Subject: [manet] DYMO-23 review

From: Ulrich Herberg <[email-masked]>
Date: Thu, 1 Nov 2012 14:38:06 -0700

Hi,

during the discussion, I noticed that many just say "I like protocol
foo1 better than foo2", without any technical argument. That is not
very productive.

Here is my review of the latest DYMO 23 draft.

The main comments (as shown in detail below) are:
  - The draft is still very difficult to read and is underspecified in
many occasions. For example, it is unclear how the blacklisting works,
how metrics are used, how the TLVs are associated with certain
addresses. Some of the parameters and TLVs specified in the IANA
section are not used. There are at least four timers for each route
entry, and it is unclear how they may affect each other. It is not
clearly specified how to update forward/reverse routes + the route to
the previous hop
  - The use of metrics is not well defined; there is an optional
distance field. It is unclear how metrics are created, whether they
are additive, how they are formatted etc. What happens if some routers
now the Distance field, others don't use it.
  - There are several extensions specified, but too few details to
assure interoperability. Some of them violate end-to-end security.
  - As messages are modified in transit, end-to-end security is not
possible. The security considerations section does not fulfill the
requirements in RFC3552.
  - Extensions, such as for security, cannot be hooked into AODVv2, as
there is no section to allow an external mechanism to provide
additional reasons to reject a message as invalid, such as done in
RFC6130.
  - The IANA section is not correct. There are no requests, no new
registries or code points in existing registries, no allocation policy
is provided.
  - There are some layer violations where tasks that are to be done by
the RFC5444 (de)multiplexer are handled in AODVv2.
  - There is a mandated order of addresses in RFC5444 messages; I
think this is a bad idea if extensions want to add addresses.
  - Originator address and sequence number are contained in address
block and address block TLV, instead of the message header, so there
is additional overhead.
  - There is no RREP_ACK or other mechanism to verify bidirectionality
of links.
  - It is unclear to me how the destination sequence number is used in
RREQ and what it serves for.
  - Intermediate route replies are hard to secure with signatures

Best regards
Ulrich

Mobile Ad hoc Networks Working Group                          C. Perkins
Internet-Draft                                                 Futurewei
Intended status: Standards Track                             I. Chakeres
Expires: April 26, 2013                                           CenGen
                                                        October 23, 2012

                Dynamic MANET On-demand (AODVv2) Routing
                        draft-ietf-manet-dymo-23

Abstract

   The Dynamic MANET On-demand (AODVv2) routing protocol is intended for
   use by mobile routers in wireless, multihop networks.

UH> It is really about dynamic topology, not "mobile routers". AODVv2
may be used in non-mobile mesh networks with a dynamic topology.

     AODVv2
   determines unicast routes among AODVv2 routers within the network in
   an on-demand fashion, offering on-demand convergence in dynamic
   topologies.

UH> What is on-demand convergence?

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on April 26, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   the Trust Legal Provisions and are provided without warranty as

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   described in the Simplified BSD License.

Table of Contents

   1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Applicability Statement  . . . . . . . . . . . . . . . . . . .  7
   4.  Data Structures  . . . . . . . . . . . . . . . . . . . . . . .  8
     4.1.  Route Table Entry  . . . . . . . . . . . . . . . . . . . .  8
     4.2.  AODVv2 Message Structure and Information Elements  . . . .  9
     4.3.  RteMsg-specific Protocol Elements  . . . . . . . . . . . . 11
     4.4.  Route Error (RERR)-specific Protocol Elements  . . . . . . 12
   5.  Detailed Operation for the Base Protocol . . . . . . . . . . . 13
     5.1.  AODVv2 Sequence Numbers  . . . . . . . . . . . . . . . . . 13
       5.1.1.  Maintaining A Node's Own Sequence Number . . . . . . . 13
       5.1.2.  Actions After OwnSeqNum Loss . . . . . . . . . . . . . 13
     5.2.  AODVv2 Routing Table Operations  . . . . . . . . . . . . . 13
       5.2.1.  Judging Routing Information's Usefulness . . . . . . . 13
       5.2.2.  Creating or Updating Route Table Entries . . . . . . . 15
       5.2.3.  Route Table Entry Timeouts . . . . . . . . . . . . . . 15
     5.3.  Routing Messages . . . . . . . . . . . . . . . . . . . . . 16
       5.3.1.  RREQ Creation  . . . . . . . . . . . . . . . . . . . . 16
       5.3.2.  RREP Creation  . . . . . . . . . . . . . . . . . . . . 17
       5.3.3.  RteMsg Handling  . . . . . . . . . . . . . . . . . . . 18
     5.4.  Route Discovery  . . . . . . . . . . . . . . . . . . . . . 20
     5.5.  Route Maintenance  . . . . . . . . . . . . . . . . . . . . 21
       5.5.1.  Active Next-hop Router Adjacency Monitoring  . . . . . 21
       5.5.2.  Updating Route Lifetimes During Packet Forwarding  . . 22
       5.5.3.  RERR Generation  . . . . . . . . . . . . . . . . . . . 22
       5.5.4.  RERR Handling  . . . . . . . . . . . . . . . . . . . . 23
     5.6.  Unknown Message and TLV Types  . . . . . . . . . . . . . . 24
     5.7.  Advertising Network Addresses  . . . . . . . . . . . . . . 24
     5.8.  Simple Internet Attachment . . . . . . . . . . . . . . . . 24
     5.9.  Multiple Interfaces  . . . . . . . . . . . . . . . . . . . 25
     5.10. AODVv2 Control Packet/Message Generation Limits  . . . . . 26
     5.11. Optional Features  . . . . . . . . . . . . . . . . . . . . 26
       5.11.1. Expanding Rings Multicast  . . . . . . . . . . . . . . 26
       5.11.2. Intermediate RREP  . . . . . . . . . . . . . . . . . . 27
       5.11.3. Precursor Notification . . . . . . . . . . . . . . . . 27
       5.11.4. Reporting Multiple Unreachable Nodes . . . . . . . . . 28
       5.11.5. Message Aggregation  . . . . . . . . . . . . . . . . . 28
       5.11.6. Adding Additional Routing Information to a RteMsg  . . 29
     5.12. Administratively Configured Parameters and Timer Values  . 30
     5.13. IANA Considerations  . . . . . . . . . . . . . . . . . . . 33
       5.13.1. AODVv2 Message Types Specification . . . . . . . . . . 33
       5.13.2. Message and Address Block TLV Type Specification . . . 33
       5.13.3. Address Block TLV Specification  . . . . . . . . . . . 34

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     5.14. Security Considerations  . . . . . . . . . . . . . . . . . 34
     5.15. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . 36
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 36
     6.1.  Normative References . . . . . . . . . . . . . . . . . . . 36
     6.2.  Informative References . . . . . . . . . . . . . . . . . . 37
   Appendix A.  Changes since the Previous Version  . . . . . . . . . 38
   Appendix B.  Shifting Network Prefix Advertisement Between
                AODVv2 Routers  . . . . . . . . . . . . . . . . . . . 39
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 39

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1.  Overview

   The Dynamic MANET On-demand (AODVv2) routing protocol [formerly named
   DYMO] enables on-demand, multihop unicast routing among AODVv2
   routers in mobile ad hod networks [MANETs][RFC2119].

UH> Why is RFC2119 cited here?

    The basic
   operations of the AODVv2 protocol are route discovery and route
   maintenance.  Route discovery is performed when an AODVv2 router must
   transmit a packet towards a destination for which it does not have a
   route.  Route maintenance is performed to avoid dropping packets,
   when a route being used to forward packets from the source to a
   destination breaks,

UH> That is something that is unclear in the draft. Would data packets
be buffered on intermediate routers along their way? Would a new RREQ
be issed from intermediate routers? If not, packets would be dropped.

   and to avoid prematurely expunging routes from
   the route table.

   During route discovery, an AODVv2 router initiates flooding of a
   Route Request message (RREQ) throughout the network to find a route
   to a particular destination, via the AODVv2 router responsible for
   this destination.  During this hop-by-hop flooding process, each
   intermediate AODVv2 router receiving the RREQ message records a route
   to the originator.  When the target's AODVv2 router receives the
   RREQ, it records a route to the originator and responds with a Route
   Reply (RREP) unicast hop-by-hop toward the originating AODVv2 router.
   Each intermediate AODVv2 router that receives the RREP creates a
   route to the target, and then the RREP is unicast hop-by-hop toward
   the originator.  When the originator's AODVv2 router receives the
   RREP, routes have then been established between the originating
   AODVv2 router and the target AODVv2 router in both directions.

   Route maintenance consists of two operations.  In order to preserve
   routes in use, AODVv2 routers extend route lifetimes upon
   successfully forwarding a packet.  In order to react to changes in
   the network topology, AODVv2 routers monitor traffic being forwarded.
   When a data packet is received for forwarding and a route for the
   destination is not known or the route is broken, then the AODVv2
   router of the source of the packet is notified.  A Route Error (RERR)
   is transmitted to indicate the route to one or more affected
   destination addresses is Broken

 UH> s/Broken/broken/

   or missing.  When the source's AODVv2
   router receives the RERR, it marks the route as broken.  Before the
   AODVv2 router can forward a packet to the same destination, it has to
   perform route discovery again for that destination.

   Similarly to AODV, AODVv2 uses sequence numbers to ensure loop
   freedom [Perkins99].

UH> Citation to AODV missing. Is AODVv2 updating or obsoleting AODV?

    Sequence numbers enable AODVv2 routers to
   determine the temporal order of AODVv2 route discovery messages,
   thereby avoiding use of stale routing information.  Also, AODVv2 uses
   RFC 5444 message and TLV formats.

UH> As this is the successor to AODV, it would help to point out what
has been improved/changed compared to AODV.

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2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].

   Additionally, this document uses some terminology from [RFC5444].

UH> Which one?

   This document defines the following terminology:

   Adjacency
      A relationship between selected bi-directional neighboring routers
      for the purpose of exchanging routing information.  Not every pair
      of neighboring routers will necessarily form an adjacency.
      Neighboring routers may form an adjacency based on various
      information or other protocols; for example, exchange of AODVv2
      routing messages, other protocols (e.g.  NDP [RFC4861] or NHDP
      [RFC6130]), or manual configuration.  Loss of a routing adjacency
      may also be based upon similar information; monitoring of
      adjacencies where packets are being forwarded is required (see
      Section 5.5.1).

   Distance (Dist)
      An unsigned integer which measures the distance a message or
      information element has traversed.  The minimum value of distance
      is the number of IP hops traversed, 0 for local information.  The
      maximum value is 254.  The value 255 is reserved to indicate that
      the distance is unknown.

UH> Is this a metrics? Why integer and not float? Is this additive?
Why is it optional in the draft. Are there different metric types
supported in the same network?

   AODVv2 Sequence Number (SeqNum)
      An AODVv2 Sequence Number is an unsigned integer maintained by
      each AODVv2 router.  This sequence number guarantees the temporal
      order of routing information to maintain loop-free routes.  The
      value zero (0) is reserved to indicate that the SeqNum for a
      destination address is unknown.

