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Versions: (draft-clausen-manet-olsrv2) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 19 RFC 7181

Mobile Ad hoc Networking (MANET)                              T. Clausen
Internet-Draft                                  LIX, Ecole Polytechnique
Intended status: Standards Track                             C. Dearlove
Expires: September 11, 2009                              BAE Systems ATC
                                                              P. Jacquet
                                                 Project Hipercom, INRIA
                                                  The OLSRv2 Design Team
                                                     MANET Working Group
                                                          March 10, 2009


          The Optimized Link State Routing Protocol version 2
                       draft-ietf-manet-olsrv2-08

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Copyright Notice



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   Copyright (c) 2009 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
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.

Abstract

   This document describes version 2 of the Optimized Link State Routing
   (OLSRv2) protocol.  The protocol embodies an optimization of the
   classical link state algorithm tailored to the requirements of a
   Mobile Ad hoc NETwork (MANET).

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  6
   3.  Applicability Statement  . . . . . . . . . . . . . . . . . . .  7
   4.  Protocol Overview and Functioning  . . . . . . . . . . . . . .  8
   5.  Protocol Parameters and Constants  . . . . . . . . . . . . . . 10
     5.1.  Local History Times  . . . . . . . . . . . . . . . . . . . 11
     5.2.  Message Intervals  . . . . . . . . . . . . . . . . . . . . 11
     5.3.  Advertised Information Validity Times  . . . . . . . . . . 12
     5.4.  Received Message Validity Times  . . . . . . . . . . . . . 13
     5.5.  Jitter . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     5.6.  Hop Limit Parameter  . . . . . . . . . . . . . . . . . . . 14
     5.7.  Willingness  . . . . . . . . . . . . . . . . . . . . . . . 14
     5.8.  Parameter Change Constraints . . . . . . . . . . . . . . . 15
   6.  Information Bases  . . . . . . . . . . . . . . . . . . . . . . 16
     6.1.  Local Information Base . . . . . . . . . . . . . . . . . . 17
       6.1.1.  Originator Set . . . . . . . . . . . . . . . . . . . . 17
       6.1.2.  Local Attached Network Set . . . . . . . . . . . . . . 17
     6.2.  Neighbor Information Base  . . . . . . . . . . . . . . . . 18
     6.3.  Topology Information Base  . . . . . . . . . . . . . . . . 18
       6.3.1.  Advertised Neighbor Set  . . . . . . . . . . . . . . . 19
       6.3.2.  Advertising Remote Router Set  . . . . . . . . . . . . 19
       6.3.3.  Topology Set . . . . . . . . . . . . . . . . . . . . . 20
       6.3.4.  Attached Network Set . . . . . . . . . . . . . . . . . 20
       6.3.5.  Routing Set  . . . . . . . . . . . . . . . . . . . . . 21
     6.4.  Processing and Forwarding Information Base . . . . . . . . 21
       6.4.1.  Received Set . . . . . . . . . . . . . . . . . . . . . 22
       6.4.2.  Processed Set  . . . . . . . . . . . . . . . . . . . . 22
       6.4.3.  Forwarded Set  . . . . . . . . . . . . . . . . . . . . 22
       6.4.4.  Relay Set  . . . . . . . . . . . . . . . . . . . . . . 23
   7.  Message Processing and Forwarding  . . . . . . . . . . . . . . 23



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     7.1.  Actions when Receiving a Message . . . . . . . . . . . . . 24
     7.2.  Message Considered for Processing  . . . . . . . . . . . . 25
     7.3.  Message Considered for Forwarding  . . . . . . . . . . . . 25
   8.  Packets and Messages . . . . . . . . . . . . . . . . . . . . . 27
     8.1.  HELLO Messages . . . . . . . . . . . . . . . . . . . . . . 28
       8.1.1.  HELLO Message TLVs . . . . . . . . . . . . . . . . . . 28
       8.1.2.  HELLO Message Address Block TLVs . . . . . . . . . . . 29
     8.2.  TC Messages  . . . . . . . . . . . . . . . . . . . . . . . 29
       8.2.1.  TC Message TLVs  . . . . . . . . . . . . . . . . . . . 30
       8.2.2.  TC Message Address Block TLVs  . . . . . . . . . . . . 31
   9.  HELLO Message Generation . . . . . . . . . . . . . . . . . . . 31
     9.1.  HELLO Message: Transmission  . . . . . . . . . . . . . . . 32
   10. HELLO Message Processing . . . . . . . . . . . . . . . . . . . 32
     10.1. Updating Willingness . . . . . . . . . . . . . . . . . . . 32
     10.2. Updating MPR Selectors . . . . . . . . . . . . . . . . . . 33
     10.3. Symmetric 1-Hop and 2-Hop Neighborhood Changes . . . . . . 33
   11. TC Message Generation  . . . . . . . . . . . . . . . . . . . . 34
     11.1. TC Message: Transmission . . . . . . . . . . . . . . . . . 35
   12. TC Message Processing  . . . . . . . . . . . . . . . . . . . . 36
     12.1. Invalid Message  . . . . . . . . . . . . . . . . . . . . . 36
     12.2. Initial TC Message Processing  . . . . . . . . . . . . . . 37
     12.3. Initial TC Message Processing  . . . . . . . . . . . . . . 38
       12.3.1. Populating the Advertising Remote Router Set . . . . . 38
       12.3.2. Populating the Topology Set  . . . . . . . . . . . . . 39
       12.3.3. Populating the Attached Network Set  . . . . . . . . . 40
     12.4. Completing TC Message Processing . . . . . . . . . . . . . 40
       12.4.1. Purging the Topology Set . . . . . . . . . . . . . . . 40
       12.4.2. Purging the Attached Network Set . . . . . . . . . . . 41
   13. Information Base Changes . . . . . . . . . . . . . . . . . . . 41
   14. Selecting MPRs . . . . . . . . . . . . . . . . . . . . . . . . 42
   15. Populating Derived Sets  . . . . . . . . . . . . . . . . . . . 43
     15.1. Populating the Relay Set . . . . . . . . . . . . . . . . . 43
     15.2. Populating the Advertised Neighbor Set . . . . . . . . . . 44
   16. Routing Set Calculation  . . . . . . . . . . . . . . . . . . . 44
     16.1. Network Topology Graph . . . . . . . . . . . . . . . . . . 44
     16.2. Populating the Routing Set . . . . . . . . . . . . . . . . 46
     16.3. Routing Set Updates  . . . . . . . . . . . . . . . . . . . 46
   17. Proposed Values for Parameters and Constants . . . . . . . . . 47
     17.1. Local History Time Parameters  . . . . . . . . . . . . . . 47
     17.2. Message Interval Parameters  . . . . . . . . . . . . . . . 47
     17.3. Advertised Information Validity Time Parameters  . . . . . 47
     17.4. Received Message Validity Time Parameters  . . . . . . . . 47
     17.5. Jitter Time Parameters . . . . . . . . . . . . . . . . . . 48
     17.6. Hop Limit Parameter  . . . . . . . . . . . . . . . . . . . 48
     17.7. Willingness Parameter and Constants  . . . . . . . . . . . 48
   18. Sequence Numbers . . . . . . . . . . . . . . . . . . . . . . . 48
   19. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 49
     19.1. Message Types  . . . . . . . . . . . . . . . . . . . . . . 49



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     19.2. Message TLV Types  . . . . . . . . . . . . . . . . . . . . 49
     19.3. Address Block TLV Types  . . . . . . . . . . . . . . . . . 50
   20. Security Considerations  . . . . . . . . . . . . . . . . . . . 51
     20.1. Confidentiality  . . . . . . . . . . . . . . . . . . . . . 51
     20.2. Integrity  . . . . . . . . . . . . . . . . . . . . . . . . 51
     20.3. Interaction with External Routing Domains  . . . . . . . . 53
   21. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 53
   22. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 54
   23. References . . . . . . . . . . . . . . . . . . . . . . . . . . 54
     23.1. Normative References . . . . . . . . . . . . . . . . . . . 54
     23.2. Informative References . . . . . . . . . . . . . . . . . . 55
   Appendix A.  Router Configuration  . . . . . . . . . . . . . . . . 55
   Appendix B.  Example Algorithm for Calculating MPRs  . . . . . . . 56
     B.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . 56
     B.2.  MPR Selection Algorithm for each OLSRv2 Interface  . . . . 57
   Appendix C.  Example Algorithm for Calculating the Routing Set . . 58
     C.1.  Add Local Symmetric Links  . . . . . . . . . . . . . . . . 58
     C.2.  Add Remote Symmetric Links . . . . . . . . . . . . . . . . 59
     C.3.  Add Attached Networks  . . . . . . . . . . . . . . . . . . 60
   Appendix D.  Example Message Layout  . . . . . . . . . . . . . . . 61
   Appendix E.  Constraints . . . . . . . . . . . . . . . . . . . . . 62
   Appendix F.  Flow and Congestion Control . . . . . . . . . . . . . 66





























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1.  Introduction

   The Optimized Link State Routing protocol version 2 (OLSRv2) is an
   update to OLSRv1 as published in [RFC3626].  Compared to [RFC3626],
   OLSRv2 retains the same basic mechanisms and algorithms, while
   providing a more flexible signaling framework and some simplification
   of the messages being exchanged.  Also, OLSRv2 accommodates either
   IPv4 and IPv6 addresses in a compact manner.

   OLSRv2 is developed for mobile ad hoc networks.  It operates as a
   table driven, proactive protocol, i.e. it exchanges topology
   information with other routers in the network regularly.  Each router
   selects a set of its neighbor routers as "MultiPoint Relays" (MPRs).
   Control traffic may be flooded through the network using hop by hop
   forwarding, but where a router only needs to forward control traffic
   directly received from its MPR selectors (routers which have selected
   it as an MPR).  This mechanism, denoted "MPR flooding", provides an
   efficient mechanism for information distribution within the MANET by
   reducing the number of transmissions required.

   Routers selected as MPRs also have a special responsibility when
   declaring link state information in the network.  A sufficient
   requirement for OLSRv2 to provide shortest (lowest hop count) path
   routes to all destinations is that routers declare link state
   information for their MPR selectors, if any.  Additional available
   link state information may be transmitted, e.g. for redundancy.
   Thus, as well as being used to facilitate MPR flooding, use of MPRs
   allows the reduction of the number and size of link state messages,
   and MPRs are used as intermediate routers in multi-hop routes.

   A router selects MPRs from among its one hop neighbors connected by
   "symmetric", i.e. bi-directional, links.  Therefore, selecting routes
   through MPRs automatically avoids the problems associated with data
   packet transfer over uni-directional links (such as the problem of
   not getting link layer acknowledgments at each hop, for link layers
   employing this technique).

   OLSRv2 is developed to work independently from other protocols.
   (Parts of OLSRv2 have been published separately as [RFC5444],
   [timetlv], [RFC5148] and [NHDP] for wider use.)  Likewise, OLSRv2
   makes no assumptions about the underlying link layer.  However,
   OLSRv2 may use link layer information and notifications when
   available and applicable, as described in [NHDP].

   OLSRv2, as OLSRv1, inherits its concept of forwarding and relaying
   from HIPERLAN (a MAC layer protocol) which is standardized by ETSI
   [HIPERLAN], [HIPERLAN2].




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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].

   MANET specific terminology is to be interpreted as described in
   [RFC5444] and [NHDP].

   Additionally, this document uses the following terminology:

   Router  - A MANET router which implements the Optimized Link State
      Routing protocol version 2 as specified in this document.

   OLSRv2 interface  - A MANET interface, running OLSRv2.  Note that all
      references to MANET interfaces in [NHDP] refer to OLSRv2
      interfaces when using [NHDP] as part of OLSRv2.

   Address  - An address, as recorded in the Information Bases specified
      by this protocol, and included in HELLO and TC messages generated
      by this protocol, may be either an address or an address prefix.
      These can be represented as a single address object in a HELLO or
      TC message, as defined by [RFC5444].  An address so represented is
      considered to have a prefix length equal to its length (in bits)
      when considered as an address object, and a similar convention is
      used in the Information Bases specified by this protocol.  Two
      addresses (address objects) are considered equal only if their
      prefix lengths are also equal.

   Willingness  - The willingness of a router is a numerical value
      between WILL_NEVER and WILL_ALWAYS (both inclusive), which
      represents the router's willingness to be selected as an MPR.

   Willing symmetric 1-hop neighbor  - A symmetric 1-hop neighbor of
      this router which has willingness not equal to WILL_NEVER.

   Symmetric strict 2-hop neighbor  - A symmetric 2-hop neighbor of this
      router which is not a symmetric 1-hop neighbor of this router, and
      is a symmetric 1-hop neighbor of a willing symmetric 1-hop
      neighbor of this router.

   Symmetric strict 2-hop neighbor through OLSRv2 interface I  - A
      symmetric strict 2-hop neighbor of this router which is a
      symmetric 1-hop neighbor of a willing symmetric 1-hop neighbor of
      this router via a symmetric link including OLSRv2 interface I.
      This router MAY elect to consider only information received over
      OLSRv2 interface I in making this determination.



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   Symmetric strict 2-hop neighborhood  - The set of the symmetric
      strict 2-hop neighbors of a router.

   Multipoint relay (MPR)  - A router which is selected by its symmetric
      1-hop neighbor, router X, to "re-transmit" all the broadcast
      messages that it receives from router X, provided that the message
      is not a duplicate, and that the hop limit field of the message is
      greater than one.

   MPR selector  - A router which has selected its symmetric 1-hop
      neighbor, router X, as one of its MPRs is an MPR selector of
      router X.

   MPR flooding  - The optimized MANET-wide information distribution
      mechanism, employed by this protocol, in which a message is
      relayed by only a reduced subset of the routers in the network.

   This document employs the same notational conventions as in [RFC5444]
   and [NHDP].

3.  Applicability Statement

   OLSRv2 is a proactive routing protocol for mobile ad hoc networks
   (MANETs) [RFC2501].  The larger and more dense a network, the more
   optimization can be achieved by using MPRs compared to the classic
   link state algorithm.  OLSRv2 enables hop-by-hop routing, i.e. each
   router using its local information provided by OLSRv2 to route
   packets.

   As OLSRv2 continuously maintains routes to all destinations in the
   network, the protocol is beneficial for traffic patterns where the
   traffic is random and sporadic between a large subset of routers, and
   where the (source, destination) pairs are changing over time.  No
   additional control traffic need be generated in this case since
   routes are maintained for all known destinations at all times.  Also,
   since routes are maintained continuously, traffic is subject to no
   delays due to buffering or to route discovery, and consequently no
   data traffic buffering is imposed.

