Mobile Ad hoc Networking (MANET) T. Clausen
Internet-Draft LIX, Ecole Polytechnique
Intended status: Standards Track C. Dearlove
Expires: January 14, 2010 BAE Systems ATC
P. Jacquet
Project Hipercom, INRIA
The OLSRv2 Design Team
MANET Working Group
July 13, 2009
The Optimized Link State Routing Protocol version 2
draft-ietf-manet-olsrv2-09
Status of This Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. This document may contain material
from IETF Documents or IETF Contributions published or made publicly
available before November 10, 2008. The person(s) controlling the
copyright in some of this material may not have granted the IETF
Trust the right to allow modifications of such material outside the
IETF Standards Process. Without obtaining an adequate license from
the person(s) controlling the copyright in such materials, this
document may not be modified outside the IETF Standards Process, and
derivative works of it may not be created outside the IETF Standards
Process, except to format it for publication as an RFC or to
translate it into languages other than English.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on January 14, 2010.
Copyright Notice
Clausen, et al. Expires January 14, 2010 [Page 1]
Internet-Draft OLSRv2 July 2009
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 for Mobile Ad hoc NETworks (MANETs).
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Applicability Statement . . . . . . . . . . . . . . . . . . . 7
4. Protocol Overview and Functioning . . . . . . . . . . . . . . 8
4.1. Routers and Interfaces . . . . . . . . . . . . . . . . . . 10
4.2. Information Base Overview . . . . . . . . . . . . . . . . 11
4.2.1. Local Information Base . . . . . . . . . . . . . . . . 11
4.2.2. Interface Information Bases . . . . . . . . . . . . . 11
4.2.3. Neighbor Information Base . . . . . . . . . . . . . . 11
4.2.4. Topology Information Base . . . . . . . . . . . . . . 12
4.2.5. Processing and Forwarding Information Base . . . . . . 13
4.3. Signaling Overview . . . . . . . . . . . . . . . . . . . . 13
5. Protocol Parameters and Constants . . . . . . . . . . . . . . 14
5.1. Protocol and Port Numbers . . . . . . . . . . . . . . . . 14
5.2. Multicast Address . . . . . . . . . . . . . . . . . . . . 15
5.3. Local History Times . . . . . . . . . . . . . . . . . . . 15
5.4. Message Intervals . . . . . . . . . . . . . . . . . . . . 15
5.5. Advertised Information Validity Times . . . . . . . . . . 16
5.6. Received Message Validity Times . . . . . . . . . . . . . 17
5.7. Jitter . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.8. Hop Limit Parameter . . . . . . . . . . . . . . . . . . . 18
5.9. Willingness . . . . . . . . . . . . . . . . . . . . . . . 18
5.10. Parameter Change Constraints . . . . . . . . . . . . . . . 19
6. Information Bases . . . . . . . . . . . . . . . . . . . . . . 20
6.1. Local Information Base . . . . . . . . . . . . . . . . . . 21
6.1.1. Originator Set . . . . . . . . . . . . . . . . . . . . 21
6.1.2. Local Attached Network Set . . . . . . . . . . . . . . 21
6.2. Neighbor Information Base . . . . . . . . . . . . . . . . 22
6.3. Topology Information Base . . . . . . . . . . . . . . . . 22
6.3.1. Advertised Neighbor Set . . . . . . . . . . . . . . . 22
6.3.2. Advertising Remote Router Set . . . . . . . . . . . . 23
6.3.3. Topology Set . . . . . . . . . . . . . . . . . . . . . 23
Clausen, et al. Expires January 14, 2010 [Page 2]
Internet-Draft OLSRv2 July 2009
6.3.4. Attached Network Set . . . . . . . . . . . . . . . . . 24
6.3.5. Routing Set . . . . . . . . . . . . . . . . . . . . . 25
6.4. Processing and Forwarding Information Base . . . . . . . . 25
6.4.1. Received Set . . . . . . . . . . . . . . . . . . . . . 25
6.4.2. Processed Set . . . . . . . . . . . . . . . . . . . . 26
6.4.3. Forwarded Set . . . . . . . . . . . . . . . . . . . . 26
6.4.4. Relay Set . . . . . . . . . . . . . . . . . . . . . . 27
7. Message Processing and Forwarding . . . . . . . . . . . . . . 27
7.1. Actions when Receiving a Message . . . . . . . . . . . . . 28
7.2. Message Considered for Processing . . . . . . . . . . . . 28
7.3. Message Considered for Forwarding . . . . . . . . . . . . 29
8. Packets and Messages . . . . . . . . . . . . . . . . . . . . . 31
8.1. HELLO Messages . . . . . . . . . . . . . . . . . . . . . . 32
8.1.1. HELLO Message TLVs . . . . . . . . . . . . . . . . . . 32
8.1.2. HELLO Message Address Block TLVs . . . . . . . . . . . 33
8.2. TC Messages . . . . . . . . . . . . . . . . . . . . . . . 33
8.2.1. TC Message TLVs . . . . . . . . . . . . . . . . . . . 34
8.2.2. TC Message Address Block TLVs . . . . . . . . . . . . 34