UH> The last sentence is unclear. The first sentence said there is one
seq. number per router. The last sentence talks about sequence numbers
for destinations, which is a different thing.

   reactive
      A protocol operation is said to be "reactive" if it is performed
      only in reaction to specific events.  As used in this document,
      "reactive" is essentially synonymous with "on-demand".

   Router Client
      An AODVv2 router may be configured with a list of other IP
      addresses and networks which correspond to other non-router nodes
      which require the services of the AODVv2 router for route
      discovery and maintenance.  An AODVv2 is always its own client, so
      that the list of client IP addresses is never empty. corresponds

UH> s/corresponds/Corresponds/

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      to the AODVv2 router process currently performing a calculation or
      processing a message.

UH> I don't think it is a good idea to introduce that terminology. It
seems to be conflicting with the IP architecture of hosts and routers.
Is a Router Client a host?

   Flooding
      In this document, flooding a message refers to the process of
      delivering the message to every AODVv2 router in the network.
      This may be done according to methods specified in [RFC5148].

UH> RFC5148 describes jitter in MANETs, not flooding methods.

   Routable Unicast IP Address
      A routable unicast IP address is a unicast IP address that when
      put into the IP.SourceAddress or IP.DestinationAddress field is

UH> Notation not defined: "IP.x"

      scoped sufficiently to be forwarded by a router.

UH> I am not quite sure what that means. Can you cite an RFC, maybe RFC4007?

        Globally-scoped
      unicast IP addresses and Unique Local Addresses (ULAs) [RFC6130]
      are examples of routable unicast IP addresses.

UH> RFC6130 is NHDP, not ULA. ULA's are not globally routable and
cannot be accessed from outside a "site".

   Originating Node (OrigNode)
      The originating node is the data source node; if it is not itself
      an AODVv2 router, its AODVv2 router creates a AODVv2 RREQ message
      on its behalf in an effort to flood some routing information.  The
      originating node is also referred to as a particular message's
      originator.

   Target Node (TargetNode)
      The TargetNode denotes the ultimate destination of a message.

UH> Is this for control packets only or for data traffic? Is that an IP address?

   This Node (ThisNode)
      ThisNode denotes the AODVv2 router currently processing an AODVv2
      message.

   Route Error (RERR)
      A RERR message is used to indicate that an AODVv2 router no longer
      has a route to one or more particular destinations.

UH> Or it may have one, and data traffic was lost when sending it to
the next hop

   Route Reply (RREP)
      A RREP message is used to supply routing information about the
      RREQ TargetNode to the RREQ OrigNode and the AODVv2 routers
      between them.

   Route Request (RREQ)
      An AODVv2 router uses a RREQ message to discover a valid route to
      a particular destination address, called the RREQ TargetNode.
      When an AODVv2 router processes a RREQ, it learns routing
      information on how to reach the RREQ OrigNode.

   Type-Length-Value structure (TLV)
      A generic way to represent information as specified in [RFC5444].

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   Unreachable Node (UnreachableNode)
      An UnreachableNode is a node for which a forwarding route is
      unknown.

UH> Or to which data traffic has been lost while forwarding to the next hop.

3.  Applicability Statement

   The AODVv2 routing protocol is designed for stub (i.e., non-transit)
   or disconnected (i.e., from the Internet) mobile ad hoc networks
   (MANETs).  AODVv2 handles a wide variety of mobility patterns by
   dynamically determining routes on-demand.  AODVv2 also handles a wide
   variety of traffic patterns.  In networks with a large number of
   routers, AODVv2 is best suited for sparse traffic scenarios where any
   particular router forwards packets to only a small percentage of the
   AODVv2 routers in the network, due to the on-demand nature of route
   discovery and route maintenance.

   AODVv2 is applicable to memory constrained devices, since little
   routing state is maintained in each AODVv2 router.  Only routing
   information related to routes between active sources and destinations
   is maintained, in contrast to proactive routing protocols that
   require routing information to all routers within the routing region
   be maintained.

   AODVv2 supports routers with multiple interfaces.  In addition to
   routing for their local processes, AODVv2 routers can also route on
   behalf of other non-routing nodes (i.e., "hosts"), reachable via
   those interfaces.  Any such node which is not itself an AODVv2 router
   SHOULD NOT be served by more than one AODVv2 router.

UH> I would rather not use RFC2119 in an applicability statement. This
is not normative.

   Although AODVv2
   is closely related to AODV [RFC3561], and has some of the features of
   DSR [RFC4728], AODVv2 is not interoperable with either of those other
   two protocols.

   AODVv2 routers perform route discovery to find a route to a
   particular destination.  Therefore, AODVv2 routers MUST must be
   configured to respond to RREQs for a certain set of addresses.  When
   AODVv2 is the only protocol interacting with the forwarding table,
   AODVv2 MAY be configured to perform route discovery for all unknown
   unicast destinations.

   At all times within an AODVv2 routing region, only one AODVv2 router
   SHOULD be serve any routing client.  The coordination among multiple
   AODVv2 routers to distribute routing information correctly for a
   shared address (i.e. an address that is advertised and can be reached
   via multiple AODVv2 routers) is not described in this document.  The
   AODVv2 router operation of shifting responsibility for a routing
   client from one AODVv2 router to another is mentioned in Appendix B

UH> I am not sure that it is a good idea to include multi-homing in a
short paragraph in Appendix B. I think this whole section can be
removed.

   Each AODVv2 router, if serving router clients other than itself, is

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   configured with information about the IP addresses of its clients.
   There is no requirement that an AODVv2 router have information about
   the router clients of other AODVv2 routers.  Address assignment
   procedures are entirely out of scope for AODVv2.

   AODVv2 only utilizes bidirectional links.  In the case of possible
   unidirectional links, either blacklists (see Section 5.13.2) or other
   means (e.g. adjacency establishment with only neighboring routers
   that have bidirectional communication as indicated by NHDP [RFC6130])

UH> The blacklisting is not specified in this document.

   of ensuring and monitoring bi-directionality is recommended.
   Otherwise, persistent packet loss could occur.

   The routing algorithm in AODVv2 may be operated at layers other than
   the network layer, using layer-appropriate addresses.

UH> Yes, but the whole document is limited to IP. It is tied to IP
headers, UDP etc at multiple places.

     The routing
   algorithm makes

UH> + "use"

   of some persistent state; if there is no persistent
   storage available for this state, recovery can exact a performance
   penalty in case of AODVv2 router reboots.

4.  Data Structures

UH> There is a mixture between information bases and message formats.
I would rather have two seperate sections for that.
UH> There are no other information sets that I believe are required
for AODV: blacklisted set, set of local interfaces, and a set of the
hosts that this router is responsible.

4.1.  Route Table Entry

   The route table entry is a conceptual data structure.
   Implementations may use any internal representation so long as it
   provides access to the same information as specified below.

   Conceptually, a route table entry has the following fields:

   Route.Address
      The (host or network) destination address of the node(s)
      associated with the routing table entry.

   Route.Prefix
      The value is the length of the netmask/prefix.

UH> in octets?

       If the value of
      the Route.Prefix is different than the length of addresses in the
      address family used by the AODVv2 routers, the associated address
      is a routing prefix, rather than a host address.

   Route.SeqNum
      The AODVv2 SeqNum associated with a route table entry.

   Route.NextHopAddress
      An IP address of the adjacent AODVv2 router on the path toward the
      Route.Address.

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   Route.NextHopInterface
      The interface used to send packets toward the Route.Address.

   Route.Broken
      A flag indicating whether this Route is broken.  This flag is set
      to true if the next-hop becomes unreachable or in response to
      processing to a RERR (see Section 5.5.4).

   The following field is optional:

   Route.Dist
      A dimensionless metric indicating the distance traversed before
      reaching the Route.Address node.

UH> Why is this optional? It makes the whole specification more
complicated, in particular interoperability. I cannot imagine cases
where you are not interested in the distance.
UH> Is this metric additive? is it only integer? is it used in
addition to hop-count or instead?

   Not including optional information may cause performance degradation,
   but it will not prohibit the protocol from discovering valid routes.

   In addition to a route table data structure, each route table entry
   may have several timers associated with the information.  Timers and
   timeouts are discussed in Section 5.2.3.

UH> That forward link makes it difficult. Why not include the
expiration timers here, similar to OLSRv2?

4.2.  AODVv2 Message Structure and Information Elements

   IP Protocol Number 138 (manet) has been reserved for MANET protocols
   [RFC5498].  In addition to using this IP protocol number, AODVv2 may
   use UDP at destination port 269 (manet) [RFC5498].

UH> may or MAY?

   AODVv2 messages are transmitted in packets that conform to the
   generalized packet and message format as described in [RFC5444].
   Here is a brief description of the format.

      A packet formatted according to RFC5444 contains zero or more
      messages.

      A message contains a message header, message TLV block, and zero
      or more address blocks.

      Each of the address blocks may also have an associated address TLV
      block.

UH> Each address block *must* have a TLV block (it may be empty though).

   All AODVv2 messages SHOULD be sent using the IP protocol number (138)
   reserved for manet protocols [RFC5498]; or the UDP destination port
   (269) reserved for manet protocols [RFC5498] and IP protocol number
   for UDP.

UH> That is redundant to the first paragraph of this section.

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   Most AODVv2 messages are sent with the IP destination address set to
   the link-local multicast address LL-MANET-Routers [RFC5498] unless
   otherwise specified.  Therefore, all AODVv2 routers SHOULD subscribe
   to LL-MANET-Routers [RFC5498] to receiving AODVv2 messages.  Note
   that multicast packets MAY be sent via unicast.

UH> That sounds confusing: multicast packets MAY be sent via unicast.
First, what is a multicast packet? (you mean an IP packet with a
multicast destination address>). Why MAY?

     For example, this
   may occur for certain link-types (non broadcast mediums), for
   manually configured router adjacencies, or in order to improve
   robustness.

UH> How would one manually configure a router adjacency?

   When describing AODVv2 protocol messages, it is necessary to refer to
   fields in several distinct parts of the overall packet.

UH> Since there is an RFC5444 demultiplexer, AODVv2 would never see
the packet. So I think it's better not to use that term here.

    These
   locations include the IP header, the UDP header, and fields from
   [RFC5444].  This document uses the notational conventions found in
   table 1.

             +---------------------------+-------------------+
             |    Information Location   | Notational Prefix |
             +---------------------------+-------------------+
             |         IP header         |        IP.        |
             |   RFC5444 message header  |      MsgHdr.      |
             |    RFC5444 message TLV    |      MsgTLV.      |
             |   RFC5444 address blocks  |      AddBlk.      |
             | RFC5444 address block TLV |      AddTLV.      |
             +---------------------------+-------------------+

                                  Table 1

   The IPv4 TTL (IPv6 Hop Limit) field for all packets containing AODVv2
   messages is set to 255.

