ACM 2nd CoNEXT Conference  on Future

              Networking Technologies, December 2006.

   [Paper-Mobile.Data.Offloading]

              Lee, K., Lee, J., Yi, Y., Rhee, I., and S. Chong, "Mobile

              Data Offloading: How Much Can WiFi Deliver?",  SIGCOMM

              2010, 2010.

   [RFC3753]  Manner, J. and M. Kojo, "Mobility Related Terminology",

              RFC 3753, June 2004.

   [RFC5213]  Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,

              and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.

   [RFC5380]  Soliman, H., Castelluccia, C., ElMalki, K., and L.

              Bellier, "Hierarchical Mobile IPv6 (HMIPv6) Mobility

              Management", RFC 5380, October 2008.

   [RFC5944]  Perkins, C., "IP Mobility Support for IPv4, Revised",

              RFC 5944, November 2010.

   [RFC6275]  Perkins, C., Johnson, D., and J. Arkko, "Mobility Support

              in IPv6", RFC 6275, July 2011.

   [RFC6301]  Zhu, Z., Wakikawa, R., and L. Zhang, "A Survey of Mobility

              Support in the Internet", RFC 6301, July 2011.

   [TS.23.401]

              3GPP, "General Packet Radio Service (GPRS) enhancements

              for Evolved Universal Terrestrial Radio Access Network

              (E-UTRAN) access", 3GPP TR 23.401 10.10.0, March 2013.

   [TS.29303]

              3GPP, "Domain Name System Procedures; Stage 3", 3GPP

              TR 23.303 11.2.0, September 2012.

Chan (Ed.), et al.      Expires February 3, 2014               [Page 16]

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Authors' Addresses

   H Anthony Chan (editor)

   Huawei Technologies (more co-authors on P. 17)

   5340 Legacy Dr. Building 3, Plano, TX 75024, USA

   Email: [email-masked]<mailto:[email-masked]>

   Dapeng Liu

   China Mobile

   Unit2, 28 Xuanwumenxi Ave, Xuanwu District,  Beijing 100053, China

   Email: [email-masked]<mailto:[email-masked]>

   Pierrick Seite

   Orange

   4, rue du Clos Courtel, BP 91226,  Cesson-Sevigne 35512, France

   Email: [email-masked]<mailto:[email-masked]>

   Hidetoshi Yokota

   KDDI Lab

   2-1-15 Ohara, Fujimino, Saitama, 356-8502 Japan

   Email: [email-masked]<mailto:[email-masked]>

   Jouni Korhonen

   Nokia Siemens Networks

   Email: [email-masked]<mailto:[email-masked]>

   -

   Charles E. Perkins

   Huawei Technologies

   Email: [email-masked]<mailto:[email-masked]>

   -

   Melia Telemaco

   Alcatel-Lucent Bell Labs

   Email: [email-masked]<mailto:[email-masked]>

   -

   Elena Demaria

   Telecom Italia

   via G. Reiss Romoli, 274, TORINO, 10148, Italy

   Email: [email-masked]<mailto:[email-masked]>

   -

   Jong-Hyouk Lee

   RSM Department, Telecom Bretagne

   Cesson-Sevigne, 35512, France

   Email: [email-masked]<mailto:[email-masked]>

   -

Chan (Ed.), et al.      Expires February 3, 2014               [Page 17]

