Mobile Ad hoc Networking (MANET) T. Clausen
Internet-Draft LIX, Ecole Polytechnique, France
Intended status: Standards Track C. Dearlove
Expires: January 10, 2008 BAE Systems Advanced Technology
Centre
P. Jacquet
Project Hipercom, INRIA
The OLSRv2 Design Team
MANET Working Group
July 9, 2007
The Optimized Link State Routing Protocol version 2
draft-ietf-manet-olsrv2-04
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Abstract
This document describes version 2 of the Optimized Link State Routing
(OLSRv2) protocol for mobile ad hoc networks. The protocol embodies
an optimization of the classical link state algorithm tailored to the
requirements of a mobile ad hoc network (MANET).
The key optimization of OLSRv2 is that of multipoint relays,
providing an efficient mechanism for network-wide broadcast of link
state information (i.e. reducing the cost of performing a network-
wide link state broadcast). A secondary optimization is that OLSRv2
employs partial link state information: each node maintains
information about all destinations, but only a subset of links.
Consequently, only selected nodes diffuse link state advertisements
(thus reducing the number of network-wide link state broadcasts) and
these advertisements contain only a subset of links (thus reducing
the size of network-wide link state broadcasts). The partial link
state information thus obtained still allows each OLSRv2 node to at
all times maintain optimal (in terms of number of hops) routes to all
destinations in the network.
OLSRv2 imposes minimum requirements on the network by not requiring
sequenced or reliable transmission of control traffic. Furthermore,
the only interaction between OLSRv2 and the IP stack is routing table
management.
OLSRv2 is particularly suitable for large and dense networks as the
technique of MPRs works well in this context.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7
3. Applicability Statement . . . . . . . . . . . . . . . . . . . 8
4. Protocol Overview and Functioning . . . . . . . . . . . . . . 9
5. Protocol Parameters and Constants . . . . . . . . . . . . . . 11
5.1. Message Intervals . . . . . . . . . . . . . . . . . . . . 11
5.2. Advertised Information Validity Times . . . . . . . . . . 12
5.3. Received Message Validity Times . . . . . . . . . . . . . 12
5.4. Jitter . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.5. Hop Limit Parameter . . . . . . . . . . . . . . . . . . . 14
5.6. Willingness . . . . . . . . . . . . . . . . . . . . . . . 14
5.7. Parameter Change Constraints . . . . . . . . . . . . . . . 14
6. Information Repositories . . . . . . . . . . . . . . . . . . . 17
6.1. Local Information Base . . . . . . . . . . . . . . . . . . 17
6.1.1. Local Attached Network Set . . . . . . . . . . . . . . 17
6.2. Neighborhood Information Base . . . . . . . . . . . . . . 18
6.3. Topology Information Base . . . . . . . . . . . . . . . . 18
6.3.1. Advertised Neighbor Set . . . . . . . . . . . . . . . 19
6.3.2. Advertising Remote Node Set . . . . . . . . . . . . . 19
6.3.3. Topology Set . . . . . . . . . . . . . . . . . . . . . 19
6.3.4. Attached Network Set . . . . . . . . . . . . . . . . . 20
6.3.5. Routing Set . . . . . . . . . . . . . . . . . . . . . 21
6.4. Processing and Forwarding Information Base . . . . . . . . 21
6.4.1. Received Set . . . . . . . . . . . . . . . . . . . . . 21
6.4.2. Processed Set . . . . . . . . . . . . . . . . . . . . 22
6.4.3. Forwarded Set . . . . . . . . . . . . . . . . . . . . 22
6.4.4. Relay Set . . . . . . . . . . . . . . . . . . . . . . 23
7. Packet Processing and Message Forwarding . . . . . . . . . . . 24
7.1. Actions when Receiving an OLSRv2 Packet . . . . . . . . . 24
7.2. Actions when Receiving an OLSRv2 Message . . . . . . . . . 24
7.3. Message Considered for Processing . . . . . . . . . . . . 25
7.4. Message Considered for Forwarding . . . . . . . . . . . . 26
8. Packets and Messages . . . . . . . . . . . . . . . . . . . . . 29
8.1. HELLO Messages . . . . . . . . . . . . . . . . . . . . . . 30
8.1.1. HELLO Message TLVs . . . . . . . . . . . . . . . . . . 30
8.1.2. HELLO Message Address Block TLVs . . . . . . . . . . . 31
8.2. TC Messages . . . . . . . . . . . . . . . . . . . . . . . 31
8.2.1. TC Message TLVs . . . . . . . . . . . . . . . . . . . 32
8.2.2. TC Message Address Block TLVs . . . . . . . . . . . . 32
9. HELLO Message Generation . . . . . . . . . . . . . . . . . . . 33
9.1. HELLO Message: Transmission . . . . . . . . . . . . . . . 33