UH> I think that's the job of the RFC5444 multiplexer.

    If a packet is received with a value other
   than 255, any AODVv2 message contained in the packet MUST be ignored
   by AODVv2.

UH> No, the packet would never be received by AODVv2. Only a message would.

     This mechanism, known as "The Generalized TTL Security
   Mechanism" (GTSM) [RFC5082] helps to ensure that packets have not
   traversed any intermediate routers.

UH> Again, part of the RFC5444 multiplexer.

   The length of an address (32 bits for IPv4 and 128 bits for IPv6)
   inside an AODVv2 message depends on the msg-addr-length (MAL) in the
   msg-header, as specified in [RFC5444].

UH> Limitation of AODVv2 to IP addresses. It could also be used for
compressed (lowpan) addresses or MAC addresses.

   IP packets containing AODVv2 protocol messages SHOULD be given
   priority queuing and channel access.

UH> Not the task of AODVv2, but the RFC5444 multiplexer

   AODVv2 messages require the following information:

   IP.SourceAddress
      The IP address of the node currently sending this packet.  This
      field is generally filled automatically by the operating system
      and should not require special handling.

UH> An AODVv2 message cannot have an IP address. That's a different
layer. The IP packet that contains an RFC5444 packet (which the IP
layer received from the RFC5444 multiplexer) has that address.
Also, it is not necessarily the node currently sending this "packet";
ThisNode could receive a message, then it is not sending this packet.

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   IP.DestinationAddress
      The IP address of the packet destination.  For multicast messages
      the IP.DestinationAddress is set to LL-MANET-Routers [RFC5498].
      For unicast messages the IP.DestinationAddress is set to the
      NextHopAddress toward the TargetNode.

   MsgHdr.HopLimit
      The remaining number of hops this message is allowed to traverse.
      If an AODVv2 message within a RFC 5444 packet has exhausted its
      hop limit, then it should be removed from the packet.

UH> This seems to be mixing normative protocol behavior with field
definitions.

4.3.  RteMsg-specific Protocol Elements

   AODVv2 message types RREQ and RREP are denoted as Routing Messages
   (RteMsgs) and used to flood routing information.

UH> RREPs are not flooded.

     RREQ and RREP have
   similar information and function, but have slightly different
   handling rules.  The main difference between the two messages is that
   RREQ messages are generally broadcast to solicit a RREP, and
   conversely a RREP is the unicast response to RREQ.  RteMsg creation
   and handling are described in Section 5.3.

   Unicast AODVv2 RteMsgs (e.g.  RREP) unless otherwise specified are
   sent with the IP destination set to the Route.NextHopAddress of the
   route to the TargetNode.

   A RteMsg REQUIRES the following information in addition to the fields
   indicated in Section 4.2:

UH> REQUIRES is not RFC2110, it's REQUIRED

   AddBlk.TargetNode.Address
      The IP address of the message TargetNode.  In a RREQ the IP
      address of the message TargetNode is the destination address for
      which route discovery is being performed.  In a RREP the
      TargetNode is the RREQ OrigNode address.  The TargetNode address
      is the first address in a routing message.

UH> I don't think it's a good idea to mandate order of addresses.
Other extensions to the protocol may add addresses before. It would be
better to associate with an address block TLV.

   AddBlk.OrigNode.Address
      The IP address of the originator and its associated prefix length.
      In a RREQ the OrigNode is the source's address and prefix.  In a
      RREP the OrigNode is the RREQ TargetNode's address and prefix for
      which a RREP is being generated.  This address is the second
      address in the message for RREQ.

UH> Again, mandating address order is dangerous.

   OrigNode.AddTLV.SeqNum
      The AODVv2 sequence number of the originator's AODVv2 router.

UH> Why not use the message sequence number? This will save several
bytes. Or at least a message TLV.

   A RteMsg may optionally include the following information:

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   TargetNode.AddTLV.SeqNum
      The last known AODVv2 sequence number of the TargetNode.

UH> Using which TLV type? (reference to IANA section)

   AddBlk.AdditionalNode.Address
      The IP address of an additional node that can be reached via the
      AODVv2 router adding this information.  Each
      AdditionalNode.Address MUST include its prefix.  Each
      AdditionalNode.Address MUST also have an associated Node.SeqNum in
      the address TLV block.

UH> Is Node.foo defined before?

   AdditionalNode.AddTLV.SeqNum
      The AODVv2 sequence number associated with this routing
      information.

UH> What is AdditionalNode?

   OrigNode.AddTLV.Dist
      A metric of the distance to reach the associated OrigNode.Address.
      This field is incremented by at least one at each intermediate
      AODVv2 router.

UH> Why not use a message TLV?

   AdditionalNode.AddTLV.Dist
      A metric of the distance to reach the associated
      AdditionalNode.Address.  This field is incremented by at least one
      at each intermediate AODVv2 router.

4.4.  Route Error (RERR)-specific Protocol Elements

   A RERR message is used to flood the information that a route is not
   available for one or more particular addresses.

UH> RERR are mostly sent unicast, not flooded.

   RERR creation and handling are described in Section 5.5.

   A RERR requires the following information in addition to the field
   indicated in Section 4.2:

   AddBlk.UnreachableNode.Address
      The address of an UnreachableNode and its associated prefix
      length.  Multiple unreachable addresses may be included in a RERR.

   A Route Error may optionally include the following information:

   UnreachableNode.AddTLV.SeqNum
      The last known AODVv2 sequence number of the unreachable node.  If
      a SeqNum for an address is zero (0) or not included, it is assumed
      to be unknown.  This case occurs when a node receives a message to
      forward to a destination for which it does not have any
      information in its routing table.

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5.  Detailed Operation for the Base Protocol

5.1.  AODVv2 Sequence Numbers

   AODVv2 sequence numbers allow AODVv2 routers to judge the freshness
   of routing information and consequently ensure loop freedom.

5.1.1.  Maintaining A Node's Own Sequence Number

   AODVv2 requires that each AODVv2 router in the network maintain its
   own AODVv2 sequence number (OwnSeqNum).  OwnSeqNum a 16-bit unsigned
   integer.  An AODVv2 router increments its OwnSeqNum under the
   circumstances described in Section 5.3.

   Incrementing an OwnSeqNum whose value is the largest largest possible
   number representable as a 16-bit unsigned integer (i.e., 65,535),
   MUST be set to one (1).  In other words, the sequence number after
   65,535 is 1.

5.1.2.  Actions After OwnSeqNum Loss

   An AODVv2 router SHOULD maintain its own sequence number in
   persistent storage.

   If an AODVv2 router's OwnSeqNum is lost, it MUST take certain actions
   to avoid creating routing loops.  To prevent this possibility after
   OwnSeqNum loss an AODVv2 router MUST wait for at least
   ROUTE_DELETE_TIMEOUT before fully participating in the AODVv2 routing
   protocol.  If an AODVv2 protocol message is received during this
   waiting period, the AODVv2 router SHOULD perform normal route table
   entry updates but MUST NOT transmit or retransmit any AODVv2 RREQ or
   RREP messages.  If a data packet is received for forwarding to
   another destination during this waiting period, the AODVv2 router
   MUST transmit a RERR message indicating that this route is not
   available and reset its waiting timeout.  At the end of the waiting
   period the AODVv2 router sets its OwnSeqNum to one (1) and begin
   participating.

   The longest a node need wait is ROUTE_SEQNUM_AGE_MAX_TIMEOUT.  At the
   end of the maximum waiting period a node SHOULD set its OwnSeqNum to
   one (1) and begins participating.

5.2.  AODVv2 Routing Table Operations

UH> This whole structure is unclear. Where do we come to this?
Wouldn't it be better to start of with message generation/processing
before saying how to update the routing tuples as a consequence to
received messages?

5.2.1.  Judging Routing Information's Usefulness

   Given a route table entry (Route.SeqNum, Route.Dist, and
   Route.Broken)

UH> A route table entry has more fields in section 4.1

   and incoming routing information for a particular

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   destination in a RteMsg (Node.SeqNum, Node.Dist, and RteMsg message
   type - RREQ/RREP), the incoming routing information is classified as
   follows:

   1. Stale (Node.SeqNum < Route.SeqNum)
      If Node.SeqNum < Route.SeqNum (using signed 16-bit arithmetic) the
      incoming information is stale.  Using stale routing information is
      not allowed, since that might result in routing loops.

UH> So what should my implementation then? Continue with the next
step? Discard the message?

   2. Not safe against loops
      If Node.SeqNum == Route.SeqNum, additional information MUST be
      examined.  If Route.Dist or Node.Dist is unknown or zero (0), or
      if Node.Dist > Route.Dist + 1, then the incoming information is
      not guaranteed to prevent routing loops.  Using such incoming
      routing information is not allowed.  The following pseudocode is
      offered to indicate the logical condition under which the incoming
      information is not guaranteed to protect against loops.

      (Node.SeqNum == Route.SeqNum) AND
      ((Node.Dist > Route.Dist + 1) OR

UH> Would cause a null-pointer exception in my implementation if Dist
is not contained in the message.

       (Route.Dist is unknown) OR (Node.Dist is unknown))

   3. Offers no improvement
      In case of known equal SeqNum, the information is considered worse
      than the existing route table information in multiple cases: (case
      i) if Node.Dist > Route.Dist (it is a more expensive route) AND
      Route.Broken == false; (case ii) if Node.Dist == Route.Dist (equal
      distance route) AND Route.Broken == false AND this RteMsg is a
      RREQ.  Such RREQs offer no improvement and SHOULD NOT be
      retransmitted.  Updating route table entries using such incoming
      routing information is not allowed.

      ((Node.SeqNum == Route.SeqNum) AND
          (((Node.Dist > Route.Dist) AND (Route.Broken == false)) OR
            ((Node.Dist == Route.Dist) AND
             (RteMsg is RREQ) AND (Route.Broken == false))))

   4. Offers improvement
      Incoming routing information that does not match any of the above
      criteria is loop-free and better than the existing routing table
      information.  We provide the following pseudo-code to determine
      whether incoming routing information should be used to update an
      existing route table entry.

      (/* signed 16-bit arithmetic */ Node.SeqNum - Route.SeqNum > 0) OR
      ((Node.SeqNum == Route.SeqNum) AND
          [(Node.Dist < Route.Dist) OR
          ((Route.Broken == true) AND (Node.Dist <= Route.Dist + 1)) OR

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          ((RteMsg is RREP) AND (Node.Dist == Route.Dist)]

5.2.2.  Creating or Updating Route Table Entries

   Each route table entry is populated with the following information:

UH> Why "each" entry? When does this happen? It seems this only sets
the route to the previous hop; what happens with a route to the
originator? What happens if a route already exists and is only
updated? How are both forward and reverse routes updated?

   1.  the Route.Address is set to Node.Address,

   2.  the Route.Prefix is set to the Node.Prefix.