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   Kostas Pentikousis

   Huawei Technologies

   Carnotstr. 4 10587 Berlin, Germany

   Email: [email-masked]<mailto:[email-masked]>

   -

   Tricci So

   ZTE

   Email: [email-masked]<mailto:[email-masked]>

   -

   Carlos J. Bernardos

   Universidad Carlos III de Madrid

   Av. Universidad, 30, Leganes, Madrid 28911, Spain

   Email: [email-masked]<mailto:[email-masked]>

   -

   Peter McCann

   Huawei Technologies

   Email: [email-masked]<mailto:[email-masked]>

   -

   Seok Joo Koh

   Kyungpook National University, Korea

   Email: [email-masked]<mailto:[email-masked]>

   -

   Wen Luo

   ZTE

   No.68, Zijinhua RD,Yuhuatai District, Nanjing, Jiangsu 210012, China

   Email: [email-masked]<mailto:[email-masked]>

   -

   Sri Gundavelli

   [email-masked]<mailto:[email-masked]>

   -

   Marco Liebsch

   NEC Laboratories Europe

   Email: [email-masked]<mailto:[email-masked]>

   -

   Carl Williams

   MCSR Labs

   Email: [email-masked]<mailto:[email-masked]>

   -

   Seil Jeon

   Instituto de Telecomunicacoes, Aveiro

   Email: [email-masked]<mailto:[email-masked]>

   -

   Sergio Figueiredo

   Universidade de Aveiro

   Email: [email-masked]<mailto:[email-masked]>

   -

   Stig Venaas

   Email: [email-masked]<mailto:[email-masked]>

Chan (Ed.), et al.      Expires February 3, 2014               [Page 18]

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   -

   Luis Miguel Contreras Murillo

   Email: [email-masked]<mailto:[email-masked]>

   -

   Juan Carlos Zuniga

   Email: [email-masked]<mailto:[email-masked]>

   -

   Alexandru Petrescu

   Email: [email-masked]<mailto:[email-masked]>

   -

   Georgios Karagiannis

   Email: [email-masked]<mailto:[email-masked]>

   -

   Julien Laganier

   [email-masked]<mailto:[email-masked]>

   -

   Wassim Michel Haddad

   [email-masked]<mailto:[email-masked]>

   -

   Dirk von Hugo

   [email-masked]<mailto:[email-masked]>

   -

   Ahmad Muhanna

   [email-masked]<mailto:[email-masked]>

   -

   Byoung-Jo Kim

   ATT Labs

   [email-masked]<mailto:[email-masked]>

   -

   Hassan Aliahmad

   Orange

   [email-masked]<mailto:[email-masked]>

   -

Chan (Ed.), et al.      Expires February 3, 2014               [Page 19]

---

From: h chan <[email-masked]>
Date: Thu, 26 Sep 2013 05:49:51 +0000

Sri,

Thanks for the comments. We are replying under different sections in separate emails.
-----------------------------------------------
Regarding your comments on Section 1, this section has been revised and reorganized in version 08 to avoid misunderstanding. Also our responses in-line. Please check.

1.  Introduction

   In the past decade a fair number of mobility protocols have been
   standardized [RFC6275] [RFC5944] [RFC5380] [RFC6301] [RFC5213].
   Although the protocols differ in terms of functions and associated
   message formats, they all employ a mobility anchor to allow a mobile
   node to remain reachable after it has moved to a different network.
   The anchor point, among other tasks, ensures connectivity by
   forwarding packets destined to, or sent from, the mobile node.  It is
   a centrally deployed mobility anchor in the sense that the deployed
   architectures today have a small number of these anchors and the
   traffic of millions of mobile nodes in an operator network are
   typically managed by the same anchor.

   Distributed mobility management (DMM) is an alternative to the above
   centralized deployment.  The background behind the interests to study
   DMM are primarily in the following.

   (1)  Mobile users are, more than ever, consuming Internet content;
        such traffic imposes new requirements on mobile core networks
        for data traffic delivery.  The presence of content providers
        closer to Internet Service Providers (ISP) network requires
        taking into account local Content Delivery Networks (CDNs) while
        providing mobility services.  Moreover, when the traffic demand
        exceeds available capacity, service providers need to implement
        new strategies such as selective traffic offload (e.g.
        [RFC6909], 3GPP work items LIPA/SIPTO [TS.23.401]) through
        alternative access networks (e.g.  WLAN) [Paper-
        Mobile.Data.Offloading].  A gateway selection mechanism also
        takes the user proximity into account within EPC [TS.29303].
        These mechanisms were not pursued in the past owing to charging
        and billing reasons.  Assigning a gateway anchor node from a
        visited network in roaming scenario has until recently been done
        and are limited to voice services only.  Charging and billing
        require solutions beyond the mobility protocol.