   OLSRv2 supports routers which have multiple interfaces which
   participate in the MANET using OLSRv2.  As described in [NHDP], each
   OLSRv2 interface may have one or more network addresses (which may
   have prefix lengths).  OLSRv2, additionally, supports routers which
   have non-OLSRv2 interfaces which may be local to a router or which
   can serve as gateways towards other networks.

   OLSRv2 uses the format specified in [RFC5444] for all messages and
   packets.  OLSRv2 is thereby able to allow for extensions via



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   "external" and "internal" extensibility.  External extensibility
   allows a protocol extension to specify and exchange new Message
   Types, which can be forwarded and delivered correctly even by routers
   which do not support that extension.  Internal extensibility allows a
   protocol extension to define additional attributes to be carried
   embedded in the standard OLSRv2 control messages detailed in this
   specification (or any new Message Types defined by other protocol
   extensions) using the TLV mechanism specified in [RFC5444], while
   still allowing routers not supporting that extension to forward
   messages including the extension, and to process messages ignoring
   the extension.

   The OLSRv2 neighborhood discovery protocol using HELLO messages is
   specified in [NHDP].  This neighborhood discovery protocol serves to
   ensure that each OLSRv2 router has available continuously updated
   Information Bases describing the router's 1-hop and symmetric 2-hop
   neighbors.  This neighborhood discovery protocol, which also uses
   [RFC5444], is extended in this document by the addition of MPR
   information.

   OLSRv2 does not make any assumption about router addresses, other
   than that each router is assumed to have at least one unique and
   routable IP address for each interface that it has which participates
   in the MANET.

   OLSRv2 can, as does [NHDP], use the link local multicast address "LL-
   MANET-Routers", and either the "manet" UDP port or the "manet" IP
   protocol number, all as specified in [manet-iana].

4.  Protocol Overview and Functioning

   OLSRv2 is a proactive routing protocol for mobile ad hoc networks.
   The protocol inherits the stability of a link state algorithm and has
   the advantage of having routes immediately available when needed due
   to its proactive nature.  OLSRv2 is an optimization of the classical
   link state protocol, tailored for mobile ad hoc networks.  The main
   tailoring and optimizations of OLSRv2 are:

   o  Unacknowledged transmission of all control messages; control
      messages are sent periodically, but may also be sent in response
      to changes in the local neighborhood.

   o  MPR flooding for MANET-wide link state information distribution.

   o  Partial topology maintenance - each router knows only a subset of
      the links in the network, sufficient for a minimum hop route to
      all destinations.




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   The MPR flooding and partial topology maintenance are based on the
   concept of MultiPoint Relays (MPRs), selected independently by
   routers based on the symmetric 1-hop and 2-hop neighbor information
   maintained using [NHDP].

   Using the message exchange format [RFC5444] and the neighborhood
   discovery protocol [NHDP], OLSRv2 also contains the following main
   components:

   o  A TLV, to be included within the HELLO messages of [NHDP],
      allowing a router to signal MPR selection.

   o  The optimized mechanism for MANET-wide information distribution,
      denoted "MPR flooding".

   o  A specification of MANET-wide signaling, denoted TC (Topology
      Control) messages.  TC messages in OLSRv2 serve to:

      *  inject link state information into the entire MANET;

      *  inject addresses of hosts and networks for which they may serve
         as a gateway into the entire network.

      TC messages are emitted periodically, thereby allowing routers to
      continuously track changes in the network.  Incomplete TC messages
      may be used to report additions to advertised information without
      repeating unchanged information.  Some TC messages may be MPR
      flooded over only part of the network, allowing a router to ensure
      that nearer routers are kept more up to date than distant routers,
      such as is used in Fisheye State Routing [FSR] and Fuzzy Sighted
      Link State routing [FSLS].

   Each router in the network selects a set of MPRs.  The MPRs of a
   router X may be any subset of router X's willing symmetric 1-hop
   neighbors, such that every router in the symmetric strict 2-hop
   neighborhood of router X has a symmetric link to at least one of
   router X's MPRs.  The MPRs of a router may thus be said to "cover"
   the router's symmetric strict 2-hop neighborhood.  Each router also
   maintains information about the set of symmetric 1-hop neighbors that
   have selected it as an MPR, its MPR selectors.

   As long as the condition above is satisfied, any algorithm selecting
   MPRs is acceptable in terms of implementation interoperability.
   However if smaller sets of MPRs are selected then the greater the
   efficiency gains that are possible.  An analysis and examples of MPR
   selection algorithms is given in [MPR].

   A router may independently determine and advertise its willingness to



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   be selected as an MPR.  A router may advertise that it always should
   be selected as an MPR or that it should never be selected as an MPR.
   In the latter case, the router will neither relay control messages,
   nor will that router be included as an intermediate router in any
   routing table calculations.  Use of variable willingness is most
   effective in dense networks.

   In OLSRv2, actual efficiency gains are based on the sizes of each
   router's Relay Set, the set of symmetric 1-hop neighbors for which it
   is to relay broadcast traffic, and its Advertised Neighbor Set, the
   set of symmetric 1-hop neighbors for which it is to advertise link
   state information into the network in TC messages.  Each of these
   sets MUST contain all MPR selectors, and MAY contain additional
   routers.  If the Advertised Neighbor Set is empty, TC messages are
   not generated by that router, unless needed for gateway reporting, or
   for a short period to accelerate the removal of outdated link state
   information.

   OLSRv2 is designed to work in a completely distributed manner and
   does not depend on any central entity.  The protocol does not require
   reliable transmission of control messages; each router sends control
   messages periodically, and can therefore sustain a reasonable loss of
   some such messages.  Such losses may occur frequently in radio
   networks due to collisions or other transmission problems.  OLSRv2
   MAY use "jitter", randomized adjustments to message transmission
   times, to reduce the incidence of collisions [RFC5148].

   OLSRv2 does not require sequenced delivery of messages.  Each TC
   message contains a sequence number which is incremented for each
   message.  Thus the recipient of a TC message can, if required, easily
   identify which information is more recent - even if messages have
   been re-ordered while in transmission.

   OLSRv2 only interacts with IP through routing table management.
   OLSRv2 sends its control messages as described in [RFC5444] and
   [NHDP].

5.  Protocol Parameters and Constants

   The parameters and constants used in this specification are those
   defined in [NHDP] plus those defined in this section.  The separation
   in [NHDP] into interface parameters, router parameters and constants
   is also used in OLSRv2, however all but one (RX_HOLD_TIME) of the
   parameters added by OLSRv2 are router parameters.  Parameters may be
   classified into the following categories:






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   o  Local history times

   o  Message intervals

   o  Advertised information validity times

   o  Received message validity times

   o  Jitter times

   o  Hop limits

   o  Willingness

   In addition, constants for particular cases of a router's willingness
   to be an MPR are defined.  These parameters and constants are
   detailed in the following sections.  As for the parameters in [NHDP],
   parameters defined in this document may be changed dynamically by a
   router, and need not be the same on different routers, even in the
   same MANET, or on different interfaces of the same router (for
   interface parameters).

5.1.  Local History Times

   The following router parameter manages the time for which local
   information is retained:

   O_HOLD_TIME  - is used to define the time for which a recently used
      and replaced originator address is used to recognize the router's
      own messages.

   The following constraint applies to this parameter:

   o  O_HOLD_TIME >= 0

5.2.  Message Intervals

   The following router parameters regulate TC message transmissions by
   a router.  TC messages are usually sent periodically, but MAY also be
   sent in response to changes in the router's Advertised Neighbor Set
   and Local Attached Network Set. With a larger value of the parameter
   TC_INTERVAL, and a smaller value of the parameter TC_MIN_INTERVAL, TC
   messages may more often be transmitted in response to changes in a
   highly dynamic network.  However because a router has no knowledge
   of, for example, routers remote to it (i.e. beyond 2 hops away)
   joining the network, TC messages MUST NOT be sent purely
   responsively.




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   TC_INTERVAL  - is the maximum time between the transmission of two
      successive TC messages by this router.  When no TC messages are
      sent in response to local network changes (by design, or because
      the local network is not changing) then TC messages SHOULD be sent
      at a regular interval TC_INTERVAL, possibly modified by jitter as
      specified in [RFC5148].

   TC_MIN_INTERVAL  - is the minimum interval between transmission of
      two successive TC messages by this router.  (This minimum interval
      MAY be modified by jitter, as specified in [RFC5148].)

   The following constraints apply to these parameters:

   o  TC_INTERVAL > 0

   o  TC_MIN_INTERVAL >= 0

   o  TC_INTERVAL >= TC_MIN_INTERVAL

   o  If INTERVAL_TIME TLVs as defined in [timetlv] are included in TC
      messages, then TC_INTERVAL MUST be representable as described in
      [timetlv].

5.3.  Advertised Information Validity Times

   The following router parameters manage the validity time of
   information advertised in TC messages:

   T_HOLD_TIME  - is used to define the minimum value in the
      VALIDITY_TIME TLV included in all TC messages sent by this router.
      If a single value of parameter TC_HOP_LIMIT (see Section 5.6) is
      used then this will be the only value in that TLV.

   A_HOLD_TIME  - is the period during which TC messages are sent after
      they no longer have any advertised information to report, but are
      sent in order to accelerate outdated information removal by other
      routers.

   The following constraints apply to these parameters:

   o  T_HOLD_TIME > 0

   o  A_HOLD_TIME >= 0

   o  T_HOLD_TIME >= TC_INTERVAL

   o  If TC messages can be lost, then both T_HOLD_TIME and A_HOLD_TIME
      SHOULD be significantly greater than TC_INTERVAL; a value >= 3 x



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      TC_INTERVAL is RECOMMENDED.

   o  T_HOLD_TIME MUST be representable as described in [timetlv].

5.4.  Received Message Validity Times

   The following parameters manage the validity time of recorded
   received message information:

   RX_HOLD_TIME  - is an interface parameter, and is the period after
      receipt of a message by the appropriate OLSRv2 interface of this
      router for which that information is recorded, in order that the
      message is recognized as having been previously received on this
      OLSRv2 interface.

   P_HOLD_TIME  - is a router parameter, and is the period after receipt
      of a message which is processed by this router for which that
      information is recorded, in order that the message is not
      processed again if received again.

   F_HOLD_TIME  - is a router parameter, and is the period after receipt
      of a message which is forwarded by this router for which that
      information is recorded, in order that the message is not
      forwarded again if received again.

   The following constraints apply to these parameters:

   o  RX_HOLD_TIME > 0

   o  P_HOLD_TIME > 0

   o  F_HOLD_TIME > 0

   o  All of these parameters SHOULD be greater than the maximum
      difference in time that a message may take to traverse the MANET,
      taking into account any message forwarding jitter as well as
      propagation, queuing, and processing delays.

5.5.  Jitter

   If jitter, as defined in [RFC5148], is used then these parameters are
   as follows:

   TP_MAXJITTER  - represents the value of MAXJITTER used in [RFC5148]
      for periodically generated TC messages sent by this router.






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   TT_MAXJITTER  - represents the value of MAXJITTER used in [RFC5148]
      for externally triggered TC messages sent by this router.

   F_MAXJITTER  - represents the default value of MAXJITTER used in
      [RFC5148] for messages forwarded by this router.  However before
      using F_MAXJITTER a router MAY attempt to deduce a more
      appropriate value of MAXJITTER, for example based on any
      INTERVAL_TIME or VALIDITY_TIME TLVs contained in the message to be
      forwarded.

   For constraints on these parameters see [RFC5148].

5.6.  Hop Limit Parameter

   The parameter TC_HOP_LIMIT is the hop limit set in each TC message.
   TC_HOP_LIMIT MAY be a single fixed value, or MAY be different in TC
   messages sent by the same router.  However each other router, at any
   hop count distance, SHOULD see a regular pattern of TC messages, in
   order that meaningful values of INTERVAL_TIME and VALIDITY_TIME TLVs
   at each hop count distance can be included as defined in [timetlv].
   Thus the pattern of TC_HOP_LIMIT SHOULD be defined to have this
   property.  For example the repeating pattern (255 4 4) satisfies this
   property (having period TC_INTERVAL at hop counts up to 4, inclusive,
   and 3 x TC_INTERVAL at hop counts greater than 4), but the repeating
   pattern (255 255 4 4) does not satisfy this property because at hop
   counts greater than 4, message intervals are alternately TC_INTERVAL
   and 3 x TC_INTERVAL.

   The following constraints apply to this parameter:

   o  The maximum value of TC_HOP_LIMIT >= the network diameter in hops,
      a value of 255 is RECOMMENDED.

   o  All values of TC_HOP_LIMIT >= 2.

5.7.  Willingness

   Each router has a WILLINGNESS parameter, which MUST be in the range
   WILL_NEVER to WILL_ALWAYS, inclusive, and represents its willingness
   to be an MPR, and hence its willingness to forward messages and be an
   intermediate router on routes.  If a router has WILLINGNESS =
   WILL_NEVER it does not perform these tasks.  A MANET using OLSRv2
   with too many routers with WILLINGNESS = WILL_NEVER will not
   function; it MUST be ensured, by administrative or other means, that
   this does not happen.

   Routers MAY have different WILLINGNESS values; however the three
   constants WILL_NEVER, WILL_DEFAULT and WILL_ALWAYS MUST have the



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   values defined in Section 5.7.  (Use of WILLINGNESS = WILL_DEFAULT
   allows a router to avoid including an MPR_WILLING TLV in its TC
   messages, use of WILLINGNESS = WILL_ALWAYS means that a router will
   always be selected as an MPR by all symmetric 1-hop neighbors.)

   The following constraints apply to this parameter:

   o  WILLINGNESS >= WILL_NEVER

   o  WILLINGNESS <= WILL_ALWAYS

5.8.  Parameter Change Constraints

   This section presents guidelines, applicable if protocol parameters
   are changed dynamically.

   O_HOLD_TIME

      *  If O_HOLD_TIME for a router changes, then O_time for all
         Originator Tuples MAY be changed.

   TC_INTERVAL

      *  If the TC_INTERVAL for a router increases, then the next TC
         message generated by this router MUST be generated according to
         the previous, shorter, TC_INTERVAL.  Additional subsequent TC
         messages MAY be generated according to the previous, shorter,
         TC_INTERVAL.

      *  If the TC_INTERVAL for a router decreases, then the following
         TC messages from this router MUST be generated according to the
         current, shorter, TC_INTERVAL.

   RX_HOLD_TIME

      *  If RX_HOLD_TIME for an OLSRv2 interface changes, then RX_time
         for all Received Tuples for that OLSRv2 interface MAY be
         changed.