   3.  the Route.SeqNum is set to the Node.SeqNum,

   4.  the Route.NextHopAddress is set to the IP.SourceAddress (i.e., an
       address of the node that last transmitted the RteMsg packet)

   5.  the Route.NextHopInterface is set to the interface on which the
       incoming AODVv2 packet was received,

   6.  the Route.Broken flag is set to false,

   7.  if known, the Route.Dist is set to the Node.Dist,

   The timer for the minimum delete timeout (ROUTE_AGE_MIN) is set to
   ROUTE_AGE_MIN_TIMEOUT.  The timer for the maximum delete timeout
   (ROUTE_SEQNUM_AGE_MAX) is set to Node.AddTLV.VALIDITY_TIME [RFC5497]
   if included; otherwise, ROUTE_SEQNUM_AGE_MAX is set to
   ROUTE_SEQNUM_AGE_MAX_TIMEOUT.  The usage of these timers and others
   are described in Section 5.2.3.

UH> I don't understand how a sequence number can expire. Also, in
section 4.1 there was no mention of the VALIDITY_TIME Tlv in a
message. What happens if it is not contained?

   With these assignments to the route table entry, a route has been
   created and the Route.Forwarding flag set.  Afterward, the route can
   be used to send any buffered data packets and to forward any incoming
   data packets for Route.Address.  This route also fulfills any
   outstanding route discovery (RREQ) attempts for Node.Address.

5.2.3.  Route Table Entry Timeouts

5.2.3.1.  Minimum Delete Timeout (ROUTE_AGE_MIN)

   When an AODVv2 router transmits a RteMsg, other AODVv2 routers expect
   the transmitting AODVv2 router to have a forwarding route to the
   RteMsg originator.  A route table entry SHOULD be kept in the route
   table for at least ROUTE_AGE_MIN after it has been updated.  Failure
   to maintain the route table entry might result in lost messages/
   packets, or several duplicate messages.

   After the ROUTE_AGE_MIN timeout a route can safely be deleted.

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5.2.3.2.  Maximum Sequence Number Delete Timeout (ROUTE_SEQNUM_AGE_MAX)

   Sequence number information for route table entries is time
   sensitive, and MUST be deleted after a time in order to ensure loop-
   free routing.

   After the ROUTE_SEQNUM_AGE_MAX timeout a route's sequence number
   information MUST be discarded.

UH> What does it mean to discard a sequence number information? To set
it to zero in the route entry? What are the relationships between
ROUTE_SEQNUM_AGE_MUX and ROUTE_AGE_MIN? (can one be smaller than the
other)

5.2.3.3.  Recently Used Timeout (ROUTE_USED)

   When a route is used to forward data packets, this timer is set to
   expire after ROUTE_USED_TIMEOUT, as discussed in Section 5.5.2.

   If a route has not been used recently, then a timer for ROUTE_DELETE
   is set to ROUTE_DELETE_TIMEOUT.

5.2.3.4.  Delete Information Timeout (ROUTE_DELETE)

   As time progresses the likelihood that old routing information is
   useful decreases, especially if the network nodes are mobile.
   Therefore, old information SHOULD be deleted.

   After the ROUTE_DELETE timeout if a forwarding route exists it SHOULD
   be removed, and the routing table entry SHOULD also be deleted.

UH> There are quite a few timers, which is confusing. What happens if
one timer fires before the other? Do we really need that many timers?

5.3.  Routing Messages

5.3.1.  RREQ Creation

   Before an AODVv2 router creates a RREQ it SHOULD increment its
   OwnSeqNum by one (1) according to the rules specified in Section 5.1.

UH> Why not MUST? What happens if one does not increase it. In
general, there are many SHOULDs in the document, which probably should
be MUSTs.

   Incrementing OwnSeqNum will ensure that all nodes with existing
   routing information will consider this new information preferable to
   existing routing table information.  If the sequence number is not
   incremented, certain AODVv2 routers might not consider this
   information preferable, if they have existing better routing
   information.

   First, ThisNode adds the AddBlk.TargetNode.Address to the RREQ; the
   unicast IP Destination Address for which a forwarding route does not
   exist.

   If a previous value of the TargetNode.SeqNum is known (from a routing
   table entry using longest-prefix matching), it SHOULD be placed in
   TargetNode.AddTLV.SeqNum in all but the last RREQ attempt.  If a
   TargetNode.SeqNum is not included, it is assumed to be unknown by
   handling nodes.  This operation ensures that no intermediate AODVv2

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   routers reply, and ensures that the TargetNode's AODVv2 router
   increments its sequence number.

   Next, ThisNode adds AddBlk.OrigNode.Address, its prefix, and the
   OrigNode.AddTLV.SeqNum (OwnSeqNum) to the RteMsg.

   The OrigNode.Address is the address of the source for which this
   AODVv2 router is initiating this route discovery.  The
   OrigNode.Address MUST be a unicast address.  This information will be
   used by nodes to create a route toward the OrigNode, enabling
   delivery of a RREP, and eventually used for proper forwarding of data
   packets.

   If OrigNode.Dist is included it is set to a number, greater than zero
   (0), representing the distance between OrigNode and ThisNode.

   The MsgHdr.HopLimit SHOULD be set to MSG_HOPLIMIT.

UH> Why SHOULD?

5.3.2.  RREP Creation

   First, the AddBlk.TargetNode.Address is added to the RREP.  The
   TargetNode is the ultimate destination of this RREP; the RREQ
   OrigNode.Address.

   Next, AddBlk.OrigNode.Address and prefix are added to the RREP.  The
   AddBlk.OrigNode.Address is the RREQ TargetNode.Address.  The
   AddBlk.OrigNode.Address MUST be a unicast IP address.  ThisNode
   SHOULD advertise the largest known prefix containing
   AddBlk.OrigNode.Address.

   When the RteMsg TargetNode's AODVv2 router creates a RREP, if the
   TargetNode.SeqNum was not included in the RREQ, ThisNode MUST
   increment its OwnSeqNum by one (1) according to the rules specified
   in Section 5.1.

   If TargetNode.SeqNum was included in the RteMsg and TargetNode.SeqNum
   - OwnSeqNum < 0 (using signed 16-bit arithmetic), OwnSeqNum SHOULD be
   incremented by one (1) according to the rules specified in
   Section 5.1.

   If TargetNode.SeqNum is included in the RteMsg and TargetNode.SeqNum
   == OwnSeqNum (using signed 16-bit arithmetic) and OrigNode.Dist will
   not be included in the RREP being generated, OwnSeqNum SHOULD be
   incremented by one (1) according to the rules specified in
   Section 5.1.

   If OwnSeqNum is not incremented the routing information might be
   considered stale.  In this case, the RREP might not reach the RREP

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   Target.

   After any of the sequence number operations above, the RREP
   OrigNode.AddTLV.SeqNum (OwnSeqNum) MUST also be added to the RREP.

   Other AddTLVs in the RREP for the OrigNode and TargetNode SHOULD be
   included and set accordingly.  If OrigNode.Dist is included it is set
   to a number greater than zero (0) and less than or equal to 254.  The
   Distance value will influence judgment of the routing information
   (Section 5.2.1) against known information at other AODVv2 routers
   that handle this RteMsg.

   The MsgHdr.HopLimit is set to MSG_HOPLIMIT.

   The IP.DestinationAddress for RREP is set to the IP address of the
   Route.NextHopAddress for the route to the RREP TargetNode.

5.3.3.  RteMsg Handling

UH> Very difficult to parse this section. Not much RFC2119 language.

UH> Is there any check for invalid messages (similar to OLSRv2/NHDP?)
External mechanisms should be allowed to add reasons to reject a
message as invalid, e.g. a security mechanism.

   First, ThisNode examines the RteMsg to ensure that it contains the
   required information: MsgHdr.HopLimit, AddBlk.TargetNode.Address,
   AddBlk.OrigNode.Address, and OrigNode.AddTLV.SeqNum.  If the required
   information does not exist, the message is discarded and further
   processing stopped.

   ThisNode MUST only handle AODVv2 messages from adjacent routers.

UH> What does that mean?

   ThisNode checks if the AddBlk.OrigNode.Address is a valid routable
   unicast address.

UH> How?

    If not, the message is ignored and further
   processing stopped.

   ThisNode also checks whether AddBlk.OrigNode.Address is an address
   handled by this AODVv2 router.

UH> How?

     If this node is the originating
   AODVv2 router, the RteMsg is dropped.

UH> Why not do this further above, before doing all the other checks?

   ThisNode checks if the AddBlk.TargetNode.Address is a valid routable
   unicast address.  If the address is not a valid unicast address, the
   message is discarded and further processing stopped.

   Next, ThisNode checks whether its routing table has an entry to the
   AddBlk.OrigNode.Address using longest-prefix matching [RFC1812].

UH> RFC1812 is IPv4 only.

     If
   a route with a valid Route.SeqNum does not exist,

UH> What is a "valid" sequence number?

   then the new
   routing information is used to create a new route table entry is
   created

UH> to "create" ... is "created"

   and updated as described in Section 5.2.2.

UH> This jumping back is difficult to parse.

    If a route table
   entry does exists and it has a known Route.SeqNum, the incoming
   routing information is compared with the route table entry following
   the procedure described in Section 5.2.1.  If the incoming routing
   information is considered preferable, the route table entry is

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   updated as described in Section 5.2.2.

   At this point, if the routing information for the OrigNode was not
   preferable then this RteMsg SHOULD be discarded and no further
   processing of this message SHOULD be performed.

UH> Why SHOULD? Why not MUST?

   If the TargetNode is a router client of ThisNode this RteMsg is a
   RREQ, then ThisNode responds with a RREP to the RREQ OrigNode (the
   new RREP's TargetNode).  The procedure for issuing a new RREP is
   described in Section 5.3.2.  Afterwards, ThisNode need not perform
   any more operations for the RteMsg being processed.

   As an alternative to issuing a RREP, ThisNode MAY choose to
   distribute routing information about ThisNode (the RREQ TargetNode)
   more widely.  That is, ThisNode MAY optionally perform a route
   discovery by issuing a RREQ with ThisNode listed as the TargetNode,
   using the procedure in Section 5.3.1.  At this point, ThisNode need
   not perform any more operations for the RteMsg being processed.

UH> I don't understand the last paragraph. Is this some remainder of
intermediate route reply? In which conditions should a router send a
RREQ instead of a RREP?

   For each address (except the TargetNode) in the RteMsg that includes
   AddTLV.Dist information, the AddTLV.Dist information is incremented
   by at least one (1).

UH> By how much then?

     The updated Distance value will influence
   judgment of the routing information (Section 5.2.1) against known
   information at other AODVv2 routers that handle this RteMsg.

   If the resulting Distance value for the OrigNode is greater than 254,
   the message is discarded.  If the resulting Distance value for
   another node is greater than 254,

UH> Which other node?

   the associated address and its
   information are removed from the RteMsg.

UH> That makes end-to-end security impossible.