10. HELLO Message Processing . . . . . . . . . . . . . . . . . . . 34
10.1. Updating Willingness . . . . . . . . . . . . . . . . . . . 34
10.2. Updating MPR Selectors . . . . . . . . . . . . . . . . . . 34
10.3. Symmetric 1-Hop and 2-Hop Neighborhood Changes . . . . . . 34
11. TC Message Generation . . . . . . . . . . . . . . . . . . . . 36
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11.1. TC Message: Transmission . . . . . . . . . . . . . . . . . 37
12. TC Message Processing . . . . . . . . . . . . . . . . . . . . 39
12.1. Initial TC Message Processing . . . . . . . . . . . . . . 39
12.1.1. Populating the Advertising Remote Node Set . . . . . . 40
12.1.2. Populating the Topology Set . . . . . . . . . . . . . 41
12.1.3. Populating the Attached Network Set . . . . . . . . . 41
12.2. Completing TC Message Processing . . . . . . . . . . . . . 42
12.2.1. Purging the Topology Set . . . . . . . . . . . . . . . 42
12.2.2. Purging the Attached Network Set . . . . . . . . . . . 42
13. Selecting MPRs . . . . . . . . . . . . . . . . . . . . . . . . 43
14. Populating Derived Sets . . . . . . . . . . . . . . . . . . . 45
14.1. Populating the Relay Set . . . . . . . . . . . . . . . . . 45
14.2. Populating the Advertised Neighbor Set . . . . . . . . . . 45
15. Routing Set Calculation . . . . . . . . . . . . . . . . . . . 46
15.1. Network Topology Graph . . . . . . . . . . . . . . . . . . 46
15.2. Populating the Routing Set . . . . . . . . . . . . . . . . 47
15.3. Routing Set Updates . . . . . . . . . . . . . . . . . . . 48
16. Proposed Values for Parameters and Constants . . . . . . . . . 49
16.1. Message Interval Parameters . . . . . . . . . . . . . . . 49
16.2. Advertised Information Validity Time Parameters . . . . . 49
16.3. Received Message Validity Time Parameters . . . . . . . . 49
16.4. Jitter Time Parameters . . . . . . . . . . . . . . . . . . 49
16.5. Hop Limit Parameter . . . . . . . . . . . . . . . . . . . 49
16.6. Willingness Parameter and Constants . . . . . . . . . . . 49
17. Sequence Numbers . . . . . . . . . . . . . . . . . . . . . . . 51
18. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 52
18.1. Message Types . . . . . . . . . . . . . . . . . . . . . . 52
18.2. TLV Types . . . . . . . . . . . . . . . . . . . . . . . . 52
19. References . . . . . . . . . . . . . . . . . . . . . . . . . . 54
19.1. Normative References . . . . . . . . . . . . . . . . . . . 54
19.2. Informative References . . . . . . . . . . . . . . . . . . 54
Appendix A. Node Configuration . . . . . . . . . . . . . . . . . 56
Appendix B. Example Algorithm for Calculating MPRs . . . . . . . 57
B.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 57
B.2. MPR Selection Algorithm for each OLSRv2 Interface . . . . 58
Appendix C. Example Algorithm for Calculating the Routing Set . 59
C.1. Add Local Symmetric Links . . . . . . . . . . . . . . . . 59
C.2. Add Remote Symmetric Links . . . . . . . . . . . . . . . . 60
C.3. Add Attached Networks . . . . . . . . . . . . . . . . . . 61
Appendix D. Packet and Message Layout . . . . . . . . . . . . . 62
Appendix D.1. Packet and Message Options . . . . . . . . . . . . . 62
Appendix D.2. Example HELLO Message . . . . . . . . . . . . . . . 64
Appendix D.3. Example TC Message . . . . . . . . . . . . . . . . . 65
Appendix E. Constraints . . . . . . . . . . . . . . . . . . . . 68
Appendix F. Security Considerations . . . . . . . . . . . . . . 72
Appendix F.1. Confidentiality . . . . . . . . . . . . . . . . . . 72
Appendix F.2. Integrity . . . . . . . . . . . . . . . . . . . . . 72
Appendix F.3. Interaction with External Routing Domains . . . . . 73
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Appendix F.4. Node Identity . . . . . . . . . . . . . . . . . . . 74
Appendix G. Flow and Congestion Control . . . . . . . . . . . . 75
Appendix H. Contributors . . . . . . . . . . . . . . . . . . . . 76
Appendix I. Acknowledgements . . . . . . . . . . . . . . . . . . 77
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 78
Intellectual Property and Copyright Statements . . . . . . . . . . 79
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1. Introduction
The Optimized Link State Routing protocol version 2 (OLSRv2) is an
update to OLSRv1 as published in RFC3626 [8]. Compared to RFC3626,
OLSRv2 retains the same basic mechanisms and algorithms, while
providing a more flexible signaling framework and some simplification
of the messages being exchanged. Also, OLSRv2 accommodates both IPv4
and IPv6 addresses in a compact manner.