   P_HOLD_TIME

      *  If P_HOLD_TIME changes, then P_time for all Processed Tuples
         MAY be changed.








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   F_HOLD_TIME

      *  If F_HOLD_TIME changes, then F_time for all Forwarded Tuples
         MAY be changed.

   TP_MAXJITTER

      *  If TP_MAXJITTER changes, then the periodic TC message schedule
         on this router MAY be changed immediately.

   TT_MAXJITTER

      *  If TT_MAXJITTER changes, then externally triggered TC messages
         on this router MAY be rescheduled.

   F_MAXJITTER

      *  If F_MAXJITTER changes, then TC messages waiting to be
         forwarded with a delay based on this parameter MAY be
         rescheduled.

   TC_HOP_LIMIT

      *  If TC_HOP_LIMIT changes, and the router uses multiple values
         after the change, then message intervals and validity times
         included in TC messages MUST be respected.  The simplest way to
         do this is to start any new repeating pattern of TC_HOP_LIMIT
         values with its largest value.

6.  Information Bases

   Each router maintains the Information Bases described in the
   following sections.  These are used for describing the protocol in
   this document.  An implementation of this protocol MAY maintain this
   information in the indicated form, or in any other organization which
   offers access to this information.  In particular note that it is not
   necessary to remove Tuples from Sets at the exact time indicated,
   only to behave as if the Tuples were removed at that time.

   The purpose of OLSRv2 is to determine the Routing Set, which may be
   used to update IP's Routing Table, providing "next hop" routing
   information for IP datagrams.  OLSRv2 maintains the following
   Information Bases:








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   Local Information Base  - as defined in [NHDP], extended by the
      addition of an Originator Set, defined in Section 6.1.1 and a
      Local Attached Network Set, defined in Section 6.1.2.

   Interface Information Bases  - as defined in [NHDP], one Interface
      Information Base for each OLSRv2 interface.

   Neighbor Information Base  - as defined in [NHDP], extended by the
      addition of three elements to each Neighbor Tuple, as defined in
      Section 6.2.

   Topology Information Base  - this Information Base is specific to
      OLSRv2, and is defined in Section 6.3.

   Processing and Forwarding Information Base  - this Information Base
      is specific to OLSRv2, and is defined in Section 6.4.

   The ordering of sequence numbers, when considering which is the
   greater, is as defined in Section 18.

6.1.  Local Information Base

   The Local Information Base as defined in [NHDP] is extended by the
   addition of an Originator Set, defined in Section 6.1.1, and a Local
   Attached Network Set, defined in Section 6.1.2.

6.1.1.  Originator Set

   A router's Originator Set records addresses that were recently used
   as originator addresses by this router.  If a router's originator
   address is immutable then this set is always empty and MAY be
   omitted.  It consists of Originator Tuples:

      (O_orig_addr, O_time)

   where:

   O_orig_addr  is a recently used originator address;

   O_time  specifies the time at which this Tuple expires and MUST be
      removed.

6.1.2.  Local Attached Network Set

   A router's Local Attached Network Set records its local non-OLSRv2
   interfaces via which it can act as gateways to other networks.  The
   Local Attached Network Set is not modified by this protocol.  This
   protocol MAY respond to changes to the Local Attached Network Set,



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   which MUST reflect corresponding changes in the router's status.  It
   consists of Local Attached Network Tuples:

      (AL_net_addr, AL_dist)

   where:

   AL_net_addr  is the network address of an attached network which can
      be reached via this router.

   AL_dist  is the number of hops to the network with address
      AL_net_addr from this router.

   Attached networks local to this router SHOULD be treated as local
   non-MANET interfaces, and added to the Local Interface Set, as
   specified in [NHDP], rather than being added to the Local Attached
   Network Set.

   An attached network MAY also be attached to other routers.

   It is not the responsibility of OLSRv2 to maintain routes from this
   router to networks recorded in the Local Attached Network Set.

   Local Attached Neighbor Tuples are removed from the Local Attached
   Network Set only when the routers' local attached network
   configuration changes, i.e. they are not subject to timer-based
   expiration or changes due to received messages.

6.2.  Neighbor Information Base

   Each Neighbor Tuple in the Neighbor Set, defined in [NHDP], has these
   additional elements:

   N_willingness  is the router's willingness to be selected as an MPR,
      in the range from WILL_NEVER to WILL_ALWAYS, both inclusive;

   N_mpr  is a boolean flag, describing if this neighbor is selected as
      an MPR by this router;

   N_mpr_selector  is a boolean flag, describing if this neighbor has
      selected this router as an MPR, i.e. is an MPR selector of this
      router.

6.3.  Topology Information Base

   The Topology Information Base stores information required for the
   generation and processing of TC messages, and information received in
   TC messages.  The Advertised Neighbor Set contains interface



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   addresses of symmetric 1-hop neighbors which are to be reported in TC
   messages.  The Advertising Remote Router Set, the Topology Set and
   the Attached Network Set record information received in TC messages.

   Additionally, a Routing Set is maintained, derived from the
   information recorded in the Neighborhood Information Base, Topology
   Set, Attached Network Set and Advertising Remote Router Set.

6.3.1.  Advertised Neighbor Set

   A router's Advertised Neighbor Set contains interface addresses of
   symmetric 1-hop neighbors which are to be advertised through TC
   messages.  It consists of Advertised Neighbor Tuples:

      (A_neighbor_iface_addr)

   In addition, an Advertised Neighbor Set Sequence Number (ANSN) is
   maintained.  Each time the Advertised Neighbor Set is updated, the
   ANSN MUST be incremented.  The ANSN MUST also be incremented if there
   is a change to the set of Local Attached Network Tuples that are to
   be advertised in the router's TC messages.

   The Advertised Neighbor Set for a router is derived from the Neighbor
   Set of that same router, and so Advertised Neighbor Tuples are
   removed when, for example, the corresponding Neighbor Tuples in the
   Neighbor Set are removed.  Advertised Neighbor Tuples are not subject
   to timer-based expiration.

6.3.2.  Advertising Remote Router Set

   A router's Advertising Remote Router Set records information
   describing each remote router in the network that transmits TC
   messages.  It consists of Advertising Remote Router Tuples:

      (AR_orig_addr, AR_seq_number, AR_iface_addr_list, AR_time)

   where:

   AR_orig_addr  is the originator address of a received TC message,
      note that this does not include a prefix length;

   AR_seq_number  is the greatest ANSN in any TC message received which
      originated from the router with originator address AR_orig_addr
      (i.e. which contributed to the information contained in this
      Tuple);






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   AR_iface_addr_list  is an unordered list of the interface addresses
      of the router with originator address AR_orig_addr;

   AR_time  is the time at which this Tuple expires and MUST be removed.

6.3.3.  Topology Set

   A router's Topology Set records topology information about the
   network.  It consists of Topology Tuples:

      (T_dest_iface_addr, T_orig_addr, T_seq_number, T_time)

   where:

   T_dest_iface_addr  is an interface address of a destination router,
      which may be reached in one hop from the router with originator
      address T_orig_addr;

   T_orig_addr  is the originator address of a router which is the last
      hop on a path towards the router with interface address
      T_dest_iface_addr, note that this does not include a prefix
      length;

   T_seq_number  is the greatest ANSN in any TC message received which
      originated from the router with originator address T_orig_addr
      (i.e. which contributed to the information contained in this
      Tuple);

   T_time  specifies the time at which this Tuple expires and MUST be
      removed.

6.3.4.  Attached Network Set

   A router's Attached Network Set records information about networks
   attached to other routers.  It consists of Attached Network Tuples:

      (AN_net_addr, AN_orig_addr, AN_dist, AN_seq_number, AN_time)

   where:

   AN_net_addr  is the network address of an attached network, which may
      be reached via the router with originator address AN_orig_addr;

   AN_orig_addr  is the originator address of a router which can act as
      gateway to the network with address AN_net_addr, note that this
      does not include a prefix length;





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   AN_dist  is the number of hops to the network with address
      AN_net_addr from the router with originator address AN_orig_addr;

   AN_seq_number  is the greatest ANSN in any TC message received which
      originated from the router with originator address AN_orig_addr
      (i.e. which contributed to the information contained in this
      Tuple);

   AN_time  specifies the time at which this Tuple expires and MUST be
      removed.

6.3.5.  Routing Set

   A router's Routing Set records the selected path to each destination
   for which a route is known.  It consists of Routing Tuples:

      (R_dest_addr, R_next_iface_addr, R_dist, R_local_iface_addr)

   where:

   R_dest_addr  is the address of the destination, either the address of
      an interface of a destination router, or the network address of an
      attached network;

   R_next_iface_addr  is the OLSRv2 interface address of the "next hop"
      on the selected path to the destination;

   R_dist  is the number of hops on the selected path to the
      destination;

   R_local_iface_addr  is the address of the local OLSRv2 interface over
      which a packet MUST be sent to reach the destination by the
      selected path.

   The Routing Set for a router is derived from the contents of the
   other sets of the router, and is updated (Routing Tuples added or
   removed) when routing paths are calculated.  Routing Tuples are not
   subject to timer-based expiration.

6.4.  Processing and Forwarding Information Base

   The Processing and Forwarding Information Base records information
   required to ensure that a message is processed at most once and is
   forwarded at most once per OLSRv2 interface of a router, using MPR
   flooding.






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6.4.1.  Received Set

   A router has a Received Set per local OLSRv2 interface.  Each
   Received Set records the signatures of messages which have been
   received over that OLSRv2 interface.  Each consists of Received
   Tuples:

      (RX_type, RX_orig_addr, RX_seq_number, RX_time)

   where:

   RX_type  is the received Message Type;

   RX_orig_addr  is the originator address of the received message;

   RX_seq_number  is the message sequence number of the received
      message;

   RX_time  specifies the time at which this Tuple expires and MUST be
      removed.

6.4.2.  Processed Set

   A router's Processed Set records signatures of messages which have
   been processed by the router.  It consists of Processed Tuples:

      (P_type, P_orig_addr, P_seq_number, P_time)

   where:

   P_type  is the processed Message Type;

   P_orig_addr  is the originator address of the processed message;

   P_seq_number  is the message sequence number of the processed
      message;

   P_time  specifies the time at which this Tuple expires and MUST be
      removed.

6.4.3.  Forwarded Set

   A router's Forwarded Set records signatures of messages which have
   been processed by the router.  It consists of Forwarded Tuples:

      (F_type, F_orig_addr, F_seq_number, F_time)

   where:



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   F_type  is the forwarded Message Type;

   F_orig_addr  is the originator address of the forwarded message;

   F_seq_number  is the message sequence number of the forwarded
      message;

   F_time  specifies the time at which this Tuple expires and MUST be
      removed.

6.4.4.  Relay Set

   A router has a Relay Set per local OLSRv2 interface.  Each Relay Set
   records the OLSRv2 interface addresses of symmetric 1-hop neighbors,
   such that the router is to forward messages received from those
   neighbors' OLSRv2 interfaces, on that local OLSRv2 interface, if not
   otherwise excluded from forwarding that message (e.g. by it having
   been previously forwarded).  It consists of Relay Tuples:

      (RY_neighbor_iface_addr)

   The Relay Set for an interface is derived from the Link Set for the
   same interface, and so Relay Tuples are removed when the
   corresponding Link Tuples in the Link Set of this interface are
   removed, or when processing otherwise suggests their removal.  Relay
   Tuples are not subject to timer-based expiration.

7.  Message Processing and Forwarding

   On receiving a packet, as defined in [RFC5444], a router divides the
   packet into the Packet Header and messages.  OLSRv2 defines, and
   hence owns, the TC Message Type, and hence receives all TC messages.
   OLSRv2 is responsible for determining whether a TC message is to be
   processed (updating Information Bases) and/or forwarded.

   OLSRv2 also receives HELLO messages, which are defined, and hence
   owned, by [NHDP].  Received HELLO messages MUST be made available to
   OLSRv2 when received on an OLSRv2 interface and after NHDP has
   completed its processing thereof.  OLSRv2 also processes HELLO
   messages, OLSRv2 does not forward HELLO messages.

   Extensions to OLSRv2 which define, and hence own, other Messages
   Types, MAY manage the processing and/or forwarding of these messages
   using the same mechanism as for TC messages.  These mechanisms
   contain elements (P_type, RX_type, F_type) required only for such
   usage.

   The processing selection and forwarding mechanisms are designed to



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   only need to parse the Message Header in order to determine whether a
   message is to be processed and/or forwarded, and not to have to parse
   the Message Body even if the message is forwarded (but not
   processed).  An implementation MAY either only parse the Message Body
   if necessary, or MAY always parse the Message Body.  An
   implementation MUST discard the message silently if it is unable to
   parse the Message Header or (if attempted) the Message Body.

   OLSRv2 does not require any part of the Packet Header.

7.1.  Actions when Receiving a Message

   If the router receives a HELLO message from NHDP, then the message is
   processed according to Section 10.

   A router MUST perform the following tasks for each received TC
   message or other Message Type defined by an extension to OLSRv2 and
   specified to use this process:

   1.  If the router recognizes from the originator address of the
       message that the message is one which the receiving router itself
       originated (i.e. is the current originator address of the router,
       or is an O_orig_addr in an Originator Tuple) then the message
       MUST be silently discarded.

   2.  Otherwise:

       1.  Otherwise:

           1.  If the message is of a type which may be processed,
               including being a TC message, then the message is
               considered for processing according to Section 7.2, AND;

           2.  If for the message is of a type which may be forwarded,
               including being a TC message, AND:

               -  <msg-hop-limit> is present and <msg-hop-limit> > 1,
                  AND;

               -  <msg-hop-count> is not present or <msg-hop-count> <
                  255

               then the message is considered for forwarding according
               to Section 7.3.







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7.2.  Message Considered for Processing

   If a message (the "current message") is considered for processing,
   then the following tasks MUST be performed:

   1.  If a Processed Tuple exists with:

       *  P_type = the Message Type of the current message, AND;

       *  P_orig_addr = the originator address of the current message,
          AND;

       *  P_seq_number = the message sequence number of the current
          message;

       then the current message MUST NOT be processed.

   2.  Otherwise:

       1.  Create a Processed Tuple with:

           +  P_type := the Message Type of the current message;

           +  P_orig_addr := the originator address of the current
              message;

           +  P_seq_number := the sequence number of the current
              message;

           +  P_time := current time + P_HOLD_TIME.

