Network Working Group                                    T. Clausen, Ed. Request for Comments: 3626                              P. Jacquet, Ed. Category: Experimental                          Project Hipercom, INRIA                                                            October 2003              Optimized Link State Routing Protocol (OLSR)
Status of this Memo
This memo defines an Experimental Protocol for the Internet
community.  It does not specify an Internet standard of any kind.
Discussion and suggestions for improvement are requested.
Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2003).  All Rights Reserved. Abstract
This document describes the Optimized Link State Routing (OLSR)
protocol for mobile ad hoc networks.  The protocol is an optimization    of the classical link state algorith
m tailored to the requirements of    a mobile wireless LAN.  The key concept used in the protocol is that    of multipoint relays (MPRs).  MPRs are selected nodes which forward
broadcast messages during the flooding process.  This technique
substantially reduces the message overhead as compared to a classical    flooding mechanism, where every node retransmits each message when it    receives the first copy of the message.  In OLSR, link state
information is generated only by nodes elected as MPRs.  Thus, a
second optimization is achieved by minimizing the number of control
messages flooded in the network.  As a third optimization, an MPR
node may chose to report only links between itself and its MPR
selectors.  Hence, as contrary to the classic link state algorithm,
partial link state information is distributed in the network.  This
information is then used for route calculation.  OLSR provides
optimal routes (in terms of number of hops).  The protocol is
particularly suitable for large and dense networks as the technique
of MPRs works well in this context.
Clausen & Jacquet            Experimental                      [Page 1]
Table of Contents
1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .  4      1.1. OLSR Terminology.  . . . . . . . . . . . . . . . . . . .  5      1.
2. Applicability. . . . . . . . . . . . . . . . . . . . . .  7      1.
3. Protocol Overview  . . . . . . . . . . . . . . . . . . .  8
1.4. Multipoint Relays  . . . . . . . . . . . . . . . . . . .  9
2.  Protocol Functioning  . . . . . . . . . . . . . . . . . . . .  9      2.1. Core Functioning  . . . . . . . . . . . . . . . . . . .  10
2.2. Auxiliary Functioning  . . . . . . . . . . . . . . . . .  12
3.  Packet Format and Forwarding  . . . . . . . . . . . . . . . .  13      3.1. Protocol and Port Number.  . . . . . . . . . . . . . . .  13      3.2. Main Address  . . . . . . . . . . . . . . . . . . . . .  13      3.3. Packet Format  . . . . . . . . . . . . . . . . . . . . .  14            3.3.1. Packet Header . . . . . . . . . . . . . . . . . .  14            3.3.2. Message Header  . . . . . . . . . . . . . . . . .  15      3.
sort of link什么意思
4. Packet Processing and Message Flooding . . . . . . . . .  16            3.4.1. Default Forwarding Algorithm. . . . . . . . . . .  18            3.4.2. Considerations on Processing and Forwarding . . .  20
3.5. Message Emission and Jitter. . . . . . . . . . . . . . .  21
4.  Information Repositories  . . . . . . . . . . . . . . . . . .  22      4.1. Multiple Interface Association Information Base  . . . .  22      4.2. Link sensing: Local Link Information Base. . . . . . . .  22            4.2.1. Link Set. . . . . . . . . . . . . . . . . . . . .  22      4.3. Neighbor Detection: Neighborhood Information Base. . . .  23            4.3.1. Neighbor Set. . . . . . . . . . . . . . . . . . .  23            4.3.2. 2-hop Neighbor Set. . .