OLSRv2 is developed for mobile ad hoc networks. It operates as a
table driven, proactive protocol, i.e. it exchanges topology
information with other nodes in the network regularly. Each node
selects a set of its neighbor nodes as "MultiPoint Relays" (MPRs).
Control traffic may be diffused through the network using hop by hop
forwarding; a node only needs to forward control traffic directly
received from its MPR selectors (nodes which have selected it as an
MPR). MPRs thus provide an efficient mechanism for diffusing control
traffic by reducing the number of transmissions required.
Nodes selected as MPRs also have a special responsibility when
declaring link state information in the network. A sufficient
requirement for OLSRv2 to provide shortest path routes to all
destinations is that nodes 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 efficient flooding, MPRs are also allow the reduction
of the number and size of link state messages. MPRs are also thus
used as intermediate nodes in multi-hop route calculations.
A node selects MPRs from among its one hop neighbors connected by
"symmetric", i.e. bi-directional, links. Therefore, selecting routes
through MPRs automatically avoids the problems associated with data
packet transfer over uni-directional links (such as the problem of
not getting link layer acknowledgments at each hop, for link layers
employing this technique).
OLSRv2 is developed to work independently from other protocols.
(Parts of OLSRv2 have been published separately as [1], [2], [3] and
[4] for wider use.) Likewise, OLSRv2 makes no assumptions about the
underlying link layer. However, OLSRv2 may use link layer
information and notifications when available and applicable, as
described in [4].
OLSRv2, as OLSRv1, inherits its concept of forwarding and relaying
from HIPERLAN (a MAC layer protocol) which is standardized by ETSI
[10], [11].
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2. Terminology
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [5].
MANET specific terminology is to be interpreted as described in [1]
and [4].
Additionally, this document uses the following terminology:
Node - 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.
Symmetric strict 2-hop neighbor - A symmetric 2-hop neighbor which
is not a symmetric 1-hop neighbor and is not a 2-hop neighbor only
through a symmetric 1-hop neighbor with willingness WILL_NEVER. A
node Z is a symmetric strict 2-hop neighbor of a node X if it is
not a symmetric 1-hop neighbor of node X and if there is a node Y
with willingness not equal to WILL_NEVER and such that there is a
symmetric link from node X to node Y, and a symmetric link from
node Y to node Z. A node Z is a symmetric strict 2-hop neighbor of
a node X by an OLSRv2 interface I of node X if in addition the
link from node X to node Y uses interface I.
Symmetric strict 2-hop neighborhood - The set of the symmetric
strict 2-hop neighbors of a node.
Multipoint relay (MPR) - A node which is selected by its symmetric
1-hop neighbor, node X, to "re-transmit" all the broadcast
messages that it receives from node 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 node which has selected its symmetric 1-hop
neighbor, node X, as one of its MPRs is an MPR selector of node X.
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3. Applicability Statement
OLSRv2 is a proactive routing protocol for mobile ad hoc networks
(MANETs) [13]. The larger and more dense a network, the more
optimization can be achieved by using MPRs compared to the classic
link state algorithm. OLSRv2 enables hop-by-hop routing, i.e. each
node using its local information provided by OLSRv2 to route packets.
As OLSRv2 continuously maintains routes to all destinations in the
network, the protocol is beneficial for traffic patterns where the
traffic is random and sporadic between a large subset of nodes, and
where the [source, destination] pairs are changing over time. No
additional control traffic need be generated in this case since
routes are maintained for all known destinations at all times. Also,
since routes are maintained continuously, traffic is subject to no
delays due to buffering or to route discovery.
OLSRv2 supports nodes which have multiple interfaces which
participate in the MANET using OLSRv2. As described in [4], each
OLSRv2 interface may have one or more network addresses (which may
have prefix lengths). OLSRv2, additionally, supports nodes which
have non-OLSRv2 interfaces which may be local or can serve as
gateways towards other networks.
OLSRv2 uses the format specified in [1] for all messages and packets.