9. HELLO Message Generation . . . . . . . . . . . . . . . . . . . 35
9.1. HELLO Message: Transmission . . . . . . . . . . . . . . . 35
10. HELLO Message Processing . . . . . . . . . . . . . . . . . . . 36
10.1. Updating Willingness . . . . . . . . . . . . . . . . . . . 36
10.2. Updating MPR Selectors . . . . . . . . . . . . . . . . . . 36
10.3. Symmetric 1-Hop and 2-Hop Neighborhood Changes . . . . . . 37
11. TC Message Generation . . . . . . . . . . . . . . . . . . . . 38
11.1. TC Message: Transmission . . . . . . . . . . . . . . . . . 39
12. TC Message Processing . . . . . . . . . . . . . . . . . . . . 40
12.1. Invalid Message . . . . . . . . . . . . . . . . . . . . . 40
12.2. Initial TC Message Processing . . . . . . . . . . . . . . 41
12.3. Initial TC Message Processing . . . . . . . . . . . . . . 42
12.3.1. Populating the Advertising Remote Router Set . . . . . 42
12.3.2. Populating the Topology Set . . . . . . . . . . . . . 43
12.3.3. Populating the Attached Network Set . . . . . . . . . 43
12.4. Completing TC Message Processing . . . . . . . . . . . . . 44
12.4.1. Purging the Topology Set . . . . . . . . . . . . . . . 44
12.4.2. Purging the Attached Network Set . . . . . . . . . . . 44
13. Information Base Changes . . . . . . . . . . . . . . . . . . . 45
14. Selecting MPRs . . . . . . . . . . . . . . . . . . . . . . . . 46
15. Populating Derived Sets . . . . . . . . . . . . . . . . . . . 48
15.1. Populating the Relay Set . . . . . . . . . . . . . . . . . 48
15.2. Populating the Advertised Neighbor Set . . . . . . . . . . 48
16. Routing Set Calculation . . . . . . . . . . . . . . . . . . . 49
16.1. Network Topology Graph . . . . . . . . . . . . . . . . . . 49
16.2. Populating the Routing Set . . . . . . . . . . . . . . . . 50
16.3. Routing Set Updates . . . . . . . . . . . . . . . . . . . 51
17. Proposed Values for Parameters and Constants . . . . . . . . . 51
17.1. Local History Time Parameters . . . . . . . . . . . . . . 51
17.2. Message Interval Parameters . . . . . . . . . . . . . . . 51
Clausen, et al. Expires January 14, 2010 [Page 3]
Internet-Draft OLSRv2 July 2009
17.3. Advertised Information Validity Time Parameters . . . . . 52
17.4. Received Message Validity Time Parameters . . . . . . . . 52
17.5. Jitter Time Parameters . . . . . . . . . . . . . . . . . . 52
17.6. Hop Limit Parameter . . . . . . . . . . . . . . . . . . . 52
17.7. Willingness Parameter and Constants . . . . . . . . . . . 52
18. Sequence Numbers . . . . . . . . . . . . . . . . . . . . . . . 52
19. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 53
19.1. Message Types . . . . . . . . . . . . . . . . . . . . . . 53
19.2. Message TLV Types . . . . . . . . . . . . . . . . . . . . 53
19.3. Address Block TLV Types . . . . . . . . . . . . . . . . . 54
20. Security Considerations . . . . . . . . . . . . . . . . . . . 55
20.1. Confidentiality . . . . . . . . . . . . . . . . . . . . . 55
20.2. Integrity . . . . . . . . . . . . . . . . . . . . . . . . 56
20.3. Interaction with External Routing Domains . . . . . . . . 57
21. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 58
22. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 58
23. References . . . . . . . . . . . . . . . . . . . . . . . . . . 58
23.1. Normative References . . . . . . . . . . . . . . . . . . . 58
23.2. Informative References . . . . . . . . . . . . . . . . . . 59
Appendix A. Router Configuration . . . . . . . . . . . . . . . . 60
Appendix B. Example Algorithm for Calculating MPRs . . . . . . . 60
B.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 61
B.2. MPR Selection Algorithm for each OLSRv2 Interface . . . . 61
Appendix C. Example Algorithm for Calculating the Routing Set . . 62
C.1. Add Local Symmetric Links . . . . . . . . . . . . . . . . 62
C.2. Add Remote Symmetric Links . . . . . . . . . . . . . . . . 63
C.3. Add Attached Networks . . . . . . . . . . . . . . . . . . 64
Appendix D. Example Message Layout . . . . . . . . . . . . . . . 65
Appendix E. Constraints . . . . . . . . . . . . . . . . . . . . . 67
Appendix F. Flow and Congestion Control . . . . . . . . . . . . . 70
Clausen, et al. Expires January 14, 2010 [Page 4]
Internet-Draft OLSRv2 July 2009
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 using
a more flexible and efficient signaling framework, and includes some
simplification of the messages being exchanged.
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. It is an
optimization of the classical link state routing protocol. The key
concept used in the protocol is that of MultiPoint Relays (MPRs).
Each router selects a set of its neighbor routers (which "cover" all
of its symmetrically connected 2-hop neighbor routers) as MPRs.