. . . . . . . . . . . . .  23            4.3.3. MPR Set . . . . . . . . . . . . . . . . . . . . .  23            4.3.4. MPR Selector Set. . . . . . . . . . . . . . . . .  23
4.4. Topology Information Base  . . . . . . . . . . . . . . .  24
5.  Main Addresses and Multiple Interfaces  . . . . . . . . . . .  24      5.1. MID Message Format . . . . . . . . . . . . . . . . . . .  25      5.2. MID Message Generation . . . . . . . . . . . . . . . . .  25      5.3. MID Message Forwarding . . . . . . . . . . . . . . . . .  26      5.4. MID Message Processing . . . . . . . . . . . . . . . . .  26
5.5. Resolving a Main Address from an Interface Address . . .  27
6.  HELLO Message Format and Generation . . . . . . . . . . . . .  27      6.1. HELLO Message Format . . . . . . . . . . . . . . . . . .  27            6.1.1. Link Code as Link Type and Neighbor Type. . . . .  29      6.2. HELLO Message Generation . . . . . . . . . . . . . . . .  30      6.3. HELLO Message Forwarding . . . . . . . . . . . . . . . .  33
6.4. HELLO Message Processing . . . . . . . . . . . . . . . .  33
7.  Link Sensing  . . . . . . . . . . . . . . . . . . . . . . . .  33      7.1. Populating the Link Set  . . . . . . . . . . . . . . . .  33
7.1.1. HELLO Message Processing  . . . . . . . . . . . .  34
8.  Neighbor Detection  . . . . . . . . . . . . . . . . . . . . .  35      8.1. Populating the Neighbor Set . . . . . . . . . . . . . . .  35            8.1.1. HELLO Message Processing  . . . . . . . . . . . .  37 Clausen & Jacquet            Experimental                      [Page 2]
8.2. Populating the 2-hop Neighbor Set. . . . . . . . . . . .  37            8.2.1. HELLO Message Processing. . . . . . . . . . . . .  37      8.3. Populating the MPR set . . . . . . . . . . . . . . . . .  38            8.3.1. MPR Computation . . . . . . . . . . . . . . . . .  39      8.4. Populating the MPR Selector Set. . . . . . . . . . . . .  41            8.4.1. HELLO Message Processing. . . . . . . . . . . . .  41
8.5. Neighborhood and 2-hop Neighborhood Changes. . . . . . .  42
9.  Topology Discovery  . . . . . . . . . . . . . . . . . . . . .  43      9.1. TC Message Format. . . . . . . . . . . . . . . . . . . .  43      9.2. Advertised Neighbor Set. . . . . . . . . . . . . . . . .  44      9.3. TC Message Generation. . . . . . . . . . . . . . . . . .  45      9.4. TC Message Forwarding. . . . . . . . . . . . . . . . . .  45
9.5. TC Message Processing. . . . . . . . . . . . . . . . . .  45
10. Routing Table Calculation . . . . . . . . . . . . . . . . . .  47
11. Node Configuration. . . . . . . . . . . . . . . . . . . . . .  50      11.1. Address Assignment. . . . . . . . . . . . . . . . . . .  50      11.2. Routing Configuration . . . . . . . . . . . . . . . . .  51
11.3. Data Packet Forwarding. . . . . . . . . . . . . . . . .  51
12. Non OLSR Interfaces . . . . . . . . . . . . . . . . . . . . .  51      12.1. HNA Message Format. . . . . . . . . . . . . . . . . . .  52      12.2. Host and Network Association Information Base . . . . .  52      12.3. HNA Message Generation. . . . . . . . . . . . . . . . .  53      12.4. HNA Message Forwarding. . . . . . . . . . . . . . . . .  53      12.5. HNA Message Processing. . . . . . . . . . . . . . . . .  53      12.6. Routing Table Calculation . . . . . . . . . . . . . . .  54
12.7. Interoperability Considerations . . . . . . . . . . . .  55
13. Link Layer Notification . . . . . . . . . . . . . . . . . . .  55
13.1. Interoperability Considerations . . . . . . . . . . . .  56
14. Link Hysteresis . . . . . . . . . . . . . . . . . . . . . . .  56      14.1. Local Link Set  . . . . . . . . . . . . . . . . . . . .  56      14.2. Hello Message Generation  . . . . . . . . . . . . . . .  57      14.3. Hysteresis Strategy . . . . . . . . . . . . . . . . . .  57
14.4. Interoperability Considerations . . . . . . . . . . . .  59
15. Redundant Topology Information. . . . . . . . . . . . . . . .  59      15.1. TC_REDUNDANCY Parameter . . . . . . . . . . . . . . . .  60
15.2. Interoperability Considerations . . . . . . . . . . . .  60
16. MPR Redundancy. . . . . . . . . . . . . . . . . . . . . . . .  60      16.1. MPR_COVERAGE Parameter. . . . . . . . . . . . . . . . .  61      16.2. MPR Computation . . . . . . . . . . . . . . . . . . . .  61
16.3. Interoperability Considerations . . . . . . . . . . . .  62
17. IPv6 Considerations . . . . . . . . . . . . . . . . . . . . .  63
18. Proposed Values for Constants . . . . . . . . . . . . . . . .  63      18.1. Setting emission interval and holding times . . . . . .  63      18.2. Emission Interval . . . . . . . . . . . . . . . . . . .  64      18.3. Holding time  . . . . . . . . . . . . . . . . . . . . .  64      18.4. Message Types . . . . . . . . . . . . . . . . . . . . .  65      18.5. Link Types. . . . . . . . . . . . . . . . . . . . . . .  65      18.6. Neighbor Types  . . . . . . . . . . . . . . . . . . . .  65 Clausen & Jacquet            Experimental                      [Page 3]