        Both traffic offloading and CDN mechanisms could benefit from
        the development of mobile architectures with fewer levels of
        routing hierarchy introduced into the data path by the mobility
        management system.  This trend towards so-called "flat networks"
        works best for direct communications among peers in the same
        geographical area.  Distributed mobility management in a truly
        flat mobile architecture would anchor the traffic closer to the
        point of attachment of the user.

   (2)  Today's mobile networks present service providers with new
        challenges.  Mobility patterns indicate that mobile nodes often
        remain attached to the same point of attachment for considerable
        periods of time [Paper-Locating.User].  Specific IP mobility
        management support is not required for applications that launch
        and complete their sessions while the mobile node is connected
        to the same point of attachment.  However, currently, IP
        mobility support is designed for always-on operation,
        maintaining all parameters of the context for each mobile
        subscriber for as long as they are connected to the network.
        This can result in a waste of resources and unnecessary costs
        for the service provider.  Infrequent node mobility coupled with
        application intelligence suggest that mobility support could be
        provided selectively, thus reducing the amount of context
        maintained in the network.

   In addition, considerations in the study of DMM are in the following.

   (1)  To optimize handovers from the perspective of mobile nodes, the
        base protocols have been extended to efficiently handle packet
        forwarding between the previous and new points of attachment.
        These extensions are necessary when applications have stringent
        requirements in terms of delay.  Notions of localization and
        distribution of local agents have been introduced to reduce
        signaling overhead at the centralized routing anchor point
        [Paper-Distributed.Centralized.Mobility].  Unfortunately, such
        protocols have not been deployed today.

   (2)  Most existing mobility protocols have not been designed for
        multiple-interface hosts which are capable to use multiple
        interfaces simultaneously.  Retrofitting the required
        functionality can result in an unnecessary increase in the
        protocol complexity.

   (3)  IP multicast support, including optimizations, have been
        introduced as an effective transport method for multimedia data
        delivery, but by "patching-up" procedure after completing the
        design of reference mobility protocol, leading to network
        inefficiency and non-optimal routing.

   The distributed mobility management (DMM) charter addresses two
   complementary aspects of mobility management procedures: the
   distribution of mobility anchors in the data-plane towards a more
   flat network and the selective activation/deactivation of mobility
   protocol support as an enabler to distributed mobility management.
   The former aims at positioning mobility anchors (e.g., HA, LMA)
   closer to the user; ideally, mobility agents could be collocated with
   the first-hop router.  The latter, facilitated by the distribution of
   mobility anchors, identifies when mobility support must be activated
   and when sessions do not require mobility management support -- thus
   reducing the amount of state information that must be maintained in
   various mobility agents of the mobile network.  It can then avoid the
   unnecessary establishment of mechanisms to forward traffic from an
   old to a new mobility anchor.

Regards
Sri

....

1.  Introduction

Accept and revised in version 08

Accept and revised in version 08

   Operators.

Accept and revised in version 08

Re-organize Section 1 in version 08 to clarify.

   routing.

Re-organize Section 1 in version 08 to clarify.

   Mobile.Data.Offloading].

Accept and revised in version 08

   the mobility protocol.

   user.

We are probably talking about the same thing. Revise in 08 to clarify.

 Infrequent node mobility

Re-organize Section 1 in version 08 to clarify.

The former aims at

Revise Section 1 in version 08 to clarify distribution for "data-plane".

   6.

---

From: h chan <[email-masked]>
Date: Thu, 26 Sep 2013 05:55:03 +0000

Thanks for the comments. We are replying under different sections in separate emails. More emails will follow.
-----------------------------------------------
We accept your comment to Section 2 and added the explanation of a few terms there in version 08. Please check.

2.1.  Terminology

   In addition, this draft introduces the following terms.

   Centrally deployed mobility anchors
      refer to the mobility management deployments in which there are
      very few mobility anchors and the traffic of millions of mobile
      nodes in an operator network are managed by the same anchor.

   Centralized mobility management
      makes use of centrally deployed mobility anchors.