Control traffic is 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. bidirectional, links. Therefore, selecting routes
through MPRs automatically avoids the problems associated with data
packet transfer over unidirectional links (such as the problem of not
getting link layer acknowledgments at each hop, for link layers
employing this technique).
OLSRv2 uses and extends [NHDP] and uses [RFC5444], [RFC5497] and,
optionally, [RFC5148]. (These other protocols and specifications
were all originally created as part of OLSRv2, but have been
specified separately for wider use.)
OLSRv2 makes no assumptions about the underlying link layer.
However, OLSRv2, through its use of [NHDP], may use link layer
information and notifications when available and applicable.
Clausen, et al. Expires January 14, 2010 [Page 5]
Internet-Draft OLSRv2 July 2009
OLSRv2, as OLSRv1, inherits its concept of forwarding and relaying
from HIPERLAN (a MAC layer protocol) which is standardized by ETSI
[HIPERLAN], [HIPERLAN2].
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].
All terms introduced in [RFC5444], including "packet", "message",
"Address Block", "TLV Block", and "TLV", are to be interpreted as
described there.
All terms introduced in [NHDP], including "interface", "MANET
interface", "address", "symmetric link", "symmetric 1-hop neighbor",
"symmetric 2-hop neighbor", "constant", "interface parameter", and
"router parameter", are to be interpreted as described there.
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] to support OLSRv2.
Originator address - An address which is unique (within the MANET)
to the selecting router. A router MUST select an originator
address; it MAY choose one of its interface addresses as its
originator address. An originator address MUST NOT have a prefix
length. An originator address MUST be included in all messages
generated by this protocol, and as specified in [RFC5444].
Willingness - 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 router, X, is a symmetric strict
2-hop neighbor of a router Y, if router X is a symmetric 2-hop
neighbor of router Y and if router X is not also a willing
symmetric 1-hop neighbor of router Y.
Clausen, et al. Expires January 14, 2010 [Page 6]
Internet-Draft OLSRv2 July 2009
Symmetric strict 2-hop neighbor through OLSRv2 interface I - A
symmetric strict 2-hop neighbor of the router with OLSRv2
interface I which is a symmetric 1-hop neighbor of a willing
symmetric 1-hop neighbor of that router via a symmetric link using
OLSRv2 interface I. The router MAY elect to consider only
information received over OLSRv2 interface I in making this
determination.
Symmetric strict 2-hop neighborhood - The symmetric strict 2-hop
neighborhood of a router X is the set of symmetric strict 2-hop
neighbors of router X.
Multipoint relay (MPR) - A router, X, is an MPR for a router, Y, if
router Y has selected 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, Y, is an MPR selector of router X if router
Y has selected router X as MPR.
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
The Optimized Link State Routing protocol version 2 (OLSRv2):
o Is a proactive routing protocol for mobile ad hoc networks
(MANETs) [RFC2501].
o Is designed to work in networks with a dynamic topology, and in
which messages may be lost, such as due to collisions in wireless
networks.
o Supports routers that each have one or more participating OLSRv2
interfaces. The set of a router's interfaces may change over
time. Each OLSRv2 interface may have one or more addresses (which
may have prefix lengths), and these may also be dynamically
changing.
o Enables hop-by-hop routing, i.e., each router can use its local
information provided by OLSRv2 to route packets.
Clausen, et al. Expires January 14, 2010 [Page 7]
Internet-Draft OLSRv2 July 2009
o Continuously maintains routes to all destinations in the network,
i.e., routes are instantly available and data traffic is subject
to no delays due to route discovery. Consequently, no data
traffic buffering is required.
o Supports routers which have non-OLSRv2 interfaces which may be
local to a router or which can serve as gateways towards other
networks.
o Is optimized for large and dense networks: the larger and more
dense a network, the more optimization can be achieved by using
MPRs, compared to the classic link state algorithm.
o Uses the message format specified in [RFC5444]. This includes the
definition of a TC Message Type, used for MANET wide signaling of
network topology information.
o Allows "external" and "internal" extensibility as enabled by
[RFC5444].
o Uses [NHDP] for discovering each OLSRv2 router's 1-hop and
symmetric 2-hop neighbors, and extends [NHDP] by addition of MPR
and willingness information.
o Is designed to work in a completely distributed manner, and does
not depend on any central entity.
4. Protocol Overview and Functioning
The objective of OLSRv2 is, for each router to, independently:
o Identify all destinations in the network.
o Identify a sufficient subset of links in the network, in order
that shortest paths can be calculated to all available
destinations.
o Provide a Routing Set, containing these shortest paths from this
router to all destinations.