18.7. Link Hysteresis . . . . . . . . . . . . . . . . . . . .  66      18.8. Willingness . . . . . . . . . . . . . . . . . . . . . .  66
18.9. Misc. Constants . . . . . . . . . . . . . . . . . . . .  67
19. Sequence Numbers. . . . . . . . . . . . . . . . . . . . . . .  67
20. Security Considerations . . . . . . . . . . . . . . . . . . .  67      20.1. Confidentiality . . . . . . . . . . . . . . . . . . . .  67      20.2. Integrity . . . . . . . . . . . . . . . . . . . . . . .  68      20.3. Interaction with External Routing Domains . . . . . . .  69
20.4. Node Identity . . . . . . . . . . . . . . . . . . . . .  70
21. Flow and congestion control . . . . . . . . . . . . . . . . .  70
22. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  70
23. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  71
24. Contributors. . . . . . . . . . . . . . . . . . . . . . . . .  71
25. References. . . . . . . . . . . . . . . . . . . . . . . . . .  73
26. Authors’ Addresses. . . . . . . . . . . . . . . . . . . . . .  74
27. Full Copyright Statement. . . . . . . . . . . . . . . . . . .  75 1.  Introduction
The Optimized Link State Routing Protocol (OLSR) is developed for
mobile ad hoc networks.  It operates as a table driven, proactive
protocol, i.e., exchanges topology information with other nodes of
the network regularly.  Each node selects a set of its neighbor nodes    as "multipoint relays" (MPR).  In OLSR, only nodes, selected as such    MPRs, are responsible for forwarding control traffic, intended for
diffusion into the entire network.  MPRs provide an efficient
mechanism for flooding control traffic by reducing the number of
transmissions required.
Nodes, selected as MPRs, also have a special responsibility when
declaring link state information in the network.  Indeed, the only
requirement for OLSR to provide shortest path routes to all
destinations is that MPR nodes declare link-state information for
their MPR selectors.  Additional available link-state information may    be utilized, e.g., for redundancy.
Nodes which have been selected as multipoint relays by some neighbor    node(s) announce this information periodically in their control
messages.  Thereby a node announces to the network, that it has
reachability to the nodes which have selected it as an MPR.  In route    calculation, the MPRs are used to form the route from a given node to    any destination in the network.  Furthermore, the protocol uses the
MPRs to facilitate efficient flooding of control messages in the
network.
A node selects MPRs from among its one hop neighbors with
"symmetric", i.e., bi-directional, linkages.  Therefore, selecting
the route through MPRs automatically avoids the problems associated Clausen & Jacquet            Experimental                      [Page 4]
with data packet transfer over uni-directional links (such as the
problem of not getting link-layer acknowledgments for data packets at    each hop, for link-layers employing this technique for unicast
traffic).
OLSR is developed to work independently from other protocols.
Likewise, OLSR makes no assumptions about the underlying link-layer.
OLSR inherits the concept of forwarding and relaying from HIPERLAN (a    MAC layer protocol) which is standardized by ETSI [3].  The protocol    is developed in the IPANEMA project (part of the Euclid program) and    in the PRIMA project (part of the RNRT program).
1.1.  OLSR Terminology
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this    document are to be interpreted as described in RFC2119 [5].
Additionally, this document uses the following terminology:
node
A MANET router which implements the Optimized Link State
Routing protocol as specified in this document.
OLSR interface
A network device participating in a MANET running OLSR.  A node          may have several OLSR interfaces, each interface assigned an
unique IP address.
non OLSR interface
A network device, not participating in a MANET running OLSR.  A          node may have several non OLSR interfaces (wireless and/or
wired).  Routing information from these interfaces MAY be
injected into the OLSR routing domain.
single OLSR interface node
A node which has a single OLSR interface, participating in an
OLSR routing domain.
multiple OLSR interface node
A node which has multiple OLSR interfaces, participating in an          OLSR routing domain.
Clausen & Jacquet            Experimental                      [Page 5]

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