OLSRv2 is thereby able to allow for extensions via "external" and
"internal" extensibility. External extensibility allows a protocol
extension to specify and exchange new message types, which can be
forwarded and delivered correctly even by nodes which do not support
that extension. Internal extensibility allows a protocol extension
to define additional attributes to be carried embedded in the
standard OLSRv2 control messages detailed in this specification (or
any new message types defined by other protocol extensions) using the
TLV mechanism specified in [1], while still allowing nodes not
supporting that extension to forward messages including the extension
and to process messages ignoring the extension.
The OLSRv2 neighborhood discovery protocol using HELLO messages is
specified in [4]; note that all references to MANET interfaces in [4]
refer to OLSRv2 interfaces when using [4] as part of OLSRv2. This
neighborhood discovery protocol serves to ensure that each OLSRv2
node has available continuously updated information repositories
describing the node's 1-hop and symmetric 2-hop neighbors. This
neighborhood discovery protocol, which also uses [1], is extended in
this document by the addition of MPR information.
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4. Protocol Overview and Functioning
OLSRv2 is a proactive routing protocol for mobile ad hoc networks.
The protocol inherits the stability of a link state algorithm and has
the advantage of having routes immediately available when needed due
to its proactive nature. OLSRv2 is an optimization of the classical
link state protocol, tailored for mobile ad hoc networks. The main
tailoring and optimizations of OLSRv2 are:
o periodic, unacknowledged transmission of all control messages;
o optimized flooding for global link state information diffusion;
o partial topology maintenance - each node knows only a subset of
the links in the network, sufficient for a minimum hop route to
all destinations.
The optimized flooding and partial topology maintenance are based on
the concept on MultiPoint Relays (MPRs), selected independently by
nodes based on the symmetric 1-hop and 2-hop neighbor information
maintained using [4].
Using the message exchange format [1] and the neighborhood discovery
protocol [4], OLSRv2 also contains the following main components:
o A TLV, to be included within the HELLO messages of [4], allowing a
node to signal MPR selection.
o An optimized flooding mechanism for global information exchange,
denoted "MPR flooding".
o A specification of global signaling, denoted TC (Topology Control)
messages. TC messages in OLSRv2 serve to:
* inject link state information into the entire network;
* inject addresses of hosts and networks for which they may serve
as a gateway into the entire network.
TC messages are emitted periodically, thereby allowing nodes to
continuously track global changes in the network. Incomplete TC
messages may be used to report additions to advertised information
without repeating unchanged information. Some TC messages may be
flooded over only part of the network, allowing a node to ensure
that nearer nodes are kept more up to date than distant nodes.
Each node in the network selects a set of MPRs. The MPRs of a node X
may be any subset of the willing nodes in node X's symmetric 1-hop
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neighborhood such that every node in the symmetric strict 2-hop
neighborhood of node X has a symmetric link to at least one of node
X's MPRs. The MPRs of a node may thus be said to "cover" the node's
symmetric strict 2-hop neighborhood. Each node also maintains
information about the set of symmetric 1-hop neighbors that have
selected it as MPR, its MPR selectors.
Note that as long as the condition above is satisfied, any algorithm
selecting MPRs is acceptable in terms of implementation
interoperability. However if smaller sets of MPRs are selected then
the greater the efficiency gains that are possible. Note that [12]
gives an analysis and example of MPR selection algorithms.
In OLSRv2, actual efficiency gains are based on the sizes of each
node's Relay Set, the set of symmetric 1-hop neighbors for which it
is to relay broadcast traffic, and its Advertised Neighbor Set, the
set of symmetric 1-hop neighbors for which it is to advertise link
state information into the network in TC messages. Each of these
sets MUST contain all MPR selectors, and MAY contain additional
nodes. If the Advertised Neighbor Set is empty, TC messages are not
generated by that node, unless needed for gateway reporting, or for a
short period to accelerate the removal of unwanted links.
OLSRv2 is designed to work in a completely distributed manner and
does not depend on any central entity. The protocol does not require
reliable transmission of control messages: each node sends control
messages periodically, and can therefore sustain a reasonable loss of
some such messages. Such losses may occur frequently in radio
networks due to collisions or other transmission problems. OLSRv2
may use "jitter", randomized adjustments to message transmission
times, to reduce the incidence of collisions [3].
OLSRv2 does not require sequenced delivery of messages. Each control
message contains a sequence number which is incremented for each
message. Thus the recipient of a control message can, if required,
easily identify which information is more recent - even if messages
have been re-ordered while in transmission.
OLSRv2 does not require any changes to the format of IP packets, any
existing IP stack can be used as is: OLSRv2 only interacts with
routing table management. OLSR sends its control messages using UDP.