These objectives are achieved for each router by:
o Using [NHDP] to identify symmetric 1-hop neighbors and symmetric
2-hop neighbors.
o Independently selecting MPRs from among its symmetric 1-hop
neighbors such that all symmetric 2-hop neighbors are reachable
via at least one symmetric 1-hop neighbor. An analysis and
Clausen, et al. Expires January 14, 2010 [Page 8]
Internet-Draft OLSRv2 July 2009
examples of MPR selection algorithms is given in [MPR], a
suggested algorithm is included in this specification. Note that
it is not necessary for routers to use the same algorithm to
interoperate.
o Signaling its MPR selection by extending [NHDP] to include this
information in outgoing HELLO messages.
o Extracting its MPR selectors from received HELLO messages.
o Reporting its willingness to be an MPR in HELLO messages. The
router's willingness to be an MPR indicates how willing it is to
participate in MPR flooding and to be an intermediate node for
routing. A node can absolutely decline to perform either role.
o Periodically signaling links between MPR selectors and itself
throughout the MANET, by using TC (Topology Control) messages,
defined in this specification.
o Diffusing TC messages by using flooding reduction mechanism,
denoted "MPR flooding": only the MPRs of a router will retransmit
messages received from (i.e., originated or last relayed by) that
router.
This specification defines, in turn:
o Parameters and constants used by OLSRv2, in addition to those
specified in [NHDP]. Parameters used by OLSRv2 may be, where
appropriate, specific to a given OLSRv2 interface, or to an OLSRv2
router. OLSRv2 allows all parameters to be changed dynamically,
and to be set independently for each OLSRv2 router or OLSRv2
interface, as appropriate.
o Extensions to the Information Bases specified in [NHDP], and new
Topology Information Base and Processing and Forwarding
Information Base.
o An Address Block TLV, to be included within the HELLO messages of
[NHDP], allowing a router to signal MPR selection.
o A Message TLV, to be included within the HELLO messages of [NHDP],
allowing a router to indicate its willingness to be an MPR.
o The MPR flooding mechanism.
o The format of the TC message that is used for MANET wide
signaling.
Clausen, et al. Expires January 14, 2010 [Page 9]
Internet-Draft OLSRv2 July 2009
o The generation of TC messages from the appropriate information in
the Information Bases.
o The updating of the Information Bases according to received TC
messages.
o The response to other events, such as the expiration of
information in the Information Bases.
OLSRv2 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 only interacts with IP through routing table management, and
the use of the sending IP address for IP datagrams containing OLSRv2
messages.
4.1. Routers and Interfaces
In order for a router to participate in a MANET, it MUST have at
least one, and possibly more, OLSRv2 interfaces. Each OLSRv2
interface:
o Is configured with one or more addresses, as specified in [NHDP].
These addresses MUST be unique within the MANET.
o Has a number of interface parameters, adding to those specified in
[NHDP].
o Has an Interface Information Base, extending that specified in
[NHDP].
o Generates and processes HELLO messages according to [NHDP],
extended as specified in Section 9 and Section 10.
In addition to a set of MANET interfaces as described above, each
router:
o Has a number of router parameters, adding to those specified in
[NHDP].
o Has a Local Information Base, extending that specified in [NHDP].
o Has a Neighbor Information Base, extending that specified in
[NHDP].
o Has a Topology Information Base, recording information required
for generation and processing of TC messages.
Clausen, et al. Expires January 14, 2010 [Page 10]
Internet-Draft OLSRv2 July 2009
o Has a Processing and Forwarding Information Base, recording
information required for MPR flooding, and to ensure that each TC
message is only processed once by a router.
o Generates and processes TC messages.
4.2. Information Base Overview
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.
4.2.1. Local Information Base
The Local Information Base is specified in [NHDP] and contains a
router's local configuration. It is extended in this specification
to also contain a router's:
o Originator Set, containing addresses that were recently used as
this router's originator address.
o Local Attached Network Set, containing addresses of networks to
which this router can act as a gateway.
The Originator Set is used to enable a router to recognize and
discard control traffic which was originated by the router itself.
The Local Attached Network Set is used to enable a router to include
advertisement of reachability to a network, for which the router can
act as a gateway, when generating TC messages.
4.2.2. Interface Information Bases
The Interface Information Bases, one for each OLSRv2 interface, are
specified in [NHDP]. In addition to the uses in [NHDP], information
recorded in the Interface Information Bases is used for completing
the Routing Set.
4.2.3. Neighbor Information Base
The Neighbor Information Base is specified in [NHDP], and is extended
to also record the willingness of each neighbor to be an MPR, as well
as this router's MPR relationships with each neighbor. Specifically,
each Neighbor Tuple is extended to record whether that neighbor is an
Clausen, et al. Expires January 14, 2010 [Page 11]
Internet-Draft OLSRv2 July 2009
MPR and/or MPR selector of this router, as well as the neighbor's
willingness to be an MPR.
In addition to the uses in [NHDP], information recorded in the
Neighbor Information Base is used to determine inclusion of the MPR
Address Block TLV, defined in this document, as well as for
populating the Advertised Neighbor Set and the Relay Sets of a
router.
4.2.4. Topology Information Base
The Topology Information Base contains:
o An Advertised Neighbor Set, describing the symmetric 1-hop
neighbors of this router that are to be advertised in TC messages.