       2.  Process the current message according to its type.  For a TC
           message this is as defined in Section 12.

7.3.  Message Considered for Forwarding

   If a message (the "current message") is considered for forwarding,
   then the following tasks MUST be performed:

   1.  If the sending interface address (the source address of the IP
       datagram containing the current message) does not match (taking
       into account any address prefix) an OLSRv2 interface address in
       an L_neighbor_iface_addr_list of a Link Tuple, with L_status =
       SYMMETRIC, in the Link Set for the OLSRv2 interface on which the
       current message was received (the "receiving interface") then the
       current message MUST be silently discarded.





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   2.  Otherwise:

       1.  If a Received Tuple exists in the Received Set for the
           receiving interface, with:

           +  RX_type = the Message Type of the current message, AND;

           +  RX_orig_addr = the originator address of the current
              message, AND;

           +  RX_seq_number = the sequence number of the current
              message;

           then the current message MUST be silently discarded.

       2.  Otherwise:

           1.  Create a Received Tuple in the Received Set for the
               receiving interface with:

               -  RX_type := the Message Type of the current message;

               -  RX_orig_addr := originator address of the current
                  message;

               -  RX_seq_number := sequence number of the current
                  message;

               -  RX_time := current time + RX_HOLD_TIME.

           2.  If a Forwarded Tuple exists with:

               -  F_type = the Message Type of the current message, AND;

               -  F_orig_addr = the originator address of the current
                  message, AND;

               -  F_seq_number = the sequence number of the current
                  message.

               then the current message MUST be silently discarded.

           3.  Otherwise if the sending interface address matches
               (taking account of any address prefix) an
               RY_neighbor_iface_addr in the Relay Set for the receiving
               interface, then:





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               1.  Create a Forwarded Tuple with:

                   o  F_type := the Message Type of the current message;

                   o  F_orig_addr := originator address of the current
                      message;

                   o  F_seq_number := sequence number of the current
                      message;

                   o  F_time := current time + F_HOLD_TIME.

               2.  The Message Header of the current message is modified
                   by:

                   o  if present, decrement <msg-hop-limit> in the
                      Message Header by 1, AND;

                   o  if present, increment <msg-hop-count> in the
                      Message Header by 1.

               3.  For each OLSRv2 interface of the router, include the
                   message in a packet to be transmitted on that OLSRv2
                   interface, as described in Section 8.  This packet
                   MAY contain other forwarded messages and/or messages
                   generated by this router, including by other
                   protocols using [RFC5444].  Forwarded messages MAY be
                   jittered as described in [RFC5148].  The value of
                   MAXJITTER used in jittering a forwarded message MAY
                   be based on information in that message (in
                   particular any INTERVAL_TIME or VALIDITY_TIME TLVs in
                   that message) or otherwise SHOULD be with a maximum
                   delay of F_MAXJITTER.  A router MAY modify the jitter
                   applied to a message in order to more efficiently
                   combine messages in packets, as long as the maximum
                   jitter is not exceeded.

8.  Packets and Messages

   The packet and message format used by OLSRv2 is defined in [RFC5444].
   Except as otherwise noted, options defined in [RFC5444] may be freely
   used, in particular alternative formats defined by packet, message,
   Address Block and TLV flags.

   OLSRv2 defines and owns the TC Message Type.  OLSRv2 also modifies
   HELLO messages (owned by [NHDP]) by adding TLVs to these messages
   when sent over OLSRv2 interfaces, and processes these HELLO messages,
   subsequent to their processing by NHDP.  Extensions to OLSRv2 MAY



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   define additional Message Types to be handled similarly to TC
   messages.

   Routers using OLSRv2 exchange information through messages.  One or
   more messages sent by a router at the same time SHOULD be combined
   into a single packet.  These messages may have originated at the
   sending router, or have originated at another router and are
   forwarded by the sending router.  Messages with different originating
   routers MAY be combined for transmission within the same packet.
   Messages from other protocols defined using [RFC5444] MAY be combined
   for transmission within the same packet.

   The remainder of this section defines, within the framework of
   [RFC5444], Message Types and TLVs specific to OLSRv2.  All references
   in this specification to TLVs that do not indicate a type extension,
   assume Type Extension = 0.  TLVs in processed messages with a type
   extension which is neither zero as so assumed, nor a specifically
   indicated non-zero type extension, are ignored.

8.1.  HELLO Messages

   A HELLO message in OLSRv2 is generated as specified in [NHDP].  In
   addition, an OLSRv2 router MUST be able to modify such messages,
   prior to these being sent on an OLSRv2 interface, so that such HELLO
   messages:

   o  MUST include TLV(s) with Type := MPR associated with all OLSRv2
      interface addresses that:

      *  are included in the HELLO message associated with a TLV with
         Type = LINK_STATUS and Value = SYMMETRIC; AND

      *  are included in a Neighbor Tuple with N_mpr = true.

   o  MUST NOT include any TLVs with Type = MPR associated with any
      other addresses.

   o  MAY include a message TLV with Type := MPR_WILLING, indicating the
      router's willingness to be selected as an MPR.

   An OLSRv2 router MUST also be able to process any HELLO message
   received on an OLSRv2 interface, subsequent to the processing
   specified in [NHDP].

8.1.1.  HELLO Message TLVs

   In a HELLO message, a router MUST include an MPR_WILLING Message TLV
   as specified in Table 1, unless WILLINGNESS = WILL_DEFAULT (in which



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   case it MAY be included).  A router MUST NOT include more than one
   MPR_WILLING Message TLV.

   +-------------+--------------+--------------------------------------+
   |     Type    | Value Length | Value                                |
   +-------------+--------------+--------------------------------------+
   | MPR_WILLING |    1 octet   | Router parameter WILLINGNESS; unused |
   |             |              | bits (based on the maximum           |
   |             |              | willingness value WILL_ALWAYS) are   |
   |             |              | RESERVED and SHOULD be set to zero.  |
   +-------------+--------------+--------------------------------------+

                                  Table 1

   If a router does not advertise an MPR_WILLING TLV in a HELLO message,
   then the router MUST be assumed to have WILLINGNESS equal to
   WILL_DEFAULT.

8.1.2.  HELLO Message Address Block TLVs

   In a HELLO message, a router MAY include MPR Address Block TLV(s) as
   specified in Table 2.

                      +------+--------------+-------+
                      | Type | Value Length | Value |
                      +------+--------------+-------+
                      |  MPR |   0 octets   | None. |
                      +------+--------------+-------+

                                  Table 2

8.2.  TC Messages

   A TC message MUST contain:

   o  <msg-orig-addr>, <msg-seq-num> and <msg-hop-limit> elements in its
      Message Header, as specified in [RFC5444].

   o  A <msg-hop-count> element in its Message Header if the message
      contains a TLV with either Type = VALIDITY_TIME or Type =
      INTERVAL_TIME indicating more than one time value according to
      distance.

   o  A single Message TLV with Type := CONT_SEQ_NUM, and Type Extension
      := COMPLETE or Type Extension := INCOMPLETE, as specified in
      Section 8.2.1 (for complete and incomplete TC messages,
      respectively).




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   o  A Message TLV with Type := VALIDITY_TIME, as specified in
      [timetlv].  The options included in [timetlv] for representing
      zero and infinite times MUST NOT be used.

   o  All of the router's interface addresses.  These MUST be included
      in the message's Address Blocks, unless:

      *  the router has a single interface, with a single interface
         address with maximum prefix length; AND

      *  that address is the router's originator address.

      In this exceptional case, the address will be included as the
      message's originator address, and MAY be omitted from the
      message's Address Blocks.

   o  TLV(s) with Type := LOCAL_IF and Value := UNSPEC_IF associated
      with all of the router's interface addresses.

   o  If the TC message is complete, all addresses in the Advertised
      Address Set and all addresses in the Local Attached Network Set,
      the latter (only) with associated GATEWAY Address Block TLV(s), as
      specified in Section 8.2.2.

   A TC message MAY contain:

   o  If the TC message is incomplete, any addresses in the Advertised
      Address Set and any addresses in the Local Attached Network Set,
      the latter (only) with associated GATEWAY Address Block TLV(s), as
      specified in Section 8.2.2.

   o  A Message TLV with Type := INTERVAL_TIME, as specified in
      [timetlv].  The options included in [timetlv] for representing
      zero and infinite times MUST NOT be used.

8.2.1.  TC Message TLVs

   In a TC message, a router MUST include a single CONT_SEQ_NUM Message
   TLV, as specified in Table 3, and with Type Extension = COMPLETE or
   Type Extension = INCOMPLETE, according to whether the TC message is
   complete or incomplete.

   +--------------+--------------+-------------------------------------+
   |     Type     | Value Length | Value                               |
   +--------------+--------------+-------------------------------------+
   | CONT_SEQ_NUM |   2 octets   | The ANSN contained in the           |
   |              |              | Advertised Neighbor Set.            |
   +--------------+--------------+-------------------------------------+



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                                  Table 3

8.2.2.  TC Message Address Block TLVs

   In a TC message, a router MAY include GATEWAY Address Block TLV(s) as
   specified in Table 4.

     +---------+--------------+-------------------------------------+
     |   Type  | Value Length | Value                               |
     +---------+--------------+-------------------------------------+
     | GATEWAY |    1 octet   | Number of hops to attached network. |
     +---------+--------------+-------------------------------------+

                                  Table 4

   GATEWAY Address Block TLV(s) MUST be associated with all attached
   network addresses, and MUST NOT be associated with any other
   addresses.

9.  HELLO Message Generation

   An OLSRv2 HELLO message is composed and generated as defined in
   [NHDP], with the following additions:

   o  A Message TLV with Type := MPR_WILLING and Value := WILLINGNESS
      MUST be included, unless WILLINGNESS = WILL_DEFAULT (in which case
      it MAY be included).

   o  For each address which is included in the message with an
      associated TLV with Type = LINK_STATUS and Value = SYMMETRIC, and
      is of an MPR (i.e. the address is in the
      N_neighbor_iface_addr_list of a Neighbor Tuple with N_mpr = true),
      that address (including a different copy of that address, in the
      same or a different Address Block) MUST be associated with an
      Address Block TLV with Type := MPR.

   o  For each address which is included in the message and is not
      associated with a TLV with Type = LINK_STATUS and Value =
      SYMMETRIC, or is not of an MPR (i.e. the address is not in the
      N_neighbor_iface_addr_list of a Neighbor Tuple with N_mpr = true),
      that address (including different copies of that address, in the
      same or different Address Blocks) MUST NOT be associated with an
      Address Block TLV with Type := MPR.

   o  An additional HELLO message MAY be sent when the router's set of
      MPRs changes, in addition to the cases specified in [NHDP], and
      subject to the same constraints.




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9.1.  HELLO Message: Transmission

   HELLO messages are included in packets as specified in [RFC5444].
   These packets may contain other messages, including TC messages.

10.  HELLO Message Processing

   All HELLO message processing, including determination of whether a
   message is invalid, considers only TLVs with Type Extension = 0.
   TLVs with any other type extension are ignored.  All references to,
   for example, a TLV with Type = MPR_WILLING refer to a TLV with Type =
   MPR_WILLING and Type Extension = 0.

   In addition to the reasons specified in [NHDP], a HELLO message MUST
   NOT:

   o  Have more than one TLV with Type = MPR_WILLING in its Message TLV
      Block, where TLVs have different Values.

   o  Contain any address associated with a TLV with Type = MPR, where
      that address (including a different copy of that address, in the
      same or a different Address Block) which is not also associated
      with the single value SYMMETRIC by a TLV with Type = LINK_STATUS
      or Type = OTHER_NEIGHB.

   Such a HELLO message MAY be discarded before processing.  If it is
   not then all TLVs with the type(s) for which an error was indicated
   MUST be ignored (treated as not present) in the following processing.

   HELLO messages are first processed as specified in [NHDP].  The
   router MUST identify the Neighbor Tuple corresponding to the
   originator of the HELLO message (the "current Neighbor Tuple") and
   update its N_willingness as described in Section 10.1 and its
   N_mpr_selector as described in Section 10.2.  Following these, the
   router MUST also perform the processing defined in Section 10.3.

10.1.  Updating Willingness

   N_willingness in the current Neighbor Tuple is updated as follows:

   1.  If the HELLO message contains a Message TLV with Type =
       MPR_WILLING then N_willingness := the value of that TLV;

   2.  Otherwise, N_willingness := WILL_DEFAULT.







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10.2.  Updating MPR Selectors

   N_mpr_selector is updated as follows:

   1.  If a router finds any of its local OLSRv2 interface addresses
       with an associated TLV with Type = MPR in the HELLO message
       (indicating that the originator router has selected the receiving
       router as an MPR) then, for the current Neighbor Tuple:

       *  N_mpr_selector := true

   2.  Otherwise, if a router finds any of its own interface addresses
       with an associated TLV with Type = LINK_STATUS and Value =
       SYMMETRIC in the HELLO message, then for the current Neighbor
       Tuple:

       *  N_mpr_selector := false

10.3.  Symmetric 1-Hop and 2-Hop Neighborhood Changes

   A router MUST also perform the following:

   1.  If N_symmetric of a Neighbor Tuple changes from true to false,
       for that Neighbor Tuple:

       *  N_mpr_selector := false

   2.  The set of MPRs of a router MUST be recalculated if:

       *  a Link Tuple is added with L_status = SYMMETRIC, OR;

       *  a Link Tuple with L_status = SYMMETRIC is removed, OR;

       *  a Link Tuple with L_status = SYMMETRIC changes to having
          L_status = HEARD or L_status = LOST, OR;

       *  a Link Tuple with L_status = HEARD or L_status = LOST changes
          to having L_status = SYMMETRIC, OR;

       *  a 2-Hop Tuple is added or removed, OR;

       *  the N_willingness of a Neighbor Tuple with N_symmetric = true
          changes from WILL_NEVER to any other value, OR;

       *  the N_willingness of a Neighbor Tuple with N_symmetric = true
          and N_mpr = true changes to WILL_NEVER from any other value,
          OR;




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       *  the N_willingness of a Neighbor Tuple with N_symmetric = true
          and N_mpr = false changes to WILL_ALWAYS from any other value.

   3.  Otherwise the set of MPRs of a router MAY be recalculated if the
       N_willingness of a Neighbor Tuple with N_symmetric = true changes
       in any other way; it SHOULD be recalculated if N_mpr = false and
       this is an increase in N_willingness or if N_mpr = true and this
       is a decrease in N_willingness.

   If the set of MPRs of a router is recalculated, this MUST be as
   described in Section 14.  Before that calculation, the N_mpr of all
   Neighbor Tuples are set false.  After that calculation the N_mpr of
   all Neighbor Tuples representing symmetric 1-hop neighbors which are
   chosen as MPRs, are set true.