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5. Protocol Parameters and Constants
The parameters and constants used in this specification are those
defined in [4] plus those defined in this section. The separation in
[4] into interface parameters, node parameters and constants is also
used in OLSRv2, however all but one (RX_HOLD_TIME) of the parameters
added in this section are node parameters. They may be classified
into the following categories:
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 node's willingness to
be an MPR are defined. These parameters and constants are detailed
in the following sections. As for the parameters in [4], parameters
defined in this document may be changed dynamically by a node, and
need not be the same on different nodes.
5.1. Message Intervals
The following interface parameters regulate TC message transmissions
by a node. TC messages are usually sent periodically, but MAY also
be sent in response to changes in the node's Advertised Neighbor Set
and Local Attached Network Set. With a larger value of parameter
TC_INTERVAL, and a smaller value of parameter TC_MIN_INTERVAL, TC
messages may often be transmitted in response to changes in a highly
dynamic network. However because a node has no knowledge of, for
example, nodes remote to it 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 node. 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 [3].
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TC_MIN_INTERVAL - is the minimum interval between transmission of
two successive TC messages by this node. (This minimum interval
MAY be modified by jitter, as defined in [3].)
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 [2] are included in TC
messages, then TC_INTERVAL MUST be representable as described in
[2].
5.2. Advertised Information Validity Times
The following 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 node.
If a single value of parameter TC_HOP_LIMIT 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
nodes.
The following constraints apply to these parameters:
o T_HOLD_TIME > 0
o A_HOLD_TIME >= 0
o If TC messages can be lost then both SHOULD be significantly
greater than TC_INTERVAL.
o T_HOLD_TIME MUST be representable as described in [2].
5.3. Received Message Validity Times
The following parameters manage the validity time of recorded
received message information:
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RX_HOLD_TIME - is an interface parameter, and is the period after
receipt of a message by the appropriate OLSRv2 interface of this
node 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 the period after receipt of a message which is
processed by this node for which that information is recorded in
order that the message is not processed again if received again.
F_HOLD_TIME - is the period after receipt of a message which is
forwarded by this node 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
variation 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.
5.4. Jitter
If jitter, as defined in [3], is used then these parameters are as
follows:
TP_MAXJITTER - represents the value of MAXJITTER used in [3] for
periodically generated TC messages sent by this node.
TT_MAXJITTER - represents the value of MAXJITTER used in [3] for
externally triggered TC messages sent by this node.
F_MAXJITTER - represents the default value of MAXJITTER used in [3]
for messages forwarded by this node. However before using
F_MAXJITTER a node 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 [3].
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5.5. 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 node. However each other node 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 [2]. 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.
The maximum value of TC_HOP_LIMIT used MUST least equal the network
diameter in hops, a value of 255 is RECOMMENDED. All values of
TC_HOP_LIMIT MUST satisfy TC_HOP_LIMIT >= 2.
5.6. Willingness
Each node 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 node on routes. If a node has WILLINGNESS == WILL_NEVER
it does not perform these tasks. A MANET using OLSRv2 with too many
nodes with WILLINGNESS == WILL_NEVER will not function; it MUST be
ensured, by administrative or other means, that this does not happen.
Nodes MAY have different WILLINGNESS values; however the three
constants WILL_NEVER, WILL_DEFAULT and WILL_ALWAYS MUST have the
values defined in Section 16.6. (Use of WILLINGNESS == WILL_DEFAULT
allows a node to avoid including a WILLINGNESS TLV in its TC
messages, use of WILLINGNESS == WILL_ALWAYS means that a node will
always be selected as an MPR by all symmetric 1-hop neighbors.)
5.7. Parameter Change Constraints
This section presents guidelines, applicable if protocol parameters
are changed dynamically.
TC_INTERVAL
* If the TC_INTERVAL for a node increases, then the next TC
message generated by this node MUST be generated according to
the previous, shorter, TC_INTERVAL. Additional subsequent TC
messages MAY be generated according to the previous, shorter,
TC_INTERVAL.
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* If the TC_INTERVAL for a node decreases, then the following TC
messages from this node SHOULD be generated according to the
current, shorter, TC_INTERVAL.
T_HOLD_TIME
* If T_HOLD_TIME changes, then T_time for all Topology Tuples,
AN_time for all Attached Network Tuples and AR_time for all
Advertising Remote Node Tuples SHOULD be changed.
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.
TP_MAXJITTER
* If TP_MAXJITTER changes, then the periodic TC message schedule
on this node MAY be changed immediately.
TT_MAXJITTER
* If TT_MAXJITTER changes, then externally triggered TC messages
on this node 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 node 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
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values with its largest value.