This set contains at least the MPR selectors of this router, and
is associated with an Advertised Neighbor Sequence Number (ANSN),
which is incremented for each change made to this Advertised
Neighbor Set.
o An Advertising Remote Router Set, describing each other router
from which TC messages have been received.
o A Topology Set, recording links between routers in the MANET, as
described by received TC messages.
o An Attached Network Set, recording networks to which a remote
router has advertised that it may act as a gateway.
o A Routing Set, calculated based on the Interface Information
Bases, the Neighbor Information Base, and the Topology Information
Base to record routes from this router to all available
destinations, The routing table is to be updated from this Routing
Set. (A router MAY choose to use any or all destination addresses
in the Routing Set to update the routing table, this selection is
outside the scope of OLSRv2.)
The Advertised Neighbor Set is used for when generating TC messages;
the Advertised Neighbor Sequence Number is included in each TC
message, thereby allowing a receiving router to identify if a TC
message contains fresh or outdated information.
The Advertising Remote Router Set, the Topology Set and the Attached
Network Set are all updated upon receipt of TC messages, and are used
when determining the contents of the Routing Set.
Clausen, et al. Expires January 14, 2010 [Page 12]
Internet-Draft OLSRv2 July 2009
4.2.5. Processing and Forwarding Information Base
The Processing and Forwarding Information Base contains:
o A Received Set, describing TC messages received by this router.
o A Processed Set, describing TC messages processed by this router.
o A Forwarded Set, describing TC messages forwarded by this router.
o A Relay Set for each OLSRv2 interface, describing the set of
neighbor routers from which received traffic is to be relayed (if
otherwise appropriate).
The Processing and Forwarding Information Base serves the MPR
flooding mechanism by enabling that received messages are forwarded
at most once, by a router. and also ensures that received messages
are processed exactly once.
4.3. Signaling Overview
OLSRv2 uses the neighborhood discovery protocol [NHDP], and generates
and processes HELLO messages according to [NHDP], extended according
to Section 9 and Section 10.
OLSRv2 specifies a single message type, the TC message.
OLSRv2 does not require reliable transmission of TC messages; each
router sends TC messages periodically, and can therefore sustain a
reasonable loss of some such messages. Such losses may occur
frequently in wireless networks due to collisions or other
transmission problems. OLSRv2 MAY use "jitter", randomized
adjustments to message transmission times, to reduce the incidence of
collisions as specified in [RFC5148].
OLSRv2 does not require sequenced delivery of TC messages. Each TC
message contains a sequence number which is incremented when the
message contents change. 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.
TC messages may be "complete" or "incomplete". A complete TC message
contains at least the set of addresses of the originating router's
MPR selectors. Complete TC messages are generated periodically (and
also, optionally, in response to neighborhood changes). Incomplete
TC messages may be used to report additions to advertised information
without repeating unchanged information.
Clausen, et al. Expires January 14, 2010 [Page 13]
Internet-Draft OLSRv2 July 2009
TC messages are MPR flooded throughout the MANET. A router
retransmits a TC message only if it is received from (i.e.,
originated from or was last relayed by) one of that router's MPR
selectors.
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]. This is enabled
in OLSRv2 by using [RFC5497].
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:
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. Protocol and Port Numbers
This protocol specifies TC messages, which are included in packets as
defined by [RFC5444]. These packets may be sent either using the
"manet" protocol number or the "manet" well-known UDP port number, as
specified in [RFC5498].
Clausen, et al. Expires January 14, 2010 [Page 14]
Internet-Draft OLSRv2 July 2009
TC messages and HELLO messages [NHDP] SHOULD, in a given deployment
of OLSRv2, both be using the same of either of IP or UDP, in order
that it is possible to combine messages of both protocols into the
same [RFC5444] packet.
5.2. Multicast Address
This protocol specifies HELLO messages, which are included in packets
as defined by [RFC5444]. These packets may be locally transmitted
using the link local multicast address "LL-MANET-Routers", as
specified in [RFC5498].
5.3. 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
5.4. 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.
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].
Clausen, et al. Expires January 14, 2010 [Page 15]
Internet-Draft OLSRv2 July 2009
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 [RFC5497] are included in TC
messages, then TC_INTERVAL MUST be representable as described in
[RFC5497].
5.5. 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 5.8) 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
TC_INTERVAL is RECOMMENDED.
o T_HOLD_TIME MUST be representable as described in [RFC5497].
Clausen, et al. Expires January 14, 2010 [Page 16]
Internet-Draft OLSRv2 July 2009
5.6. 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.
5.7. 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.
TT_MAXJITTER - represents the value of MAXJITTER used in [RFC5148]
for externally triggered TC messages sent by this router.
Clausen, et al. Expires January 14, 2010 [Page 17]
Internet-Draft OLSRv2 July 2009
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].
5.8. 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 [RFC5497].
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.
5.9. 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
values defined in Section 17. (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
Clausen, et al. Expires January 14, 2010 [Page 18]
Internet-Draft OLSRv2 July 2009
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
5.10. 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.
F_HOLD_TIME
* If F_HOLD_TIME changes, then F_time for all Forwarded Tuples
MAY be changed.
Clausen, et al. Expires January 14, 2010 [Page 19]
Internet-Draft OLSRv2 July 2009
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
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:
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.