11.  TC Message Generation

   A router with one or more OLSRv2 interfaces, and with a non-empty
   Advertised Neighbor Set or a non-empty Local Attached Network Set
   MUST generate TC messages.  A router with an empty Advertised
   Neighbor Set and empty Local Attached Network Set SHOULD also
   generate "empty" TC messages for a period A_HOLD_TIME after it last
   generated a non-empty TC message.  TC messages (non-empty and empty)
   are generated according to the following:

   1.  The message hop count, if included, MUST be set to zero.

   2.  The message hop limit MUST be set to a value greater than 1.  A
       router MAY use the same hop limit TC_HOP_LIMIT in all TC
       messages, or use different values of the hop limit TC_HOP_LIMIT
       in TC messages, see Section 5.6.

   3.  The message MUST contain a Message TLV with Type := CONT_SEQ_NUM
       and Value := ANSN from the Advertised Neighbor Set. If the TC
       message is complete then this Message TLV MUST have Type
       Extension := COMPLETE, otherwise it MUST have Type Extension :=
       INCOMPLETE.

   4.  The message MUST contain a Message TLV with Type :=
       VALIDITY_TIME, as specified in [timetlv].  If all TC messages are
       sent with the same hop limit then this TLV MUST have Value :=
       T_HOLD_TIME.  If TC messages are sent with different hop limits
       (more than one value of TC_HOP_LIMIT) then this TLV MUST specify
       times which vary with the number of hops distance appropriate to
       the chosen pattern of TC message hop limits, as specified in
       [timetlv], these times SHOULD be appropriate multiples of
       T_HOLD_TIME.




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   5.  The message MAY contain a Message TLV with Type := INTERVAL_TIME,
       as specified in [timetlv].  If all TC messages are sent with the
       same hop limit then this TLV MUST have Value := TC_INTERVAL.  If
       TC messages are sent with different hop limits, then this TLV
       MUST specify times which vary with the number of hops distance
       appropriate to the chosen pattern of TC message hop limits, as
       specified in [timetlv], these times SHOULD be appropriate
       multiples of TC_INTERVAL.

   6.  Unless the router has a single interface, with a single interface
       address with maximum prefix length, and that address is the
       router's originator address, the message MUST contain all of the
       router's interface addresses (i.e. all addresses in an
       I_local_iface_addr_list) in its Address Blocks.

   7.  All addresses of the router's interfaces that are included in an
       Address Block MUST each be associated with a TLV with Type :=
       LOCAL_IF and Value := UNSPEC_IF.

   8.  A complete message MUST include, and an incomplete message MAY
       include, in its Address Blocks:

       1.  Each A_neighbor_iface_addr from the Advertised Neighbor Set;

       2.  AL_net_addr from each Local Attached Neighbor Tuple, each
           associated with a TLV with Type := GATEWAY and Value :=
           AL_dist.

11.1.  TC Message: Transmission

   Complete TC messages are generated and transmitted periodically on
   all OLSRv2 interfaces, with a default interval between two
   consecutive TC transmissions by the same router of TC_INTERVAL.

   TC messages MAY be generated in response to a change of contents,
   indicated by a change in ANSN.  In this case a router MAY send a
   complete TC message, and if so MAY re-start its TC message schedule.
   Alternatively a router MAY send an incomplete TC message with at
   least the new content in its Address Blocks.  Note that a router
   cannot report removal of advertised content using an incomplete TC
   message.

   When sending a TC message in response to a change of contents, a
   router must respect a minimum interval of TC_MIN_INTERVAL between
   generated TC messages.  Sending an incomplete TC message MUST NOT
   cause the interval between complete TC messages to be increased, and
   thus a router MUST NOT send an incomplete TC message if within
   TC_MIN_INTERVAL of the next scheduled complete TC message.



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   The generation of TC messages, whether scheduled or triggered by a
   change of contents MAY be jittered as described in [RFC5148].  The
   values of MAXJITTER used SHOULD be:

   o  TP_MAXJITTER for periodic TC message generation;

   o  TT_MAXJITTER for responsive TC message generation.

   TC messages are included in packets as specified in [RFC5444].  These
   packets MAY contain other messages, including HELLO messages and TC
   messages with different originator addresses.  TC messages are
   forwarded according to the specification in Section 7.3.

12.  TC Message Processing

   On receiving a TC message, a router MUST first check if the message
   is invalid for processing by this router, as defined in Section 12.1.
   Otherwise the receiving router MUST update its appropriate Interface
   Information Base and its Router Information Base as specified in
   Section 12.2.

   All TC message processing, including determination of whether a
   message is invalid, unless otherwise noted considers only TLVs with
   Type Extension = 0.  TLVs with any other type extension (or any
   unmentioned type extension when other type extensions are considered)
   are ignored.  All references to, for example, a TLV with Type =
   VALIDITY_TIME refer to a TLV with Type = VALIDITY_TIME and Type
   Extension = 0.

12.1.  Invalid Message

   A received TC message is invalid for processing by this router if any
   of the following conditions are true.

   o  The Message Header does not include an originator address, a
      message sequence number, and at least one of a hop limit and a hop
      count.

   o  The message does not have a TLV with Type = VALIDITY_TIME in its
      Message TLV Block.

   o  The message has more than one TLV with Type = VALIDITY_TIME in its
      Message TLV Block, and these TLVs indicate different validity
      times, as specified by [timetlv].

   o  The message has more than one TLV with Type = INTERVAL_TIME in its
      Message TLV Block, and these TLVs indicate different interval
      times, as specified by [timetlv].



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   o  The message does not have a TLV with Type = CONT_SEQ_NUM and Type
      Extension = COMPLETE or Type Extension = INCOMPLETE in its Message
      TLV Block.

   o  The message has more than one TLV with Type = CONT_SEQ_NUM and
      Type Extension = COMPLETE or Type Extension = INCOMPLETE in its
      Message TLV Block, and these do not have the same type extension
      and the same Value.

   o  The message has any Address Block TLV(s) with Type = LOCAL_IF and
      any single value(s) which are not equal to UNSPEC_IF.

   o  Any address associated with a TLV with Type = LOCAL_IF is one of
      the receiving router's current or recently used interface
      addresses (i.e. is in any I_local_iface_addr_list in the Local
      Interface Set or is equal to any IR_local_iface_addr in the
      Removed Interface Address Set).

   o  Any address (including different copies of an address, in the same
      or different Address Blocks) is associated with more than one
      single value by one or more TLV(s) with Type = GATEWAY.

   An invalid message MUST be silently discarded, without updating the
   router's Information Bases.  A router MAY recognize additional
   reasons for identifying that a message is badly formed and discard
   such messages.

12.2.  Initial TC Message Processing

   When, according to Section 7.2, a TC message is to be "processed
   according to its type", this means that:

   o  If the TC message contains a Message TLV with Type = CONT_SEQ_NUM
      and Type Extension = COMPLETE, then processing according to
      Section 12.3 and then according to Section 12.4 is carried out.

   o  If the TC message contains a Message TLV with Type = CONT_SEQ_NUM
      and Type Extension = INCOMPLETE, then only processing according to
      Section 12.3 is carried out.

   For the purposes of this section:

   o  "originator address" refers to the originator address in the TC
      Message Header.

   o  "validity time" is calculated from a VALIDITY_TIME Message TLV in
      the TC message according to the specification in [timetlv].  All
      information in the TC message has the same validity time.



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   o  "ANSN" is defined as being the Value of a Message TLV with Type =
      CONT_SEQ_NUM.

   o  "sending address list" refers to the list of addresses in all
      Address Blocks which have associated TLV(s) with Type = LOCAL_IF
      and Value = UNSPEC_IF.  If the sending address list is otherwise
      empty, then the message's originator address is added to the
      sending address list, with maximum prefix length.

   o  Comparisons of sequence numbers are carried out as specified in
      Section 18.

12.3.  Initial TC Message Processing

   The TC message is processed as follows:

   1.  The Advertising Remote Router Set is updated according to
       Section 12.3.1; if the TC message is indicated as discarded in
       that processing then the following steps are not carried out.

   2.  The Topology Set is updated according to Section 12.3.2.

   3.  The Attached Network Set is updated according to Section 12.3.3.

12.3.1.  Populating the Advertising Remote Router Set

   The router MUST update its Advertising Remote Router Set as follows:

   1.  If there is an Advertising Remote Router Tuple with:

       *  AR_orig_addr = originator address; AND

       *  AR_seq_number > ANSN

       then the TC message MUST be discarded.

   2.  Otherwise:

       1.  If there is no Advertising Remote Router Tuple such that:

           +  AR_orig_addr = originator address;

           then create an Advertising Remote Router Tuple with:

           +  AR_orig_addr := originator address.






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       2.  This Advertising Remote Router Tuple (existing or new, the
           "current tuple") is then modified as follows:

           +  AR_seq_number := ANSN;

           +  AR_time := current time + validity time.

           +  AR_iface_addr_list := sending address list

       3.  For each other Advertising Remote Router Tuple (with a
           different AR_orig_addr, the "other tuple") whose
           AR_iface_addr_list contains any address in the
           AR_iface_addr_list of the current tuple:

           1.  remove all Topology Tuples with T_orig_addr =
               AR_orig_addr of the other tuple;

           2.  remove all Attached Network Tuples with AN_orig_addr =
               AR_orig_addr of the other tuple;

           3.  remove the other tuple.

12.3.2.  Populating the Topology Set

   The router MUST update its Topology Set as follows:

   1.  For each address (henceforth advertised address) in an Address
       Block that does not have an associated TLV with Type = LOCAL_IF,
       or an associated TLV with Type = GATEWAY:

       1.  If there is no Topology Tuple such that:

           +  T_dest_iface_addr = advertised address; AND

           +  T_orig_addr = originator address

           then create a new Topology Tuple with:

           +  T_dest_iface_addr := advertised address;

           +  T_orig_addr := originator address.

       2.  This Topology Tuple (existing or new) is then modified as
           follows:

           +  T_seq_number := ANSN;





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           +  T_time := current time + validity time.

12.3.3.  Populating the Attached Network Set

   The router MUST update its Attached Network Set as follows:

   1.  For each address (henceforth network address) in an Address Block
       that does not have an associated TLV with Type = LOCAL_IF, and
       does have an associated TLV with Type = GATEWAY:

       1.  If there is no Attached Network Tuple such that:

           +  AN_net_addr = network address; AND

           +  AN_orig_addr = originator address

           then create a new Attached Network Tuple with:

           +  AN_net_addr := network address;

           +  AN_orig_addr := originator address

       2.  This Attached Network Tuple (existing or new) is then
           modified as follows:

           +  AN_dist := the value of the associated GATEWAY TLV;

           +  AN_seq_number := ANSN;

           +  AN_time := current time + validity time.

12.4.  Completing TC Message Processing

   The TC message is processed as follows:

   1.  The Topology Set is updated according to Section 12.4.1.

   2.  The Attached Network Set is updated according to Section 12.4.2.

12.4.1.  Purging the Topology Set

   The Topology Set MUST be updated as follows:

   1.  Any Topology Tuples with:

       *  T_orig_addr = originator address; AND





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       *  T_seq_number < ANSN

       MUST be removed.

12.4.2.  Purging the Attached Network Set

   The Attached Network Set MUST be updated as follows:

   1.  Any Attached Network Tuples with:

       *  AN_orig_addr = originator address; AND

       *  AN_seq_number < ANSN

       MUST be removed.

13.  Information Base Changes

   1.  The Originator Set in the Local Information Base MUST be updated
       when the router changes originator address.  If there is no
       Originator Tuple with:

       *  O_orig_addr = old originator address

       then create an Originator Tuple with:

       *  O_orig_addr := old originator address

       This Originator Tuple (existing or new) is then modified as
       follows:

       *  O_time := current time + O_HOLD_TIME

   2.  The Topology Information Base MUST be changed when an Advertising
       Remote Router Tuple expires (AR_time is reached).  The following
       changes are required before the Advertising Remote Router Tuple
       is removed:

       1.  All Topology Tuples with:

           +  T_orig_addr = AR_orig_addr of the Advertising Remote
              Router Tuple

           are removed.

       2.  All Attached Network Tuples with:





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           +  AN_orig_addr = AR_orig_addr of the Advertising Remote
              Router Tuple

           are removed.

14.  Selecting MPRs

   Each router MUST select, from among its willing symmetric 1-hop
   neighbors, a subset of routers as MPRs.  MPRs are used to flood
   control messages from a router into the network, while reducing the
   number of retransmissions that will occur in a region.  Thus, the
   concept of MPR flooding is an optimization of a classical flooding
   mechanism.  MPRs MAY also be used to reduce the shared topology
   information in the network.  Consequently, while it is not essential
   that the set of MPRs is minimal, keeping the number of MPRs small
   ensures that the overhead of OLSRv2 is kept at a minimum.

   A router MUST select MPRs for each of its OLSRv2 interfaces, but then
   forms the union of those sets as its single set of MPRs.  This union
   MUST include all symmetric 1-hop neighbors with willingness
   WILL_ALWAYS.  Only this overall set of MPRs is relevant, the recorded
   and used MPR relationship is one of routers, not interfaces.  Routers
   MAY select their MPRs by any process which satisfies the conditions
   which follow.  Routers can freely interoperate whether they use the
   same or different MPR selection algorithms.

   For each OLSRv2 interface a router MUST select a set of MPRs.  This
   set MUST have the properties that:

   o  All of the selected MPRs are willing symmetric 1-hop neighbors,
      AND;

   o  If the selecting router sends a message on that OLSRv2 interface,
      and that message is successfully forwarded by all of the selected
      MPRs for that interface, then all symmetric strict 2-hop neighbors
      of the selecting router through that OLSRv2 interface will receive
      that message on a symmetric link.

   Note that it is always possible to select a valid set of MPRs.  The
   set of all willing symmetric 1-hop neighbors of a router is a
   (maximal) valid set of MPRs for that router.  However a router SHOULD
   NOT select a symmetric 1-hop neighbor with Willingness != WILL_ALWAYS
   as an MPR if there are no symmetric strict 2-hop neighbors with a
   symmetric link to that symmetric 1-hop neighbor.  Thus a router with
   no symmetric 1-hop neighbors with willingness WILL_ALWAYS and with no
   symmetric strict 2-hop neighbors SHOULD NOT select any MPRs.