   Distributed mobility management
      is not centralized so that traffic does not need to traverse
      centrally deployed mobility anchors.

   Flat mobile network
      has few levels of routing hierarchy introduced into the data path
      by the mobility management system.

   Mobility context

Regards
Sri

2.1.  Terminology

   as per [RFC3753].

   Mobility context

Accept and added explanation of this term. Also added the explanation of a few other terms.

---

From: h chan <[email-masked]>
Date: Thu, 26 Sep 2013 06:08:24 +0000

Sri,

Thanks for the comments. We are replying under different sections in separate emails. More emails will follow.
-----------------------------------------------
We have revised Section 3 in version 08. Our responses are in-line. Please check.

   Mobility management functions may be implemented at different layers
   of the protocol stack.  At the IP (network) layer, mobility
   management can be client-based or network-based.

   An IP-layer mobility management protocol is typically based on the
   principle of distinguishing between session identifier and routing
   address and maintaining a mapping between the two.  In Mobile IP, the
   home address serves as the session identifier whereas the care-of-
   address (CoA) takes the role of the routing address.  The binding
   between these two is maintained at the home agent (mobility anchor).
   If packets addressed to the home address of a mobile node can be
   continuously delivered to the node, then all sessions using that home
   address are unaffected even though the routing address (CoA) changes.

   In centralized mobility management, the mapping information between
   the session identifier and the locator IP address of a mobile node
   (MN) is kept at a single mobility anchor.  At the same time, packets
   destined to the MN are routed via this anchor.  In other words, such
   mobility management systems are centralized in both the control plane
   and the data plane (mobile node IP traffic).

   Mobility management may be partially or fully distributed
   [I-D.yokota-dmm-scenario].  In the former case only the data plane is
   distributed, implicitly assuming separation of data and control
   planes as described in [I-D.wakikawa-netext-pmip-cp-up-separtion].
   Fully distributed mobility management implies that both the data
   plane and the control plane are distributed.  While mobility
   management can be distributed, it is not necessary for other
   functions such as subscription management, subscription database, and
   network access authentication to be similarly distributed.

   A distributed mobility management scheme for a flat mobile network of
   access nodes is proposed in [Paper-Distributed.Dynamic.Mobility].
   Its benefits over centralized mobility management are shown through
   simulations in [Paper-Distributed.Centralized.Mobility].  Moreover,
   the (re)use and extension of existing protocols in the design of both
   fully distributed mobility management [Paper-Migrating.Home.Agents]
   [Paper-Distributed.Mobility.SAE] and partially distributed mobility
   management [Paper-Distributed.Mobility.PMIP] [Paper-
   Distributed.Mobility.MIP] have been reported in the literature.
   Therefore, before designing new mobility management protocols for a
   future distributed architecture, it is recommended to first consider
   whether existing mobility management protocols can be extended.

Regards
Sri

   between the two.

Delete session continuity, but also keep the discussion general and not specific to MIP.

Revised this section but tried to keep it general and not specific to MIP.

Revised this section but tried to keep this section general and not specific to MIP

  In other

   in a hierarchy.

            /\                      /\                      /\

           /  \                    /  \                    /  \

          /    \                  /    \                  /    \

         /      \                /      \                /      \

        /        \              /        \              /        \

       /          \            /          \            /          \

      /            \          /            \          /            \

     /\            /\

    /  \          /  \

   /    \        /    \

+---+  +---+  +---+  +---+

|RNC|  |RNC|  |RNC|  |RNC|

+---+  +---+  +---+  +---+

                                           |

                                         +----+

                                         | MN |

                                         +----+

   similarly distributed.

Already quoted the yokota reference but added this reference anyway.

Added the term "flat mobile network" and revised in version 08

---

From: h chan <[email-masked]>
Date: Thu, 26 Sep 2013 15:21:24 +0000

Sri,

We have revised the problem statements in Section 4 in version 08. Our responses are in-line. Please check again.