Clausen, et al. Expires January 14, 2010 [Page 20]
Internet-Draft OLSRv2 July 2009
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,
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
Clausen, et al. Expires January 14, 2010 [Page 21]
Internet-Draft OLSRv2 July 2009
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 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 addresses of symmetric
1-hop neighbors which are to be advertised through TC messages. It
consists of Advertised Neighbor Tuples:
Clausen, et al. Expires January 14, 2010 [Page 22]
Internet-Draft OLSRv2 July 2009
(A_neighbor_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, specifically, each address in the
N_neighbor_addr_list of a Neighbor Tuple MUST be an A_neighbor_addr
if the corresponding N_mpr_selector = true, and MAY be an
A_neighbor_addr if the corresponding N_mpr_selector = false. No
other address may be an A_neighbor_addr. The Advertised Neighbor Set
MUST therefore be updated when the Neighbor Set changes, see
Section 13. 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_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);
AR_addr_list is an unordered list of the 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_addr, T_orig_addr, T_seq_number, T_time)
Clausen, et al. Expires January 14, 2010 [Page 23]
Internet-Draft OLSRv2 July 2009
where:
T_dest_addr is an 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 address T_dest_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;
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.
Clausen, et al. Expires January 14, 2010 [Page 24]
Internet-Draft OLSRv2 July 2009
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 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.
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:
Clausen, et al. Expires January 14, 2010 [Page 25]
Internet-Draft OLSRv2 July 2009
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:
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;
Clausen, et al. Expires January 14, 2010 [Page 26]
Internet-Draft OLSRv2 July 2009
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 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
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.
Clausen, et al. Expires January 14, 2010 [Page 27]
Internet-Draft OLSRv2 July 2009
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.
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;
Clausen, et al. Expires January 14, 2010 [Page 28]
Internet-Draft OLSRv2 July 2009
* 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 address (i.e., the source address of the IP
datagram containing the current message) does not match (taking
into account any address prefix) an 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.
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;
Clausen, et al. Expires January 14, 2010 [Page 29]
Internet-Draft OLSRv2 July 2009
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 address matches (taking account
of any address prefix) an RY_neighbor_iface_addr in the
Relay Set for the receiving interface, then:
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:
Clausen, et al. Expires January 14, 2010 [Page 30]
Internet-Draft OLSRv2 July 2009
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
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,
Clausen, et al. Expires January 14, 2010 [Page 31]
Internet-Draft OLSRv2 July 2009
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 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
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,
Clausen, et al. Expires January 14, 2010 [Page 32]
Internet-Draft OLSRv2 July 2009
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. (A TC message MAY contain <msg-hop-count> even if it
does not need to.)
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).
o A Message TLV with Type := VALIDITY_TIME, as specified in
[RFC5497]. The options included in [RFC5497] for representing
zero and infinite times MUST NOT be used.
o All of the router's addresses. These MUST be included in the
message's Address Blocks, unless:
* the router has a single interface, with a single 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
Clausen, et al. Expires January 14, 2010 [Page 33]
Internet-Draft OLSRv2 July 2009
message's Address Blocks.
o TLV(s) with Type := LOCAL_IF and Value := UNSPEC_IF associated
with all of the router's 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
[RFC5497]. The options included in [RFC5497] 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. |
+--------------+--------------+-------------------------------------+
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.
Clausen, et al. Expires January 14, 2010 [Page 34]
Internet-Draft OLSRv2 July 2009
+---------+--------------+-------------------------------------+
| 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_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_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.
9.1. HELLO Message: Transmission
HELLO messages are included in packets as specified in [RFC5444].
These packets may contain other messages, including TC messages.
Clausen, et al. Expires January 14, 2010 [Page 35]
Internet-Draft OLSRv2 July 2009
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], for discarding a
HELLO message on reception, 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.
10.2. Updating MPR Selectors
N_mpr_selector is updated as follows:
1. If a router finds any of its local 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:
Clausen, et al. Expires January 14, 2010 [Page 36]
Internet-Draft OLSRv2 July 2009
* N_mpr_selector := true
2. Otherwise, if a router finds any of its own 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;
* 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
Clausen, et al. Expires January 14, 2010 [Page 37]
Internet-Draft OLSRv2 July 2009
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 originator address MUST be set to the router's
originator address.
2. The message hop count, if included, MUST be set to zero.
3. 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 5.8.
4. 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.
5. The message MUST contain a Message TLV with Type :=
VALIDITY_TIME, as specified in [RFC5497]. 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
[RFC5497], these times SHOULD be appropriate multiples of
T_HOLD_TIME.
6. The message MAY contain a Message TLV with Type := INTERVAL_TIME,
as specified in [RFC5497]. 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 [RFC5497], these times SHOULD be appropriate
Clausen, et al. Expires January 14, 2010 [Page 38]
Internet-Draft OLSRv2 July 2009
multiples of TC_INTERVAL.
7. Unless the router has a single interface, with a single address
with maximum prefix length, and that address is the router's
originator address, the message MUST contain all of the router's
addresses (i.e. all addresses in an I_local_iface_addr_list) in
its Address Blocks.
8. 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.