   A router MAY select its MPRs for each OLSRv2 interface independently,



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   or it MAY coordinate its MPR selections across its OLSRv2 interfaces,
   as long as the required condition is satisfied for each OLSRv2
   interface.  Each router MAY select its MPRs independently from the
   MPR selection by other routers, or it MAY, for example, give
   preference to routers that either are, or are not, already selected
   as MPRs by other routers.

   When selecting MPRs for each OLSRv2 interface independently, this MAY
   be done using information from the Link Set and 2-Hop Set of that
   OLSRv2 interface, and the Neighbor Set of the router (specifically
   the N_willingness elements).

   The selection of MPRs (overall, not per OLSRv2 interface) is recorded
   in the Neighbor Set of the router (using the N_mpr elements).  A
   selected MPR MUST be a willing symmetric 1-hop neighbor (i.e. the
   corresponding N_symmetric = true, and the corresponding N_willingness
   != WILL_NEVER).

   A router MUST recalculate its MPRs whenever the currently selected
   set of MPRs does not still satisfy the required conditions.  It MAY
   recalculate its MPRs if the current set of MPRs is still valid, but
   could be more efficient.  It is sufficient to recalculate a router's
   MPRs when there is a change to any of the router's Link Sets
   affecting the symmetry of any link (addition or removal of a Link
   Tuple with L_status = SYMMETRIC, or change of any L_status to or from
   SYMMETRIC), any change to any of the router's 2-Hop Sets, or a change
   of the N_willingness (to or from WILL_NEVER or to WILL_ALWAYS is
   sufficient) of any Neighbor Tuple with N_symmetric = true.

   An algorithm that creates a set of MPRs that satisfies the required
   conditions is given in Appendix B.

15.  Populating Derived Sets

   The Relay Sets and the Advertised Neighbor Set of a router are
   denoted derived sets, since updates to these sets are not directly a
   function of message exchanges, but rather are derived from updates to
   other sets, in particular to the MPR selector status of other routers
   recorded in the Neighbor Set.

15.1.  Populating the Relay Set

   The Relay Set for an OLSRv2 interface contains the set of OLSRv2
   interface addresses of those symmetric 1-hop neighbors for which this
   OLSRv2 interface is to relay broadcast traffic.  This set MUST
   contain only addresses of OLSRv2 interfaces with which this OLSRv2
   interface has a symmetric link.  This set MUST include all such
   addresses of all such OLSRv2 interfaces of routers which are MPR



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   selectors of this router.

   The Relay Set for an OLSRv2 interface of this router is thus created
   by:

   1.  For each Link Tuple in the Link Set for this OLSRv2 interface
       with L_status = SYMMETRIC, and the corresponding Neighbor Tuple
       with N_neighbor_iface_addr_list containing
       L_neighbor_iface_addr_list:

       1.  All addresses from L_neighbor_iface_addr_list MUST be
           included in the Relay Set of this OLSRv2 interface if
           N_mpr_selector = true, and otherwise MAY be so included.

15.2.  Populating the Advertised Neighbor Set

   The Advertised Neighbor Set of a router contains all interface
   addresses of those symmetric 1-hop neighbors to which the router
   advertises a link in its TC messages.  This set MUST include all
   addresses in all MPR selector of this router.

   The Advertised Neighbor Set for this router is thus created by:

   1.  For each Neighbor Tuple with N_symmetric = true:

       1.  All addresses from N_neighbor_iface_addr_list MUST be
           included in the Advertised Neighbor Set if N_mpr_selector =
           true, and otherwise MAY be so included.

   Whenever address(es) are added to or removed from the Advertised
   Neighbor Set, its ANSN MUST be incremented.

16.  Routing Set Calculation

   The Routing Set of a router is populated with Routing Tuples that
   represent paths from that router to all destinations in the network.
   These paths are calculated based on the Network Topology Graph, which
   is constructed from information in the Information Bases, obtained
   via HELLO and TC message exchange.

16.1.  Network Topology Graph

   The Network Topology Graph is formed from information from the
   router's Link Sets, Neighbor Set, Topology Set and Attached Network
   Set. The Network Topology Graph SHOULD also use information from the
   router's 2-Hop Sets.  The Network Topology Graph forms that router's
   topological view of the network in form of a directed graph,
   containing the following arcs:



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   o  Local symmetric links - all arcs X -> Y such that:

      *  X is an address in the I_local_iface_addr_list of a Local
         Interface Tuple of this router, AND;

      *  Y is an address in the L_neighbor_iface_addr_list of a Link
         Tuple in the corresponding (to the OLSRv2 interface of that
         I_local_iface_addr_list) Link Set which has L_status =
         SYMMETRIC.

   o  2-hop symmetric links - all arcs Y -> Z such that:

      *  Y is an address in the L_neighbor_iface_addr_list of a Link
         Tuple, in any of the router's Link Sets, which has L_status =
         SYMMETRIC, AND;

      *  the Neighbor Tuple with Y in its N_neighbor_iface_addr_list has
         N_willingness not equal to WILL_NEVER, AND;

      *  Z is the N2_2hop_iface_addr of a 2-Hop Tuple in the 2-Hop Set
         corresponding to the OLSRv2 interface of the chosen Link Set.

   o  Advertised symmetric links - all arcs U -> V such that there
      exists a Topology Tuple and a corresponding Advertising Remote
      Router Tuple (i.e. with AR_orig_addr = T_orig_addr) with:

      *  U is in the AR_iface_addr_list of the Advertising Remote Router
         Tuple, AND;

      *  V is the T_dest_iface_addr of the Topology Tuple.

   o  Symmetric 1-hop neighbor addresses - all arcs Y -> W such that:

      *  Y is, and W is not, an address in the
         L_neighbor_iface_addr_list of a Link Tuple, in any of the
         router's Link Sets, which has L_status = SYMMETRIC, AND;

      *  W and Y are included in the same N_neighbor_iface_addr_list
         (i.e. the one in the Neighbor Tuple whose
         N_neighbor_iface_addr_list contains the
         L_neighbor_iface_addr_list that includes Y).

   o  Attached network addresses - all arcs U -> T such that there
      exists an Attached Network Tuple and a corresponding Advertising
      Remote Router Tuple (i.e. with AR_orig_addr = AN_orig_addr) with:

      *  U is in the AR_iface_addr_list of the Advertising Remote Router
         Tuple, AND;



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      *  T is the AN_net_addr of the Attached Network Tuple.

   All links in the first three cases above have a hop count of one, the
   symmetric 1-hop neighbor addresses have a hop count of zero, and the
   attached network addresses have a hop count given by the appropriate
   value of AN_dist.

16.2.  Populating the Routing Set

   The Routing Set MUST contain the shortest paths for all destinations
   from all local OLSRv2 interfaces using the Network Topology Graph.
   This calculation MAY use any algorithm, including any means of
   choosing between paths of equal length.

   Using the notation of Section 16.1, each path will have as its first
   arc a local symmetric link X -> Y. There will be a path for each
   terminating Y, Z, V, W and T which can be connected to local OLSRv2
   interface address X using the indicated arcs.  The corresponding
   Routing Tuple for this path will have:

   o  R_dest_addr := the terminating Y, Z, V, W or T;

   o  R_next_iface_addr := the first arc's Y;

   o  R_dist := the total hop count of the path;

   o  R_local_iface_addr := the first arc's X.

   An example algorithm for calculating the Routing Set of a router is
   given in Appendix C.

16.3.  Routing Set Updates

   The Routing Set MUST be updated when changes in the Neighborhood
   Information Base or the Topology Information Base indicate a change
   of the known symmetric links and/or attached networks in the MANET.
   It is sufficient to consider only changes which affect at least one
   of:

   o  The Link Set of any OLSRv2 interface, and to consider only Link
      Tuples which have, or just had, L_status = SYMMETRIC (including
      removal of such Link Tuples).

   o  The Neighbor Set of the router, and to consider only Neighbor
      Tuples that have, or just had, N_symmetric = true.

   o  The 2-Hop Set of any OLSRv2 interface.




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   o  The Advertising Remote Router Set of the router.

   o  The Topology Set of the router.

   o  The Attached Network Set of the router.

   Updates to the Routing Set do not generate or trigger any messages to
   be transmitted.  The state of the Routing Set SHOULD, however, be
   reflected in the IP routing table by adding and removing entries from
   the IP routing table as appropriate.

17.  Proposed Values for Parameters and Constants

   OLSRv2 uses all parameters and constants defined in [NHDP] and
   additional parameters and constants defined in this document.  All
   but one (RX_HOLD_TIME) of these additional parameters are router
   parameters as defined in [NHDP].  These proposed values of the
   additional parameters are appropriate to the case where all
   parameters (including those defined in [NHDP]) have a single value.
   Proposed values for parameters defined in [NHDP] are given in that
   document.

17.1.  Local History Time Parameters

   o  O_HOLD_TIME := 30 seconds

17.2.  Message Interval Parameters

   o  TC_INTERVAL := 5 seconds

   o  TC_MIN_INTERVAL := TC_INTERVAL/4

17.3.  Advertised Information Validity Time Parameters

   o  T_HOLD_TIME := 3 x TC_INTERVAL

   o  A_HOLD_TIME := T_HOLD_TIME

17.4.  Received Message Validity Time Parameters

   o  RX_HOLD_TIME := 30 seconds

   o  P_HOLD_TIME := 30 seconds

   o  F_HOLD_TIME := 30 seconds






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17.5.  Jitter Time Parameters

   o  TP_MAXJITTER := HP_MAXJITTER

   o  TT_MAXJITTER := HT_MAXJITTER

   o  F_MAXJITTER := TT_MAXJITTER

17.6.  Hop Limit Parameter

   o  TC_HOP_LIMIT := 255

17.7.  Willingness Parameter and Constants

   o  WILLINGNESS := WILL_DEFAULT

   o  WILL_NEVER := 0

   o  WILL_DEFAULT := 3

   o  WILL_ALWAYS := 7

18.  Sequence Numbers

   Sequence numbers are used in OLSRv2 with the purpose of discarding
   "old" information, i.e. messages received out of order.  However with
   a limited number of bits for representing sequence numbers, wrap-
   around (that the sequence number is incremented from the maximum
   possible value to zero) will occur.  To prevent this from interfering
   with the operation of OLSRv2, the following MUST be observed when
   determining the ordering of sequence numbers.

   The term MAXVALUE designates in the following one more than the
   largest possible value for a sequence number.  For a 16 bit sequence
   number (as are those defined in this specification) MAXVALUE is
   65536.

   The sequence number S1 is said to be "greater than" the sequence
   number S2 if:

   o  S1 > S2 AND S1 - S2 < MAXVALUE/2 OR

   o  S2 > S1 AND S2 - S1 > MAXVALUE/2

   When sequence numbers S1 and S2 differ by MAXVALUE/2 their ordering
   cannot be determined.  In this case, which should not occur, either
   ordering may be assumed.




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   Thus when comparing two messages, it is possible - even in the
   presence of wrap-around - to determine which message contains the
   most recent information.

19.  IANA Considerations

19.1.  Message Types

   This specification defines one Message Type, to be allocated from the
   0-223 range of the "Message Types" namespace defined in [RFC5444], as
   specified in Table 5.

         +------+------+-----------------------------------------+
         | Name | Type | Description                             |
         +------+------+-----------------------------------------+
         |  TC  | TBD1 | Topology Control (MANET-wide signaling) |
         +------+------+-----------------------------------------+

                                  Table 5

19.2.  Message TLV Types

   This specification defines two Message TLV Types, which must be
   allocated from the "Message TLV Types" namespace defined in
   [RFC5444].  IANA are requested to make allocations in the 8-127 range
   for these types.  This will create two new type extension registries
   with assignments as specified in Table 6 and Table 7.  Specifications
   of these TLVs are in Section 8.1.1 and Section 8.2.1.

   +-------------+------+-----------+----------------------------------+
   |     Name    | Type |    Type   | Description                      |
   |             |      | extension |                                  |
   +-------------+------+-----------+----------------------------------+
   | MPR_WILLING | TBD2 |     0     | Specifies the originating        |
   |             |      |           | router's willingness to act as a |
   |             |      |           | relay and to partake in network  |
   |             |      |           | formation                        |
   |             |      |   1-255   | Expert Review                    |
   +-------------+------+-----------+----------------------------------+

                                  Table 6










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   +--------------+------+----------------+----------------------------+
   |     Name     | Type | Type extension | Description                |
   +--------------+------+----------------+----------------------------+
   | CONT_SEQ_NUM | TBD3 |  0 (COMPLETE)  | Specifies a content        |
   |              |      |                | sequence number for this   |
   |              |      |                | complete message           |
   |              |      | 1 (INCOMPLETE) | Specifies a content        |
   |              |      |                | sequence number for this   |
   |              |      |                | incomplete message         |
   |              |      |      2-255     | Expert Review              |
   +--------------+------+----------------+----------------------------+

                                  Table 7

   Type extensions indicated as Expert Review SHOULD be allocated as
   described in [RFC5444], based on Expert Review as defined in
   [RFC5226].

19.3.  Address Block TLV Types

   This specification defines two Address Block TLV Types, which must be
   allocated from the "Address Block TLV Types" namespace defined in
   [RFC5444].  IANA are requested to make allocations in the 8-127 range
   for these types.  This will create two new type extension registries
   with assignments as specified in Table 8 and Table 9.  Specifications
   of these TLVs are in Section 8.1.2 and Section 8.2.2.

   +------+------+-----------+-----------------------------------------+
   | Name | Type |    Type   | Description                             |
   |      |      | extension |                                         |
   +------+------+-----------+-----------------------------------------+
   |  MPR | TBD4 |     0     | Specifies that a given address is of a  |
   |      |      |           | router selected as an MPR               |
   |      |      |   1-255   | Expert Review                           |
   +------+------+-----------+-----------------------------------------+

                                  Table 8

   +---------+------+-----------+--------------------------------------+
   |   Name  | Type |    Type   | Description                          |
   |         |      | extension |                                      |
   +---------+------+-----------+--------------------------------------+
   | GATEWAY | TBD5 |     0     | Specifies that a given address is    |
   |         |      |           | reached via a gateway on the         |
   |         |      |           | originating router                   |
   |         |      |   1-255   | Expert Review                        |
   +---------+------+-----------+--------------------------------------+




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                                  Table 9

   Type extensions indicated as Expert Review SHOULD be allocated as
   described in [RFC5444], based on Expert Review as defined in
   [RFC5226].

   The Address Block TLV with Type = LOCAL_IF defined in [NHDP] is
   extended to also permit inclusion of the value UNSPEC_IF = 2,
   representing a local interface address which may or may not be that
   on which this message is transmitted.