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6. Information Repositories
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 four information
repositories:
Local Information Base - as defined in [4], extended by the addition
of a Local Attached Network Set, defined in Section 6.1.1.
Neighborhood Information Base - as defined in [4], extended by the
addition of 3 elements to each Neighbor Tuple, as defined in
Section 6.2.
Topology Information Base - this information base is specific to
OLSRv2, defined in Section 6.3.
Processing and Forwarding Information Base - this information base
is specific to OLSRv2, defined in Section 6.4.
All addresses, other than originator addresses, recorded in the
information repositories MUST all be recorded with prefix lengths, in
order to allow comparison with addresses received in HELLO and TC
messages.
The ordering of sequence numbers, when considering which is the
greatest, is as defined in Section 17.
6.1. Local Information Base
The Local Information Base as defined in [4] is extended by the
addition of a Local Attached Network Set, defined in Section 6.1.1.
6.1.1. Local Attached Network Set
A node's Local Attached Network Set records its local non-OLSRv2
interfaces that 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 node's status. It consists of
Local Attached Network Tuples:
(AL_net_addr, AL_dist)
where:
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AL_net_addr is the network address of an attached network which can
be reached via this node.
AL_dist is the number of hops to the network with address
AL_net_addr from this node.
Attached networks with AL_dist == 0 MUST be local to this node and
MUST NOT be attached to any other node. Attached networks with
AL_dist > 0 MAY also be attached to other nodes.
Attached networks with AL_dist > 0 MUST be advertised in TC messages
generated by this node, this may result in the node originating TC
messages when it has no other reason to do so. Attached networks
with AL_dist == 0 MAY be advertised in HELLO messages (which causes
the MPRs of this node to advertise them in their TC messages) or MAY
be advertised in TC messages; they MUST be advertised in one type of
message and SHOULD NOT be advertised in both. If a node is sending
TC messages for any other reason, then advertising attached networks
in TC messages is more efficient. A node MAY decide which form of
advertisement to use depending on its circumstances.
It is not the responsibility of OLSRv2 to maintain routes to networks
recorded in the Local Attached Network Set.
6.2. Neighborhood Information Base
Each Neighbor Tuple in the Neighbor Set has these additional
elements:
N_willingness is the node'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 the neighbor is selected as
an MPR by this node;
N_mpr_selector is a boolean flag, describing if this neighbor has
selected this node as an MPR, i.e. is an MPR selector of this
node.
6.3. Topology Information Base
The Topology Information Base stores information required for the
generation and processing of TC messages, and received in TC
messages. The Advertised Neighbor Set contains interface addresses
of symmetric 1-hop neighbors which are to be reported in TC messages.
The Topology Set and Attached Network Set both record information
received in TC messages. The Advertising Remote Node Set is both
used and populated when processing TC messages.
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Additionally, a Routing Set is maintained, derived from the
information recorded in the Neighborhood Information Base, Topology
Set, Attached Network Set and Advertising Remote Node Set.
6.3.1. Advertised Neighbor Set
A node's Advertised Neighbor Set contains interface addresses of
symmetric 1-hop neighbors which are to be advertised through TC
messages:
{A_neighbor_iface_addr}
In addition, an Advertised Neighbor Set Sequence Number (ANSN) is
maintained. Each time the Advertised Neighbor Set is updated, the
ANSN MUST be incremented. The ANSN MUST also be incremented if there
is a change to the set of Local Attached Network Tuples that are to
be advertised in the node's TC messages.
6.3.2. Advertising Remote Node Set
A node's Advertising Remote Node Set records information describing
each remote node in the network that transmits TC messages. It
consists of Advertising Remote Node Tuples:
(AR_orig_addr, AR_seq_number, AR_iface_addr_list, AR_time)
where:
AR_orig_addr is the originator address of a received TC message,
note that this does not include a prefix length;
AR_seq_number is the greatest ANSN in any TC message received which
originated from the node with originator address AR_orig_addr;
AR_iface_addr_list is the list of the interface addresses of the
node 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 node's Topology Set records topology information about the network.
It consists of Topology Tuples:
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(T_dest_iface_addr, T_orig_addr, T_seq_number, T_time)
where:
T_dest_iface_addr is an interface address of a destination node,
which may be reached in one hop from the node with originator
address T_orig_addr;
T_orig_addr is the originator address of a node which is the last
hop on a path towards the node with interface address
T_dest_iface_addr, note that this does not include a prefix
length;
T_seq_number is the greatest received ANSN associated with 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 node's Attached Network Set records information about networks
attached to other nodes. 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 node with originator address AN_orig_addr;
AN_orig_addr is the originator address of a node 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 node with originator address AN_orig_addr;
AN_seq_number is the greatest received ANSN associated with the
information contained in this Tuple;
AN_time specifies the time at which this Tuple expires and MUST be
removed.