   If the MsgHdr.HopLimit is
   equal to one (1), then the message is discarded.  Otherwise, the
   MsgHdr.HopLimit is decremented by one (1).

   If ThisNode is not the TargetNode, AND this RteMsg is a RREQ, then
   the current RteMsg (as altered by the procedure defined above) SHOULD
   be sent to the IP multicast address LL-MANET-Routers [RFC5498].  If
   the RREQ is unicast, the IP.DestinationAddress is set to the
   NextHopAddress.

UH> The unicast RREQ mechanism is not really explained anywhere. Where
is the nexthopaddress acquired from?

   If ThisNode is not the TargetNode, AND this RteMsg is a RREP, then
   the current RteMsg is sent to the Route.NextHopAddress for the RREP's
   TargetNode.Address.  If no forwarding route exists to
   TargetNode.Address, then a RERR SHOULD be issued to the OrigNode of
   the RREP.

   By sending the updated RteMsg, ThisNode advertises that it will route
   for addresses contained in the outgoing RteMsg based on the
   information enclosed.  ThisNode MAY choose not to send the RteMsg,
   though not resending this RteMsg could decrease connectivity in the

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   network or result in a non-shortest distance path.

   The circumstances under which ThisNode might choose to not re-issue a
   RteMsg are not specified in this document.  Some examples might
   include the following:

   o  if ThisNode does not want to advertise routing for the contained
      addresses because it is already heavily loaded

   o  if ThisNode has already issued identical routing information (e.g.
      ThisNode had recently issued a RteMsg with the same distance)

   o  if ThisNode is low on energy and does not want to expend energy
      for protocol message sending or packet forwarding

5.4.  Route Discovery

   When an AODVv2 router needs to forward a data packet and it does not
   have a forwarding route to the destination address, it sends a RREQ
   (described in Section 5.3.1) to discover a route to the particular
   destination (TargetNode).

   After issuing a RREQ, the AODVv2 router (OrigNode) waits for a RREP
   indicating the next hop for a route to the TargetNode.  If a route is
   not created within RREQ_WAIT_TIME, OrigNode may again try to discover
   a route by issuing another RREQ using the procedure defined in
   Section 5.3.1 again.  Route discovery SHOULD be considered to have
   failed after DISCOVERY_ATTEMPTS_MAX and the corresponding wait time
   for a response to the final RREQ.

   To reduce congestion in a network, repeated attempts at route
   discovery for a particular TargetNode SHOULD utilize an binary
   exponential backoff.

   Data packets awaiting a route SHOULD be buffered by the source's
   AODVv2 router.  This buffer SHOULD have a fixed limited size
   (BUFFER_SIZE_PACKETS or BUFFER_SIZE_BYTES).  Determining which
   packets to discard first is a matter of policy at each AODVv2 router;
   in the absence of policy constraints, by default older data packets
   SHOULD be discarded first.  Buffering of data packets can have both
   positive and negative effects, and therefore settings for buffering
   (BUFFER_DURING_DISCOVERY) SHOULD be administratively configurable.
   Nodes without sufficient memory available for buffering may be
   configured with BUFFER_DURING_DISCOVERY = FALSE; this will affect the
   latency required for launching TCP applications to new destinations.

UH> I am against including this buffering mechanism in this document.
This is a mixture of the routing plane and the data plane. There are
other forwarding mechanisms that would be affected by this
specification.

   If a route discovery attempt has failed (i.e. an attempt or multiple
   attempts have been made without receiving a RREP) to find a route to

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   the TargetNode, any data packets buffered for the corresponding
   TargetNode MUST BE dropped and a Destination Unreachable ICMP message
   (Type 3) SHOULD be delivered to the source of the data packet.  The
   code for the ICMP message is 1 (Host unreachable error).  If the
   AODVv2 router is not the source (OrigNode), then the ICMP is sent
   over the interface from which the source sent the packet to the
   AODVv2 router.

5.5.  Route Maintenance

   A RERR SHOULD be issued if a data packet is to be forwarded and it
   cannot be delivered to the next-hop because no forwarding route for
   the IP.DestinationAddress exists; RERR generation is described in
   Section 5.5.3.

   Upon this condition, an ICMP Destination Unreachable message SHOULD
   NOT be generated unless this router is responsible for the
   IP.DestinationAddress and that IP.DestinationAddress is known to be
   unreachable.

UH> How is that generated (with which content)?

   In addition to inability to forward a data packet, a RERR SHOULD be
   issued immediately after detecting a broken link (see Section 5.5.1)
   of a forwarding route to quickly notify AODVv2 routers that certain
   routes are no longer available.  If a newly unavailable route has not
   been used recently (indicated by ROUTE_USED), the RERR SHOULD NOT be
   generated.

UH> SHOULD NOT or MUST NOT? What are the consequences of doing so when
using SHOULD NOT?

5.5.1.  Active Next-hop Router Adjacency Monitoring

   Nodes SHOULD monitor connectivity to adjacent next-hop AODVv2 routers
   on forwarding routes.  This monitoring can be accomplished by one or
   several mechanisms, including:

   o  Neighborhood discovery [RFC6130]

   o  Route timeout

   o  Lower layer trigger that a neighboring router is no longer
      reachable

   o  Other monitoring mechanisms or heuristics

   Upon determining that a next-hop AODVv2 router has become
   unreachable, ThisNode MUST remove the affected forwarding routes
   (those using the unreachable next-hop) and unset the Route.Forwarding
   flag.  ThisNode also flags the associated routes in AODVv2's routing
   table as Broken.  For each broken route the timer for ROUTE_DELETE is
   set to ROUTE_DELETE_TIMEOUT.

UH> How can the flags be set if the routes are removed before?

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5.5.2.  Updating Route Lifetimes During Packet Forwarding

   To avoid removing the forwarding route to reach an IP.SourceAddress,
   ThisNode SHOULD set the "ROUTE_USED" timeout to the value
   ROUTE_USED_TIMEOUT for the route to that IP.SourceAddress upon
   receiving a data packet or an AODVv2 message.  If the timer for
   ROUTE_DELETE is set, that timer is removed.  The Route.Broken flag is
   unset.

   To avoid removing the forwarding route to the IP.DestinationAddress
   that is being used, ThisNode SHOULD set the "ROUTE_USED" timeout to
   the value ROUTE_USED_TIMEOUT for the route to the
   IP.DestinationAddress upon sending a data packet or an AODVv2
   message.  If the timer for ROUTE_DELETE is set, it is removed.  The
   Route.Broken flag is unset.

5.5.3.  RERR Generation

   When an AODVv2 router receives a packet (from PrevHopAddress), and
   the router (ThisNode) does not have a route available for the
   destination of the packet, ThisNode uses an RERR message is used to

UH> "uses".. ."is used"

   inform one or more neighboring AODVv2 routers that its route to the
   packet destination is no longer available.

   When ThisNode creates a new RERR, the address of the first
   UnreachableNode (IP.DestinationAddress from a data packet or
   RREP.TargetNode.Address) is inserted into an Address Block
   AddBlk.UnreachableNode.Address.  If a prefix is known for the
   UnreachableNode.Address, it SHOULD be included.  Otherwise, the
   UnreachableNode.Address is assumed to be a host address with a full
   length prefix.  If a value for the UnreachableNode's SeqNum
   (UnreachableNode.AddTLV.SeqNum) is known, it SHOULD be placed in the
   RERR.  The MsgHdr.HopLimit SHOULD be set to MSG_HOPLIMIT.

   If SeqNum information is not known or not included in the RERR, all
   nodes handling the RERR will assume their routing information
   associated with the UnreachableNode is no longer valid and flag those
   routes as broken.

   A RERR MAY be sent to the multicast address LL-MANET-Routers
   [RFC5498], thus notifying all nearby AODVv2 routers that might depend
   on the now broken link.  If the RERR is unicast, the
   IP.DestinationAddress is set to the PrevHopAddress.

   After sending the RERR, ThisNode SHOULD discard the packet or message

UH> Why packet or message? Is this data traffic or control traffic?

   that triggered generation of the RERR.

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5.5.4.  RERR Handling

   First, ThisNode examines the incoming RERR to ensure that it contains
   MsgHdr.HopLimit and AddBlk.UnreachableNode.Address.  If the required
   information does not exist, the incoming RERR message is discarded
   and further processing stopped.

   When an AODVv2 router handles a RERR, it examines the information for
   each UnreachableNode.

UH> How exactly does it do that? Which information is used, and how?

   The AODVv2 router removes the forwarding
   route, unsets the Route.Forwarding flag, sets the Route.Broken flag,
   and the timer for ROUTE_DELETE is set to ROUTE_DELETE_TIMEOUT for
   each UnreachableNode.Address found using longest prefix matching that
   meets all of the following conditions:

   1.  The UnreachableNode.Address is a routable unicast address.

   2.  The Route.NextHopAddress is the same as the RERR
       IP.SourceAddress.

   3.  The Route.NextHopInterface is the same as the interface on which
       the RERR was received.

   4.  The Route.SeqNum is zero (0), unknown, OR the
       UnreachableNode.SeqNum is zero (0), unknown, OR Route.SeqNum -
       UnreachableNode.SeqNum <= 0 (using signed 16-bit arithmetic).

   If Route.SeqNum is zero (0) or unknown and UnreachableNode.SeqNum
   exists in the RERR and is not zero (0), then Route.SeqNum SHOULD be
   set to UnreachableNode.SeqNum.  Setting Route.SeqNum can reduce
   future RERR handling and forwarding.

UH> How?

   Each UnreachableNode that did not result in marking a route table
   entry as broken route is removed from the RERR, since propagation of
   such information will not result in any benefit.

UH> Makes end-to-end security impossible.

   Each UnreachableNode that did indicate a broken route SHOULD remain
   in the RERR.

   If any UnreachableNode was removed, all other information (AddTLVs)
   associated with the UnreachableNode address(es) MUST also be removed.

   If Route.SeqNum is known and an UnreachableNode.SeqNum is not
   included in the RERR, then Route.SeqNum (i.e.
   UnreachableNode.SeqNum) MAY be included with the RERR.  Including
   UnreachableNode.SeqNum can reduce future RERR handling and
   forwarding.

   If no UnreachableNode addresses remain in the RERR, or if the

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   MsgHdr.HopLimit is equal to one (1), then the RERR MUST be discarded.

   Otherwise, the MsgHdr.HopLimit is decremented by one (1).  The RERR
   SHOULD be sent to the multicast address LL-MANET-Routers [RFC5498].
   Alternatively, if the RERR is unicast, the IP.DestinationAddress is
   set to the PrevHopAddress.

5.6.  Unknown Message and TLV Types

   If a message with an unknown type is received, the message is
   ignored.

   For handling of messages that contain unknown TLV types, ignore the
   information for processing, preserve it unmodified for forwarding.