4.  Problem Statement

   PS1:  Non-optimal routes

         Routing via a centralized anchor often results in non-optimal
         routes, thereby increasing the end-to-end delay.  The problem
         is manifested, for example, when accessing a local server or
         servers of a Content Delivery Network (CDN), or when receiving
         locally available IP multicast or sending IP multicast packets.

   PS5:  Unnecessary mobility support to nodes that do not need it

         application gain.

The following have contributed to the above revisions in draft 08: Pierrick, Dapeng, and Jouni

Regards
Sri

4.  Problem Statement

   following:

   PS1:  Non-optimal routes

         route.

         multicast packets.

CDN example is also an important driver: distributing the mobility anchor is more compatible with distributing and replicating the contents, which may be more general to the particular protocol solutions. It may also include the case that there is a CDN server is in a neighboring network. Suggestions to reword (for version 09) are welcome.

Our response is similar to that in PS1. Also PS2 is referring to flat mobile network.

         context maintenance

We need to find a suitable place to add these references. One place is to append to the end of Section 3 where it is talking about DMM work. The other possibility is to add it as one of the considerations list in the Introduction. Any suggestion?

         communication

Both PS5 and PS6 have been revised in version 08. If desired, we can clarify further (version 09?) that PS6 is about turning off the tunneling and signaling.

         mobility environment.

It is one example.

---

From: h chan <[email-masked]>
Date: Thu, 26 Sep 2013 19:11:01 +0000

Sri,

Regarding your comments on the requirements, the motivation of REQ2 has been revised in version 08. The responses to your comments are in-line.  Please check.

          Motivation: The motivation of this requirement is to enable
          more efficient routing and more efficient use of network
          resources by selecting an IP address or prefix according to
          whether mobility support is needed and by not maintaining
          context at the mobility anchor when there is no such need.

5.  Requirements

   requirements:

The requirements are general. In addition, whether specific solutions are sufficient is the role of the separate draft on gap analysis

          there is no such need.

---

From: h chan <[email-masked]>
Date: Sat, 28 Sep 2013 15:25:29 +0000

Sri,

We have revised the Introduction Section and PS1 in version 09. Our responses are in-line.

The following have contributed to the above revisions in draft 09: Pierrick, Dapeng, and Jouni

Regards
Sri

.......

4.  Problem Statement

   following:

   PS1:  Non-optimal routes

         route.

         multicast packets.

RFC6909 is clarified further in the Introduction Section in version 09.
        new strategies such as selective IPv4 traffic offload (e.g.

        Mobile.Data.Offloading].

RFC6705 is clarified under PS1 in version 09
   PS1:  Non-optimal routes

         Routing via a centralized anchor often results in non-optimal
         routes, thereby increasing the end-to-end delay.  The problem
         is manifested, for example, when accessing a nearby server or
         servers of a Content Delivery Network (CDN), or when receiving
         locally available IP multicast or sending IP multicast packets.
         (Existing route optimization is only a host-based solution.  On
         the other hand, localized routing with PMIPv6 [RFC6705]
         addresses only a part of the problem where both the MN and the
         CN are located in the PMIP domain and attached to a MAG, and is
         not applicable when the CN is outside the PMIP domain or does
         not behave like an MN.)

         context maintenance

These references have been added in the Introduction Section in version 09

        provided selectively such as in [I-D.bhandari-dhc-class-based-
        prefix] and [I-D.korhonen-6man-prefix-properties], thus reducing
        the amount of context maintained in the network.

---

From: h chan <[email-masked]>
Date: Sat, 28 Sep 2013 15:28:29 +0000

Sri,
It appears that version 09 has attempted to address all your comments. Please check.

H Anthony Chan

From: h chan
Sent: Saturday, September 28, 2013 10:25 AM
To: 'Sri Gundavelli (sgundave)'; [email-masked]'
Subject: RE: [DMM] I-D Action: draft-ietf-dmm-requirements-07.txt

Sri,

Regards
Sri

.......

4.  Problem Statement

   following:

   PS1:  Non-optimal routes

         route.

         multicast packets.

        Mobile.Data.Offloading].

         context maintenance