20.  Security Considerations

   Currently, OLSRv2 does not specify any special security measures.  As
   a proactive routing protocol, OLSRv2 makes a target for various
   attacks.  The various possible vulnerabilities are discussed in this
   section.

20.1.  Confidentiality

   Being a proactive protocol, OLSRv2 periodically MPR floods
   topological information to all routers in the network.  Hence, if
   used in an unprotected wireless network, the network topology is
   revealed to anyone who listens to OLSRv2 control messages.

   In situations where the confidentiality of the network topology is of
   importance, regular cryptographic techniques, such as exchange of
   OLSRv2 control traffic messages encrypted by PGP [RFC4880] or
   encrypted by some shared secret key, can be applied to ensure that
   control traffic can be read and interpreted by only those authorized
   to do so.

20.2.  Integrity

   In OLSRv2, each router is injecting topological information into the
   network through transmitting HELLO messages and, for some routers, TC
   messages.  If some routers for some reason, malicious or malfunction,
   inject invalid control traffic, network integrity may be compromised.
   Therefore, message authentication is recommended.

   Different such situations may occur, for instance:

   1.  a router generates TC messages, advertising links to non-neighbor
       routers;

   2.  a router generates TC messages, pretending to be another router;





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   3.  a router generates HELLO messages, advertising non-neighbor
       routers;

   4.  a router generates HELLO messages, pretending to be another
       router;

   5.  a router forwards altered control messages;

   6.  a router does not forward control messages;

   7.  a router does not select multipoint relays correctly;

   8.  a router forwards broadcast control messages unaltered, but does
       not forward unicast data traffic;

   9.  a router "replays" previously recorded control traffic from
       another router.

   Authentication of the originator router for control messages (for
   situations 2, 4 and 5) and on the individual links announced in the
   control messages (for situations 1 and 3) may be used as a
   countermeasure.  However to prevent routers from repeating old (and
   correctly authenticated) information (situation 9) temporal
   information is required, allowing a router to positively identify
   such delayed messages.

   In general, digital signatures and other required security
   information may be transmitted as a separate OLSRv2 Message Type, or
   signatures and security information may be transmitted within the
   OLSRv2 HELLO and TC messages, using the TLV mechanism.  Either option
   permits that "secured" and "unsecured" routers can coexist in the
   same network, if desired,

   Specifically, the authenticity of entire OLSRv2 control packets can
   be established through employing IPsec authentication headers,
   whereas authenticity of individual links (situations 1 and 3) require
   additional security information to be distributed.

   An important consideration is that all control messages in OLSRv2 are
   transmitted either to all routers in the neighborhood (HELLO
   messages) or broadcast to all routers in the network (TC messages).

   For example, a control message in OLSRv2 is always a point-to-
   multipoint transmission.  It is therefore important that the
   authentication mechanism employed permits that any receiving router
   can validate the authenticity of a message.  As an analogy, given a
   block of text, signed by a PGP private key, then anyone with the
   corresponding public key can verify the authenticity of the text.



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20.3.  Interaction with External Routing Domains

   OLSRv2 does, through the use of TC messages, provide a basic
   mechanism for injecting external routing information to the OLSRv2
   domain.  Appendix A also specifies that routing information can be
   extracted from the topology table or the routing table of OLSRv2 and,
   potentially, injected into an external domain if the routing protocol
   governing that domain permits.

   Other than as described in Appendix A, when operating routers
   connecting OLSRv2 to an external routing domain, care MUST be taken
   not to allow potentially insecure and untrustworthy information to be
   injected from the OLSRv2 domain to external routing domains.  Care
   MUST be taken to validate the correctness of information prior to it
   being injected as to avoid polluting routing tables with invalid
   information.

   A recommended way of extending connectivity from an existing routing
   domain to an OLSRv2 routed MANET is to assign an IP prefix (under the
   authority of the routers/gateways connecting the MANET with the
   exiting routing domain) exclusively to the OLSRv2 MANET area, and to
   configure the gateways statically to advertise routes to that IP
   sequence to routers in the existing routing domain.

21.  Contributors

   This specification is the result of the joint efforts of the
   following contributors -- listed alphabetically.

   o  Cedric Adjih, INRIA, France, <Cedric.Adjih@inria.fr>

   o  Emmanuel Baccelli, INRIA , France, <Emmanuel.Baccelli@inria.fr>

   o  Thomas Heide Clausen, LIX, France, <T.Clausen@computer.org>

   o  Justin Dean, NRL, USA, <jdean@itd.nrl.navy.mil>

   o  Christopher Dearlove, BAE Systems, UK,
      <chris.dearlove@baesystems.com>

   o  Satoh Hiroki, Hitachi SDL, Japan, <hiroki.satoh.yj@hitachi.com>

   o  Philippe Jacquet, INRIA, France, <Philippe.Jacquet@inria.fr>

   o  Monden Kazuya, Hitachi SDL, Japan, <kazuya.monden.vw@hitachi.com>

   o  Kenichi Mase, Niigata University, Japan, <mase@ie.niigata-u.ac.jp>




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   o  Ryuji Wakikawa, KEIO University, Japan, <ryuji@sfc.wide.ad.jp>

22.  Acknowledgments

   The authors would like to acknowledge the team behind OLSRv1,
   specified in RFC3626, including Anis Laouiti (INT, Paris), Pascale
   Minet (INRIA, France), Laurent Viennot (INRIA, France), and Amir
   Qayyum (M.A. Jinnah University, Islamabad) for their contributions.

   The authors would like to gratefully acknowledge the following people
   for intense technical discussions, early reviews and comments on the
   specification and its components (listed alphabetically): Khaldoun Al
   Agha (LRI), Song-Yean Cho (LIX), Alan Cullen (BAE Systems), Louise
   Lamont (CRC), Li Li (CRC), Joe Macker (NRL), Richard Ogier (SRI),
   Charles E. Perkins (WiChorus), Shubhranshu Singh (Samsung AIT), and
   the entire IETF MANET working group.

23.  References

23.1.  Normative References

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

   [timetlv]     Clausen, T. and C. Dearlove, "Representing multi-value
                 time in MANETs", Work In
                 Progress draft-ietf-manet-timetlv-08.txt,
                 September 2008.

   [RFC5148]     Clausen, T., Dearlove, C., and B. Adamson, "Jitter
                 considerations in MANETs", RFC 5148, February 2008.

   [NHDP]        Clausen, T., Dean, J., and C. Dearlove, "MANET
                 Neighborhood Discovery Protocol (NHDP)", work in
                 progress draft-ietf-manet-nhdp-08.txt, February 2009.

   [manet-iana]  Chakeres, I., "IANA Allocations for MANET Protocols",
                 Work In Progress draft-ietf-manet-iana-07.txt,
                 November 2007.

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

   [RFC5226]     Narten, T. and H. Alvestrand, "Guidelines for Writing
                 an IANA Considerations Section in RFCs", RFC 5226,
                 BCP 26, May 2008.




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23.2.  Informative References

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

   [RFC3626]     Clausen, T. and P. Jacquet, "The Optimized Link State
                 Routing Protocol", RFC 3626, October 2003.

   [RFC4880]     Callas, J., Donnerhacke, L., Finney, H., and R. Thayer,
                 "OpenPGP message format", RFC 4880, November 2007.

   [HIPERLAN]    ETSI, "ETSI STC-RES10 Committee. Radio equipment and
                 systems: HIPERLAN type 1, functional specifications ETS
                 300-652", June 1996.

   [HIPERLAN2]   Jacquet, P., Minet, P., Muhlethaler, P., and N.
                 Rivierre, "Increasing reliability in cable free radio
                 LANs: Low level forwarding in HIPERLAN.", 1996.

   [MPR]         Qayyum, A., Viennot, L., and A. Laouiti, "Multipoint
                 relaying: An efficient technique for flooding in mobile
                 wireless networks.", 2001.

   [FSR]         Pei, G., Gerla, M., and T. Chen, "Fisheye state routing
                 in mobile ad hoc networks", 2000.

   [FSLS]        Santivanez, C., Ramanathan, R., and I. Stavrakakis,
                 "Making link-state routing scale for ad hoc networks",
                 2000.

Appendix A.  Router Configuration

   OLSRv2 does not make any assumption about router addresses, other
   than that each router is assumed to have at least one unique and
   routable IP address for each interface that it has which participates
   in the MANET.

   When applicable, a recommended way of connecting an OLSRv2 network to
   an existing IP routing domain is to assign an IP prefix (under the
   authority of the routers/gateways connecting the MANET with the
   routing domain) exclusively to the OLSRv2 area, and to configure the
   gateways statically to advertise routes to that IP sequence to
   routers in the existing routing domain.







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Appendix B.  Example Algorithm for Calculating MPRs

   The following specifies an algorithm which MAY be used to select
   MPRs.  MPRs are calculated per OLSRv2 interface, but then a single
   set of MPRs is formed from the union of the MPRs for all OLSRv2
   interfaces.  (As noted in Section 14 a router MAY improve on this, by
   coordination between OLSRv2 interfaces.)  A router's MPRs are
   recorded using the element N_mpr in Neighbor Tuples.

   If using this algorithm then the following steps MUST be executed in
   order for a router to select its MPRs:

   1.  Set N_mpr := false in all Neighbor Tuples;

   2.  For each Neighbor Tuple with N_symmetric = true and N_willingness
       = WILL_ALWAYS, set N_mpr := true;

   3.  For each OLSRv2 interface of the router, use the algorithm in
       Appendix B.2.  Note that this sets N_mpr := true for some
       Neighbor Tuples, these routers are already selected as MPRs when
       using the algorithm for following OLSRv2 interfaces.

   4.  OPTIONALLY, consider each selected MPR in turn, and if the set of
       selected MPRs without that router still satisfies the necessary
       conditions, for all OLSRv2 interfaces, then that router MAY be
       removed from the set of MPRs.  This process MAY be repeated until
       no MPRs are removed.  Routers MAY be considered in order of
       increasing N_willingness.

   Symmetric 1-hop neighbor routers with N_willingness = WILL_NEVER MUST
   NOT be selected as MPRs, and MUST be ignored in the following
   algorithm, as MUST be symmetric 2-hop neighbor routers which are also
   symmetric 1-hop neighbor routers (i.e. when considering 2-Hop Tuples,
   ignore any 2-Hop Tuples whose N2_2hop_iface_addr is in the
   N_neighbor_iface_addr_list of any Neighbor Tuple, or whose
   N2_neighbor_iface_addr_list is included in the
   N_neighbor_iface_addr_list of any Neighbor Tuple with N_willingness =
   WILL_NEVER).

B.1.  Terminology

   The following terminology will be used when selecting MPRs for the
   OLSRv2 interface I:

   N(I)  - The set of symmetric 1-hop neighbors which have a symmetric
      link to I.





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   N2(I)  - The set of addresses of interfaces of a router with a
      symmetric link to a router in N(I); this MAY be restricted to
      considering only information received over I (in which case N2(I)
      is the set of N2_2hop_iface_addr in 2-Hop Tuples in the 2-Hop Set
      for OLSRv2 interface I).

   Connected to I via Y  - An address A in N2(I) is connected to I via a
      router Y in N(I) if A is an address of an interface of a symmetric
      1-hop neighbor of Y (i.e.  A is the N2_2hop_iface_addr in a 2-Hop
      Tuple in the 2-Hop Set for OLSRv2 interface I, and whose
      N2_neighbor_iface_addr_list is contained in the set of interface
      addresses of Y).

   D(Y, I)  - For a router Y in N(I), the number of addresses in N2(I)
      which are connected to I via Y.

   R(Y, I):  - For a router Y in N(I), the number of addresses in N2(I)
      which are connected to I via Y, but are not connected to I via any
      router which has already been selected as an MPR.

B.2.  MPR Selection Algorithm for each OLSRv2 Interface

   When selecting MPRs for the OLSRv2 interface I:

   1.  For each address A in N2(I) for which there is only one router Y
       in N(I) such that A is connected to I via Y, select that router Y
       as an MPR (i.e. set N_mpr := true in the Neighbor Tuple
       corresponding to Y).

   2.  While there exists any router Y in N(I) with R(Y, I) > 0:

       1.  Select a router Y in N(I) with R(Y, I) > 0 in the following
           order of priority:

           +  greatest N_willingness in the Neighbor Tuple corresponding
              to Y, THEN;

           +  greatest R(Y, I), THEN;

           +  greatest D(Y, I), THEN;

           +  N_mpr_selector is equal to true, if possible, THEN;

           +  any choice.

       2.  Select Y as an MPR (i.e. set N_mpr := true in the Neighbor
           Tuple corresponding to Y).




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Appendix C.  Example Algorithm for Calculating the Routing Set

   The following procedure is given as an example for calculating the
   Routing Set using a variation of Dijkstra's algorithm.  First all
   Routing Tuples are removed, and then the procedures in the following
   sections are applied in turn.

C.1.  Add Local Symmetric Links

   1.  For each Local Interface Tuple:

       1.  Select an address (the "local address") in
           I_local_iface_addr_list.

       2.  For each Link Tuple for this local interface with L_status =
           SYMMETRIC:

           1.  For each address (the "current address") in
               L_neighbor_iface_addr_list, if there is no Routing Tuple
               with R_dest_addr = current address, then add a Routing
               Tuple with:

               -  R_dest_addr := current address;

               -  R_next_iface_addr := current address;

               -  R_dist := 1;

               -  R_local_iface_addr := local address.

   2.  For each Neighbor Tuple whose N_neighbor_iface_addr_list contains
       the R_dest_addr of a Routing Tuple (the "previous Tuple"):

       1.  For each address (the "current address") in
           N_neighbor_iface_addr_list, if there is no Routing Tuple with
           R_dest_addr = current address, then add a Routing Tuple with:

           +  R_dest_addr := current address;

           +  R_next_iface_addr := R_dest_addr of the previous Tuple;

           +  R_dist := 1;

           +  R_local_iface_addr := R_local_iface_addr of the previous
              Tuple.






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C.2.  Add Remote Symmetric Links

   The following procedure, which adds Routing Tuples for destination
   routers h+1 hops away, MUST be executed for each value of h, starting
   with h := 1 and incrementing by 1 for each iteration.  The execution
   MUST stop if no new Routing Tuples are added in an iteration.