5.7.  Advertising Network Addresses

   AODVv2 routers MAY specify a prefix length for each advertised
   address.  Any nodes (other than the advertising AODVv2 router) within
   the advertised prefix MUST NOT participate in the AODVv2 protocol
   directly.  For example, advertising 192.0.2.1 with a prefix length of
   24 indicates that all nodes with the matching 192.0.2.X are reachable
   through this AODVv2 router.  An AODVv2 router MUST NOT advertise
   network addresses unless it can guarantee its ability for forwarding
   packets to any host address within the address range of the
   corresponding network.

5.8.  Simple Internet Attachment

   Simple Internet attachment consists of a stub (i.e., non-transit)
   network of AODVv2 routers connected to the Internet via a single
   Internet AODVv2 router (IAR).

UH> Why a new defition? Is that not just a border router? Also, it
does not matter if it's connected to the "Internet", just if it's a
border gateway with two interfaces, connecting two different routing
domains (which could still not be connected to the Internet).

   As in any Internet-attached network,

UH> What's an Internet-attached network? Is that defined in an IP
architecture RFC?

    AODVv2 routers, and hosts behind
   these routers, wishing to be reachable from hosts on the Internet
   MUST have IP addresses within the IAR's routable and topologically
   correct prefix (e.g. 192.0.2.0/24).

   The IAR is responsible for generating RREQ to find nodes within the
   AODVv2 Region on behalf of nodes on the Internet, as well as
   responding to route requests from the AODVv2 region on behalf of the
   nodes on the Internet.

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         /--------------------------\
        /          Internet          \
        \                            /
         \------------+-------------/
                      |
       Routable &     |
       Topologically  |
       Correct        |
       Prefix         |
                +-----+--------+
                |  Internet    |
         /------|  AODVv2      |-------\
        /       |  Router      |        \
       /        |192.0.2.1/32  |         \
       |        |Responsible   |         |
       |        |  for         |         |
       |        |AODVv2 Region |         |
       |        |192.0.2.0/24  |         |
       |        +--------------+         |
       | +----------------+              |
       | | AODVv2 Router  |              |
       | | 192.0.2.2/32   |              |
       | +----------------+              |
       |              +----------------+ |
       |              | AODVv2 Router  | |
       |              | 192.0.2.3/32   | |
       \              +----------------+ /
        \                               /
         \-----------------------------/

               Figure 1: Simple Internet Attachment Example

   When an AODVv2 router within the AODVv2 Region wants to discover a
   route to a node on the Internet, it uses the normal AODVv2 route
   discovery for that IP Destination Address.  The IAR MUST respond to
   RREQ on behalf of the Internet destination.

UH> How? Where is that specified?

   When a packet from a node on the Internet destined for a node in the
   AODVv2 region reaches the IAR, if the IAR does not have a route to
   that destination it will perform normal AODVv2 route discovery for
   that destination.

UH> How? With which originator address, target etc? Where are RERRs /
ICMP unreachable sent to in case of a broken data traffic?

5.9.  Multiple Interfaces

   AODVv2 may be used with multiple interfaces; therefore, the
   particular interface over which packets arrive MUST be known whenever
   a packet is received.  Whenever a new route is created, the interface
   through which the Route.Address can be reached is also recorded in

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   the route table entry.

   When multiple interfaces are available, a node transmitting a
   multicast packet with IP.DestinationAddress set to LL-MANET-Routers
   SHOULD send the packet on all interfaces that have been configured
   for AODVv2 operation.

   Similarly, AODVv2 routers SHOULD subscribe to LL-MANET-Routers on all
   their AODVv2 interfaces.

5.10.  AODVv2 Control Packet/Message Generation Limits

UH> There is no AODVv2 Control Packet.

   To ensure predictable messaging overhead, AODVv2 router's rate of
   packet/message generation SHOULD be limited.  The rate and algorithm
   for limiting messages (CONTROL_TRAFFIC_LIMITS) is left to the
   implementor and should be administratively configurable.  AODVv2
   messages SHOULD be discarded in the following order of preference:
   RREQ, RREP, and finally RERR.

5.11.  Optional Features

   Several optional features of AODVv2, and associated with AODV, are
   not required by minimal implementations.  These features are expected
   to be useful in networks with greater mobility, or larger node
   populations, or requiring shorter latency for application launches.
   The optional features are as follows:

   o  Expanding Rings Multicast

   o  Intermediate RREPs (iRREPs): Without iRREP, only the destination
      can respond to a RREQ.

   o  Precursor lists.

   o  Reporting Multiple Unreachable Nodes.  An RERR message can carry
      more than one Unreachable Destination node for cases when a single
      link breakage causes multiple destinations to become unreachable
      from an intermediate router.

UH> This seems to be different from section 5.11.6, which talks about
adding additional information to a RREQ.

UH> None of the extensions is sufficiently specified, and it is
unclear how it would affect interoperability if some nodes support the
extension and others don't.

5.11.1.  Expanding Rings Multicast

   For multicast RREQ, the MsgHdr.HopLimit MAY be set in accordance with
   an expanding ring search as described in [RFC3561] to limit the RREQ
   propagation to a subset of the local network and possibly reduce
   route discovery overhead.

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5.11.2.  Intermediate RREP

   This specification has been published as a separate Internet Draft .

5.11.3.  Precursor Notification

   The Dynamic MANET On-demand (AODVv2) routing protocol is intended for
   use by mobile routers in wireless, multihop networks.  AODVv2
   determines unicast routes among AODVv2 routers within the network in
   an on-demand fashion, offering on-demand convergence in dynamic
   topologies.  This document specifies a simple modification to AODVv2
   (and possibly other reactive routing protocols) enabling faster
   notifications to known sources of traffic upon determination that a
   route for such traffic's destination has become Broken.

5.11.3.1.  Overview

   If an AODVv2 router, while attempting to forward a packet to a
   particular destination, determines that the next hop (one of its
   neighbors) is no longer reachable, AODVv2 specifies that the router
   notify the source of that packet that the route to the destination
   has become Broken.  In the existing specification, the notification
   to the source is a unicast RERR message.

   However, in many cases there will be several sources of of traffic
   for that particular destination.  In fact, the broken link for the
   next hop in question may be a path component of numerous other routes
   for other destinations, and in that case the node detecting the
   broken link must mark as Broken multiple routes, one for each of the
   newly unreachable destinations.  Each route that uses the newly
   broken link is no longer valid.  For each such route, every node
   along the way from the source using that route, to the node detecting
   the broken link, is known as a "precursor" for the broken next hop.
   All the precursors for a particular next hop should be notified about
   the change in status of their route to a destination downstream from
   the broken next hop.

5.11.3.2.  Precursor Notification

   During normal operation, each node wishing to enable the improved
   notification for precursors of any links to its next hop neighbors
   has to keep track of the precursors.  This is done by maintaining a
   precursor table and updating the table whenever the node initiates or
   relays a RREP message back to a node originating a RREQ message.
   When the node transmits the RREP message, it is implicitly agreeing
   to forward traffic from the RREQ originator towards the RREP
   originator (i.e., along the next hop link to the neighbor from which
   the RREP was received).  The "other" next hop, which is the neighbor

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   along the way towards the originator of the RREQ message, is then the
   next precursor for the route towards the destination requested by the
   RREQ.

   Each such precursor should then be recorded as a precursor for a
   route along the next hop.  The same next hop may be in service for
   routes to multiple destinations, but for precursor list management it
   is only important to keep track of precursors for a particular next
   hop; the exact destination does not matter, only the particular next
   hop towards the destination(s).

   When a node observes that one of its neighbors is no longer
   reachable, the node first checks to see whether the link to that
   neighbor is a next hop for any more distant destination in its route
   table.  If not, then the node simply updates any relevant neighorhood
   information and takes no further action.

   Otherwise, for all destinations no longer reachable because of the
   changed status of the next hop, the node first checks to see whether
   the link to that neighbor is a next hop for any more distant
   destination in its route table.  If not, then the node simply updates
   any relevant neighorhood information and takes no further action.

   For each precursor of the next hop, the node MAY notify the precursor
   in one of three ways:

   o  unicast RERR

   o  broadcast RERR

   o  multicast RERR to multicast group PRECURSOR_RERR_RECEIVERS

UH> I don't see an allocation request in the IANA section.

   Each precursor then MAY execute the same procedure until all affected
   traffic sources have received the RERR route maintenance information.

   When a precursor receives a unicast RERR, the precursor MUST further
   unicast the RERR message towards the affected traffic source.  If a
   precursor receives a broadcast or multicast RERR, the precursor MAY
   further retransmit the RERR towards the traffic source.

5.11.4.  Reporting Multiple Unreachable Nodes

5.11.5.  Message Aggregation

   The aggregation of multiple messages into a packet is not specified
   in this document, but if aggregation does occur the IP.SourceAddress
   and IP.DestinationAddress of all contained messages MUST be the same.

UH> That is part of the RFC5444 multiplexer and not of AODVv2.

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   Implementations MAY choose to temporarily delay transmission of
   messages for the purpose of aggregation (into a single packet) or to
   improve performance by using jitter [RFC5148].

5.11.6.  Adding Additional Routing Information to a RteMsg

UH> This section is unclear to me. What is the purpose? What kind of
information would you add? How can this interoperate? By adding
information en-route, end-to-end security is not possible.

   DSR [RFC4728] includes source routes as part of the data of its RREPs
   and RREQs.  Doign so allows additional topology information to be
   flooded along with the RteMsg, and potentially allows updating for
   stale routing information at MANET routers along new paths between
   source and destination.  To maintain this functionality, AODVv2 has
   defined a somewhat more general method that enables inclusion of
   source routes in RteMsgs.

   Appending routing information can alleviate route discovery attempts
   to the nodes whose information is included, if other AODVv2 routers
   use this information to update their routing tables.

   Note that, since the initial merger of DSR with AODV to create this
   protocol, further experimentation has shown that including the
   additional routing information is not always helpful.  Sometimes it
   seems to help, and other times it seems to reduct overall
   performance.

   AODVv2 routers can append routing information to a RteMsg.  This is
   controllable by an option (APPEND_INFORMATION) which SHOULD be
   administratively configurable or controlled according to the traffic
   characteristics of the network.

   Prior to appending an address controlled by this AODVv2 router to a
   RteMsg, ThisNode MAY increment its OwnSeqNum as defined in
   Section 5.1.  If OwnSeqNum is not incremented the appended routing
   information might not be considered preferable, when received by
   nodes with existing routing information.  Incrementation of the
   sequence number when appending information to a RteMsg in transit
   (APPEND_INFORMATION_SEQNUM) SHOULD be administratively configurable.
   Note that, during handling of this RteMsg OwnSeqNum may have already
   been incremented; and in this case OwnSeqNum need not be incremented
   again.

   If an address controlled by this AODVv2 router includes
   ThisNode.Dist, it is set to a number greater than zero (0).

   For added addresses (and their prefixes) not controlled by this
   AODVv2 router, Route.Dist can be included if known.