9. A complete message MUST include, and an incomplete message MAY
include, in its Address Blocks:
1. Each A_neighbor_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.
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;
Clausen, et al. Expires January 14, 2010 [Page 39]
Internet-Draft OLSRv2 July 2009
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 a hop limit.
o The Message Header a hop count, and contains a multi-value TLV
with Type = VALIDITY_TIME or Type == INTERVAL_TIME, as defined in
[RFC5497].
o The message does not have a single TLV with Type = VALIDITY_TIME
in its Message TLV Block.
o The message has more than one TLV with Type = INTERVAL_TIME in its
Message TLV Block.
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
Clausen, et al. Expires January 14, 2010 [Page 40]
Internet-Draft OLSRv2 July 2009
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 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.
A router MAY recognize additional reasons for identifying that a
message is invalid. An invalid message MUST be silently discarded,
without updating the router's Information Bases.
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 [RFC5497]. All
information in the TC message has the same validity time.
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
Clausen, et al. Expires January 14, 2010 [Page 41]
Internet-Draft OLSRv2 July 2009
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.
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_addr_list := sending address list
Clausen, et al. Expires January 14, 2010 [Page 42]
Internet-Draft OLSRv2 July 2009
3. For each other Advertising Remote Router Tuple (with a
different AR_orig_addr, the "other tuple") whose AR_addr_list
contains any address in the AR_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_addr = advertised address; AND
+ T_orig_addr = originator address
then create a new Topology Tuple with:
+ T_dest_addr := advertised address;
+ T_orig_addr := originator address.
2. This Topology Tuple (existing or new) is then modified as
follows:
+ T_seq_number := ANSN;
+ 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:
Clausen, et al. Expires January 14, 2010 [Page 43]
Internet-Draft OLSRv2 July 2009
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
* 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:
Clausen, et al. Expires January 14, 2010 [Page 44]
Internet-Draft OLSRv2 July 2009
* 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 Advertised Neighbor Set in the Topology Information Base MUST
be changed when the Neighbor Set changes. The following changes
are required:
1. If an address in an N_neighbor_addr_list in a Neighbor Tuple
is removed (including when that Neighbor Tuple is removed)
and that address is also an A_neighbor_addr in an Advertised
Neighbor Tuple, then that Advertised Neighbor Tuple MUST be
removed.
2. If an address is added to an N_neighbor_addr_list in a
Neighbor Tuple with N_mpr_selector = true (including when
such a Neighbor Tuple is added) or for each address in an
N_neighbor_addr_list in a Neighbor Tuple whose N_mpr_selector
has changed from false to true, and that address is not
already an A_neighbor_addr in an Advertised Neighbor Tuple,
then an Advertised Neighbor Tuple MUST be added to the
Advertised Neighbor Set with A_neighbor_addr equal to that
address.
Other changes to the Advertised Neighbor Set MAY be made when the
Neighbor Set changes, in particular if the N_mpr_selector of a
Neighbor Tuple changes from true to false, then the Advertised
Neighbor Tuples whose A_neighbor_addr are addresses in the
N_neighbor_addr_list of that Neighbor Tuple MAY be removed.
Clausen, et al. Expires January 14, 2010 [Page 45]
Internet-Draft OLSRv2 July 2009
3. The Topology Set and the Attached Network Set in 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:
+ 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;
Clausen, et al. Expires January 14, 2010 [Page 46]
Internet-Draft OLSRv2 July 2009
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,
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.
Clausen, et al. Expires January 14, 2010 [Page 47]
Internet-Draft OLSRv2 July 2009
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
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_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 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_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.
Clausen, et al. Expires January 14, 2010 [Page 48]
Internet-Draft OLSRv2 July 2009
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:
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_addr_list has
N_willingness not equal to WILL_NEVER, AND;
* Z is the N2_2hop_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_addr_list of the Advertising Remote Router
Tuple, AND;
* V is the T_dest_addr of the Topology Tuple.
Clausen, et al. Expires January 14, 2010 [Page 49]
Internet-Draft OLSRv2 July 2009
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_addr_list (i.e. the
one in the Neighbor Tuple whose N_neighbor_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_addr_list of the Advertising Remote Router
Tuple, AND;
* 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
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.
Clausen, et al. Expires January 14, 2010 [Page 50]
Internet-Draft OLSRv2 July 2009
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.
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
Clausen, et al. Expires January 14, 2010 [Page 51]
Internet-Draft OLSRv2 July 2009
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
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.
Clausen, et al. Expires January 14, 2010 [Page 52]
Internet-Draft OLSRv2 July 2009
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.
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.
Clausen, et al. Expires January 14, 2010 [Page 53]
Internet-Draft OLSRv2 July 2009
+-------------+------+-----------+----------------------------------+
| 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 |
| Unassigned | TBD2 | 1-255 | Expert Review |
+-------------+------+-----------+----------------------------------+
Table 6
+--------------+------+----------------+----------------------------+
| Name | Type | Type extension | Description |
+--------------+------+----------------+----------------------------+
| CONT_SEQ_NUM | TBD3 | 0 (COMPLETE) | Specifies a content |
| | | | sequence number for this |
| | | | complete message |
| CONT_SEQ_NUM | TBD3 | 1 (INCOMPLETE) | Specifies a content |
| | | | sequence number for this |
| | | | incomplete message |
| Unassigned | TBD3 | 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.