   1.  For each Topology Tuple, if:

       *  T_dest_iface_addr is not equal to R_dest_addr of any Routing
          Tuple, AND;

       *  for the Advertising Remote Router Tuple with AR_orig_addr =
          T_orig_addr, there is an address in the AR_iface_addr_list
          which is equal to the R_dest_addr of a Routing Tuple (the
          "previous Routing Tuple") whose R_dist = h

       then add a new Routing Tuple, with:

       *  R_dest_addr := T_dest_iface_addr;

       *  R_next_iface_addr := R_next_iface_addr of the previous Routing
          Tuple;

       *  R_dist := h+1;

       *  R_local_iface_addr := R_local_iface_addr of the previous
          Routing Tuple.

       More than one Topology Tuple may be usable to select the next hop
       R_next_iface_addr for reaching the address R_dest_addr.  Ties
       should be broken such that routers with greater willingness are
       preferred, and between routers of equal willingness, MPR
       selectors are preferred over non-MPR selectors.

   2.  After the above iteration has completed, if h = 1, for each 2-Hop
       Neighbor Tuple where:

       *  N2_2hop_iface_addr is not equal to R_dest_addr of any Routing
          Tuple, AND;

       *  The Neighbor Tuple whose N_neighbor_iface_addr_list contains
          N2_neighbor_iface_addr_list has N_willingness not equal to
          WILL_NEVER

       select a Routing Tuple (the "previous Routing Tuple") whose
       R_dest_addr is contained in N2_neighbor_iface_addr_list, and add
       a new Routing Tuple with:



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       *  R_dest_addr := N2_2hop_iface_addr;

       *  R_next_iface_addr := R_next_iface_addr of the previous Routing
          Tuple;

       *  R_dist := 2;

       *  R_local_iface_addr := R_local_iface_addr of the previous
          Routing Tuple.

       More than one 2-Hop Neighbor Tuple may be usable to select the
       next hop R_next_iface_addr for reaching the address R_dest_addr.
       Ties should be broken such that routers with greater willingness
       are preferred, and between routers of equal willingness, MPR
       selectors are preferred over non-MPR selectors.

C.3.  Add Attached Networks

   1.  For each Attached Network Tuple, if for the Advertising Remote
       Router Tuple with AR_orig_addr = AN_orig_addr, there is an
       address in the AR_iface_addr_list which is equal to the
       R_dest_addr of a Routing Tuple (the "previous Routing Tuple"),
       then:

       1.  If there is no Routing Tuple with R_dest_addr = AN_net_addr,
           then add a new Routing Tuple with:

           +  R_dest_addr := AN_net_addr;

           +  R_next_iface_addr := R_next_iface_addr of the previous
              Routing Tuple;

           +  R_dist := (R_dist of the previous Routing Tuple) +
              AN_dist;

           +  R_local_iface_addr := R_local_iface_addr of the previous
              Routing Tuple.

       2.  Otherwise if the Routing Tuple with R_dest_addr = AN_net_addr
           (the "current Routing Tuple") has R_dist > (R_dist of the
           previous Routing Tuple) + AN_dist, then modify the current
           Routing Tuple by:

           +  R_next_iface_addr := R_next_iface_addr of the previous
              Routing Tuple;

           +  R_dist := (R_dist of the previous Routing Tuple) +
              AN_dist;



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           +  R_local_iface_addr := R_local_iface_addr of the previous
              Routing Tuple.

Appendix D.  Example Message Layout

   An example TC message is as follows.  The message has full Message
   Header (four bit flags field value is 15).  Its four bit Message
   Address Length field has value 3 and hence addresses in the message
   have length four octets, here being IPv4 addresses.  The overall
   message length is 65 octets.

   The message has a Message TLV Block with content length 13 octets
   containing three TLVs.  The first two TLVs are interval and validity
   times for the message.  The third TLV is the content sequence number
   TLV used to carry the 2 octet ANSN, and (with default type extension
   zero, i.e.  COMPLETE) indicating that the TC message is complete.
   Each TLV uses a TLV with flags octet value 16, indicating that it has
   a value, but no type extension or start and stop indexes.  The first
   two TLVs have a value length of 1 octet, the last has a value length
   of 2 octets.

   The message has two Address Blocks.  The first Address Block contains
   6 addresses, with flags octet value 128, hence with a Head section,
   (with length 2 octets) but no Tail section, and hence Mid sections
   with length two octets.  The following TLV Block (content length 6
   octets) contains a single LOCAL_IF TLV (flags octet value 48)
   indicating that the first three addresses (indexes 0 to 2) are
   associated with the value (length 1 octet) UNSPEC_IF, i.e. they are
   the originating router's local interface addresses.  The remaining
   three addresses have no associated TLV, they are the interface
   addresses of advertised neighbors.

   The second Address Block contains 1 address, with flags octet 176
   indicating that there is a Head section (with length 2 octets), that
   the Tail section (length 2 octets) consists of zero valued octets
   (not included), and that there is a single prefix length, which is
   16.  The network address is thus Head.0.0/16.  The following TLV
   Block (content length 8 octets) includes one TLV that indicates that
   the originating router is a gateway to this network, at a given
   number of hops distance (value length 1 octet).  The TLV flags octet
   value of 16 indicates that no indexes are needed.










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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      TC       |1 1 1 1 0 0 1 1|0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      Originator Address                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Hop Limit   |   Hop Count   |    Message Sequence Number    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 1| INTERVAL_TIME |0 0 0 1 0 0 0 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 0 0 1|     Value     | VALIDITY_TIME |0 0 0 1 0 0 0 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 0 0 1|     Value     | CONT_SEQ_NUM  |0 0 0 1 0 0 0 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 0 1 0|         Value (ANSN)          |0 0 0 0 0 1 1 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |1 0 0 0 0 0 0 0|0 0 0 0 0 0 1 0|             Head              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |              Mid              |              Mid              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |              Mid              |              Mid              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |              Mid              |              Mid              |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0|   LOCAL_IF    |0 0 1 1 0 0 0 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 0 0 0|0 0 0 0 0 0 1 0|0 0 0 0 0 0 0 1|   UNSPEC_IF   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 0 0 1|1 0 1 1 0 0 0 0|0 0 0 0 0 0 1 0|     Head      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Head (cont)  |0 0 0 0 0 0 1 0|0 0 0 1 0 0 0 0|0 0 0 0 0 0 0 0|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 1 0 0|    GATEWAY    |0 0 0 1 0 0 0 0|0 0 0 0 0 0 0 1|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Number Hops  |
     +-+-+-+-+-+-+-+-+

Appendix E.  Constraints

   Any process which updates the Local Information Base, the
   Neighborhood Information Base or the Topology Information Base MUST
   ensure that all constraints specified in this appendix are
   maintained, as well as those specified in [NHDP].

   In each Originator Tuple:





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   o  O_orig_addr MUST NOT equal any other O_orig_addr.

   o  O_orig_addr MUST NOT equal this router's originator address.

   In each Local Attached Network Tuple:

   o  AL_net_addr MUST NOT equal any other AL_net_addr.

   o  AL_net_addr MUST NOT be in the I_local_iface_addr_list of any
      Local Interface Tuple or be equal to the IR_local_iface_addr of
      any Removed Interface Address Tuple.

   o  AL_dist MUST NOT be less than zero.

   In each Link Tuple:

   o  L_neighbor_iface_addr_list MUST NOT contain the AL_net_addr of any
      Local Attached Network Tuple.

   o  If L_status = SYMMETRIC and the Neighbor Tuple whose
      N_neighbor_iface_addr_list contains L_neighbor_iface_addr_list has
      N_mpr_selector = true, then, for each address in this
      L_neighbor_iface_addr_list, there MUST be an equal
      RY_neighbor_iface_addr in the Relay Set associated with the same
      OLSRv2 interface.

   In each Neighbor Tuple:

   o  N_neighbor_iface_addr_list MUST NOT contain the AL_net_addr of any
      Local Attached Network Tuple.

   o  If N_willingness MUST be in the range from WILL_NEVER to
      WILL_ALWAYS, inclusive.

   o  If N_mpr = true, then N_symmetric MUST be true and N_willingness
      MUST NOT equal WILL_NEVER.

   o  If N_symmetric = true and N_mpr = false, then N_willingness MUST
      NOT equal WILL_ALWAYS.

   o  If N_mpr_selector = true, then N_symmetric MUST be true.

   o  If N_mpr_selector = true, then, for each address in this
      N_neighbor_iface_addr_list, there MUST be an equal
      A_neighbor_iface_addr in the Advertised Neighbor Set.

   In each Lost Neighbor Tuple:




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   o  NL_neighbor_iface_addr MUST NOT equal the AL_net_addr of any Local
      Attached Network Tuple.

   In each 2-Hop Tuple:

   o  N2_2hop_iface_addr MUST NOT equal the AL_net_addr of any Local
      Attached Network Tuple.

   In each Received Tuple:

   o  RX_orig_addr MUST NOT equal this router's originator address or
      any O_orig_addr.

   o  Each ordered triple (RX_type, RX_orig_addr, RX_seq_number) MUST
      NOT equal the corresponding triple in any other Received Tuple in
      the same Received Set.

   In each Processed Tuple:

   o  P_orig_addr MUST NOT equal this router's originator address or any
      O_orig_addr.

   o  Each ordered triple (P_type, P_orig_addr, P_seq_number) MUST NOT
      equal the corresponding triple in any other Processed Tuple.

   In each Forwarded Tuple:

   o  F_orig_addr MUST NOT equal this router's originator address or any
      O_orig_addr.

   o  Each ordered triple (F_type, F_orig_addr, F_seq_number) MUST NOT
      equal the corresponding triple in any other Forwarded Tuple.

   In each Relay Tuple:

   o  RY_neighbor_iface_addr MUST NOT equal the RY_neighbor_iface_addr
      in any other Relay Tuple in the same Relay Set.

   o  RY_neighbor_iface_addr MUST be in the L_neighbor_iface_addr_list
      of a Link Tuple with L_status = SYMMETRIC.

   In the Advertised Neighbor Set:

   o  Each A_neighbor_iface_addr MUST NOT equal any other
      A_neighbor_iface_addr.

   o  Each A_neighbor_iface_addr MUST be in the
      N_neighbor_iface_addr_list of a Neighbor Tuple with N_symmetric =



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      true.

   In each Advertising Remote Router Tuple:

   o  AR_orig_addr MUST NOT equal this router's originator address or
      any O_orig_addr.

   o  AR_orig_addr MUST NOT equal the AR_orig_addr in any other ANSN
      History Tuple.

   o  AR_iface_addr_list MUST NOT be empty.

   o  AR_iface_addr_list MUST NOT contain any duplicated addresses.

   o  AR_iface_addr_list MUST NOT contain any address which is in the
      I_local_iface_addr_list of any Local Interface Tuple or be equal
      to the IR_local_iface_addr of any Removed Interface Address Tuple.

   o  AR_iface_addr_list MUST NOT contain any address which is the
      AL_net_addr of any Local Attached Network Tuple.

   In each Topology Tuple:

   o  T_dest_iface_addr MUST NOT be in the I_local_iface_addr_list of
      any Local Interface Tuple or be equal to the IR_local_iface_addr
      of any Removed Interface Address Tuple.

   o  T_dest_iface_addr MUST NOT equal the AL_net_addr of any Local
      Attached Network Tuple.

   o  There MUST be an Advertising Remote Router Tuple with AR_orig_addr
      = T_orig_addr.

   o  T_dest_iface_addr MUST NOT be in the AR_iface_addr_list of the
      Advertising Remote Router Tuple with AR_orig_addr = T_orig_addr.

   o  T_seq_number MUST NOT be greater than AR_seq_number of the
      Advertising Remote Router Tuple with AR_orig_addr = T_orig_addr.

   o  The ordered pair (T_dest_iface_addr, T_orig_addr) MUST NOT equal
      the corresponding pair in any other Topology Tuple.

   In each Attached Network Tuple:

   o  AN_net_addr MUST NOT be in the I_local_iface_addr_list of any
      Local Interface Tuple or be equal to the IR_local_iface_addr of
      any Removed Interface Address Tuple.




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   o  AN_net_addr MUST NOT equal the AL_net_addr of any Local Attached
      Network Tuple.

   o  There MUST be an Advertising Remote Router Tuple with AR_orig_addr
      = AN_orig_addr.

   o  AN_seq_number MUST NOT be greater than AR_seq_number of the
      Advertising Remote Router Tuple with AR_orig_addr = AN_orig_addr.

   o  AN_dist MUST NOT be less than zero.

   o  The ordered pair (AN_net_addr, AN_orig_addr) MUST NOT equal the
      corresponding pair in any other Attached Network Tuple.

Appendix F.  Flow and Congestion Control

   Due to its proactive nature, the OLSRv2 protocol has a natural
   control over the flow of its control traffic.  Routers transmit
   control messages at predetermined rates specified and bounded by
   message intervals.

   OLSRv2 employs [NHDP] for local signaling, embedding MPR selection
   advertisement through a simple Address Block TLV, and router
   willingness advertisement (if any) as a single Message TLV.  OLSRv2
   local signaling, therefore, shares the characteristics and
   constraints of [NHDP].

   Furthermore, MPR flooding greatly reduces signaling overhead from
   from link state information dissemination in two ways.  First, the
   amount of link state information for a router to declare is reduced
   to only contain that router's MPR selectors.  This reduces the size
   of a link state declaration as compared to declaring full link state
   information.  In particular some routers may not need to declare any
   such information.  Second, using MPR flooding, the cost of
   distributing link state information throughout the network is greatly
   reduced, as compared to when using classic flooding, since only MPRs
   need to forward link state declaration messages.  In dense networks,
   the reduction of control traffic can be of several orders of
   magnitude compared to routing protocols using classical flooding
   [MPR].  This feature naturally provides more bandwidth for useful
   data traffic and pushes further the frontier of congestion.

   Since the control traffic is continuous and periodic, it keeps the
   quality of the links used in routing more stable.  However, using
   certain OLSRv2 options, some control messages (HELLO messages or TC
   messages) may be intentionally sent in advance of their deadline in
   order to increase the responsiveness of the protocol to topology
   changes.  This may cause a small, temporary, and local increase of



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   control traffic, however this is at all times bounded by the use of
   minimum message intervals.

Authors' Addresses

   Thomas Heide Clausen
   LIX, Ecole Polytechnique

   Phone: +33 6 6058 9349
   EMail: T.Clausen@computer.org
   URI:   http://www.ThomasClausen.org/


   Christopher Dearlove
   BAE Systems ATC

   Phone: +44 1245 242194
   EMail: chris.dearlove@baesystems.com
   URI:   http://www.baesystems.com/


   Philippe Jacquet
   Project Hipercom, INRIA

   Phone: +33 1 3963 5263
   EMail: philippe.jacquet@inria.fr


   The OLSRv2 Design Team
   MANET Working Group





















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