   The VALIDITY_TIME of routing information for appended address(es)
   MUST be included, to inform routers about when to delete this

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   information.  The VALIDITY_TIME TLV is defined in Section 5.13.3.

   Additional information (e.g.  SeqNum and Dist) about any appended
   address(es) SHOULD be included.

   Note that the routing information about the TargetNode MUST NOT be
   added.  Also, duplicate address entries SHOULD NOT be added.
   Instead, only the best routing information (Section 5.2.1) for a
   particular address SHOULD be included.

   Intermediate nodes obey the following procedures when processing
   AddBlk.AdditionalNode.Address information and other associated TLVs
   that are included with a RteMsg.  For each address (except the
   TargetNode) in the RteMsg that includes AddTLV.Dist information, the
   AddTLV.Dist information MUST be incremented.  If the resulting
   Distance value for the OrigNode is greater than 254, the message is
   discarded.  If the resulting Distance value for another node is
   greater than 254, the associated address and its information are
   removed from the RteMsg.

   After handling the OrigNode's routing information, then each address
   that is not the TargetNode MAY be considered for creating and
   updating routes.  Creating and updating routes to other nodes can
   eliminate RREQ for those IP destinations, in the event that data
   needs to be forwarded to the IP destination(s) now or in the near
   future.

   For each of the additional addresses considered, ThisNode first
   checks that the address is a routable unicast address.  If the
   address is not a unicast address, then the address and all related
   information MUST be removed.

   If the routing table does not have a matching route with a known
   Route.SeqNum for this additional address using longest-prefix
   matching, then a route MAY be created and updated as described in
   Section 5.2.2.  If a route table entry exists with a known
   Route.SeqNum, the incoming routing information is compared with the
   route table entry following the procedure described in Section 5.2.1.
   If the incoming routing information is used, the route table entry
   SHOULD be updated as described in Section 5.2.2.

   If the routing information for an AdditionalNode.Address is not used,
   then it is removed from the RteMsg.

5.12.  Administratively Configured Parameters and Timer Values

   AODVv2 contains several parameters which MUST be administratively
   configured.  The list of these follows:

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              Required Administratively Configured Parameters

   +------------------------+------------------------------------------+
   |          Name          |                Description               |
   +------------------------+------------------------------------------+
   |  RESPONSIBLE_ADDRESSES |  List of addresses or routing prefixes,  |
   |                        |      for which this AODVv2 router is     |
   |                        |  responsible.  If, RESPONSIBLE_ADDRESSES |
   |                        |    is zero, this AODVv2 router is only   |
   |                        |    responsible for its own addresses.    |
   |    AODVv2_INTERFACES   |  List of the interfaces participating in |
   |                        |         AODVv2 routing protocol.         |
   +------------------------+------------------------------------------+

                                  Table 2

   AODVv2 contains a number of timers.  The default timing parameter
   values follow:

                      Default Timing Parameter Values

           +------------------------------+-------------------+
           |             Name             |       Value       |
           +------------------------------+-------------------+
           |         ROUTE_TIMEOUT        |     5 seconds     |
           |     ROUTE_AGE_MIN_TIMEOUT    |      1 second     |
           | ROUTE_SEQNUM_AGE_MAX_TIMEOUT |    600 seconds    |
           |      ROUTE_USED_TIMEOUT      |   ROUTE_TIMEOUT   |
           |     ROUTE_DELETE_TIMEOUT     | 2 * ROUTE_TIMEOUT |
           |     ROUTE_RREQ_WAIT_TIME     |     2 seconds     |
           | UNICAST_MESSAGE_SENT_TIMEOUT |      1 second     |

UH> UNICAST_MESSAGE_SENT_TIMEOUT is never used in this specification

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

                                  Table 3

   The above timing parameter values work well for small and medium
   well-connected networks with moderate topology changes.

UH> That also depends on the traffic patterns, on the lossy-ness of
the links, on the density of the routers etc.

   The timing parameters SHOULD be administratively configurable for the
   network where AODVv2 is used.  Ideally, for networks with frequent
   topology changes the AODVv2 parameters should be adjusted using
   either experimentally determined values or dynamic adaptation.  For
   example, in networks with infrequent topology changes
   ROUTE_USED_TIMEOUT may be set to a much larger value.

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                         Default Parameter Values

   +------------------------+-------+----------------------------------+
   |          Name          | Value |            Description           |
   +------------------------+-------+----------------------------------+
   |      MSG_HOPLIMIT      |   20  |  This value MUST be larger than  |
   |                        |  hops |   the AODVv2 network diameter.   |

UH> How would the network diameter be determined?

   |                        |       |  Otherwise, routing messages may |
   |                        |       |     not reach their intended     |
   |                        |       |           destinations.          |
   | DISCOVERY_ATTEMPTS_MAX |   3   |   The number of route discovery  |
   |                        |       |      attempts to make before     |
   |                        |       |   indicating that a particular   |
   |                        |       |     address is not reachable.    |
   +------------------------+-------+----------------------------------+

                                  Table 4

   In addition to the above parameters and timing values, several
   administrative options exist.  These options have no influence on
   correct routing behavior, although they may potentially reduce AODVv2
   protocol messaging in certain situations.  The default behavior is to
   NOT enable any of these options; and although many of these options
   can be administratively controlled, they may be better served by
   intelligent control.  The following table enumerates several of the
   options.

                    Administratively Controlled Options

   +--------------------------+----------------------------------------+
   |           Name           |               Description              |
   +--------------------------+----------------------------------------+
   |  BUFFER_DURING_DISCOVERY |   Whether and how much data to buffer  |
   |                          |         during route discovery.        |

UH> Whether and how much? Is it a boolean flag or a number?

   | APPEND_EXTRA_UNREACHABLE |      Whether to append additional      |
   |                          |    Unreachable information to RERR.    |
   |  CONTROL_TRAFFIC_LIMITS  |  AODVv2 messaging SHOULD be limited to |
   |                          |     avoid consuming all the network    |
   |                          |               bandwidth.               |

UH> What is the unit or the meaning of this? Bytes per second?

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

                                  Table 5

   Note: several fields have limited size (bits or bytes) these sizes
   and their encoding may place specific limitations on the values that
   can be set.  For example, MsgHdr.HopLimit is a 8-bit field and
   therefore MSG_HOPLIMIT cannot be larger than 255.

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5.13.  IANA Considerations

UH> This is not a valid IANA section. There are no requests for
registries or for TLV code points. There is no allocation policy.
Refer to RFC5526.

   In its default mode of operation, AODVv2 uses the UDP port 269
   [RFC5498] to carry protocol packets.  AODVv2 also uses the link-local
   multicast address LL-MANET-Routers [RFC5498].

   This section specifies several message types, message tlv-types, and
   address tlv-types.

5.13.1.  AODVv2 Message Types Specification

                           AODVv2 Message Types

                   +------------------------+----------+
                   |          Name          |   Type   |
                   +------------------------+----------+
                   |  Route Request (RREQ)  | 10 - TBD |
                   |   Route Reply (RREP)   | 11 - TBD |
                   |   Route Error (RERR)   | 12 - TBD |
                   +------------------------+----------+

                                  Table 6

5.13.2.  Message and Address Block TLV Type Specification

                             Message TLV Types

   +-------------------+------+--------+-------------------------------+
   |        Name       | Type | Length | Value                         |
   +-------------------+------+--------+-------------------------------+
   |  Unicast Response | 10 - |    0   | Indicates to the processing   |
   |      Request      |  TBD | octets | node that the previous hop    |
   |                   |      |        | (IP.SourceAddress) expects a  |
   |                   |      |        | unicast reply message within  |
   |                   |      |        | UNICAST_MESSAGE_SENT_TIMEOUT. |
   |                   |      |        | Any unicast packet will serve |
   |                   |      |        | this purpose, and it MAY be   |
   |                   |      |        | an ICMP REPLY message.  If    |
   |                   |      |        | the reply is not received,    |
   |                   |      |        | then the previous hop can     |
   |                   |      |        | assume that the link is       |
   |                   |      |        | unidirectional and MAY        |
   |                   |      |        | blacklist the link to this    |
   |                   |      |        | node.                         |
   +-------------------+------+--------+-------------------------------+

UH> It is never specified where and how to use this TLV? Is it a
message-specifid TLV? To which registry do you want to add it? What is
the allocation policy? What are the registered type extensions?

                                  Table 7

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5.13.3.  Address Block TLV Specification

                          Address Block TLV Types

   +----------------+------------+----------+--------------------------+
   |      Name      |    Type    |  Length  | Value                    |
   +----------------+------------+----------+--------------------------+
   |     AODVv2     |  10 - TBD  |  up to 2 | The AODVv2 sequence num  |
   |    Sequence    |            |  octets  | associated with this     |
   |     Number     |            |          | address.  The sequence   |
   | (AODVv2SeqNum) |            |          | number may be the last   |
   |                |            |          | known sequence number.   |
   |    Distance    |  11 - TBD  |  up to 2 | A metric of the distance |
   |                |            |  octets  | traversed by the         |
   |                |            |          | information associated   |
   |                |            |          | with this address.       |

UH> How is the distance formatted?

   |  VALIDITY_TIME | 1[RFC5497] |          | The maximum amount of    |
   |                |            |          | time that information    |
   |                |            |          | can be maintained before |
   |                |            |          | being deleted.  The      |
   |                |            |          | VALIDITY_TIME TLV is     |
   |                |            |          | defined in [RFC5497].    |
   +----------------+------------+----------+--------------------------+

                                  Table 8

5.14.  Security Considerations

UH> This will not suffice; see RFC3552 for guidelines how to write
security considerations.

UH> Notably, there is no mention of possible threats to AODVv2. Also,
there is some text to protect messages; but it is impossible to do so,
as messages are changed in transit. Also, since there is no way to
hook in security extensions (such as done in RFC6130) for rejecting
messages, there is currently no security possible for DYMO.

   The objective of the AODVv2 protocol is for each router to
   communicate reachability information to addresses for which it is
   responsible.  Positive routing information (i.e. a route exists) is
   distributed via RteMsgs and negative routing information (i.e. a
   route does not exist) via RERRs.  AODVv2 routers that handle these
   messages store the contained information to properly forward data
   packets, and they generally provide this information to other AODVv2
   routers.

   This section does not mandate any specific security measures.
   Instead, this section describes various security considerations and
   potential avenues to secure AODVv2 routing.

   The most important security mechanisms for AODVv2 routing are
   integrity/authentication and confidentiality.

   In situations where routing information or router identity are
   suspect, integrity and authentication techniques SHOULD be applied to
   AODVv2 messages.

UH> How? Messages change in transit (addresses added or removed etc).

   In these situations, routing information that is
   distributed over multiple hops SHOULD also verify the integrity and

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   identity of information based on originator of the routing
   information.

UH> How?

   A digital signature could be used to identify the source of AODVv2
   messages and information, along with its authenticity.  A nonce or
   timestamp SHOULD also be used to protect against replay attacks.
   S/MIME and OpenPGP are two authentication/integrity protocols that
   could be adapted for this purpose.