Clausen, et al. Expires January 14, 2010 [Page 54]
Internet-Draft OLSRv2 July 2009
+------------+------+-----------+-----------------------------------+
| Name | Type | Type | Description |
| | | extension | |
+------------+------+-----------+-----------------------------------+
| MPR | TBD4 | 0 | Specifies that a given address is |
| | | | of a router selected as an MPR |
| Unassigned | TBD4 | 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 |
| Unassigned | TBD5 | 1-255 | Expert Review |
+------------+------+-----------+-----------------------------------+
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 address which may or may not be that of the
interface 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
Clausen, et al. Expires January 14, 2010 [Page 55]
Internet-Draft OLSRv2 July 2009
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;
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
Clausen, et al. Expires January 14, 2010 [Page 56]
Internet-Draft OLSRv2 July 2009
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.
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.
Clausen, et al. Expires January 14, 2010 [Page 57]
Internet-Draft OLSRv2 July 2009
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>
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
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, BCP 14, March 1997.
Clausen, et al. Expires January 14, 2010 [Page 58]
Internet-Draft OLSRv2 July 2009
[RFC5148] Clausen, T., Dearlove, C., and B. Adamson, "Jitter
considerations in MANETs", RFC 5148, February 2008.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 5226, BCP 26,
May 2008.
[RFC5444] Clausen, T., Dean, J., Dearlove, C., and C. Adjih,
"Generalized MANET Packet/Message Format", RFC 5444,
February 2009.
[RFC5497] Clausen, T. and C. Dearlove, "Representing multi-value
time in MANETs", RFC 5497, March 2009.
[RFC5498] Chakeres, I., "IANA Allocations for MANET Protocols",
RFC 5498, March 2009.
[NHDP] Clausen, T., Dean, J., and C. Dearlove, "MANET
Neighborhood Discovery Protocol (NHDP)", work in
progress draft-ietf-manet-nhdp-10.txt, July 2009.
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.
Clausen, et al. Expires January 14, 2010 [Page 59]
Internet-Draft OLSRv2 July 2009
[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.
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
Clausen, et al. Expires January 14, 2010 [Page 60]
Internet-Draft OLSRv2 July 2009
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_addr is in the
N_neighbor_addr_list of any Neighbor Tuple, or whose
N2_neighbor_iface_addr_list is included in the N_neighbor_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.
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_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_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:
Clausen, et al. Expires January 14, 2010 [Page 61]
Internet-Draft OLSRv2 July 2009
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).
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.
Clausen, et al. Expires January 14, 2010 [Page 62]
Internet-Draft OLSRv2 July 2009
2. For each Neighbor Tuple whose N_neighbor_addr_list contains the
R_dest_addr of a Routing Tuple (the "previous Tuple"):
1. For each address (the "current address") in
N_neighbor_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.
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_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_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_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
Clausen, et al. Expires January 14, 2010 [Page 63]
Internet-Draft OLSRv2 July 2009
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_addr is not equal to R_dest_addr of any Routing Tuple,
AND;
* The Neighbor Tuple whose N_neighbor_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:
* R_dest_addr := N2_2hop_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_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;
Clausen, et al. Expires January 14, 2010 [Page 64]
Internet-Draft OLSRv2 July 2009
+ 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;
+ 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 (with Value Length 1 octet) UNSPEC_IF, i.e.
they are the originating router's local addresses. The remaining
three addresses have no associated TLV, they are the addresses of
advertised neighbors.
Clausen, et al. Expires January 14, 2010 [Page 65]
Internet-Draft OLSRv2 July 2009
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.
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 |
+-+-+-+-+-+-+-+-+
Clausen, et al. Expires January 14, 2010 [Page 66]
Internet-Draft OLSRv2 July 2009
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:
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_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_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.
Clausen, et al. Expires January 14, 2010 [Page 67]
Internet-Draft OLSRv2 July 2009
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_addr_list, there MUST be an equal A_neighbor_addr in
the Advertised Neighbor Set.
In each Lost Neighbor Tuple:
o NL_neighbor_addr MUST NOT equal the AL_net_addr of any Local
Attached Network Tuple.
In each 2-Hop Tuple:
o N2_2hop_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.
Clausen, et al. Expires January 14, 2010 [Page 68]
Internet-Draft OLSRv2 July 2009
In the Advertised Neighbor Set:
o Each A_neighbor_addr MUST NOT equal any other A_neighbor_addr.
o Each A_neighbor_addr MUST be in the N_neighbor_addr_list of a
Neighbor Tuple with N_symmetric = 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_addr_list MUST NOT be empty.
o AR_addr_list MUST NOT contain any duplicated addresses.
o AR_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_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_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_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_addr MUST NOT be in the AR_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_addr, T_orig_addr) MUST NOT equal the
corresponding pair in any other Topology Tuple.
In each Attached Network Tuple:
Clausen, et al. Expires January 14, 2010 [Page 69]
Internet-Draft OLSRv2 July 2009
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.
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
Clausen, et al. Expires January 14, 2010 [Page 70]
Internet-Draft OLSRv2 July 2009
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
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
Clausen, et al. Expires January 14, 2010 [Page 71]