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6.3.5. Routing Set
A node'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 node, or the network address of an
attached network;
R_next_iface_addr is the OLSRv2 interface address of the "next hop"
on the selected path to the destination;
R_dist is the number of hops on the selected path to the
destination;
R_local_iface_addr is the address of the local interface over which
a packet MUST be sent to reach the destination by the selected
path.
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 interface of a node.
6.4.1. Received Set
A node's Received Sets, one per local OLSRv2 interface, each record
the signatures of messages which have been received over that
interface. Each consists of Received Tuples:
(RX_type, RX_orig_addr, RX_seq_number, RX_time)
where:
RX_type is the received message type, or zero if the received
message sequence number is not type-specific;
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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 node's Processed Set records signatures of messages which have been
processed by the node. It consists of Processed Tuples:
(P_type, P_orig_addr, P_seq_number, P_time)
where:
P_type is the processed message type, or zero if the processed
message sequence number is not type-specific;
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 node's Forwarded Set records signatures of messages which have been
processed by the node. It consists of Forwarded Tuples:
(F_type, F_orig_addr, F_seq_number, F_time)
where:
F_type is the forwarded message type, or zero if the forwarded
message sequence number is not type-specific;
F_orig_addr is the originator address of the forwarded message;
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F_seq_number is the message sequence number of the forwarded
message;
F_time specifies the time at which this Tuple expires and MUST be
removed.
6.4.4. Relay Set
A node's Relay Sets, one per local OLSRv2 interface, each records the
OLSRv2 interface addresses of symmetric 1-hop neighbors, such that
the node is to forward messages received from those neighbor's OLSRv2
interfaces, on that local OLSRv2 interface, if not otherwise excluded
from forwarding that message (e.g. by it having been previously
forwarded):
{RY_neighbor_iface_addr}
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7. Packet Processing and Message Forwarding
On receiving a packet, as defined in [1], a node examines the packet
header and each of the message headers. If the message type is known
to the node, the message is processed locally according to the
specifications for that message type. The message is also
independently evaluated for forwarding.
7.1. Actions when Receiving an OLSRv2 Packet
On receiving a packet, a node MUST perform the following tasks:
1. The packet MAY be fully parsed on reception, or the packet and
its messages MAY be parsed only as required. (It is possible to
parse the packet header, or determine its absence, without
parsing any messages. It is possible to divide the packet into
messages without even fully parsing their headers. It is
possible to determine whether a message is to be forwarded, and
to forward it, without parsing its body. It is possible to
determine whether a message is to be processed without parsing
its body.)
2. If parsing fails at any point the relevant entity (packet or
message) MUST be silently discarded, other parts of the packet
(up to the whole packet) MAY be silently discarded;
3. Otherwise if the packet header is present and it contains a
packet TLV block, then each TLV in it is processed according to
its type if recognized, otherwise the TLV is ignored;
4. Otherwise each message in the packet, if any, is treated
according to Section 7.2.
7.2. Actions when Receiving an OLSRv2 Message
A node MUST perform the following tasks for each received message:
1. If the message header cannot be correctly parsed according to the
specification in [1], or if the node recognizes from the
originator address of the message that the message is one which
the receiving node itself originated, then the message MUST be
silently discarded.
2. Otherwise:
1. If the message is a HELLO message, then the message is
processed according to Section 10.
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2. Otherwise:
1. If the message is of a known type, then the message is
considered for processing according to Section 7.3, AND;
2. If for the message (<hop-limit> + <hop-count>) > 1, then
the message is considered for forwarding according to
Section 7.4.
7.3. 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, or 0 if the
typedep bit in the message semantics octet in the message
header of the current message is cleared ('0'), AND;
* P_orig_addr == the originator address of the current message,
AND;
* P_seq_number == the message sequence number of the current
message;
then the current message MUST NOT be processed.
2. Otherwise:
1. Create a Processed Tuple with:
+ P_type = the message type of the current message, or 0 if
the typedep bit in the message semantics octet in the
message header of the current message is cleared ('0');
+ 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.
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7.4. Message Considered for Forwarding
If a message is considered for forwarding, and it is either of a
message type defined in this document (i.e. is a TC message) or of an
unknown message type, then it MUST use the following algorithm. A
message of a message type not defined in this document MAY, in an
extension to this protocol, specify the use of this, or another
algorithm. (Such an other algorithm MAY use the Received Set for the
receiving interface, it SHOULD use the Forwarded Set similarly to the
following algorithm.)