   In situations where confidentiality of AODVv2 messages is important,
   cryptographic techniques can be applied.

   In certain situations, for example sending a RREP or RERR, an AODVv2
   router could include proof that it has previously received valid
   routing information to reach the destination, at one point of time in
   the past.  In situations where routers are suspected of transmitting
   maliciously erroneous information, the original routing information
   along with its security credentials SHOULD be included.

   Note that if multicast is used, any confidentiality and integrity
   algorithms used MUST permit multiple receivers to handle the message.

   Routing protocols, however, are prime targets for impersonation
   attacks.  In networks where the node membership is not known, it is
   difficult to determine the occurrence of impersonation attacks, and
   security prevention techniques are difficult at best.  However, when
   the network membership is known and there is a danger of such
   attacks, AODVv2 messages must be protected by the use of
   authentication techniques, such as those involving generation of
   unforgeable and cryptographically strong message digests or digital
   signatures.  While AODVv2 does not place restrictions on the
   authentication mechanism used for this purpose, IPsec Authentication
   Message (AH) is an appropriate choice for cases where the nodes share
   an appropriate security association that enables the use of AH.

UH> That only works for a single hop, not end-to-end, as the IP
packets are not forwarded.

   In particular, routing messages SHOULD be authenticated to avoid
   creation of spurious routes to a destination.  Otherwise, an attacker
   could masquerade as that destination and maliciously deny service to
   the destination and/or maliciously inspect and consume traffic
   intended for delivery to the destination.  RERR messages SHOULD be
   authenticated in order to prevent malicious nodes from disrupting
   active routes between communicating nodes.

   If the mobile nodes in the ad hoc network have pre-established
   security associations, the purposes for which the security
   associations are created should include that of authorizing the
   processing of AODVv2 control packets.  Given this understanding, the
   mobile nodes should be able to use the same authentication mechanisms

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   based on their IP addresses as they would have used otherwise.

5.15.  Acknowledgments

   AODVv2 is a descendant of the design of previous MANET on-demand
   protocols, especially AODV [RFC3561] and DSR [RFC4728].  Changes to
   previous MANET on-demand protocols stem from research and
   implementation experiences.  Thanks to Elizabeth Belding-Royer for
   her long time authorship of AODV.  Additional thanks to Luke Klein-
   Berndt, Pedro Ruiz, Fransisco Ros, Koojana Kuladinithi, Ramon
   Caceres, Thomas Clausen, Christopher Dearlove, Seung Yi, Romain
   Thouvenin, Tronje Krop, Henner Jakob, Alexandru Petrescu, Christoph
   Sommer, Cong Yuan, Lars Kristensen, and Derek Atkins for reviewing of
   AODVv2, as well as several specification suggestions.

   This revision of AODVv2 isolates the minimal base specification and
   other optional features to simplify the process of ensuring
   compatibility with the existing LOADng specification
   [I-D.clausen-lln-loadng] (minimal reactive routing protocol
   specification).  Thanks are due to T. Clausen, A. Colin de Verdiere,
   J. Yi, A. Niktash, Y. Igarashi, Satoh.  H., and U. Herberg for their
   development of LOADng and sharing details for ensuring
   appropriateness of AODVv2 for LLNs.

6.  References

6.1.  Normative References

   [RFC1812]  Baker, F., "Requirements for IP Version 4 Routers",
              RFC 1812, June 1995.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5082]  Gill, V., Heasley, J., Meyer, D., Savola, P., and C.
              Pignataro, "The Generalized TTL Security Mechanism
              (GTSM)", RFC 5082, October 2007.

   [RFC5444]  Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
              "Generalized Mobile Ad Hoc Network (MANET) Packet/Message
              Format", RFC 5444, February 2009.

   [RFC5497]  Clausen, T. and C. Dearlove, "Representing Multi-Value
              Time in Mobile Ad Hoc Networks (MANETs)", RFC 5497,
              March 2009.

   [RFC5498]  Chakeres, I., "IANA Allocations for Mobile Ad Hoc Network

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              (MANET) Protocols", RFC 5498, March 2009.

6.2.  Informative References

   [I-D.clausen-lln-loadng]
              Clausen, T., Verdiere, A., Yi, J., Niktash, A., Igarashi,
              Y., Satoh, H., Herberg, U., Lavenu, C., Lys, T., and C.
              Perkins, "The LLN On-demand Ad hoc Distance-vector Routing
              Protocol - Next Generation (LOADng)",
              draft-clausen-lln-loadng-05 (work in progress), July 2012.

   [Perkins99]
              Perkins, C. and E. Belding-Royer, "Ad hoc On-Demand
              Distance Vector (AODV) Routing", Proceedings of the 2nd
              IEEE Workshop on Mobile Computing Systems and
              Applications, New Orleans, LA, pp. 90-100, February 1999.

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.

   [RFC2501]  Corson, M. and J. Macker, "Mobile Ad hoc Networking
              (MANET): Routing Protocol Performance Issues and
              Evaluation Considerations", RFC 2501, January 1999.

   [RFC3561]  Perkins, C., Belding-Royer, E., and S. Das, "Ad hoc On-
              Demand Distance Vector (AODV) Routing", RFC 3561,
              July 2003.

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, October 2005.

   [RFC4728]  Johnson, D., Hu, Y., and D. Maltz, "The Dynamic Source
              Routing Protocol (DSR) for Mobile Ad Hoc Networks for
              IPv4", RFC 4728, February 2007.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              September 2007.

   [RFC5148]  Clausen, T., Dearlove, C., and B. Adamson, "Jitter
              Considerations in Mobile Ad Hoc Networks (MANETs)",
              RFC 5148, February 2008.

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, July 2008.

   [RFC6130]  Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc
              Network (MANET) Neighborhood Discovery Protocol (NHDP)",
              RFC 6130, April 2011.

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   [RFC6549]  Lindem, A., Roy, A., and S. Mirtorabi, "OSPFv2 Multi-
              Instance Extensions", RFC 6549, March 2012.

   [RFC6621]  Macker, J., "Simplified Multicast Forwarding", RFC 6621,
              May 2012.

Appendix A.  Changes since the Previous Version

   o  Internet-Facing AODVv2 router renamed to be IAR

   o  "Optional Features" section created to contain features not
      required within base specification, including:

   o

      *  Intermediate RREPs (iRREPs): Without iRREP, only the
         destination can respond to a RREQ.

      *  Precursor lists.

      *  An RERR may reporting multiple unreachable nodes.

      *  Message Aggregation.

   o  Sequence number MUST (instead of SHOULD) be set to 1 after
      rollover.

   o  ThisNode MUST (instead of SHOULD) only handle AODVv2 messages from
      adjacent routers.

   o  Clarification that Additional Routing information in RteMsgs is
      optional (MAY) to use.

   o  Clarification that if Additional Routing information in RteMsgs is
      used, then the Route Table Entry SHOULD be updated using normal
      procedures as described in Section 5.2.2.

   o  Clarification in Section 5.4 that nodes may be configured to
      buffer zero packets.

   o  Clarification in Section 5.4 that buffered packets MUST be dropped
      if route discovery fails.

   o  In Section 5.5.1, relax mandate for monitoring connectivity to
      next-hop AODVv2 neighbors (from MUST to SHOULD), in order to allow
      for minimal implementations

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   o  Remove Route.Forwarding flag; identical to "NOT" Route.Broken.

   o  Routing Messages MUST be originated with the MsgHdr.HopLimit set
      to MSG_HOPLIMIT.  Previously, this was not mandated.

   o  Maximum hop count set to 254, with 255 reserved for "unknown".
      Since the current draft only uses hop-count as distance, this is
      also the current maximum distance.

Appendix B.  Shifting Network Prefix Advertisement Between AODVv2
             Routers

   Only one AODVv2 router within a routing region SHOULD be responsible
   for a particular address at any time.  If two AODVv2 routers
   dynamically shift the advertisement of a network prefix, correct
   AODVv2 routing behavior must be observed.  The AODVv2 router adding
   the new network prefix must wait for any existing routing information
   about this network prefix to be purged from the network.  Therefore,
   it must wait at least ROUTER_SEQNUM_AGE_MAX_TIMEOUT after the
   previous AODVv2 router for this address stopped advertising routing
   information on its behalf.

Authors' Addresses

   Charles E. Perkins
   Futurewei Inc.
   2330 Central Expressway
   Santa Clara, CA  95050
   USA

   Phone: +1-408-330-5305
   Email: [email-masked]

   Ian D Chakeres
   CenGen
   9250 Bendix Road North
   Columbia, Maryland  21045
   USA

   Email: [email-masked]
   URI:   http://www.ianchak.com/

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---

From: C Chauvenet <[email-masked]>
Date: Thu, 1 Nov 2012 23:43:00 +0000

Hi, 

> foo1 better than foo2", without any technical argument. That is not

I think it is because chairs proposed 3 options and ask WG to give their opinion on these 3 solutions.
Of course, we could have very deep technical discussions, and expand the message storm on the list  but from what I understood chairs are mostly waiting for opinions on these 3 choices.

Cédric.

> _______________________________________________
> manet mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/manet
>

---

From: Ulrich Herberg <[email-masked]>
Date: Thu, 1 Nov 2012 16:55:47 -0700

Cédric,

On Thu, Nov 1, 2012 at 4:43 PM, C Chauvenet <[email-masked]> wrote:
[...]
> Of course, we could have very deep technical discussions, and expand the message storm on the list  but from what I understood chairs are mostly waiting for opinions on these 3 choices.

Well, I think we need the technical discussions. Otherwise, it's not
productive to say "I prefer option A over B" without stating technical
reasons (and maybe without even having read both drafts). There may be
political rather than technical reasons for such a choice, and we
should absolutely avoid that.

Best regards
Ulrich

---

From: "JP Vasseur (jvasseur)" <[email-masked]>
Date: Fri, 2 Nov 2012 08:04:22 +0000

> should absolutely avoid that.

JP> Indeed. But … that was the questions the chairs asked us to answer.

---

From: "JP Vasseur (jvasseur)" <[email-masked]>
Date: Mon, 5 Nov 2012 01:38:06 +0000

Hi,

I think that we can agree with some of your comments.

Should we start opening tickets and address those points ?

Thanks.

JP.

---

From: Jon Black <[email-masked]>
Date: Sun, 4 Nov 2012 18:07:15 -0800 (PST)

No we should not.  That would be a waste of time if the WG decided to move forward with LOADng.  I do not believe that we have arrived at that a decision.

Jon

________________________________
 From: JP Vasseur (jvasseur) <[email-masked]>
To: Ulrich Herberg <[email-masked]> 
Cc: "<[email-masked]>" <[email-masked]> 
Sent: Sunday, November 4, 2012 6:38 PM
Subject: Re: [manet] DYMO-23 review
 
Hi,

Thanks.

JP.