If a message (the "current message") is considered for forwarding
according to this algorithm, the following tasks MUST be performed:
1. If the sending interface address (the source address of the IP
datagram containing the current message) does not match (taking
into account any address prefix of) an OLSRv2 interface address
in an L_neighbor_iface_addr_list of a Link Tuple, with L_status
== SYMMETRIC, in the Link Set for the OLSRv2 interface on which
the current message was received (the "receiving interface") then
the current message MUST be silently discarded.
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, or 0
if the typedep bit in the message semantics octet in the
message header of the current message is cleared ('0'),
AND;
+ RX_orig_addr == the originator address of the current
message, AND;
+ RX_seq_number == the sequence number of the current
message;
then the current message MUST be silently discarded.
2. Otherwise:
1. Create a Received Tuple in the Received Set for the
receiving interface with:
- RX_type = the message type of the current message, or
0 if the typedep bit in the message semantics octet in
the message header of the current message is cleared
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('0');
- 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, or
0 if the typedep bit in the message semantics octet in
the message header of the current message is cleared
('0');
- F_orig_addr == the originator address of the current
message, AND;
- F_seq_number == the sequence number of the current
message.
then the current message MUST be silently discarded.
3. Otherwise if the sending interface address matches
(taking account of any address prefix of) 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,
or 0 if the typedep bit in the message semantics
octet in the message header of the current message
is cleared ('0');
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:
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o decrement <hop-limit> in the message header by 1;
o increment <hop-count> in the message header by 1.
3. For each OLSRv2 interface of the node, 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 node. Forwarded messages may be
jittered as described in [3]. 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 maximum delay of
F_MAXJITTER. A node MAY reduce the jitter applied to
a message in order to more efficiently combine
messages in packets.
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8. Packets and Messages
Nodes using OLSRv2 exchange information through messages. One or
more messages sent by a node at the same time SHOULD be combined into
a single packet. These messages may have originated at the sending
node, or have originated at another node and are forwarded by the
sending node. Messages with different originators MAY be combined in
the same packet. Messages from other protocols defined using [1] MAY
be combined in the same packet.
OLSRv2 packets are sent using UDP, on the port "manet" defined in
[6]. Their IP datagrams are transmitted using the well-known
multicast address "LL MANET Routers" defined in [6].
The packet and message format used by OLSRv2 is defined in [1].
However this specification contains some options which are not used
by OLSRv2. In particular (using the syntactical entities defined in
[1]):
o All OLSRv2 packets, not limited to those defined in this document,
include a <packet-header>.
o All OLSRv2 packets, not limited to those defined in this document,
have the pseqnum bit of <packet-semantics> cleared ('0'), i.e.
they include a packet sequence number.
o OLSRv2 packets MAY include packet TLVs, however OLSRv2 itself does
not specify any packet TLVs.
o All OLSRv2 messages, not limited to those defined in this
document, include a full <msg-header> and hence have the noorig,
nohoplimit, nohopcount and noseqnum bits of <msg-semantics>
cleared ('0').
o All OLSRv2 messages defined in this document have the typedep bit
of <msg-semantics> cleared ('0').
o All references in this document to specific TLVs in generating and
processing HELLO and TC messages refer to TLVs with Subtype == 0.
TLVs with nonzero subtype are treated as of unknown type when
processing messages, i.e. they are ignored.
Other options defined in [1] may be freely used, in particular any
other values of <packet-semantics>, <addr-semantics> or <tlv-
semantics> consistent with their specifications.
The remainder of this section defines, within the framework of [1],
message types and TLVs specific to OLSRv2.
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8.1. HELLO Messages
A HELLO message in OLSRv2 is generated as specified in [4].
Additionally, an OLSRv2 node:
o MUST include TLV(s) with Type == MPR associated with all OLSRv2
interface addresses included in the HELLO message with a TLV with
Type == LINK_STATUS and Value == SYMMETRIC if that address is also
included in Neighbor Tuple with N_mpr == true. (If there is more
than one copy of such an address in the HELLO message, then this
applies to the specific copy of the address with which the
LINK_STATUS TLV is associated.)
o MUST NOT include any TLVs with Type == MPR associated with any
other addresses.
o MAY include a message TLV with Type == WILLINGNESS, indicating the
node's willingness to be selected as an MPR.
8.1.1. HELLO Message TLVs
In a HELLO message, a node MAY include a WILLINGNESS message TLV as
specified in Table 1. A node MUST NOT include more than one
WILLINGNESS message TLV.
+-------------+------+---------+--------+---------------------------+
| Name | Type | Subtype | Length | Value |
+-------------+------+---------+--------+---------------------------+
| WILLINGNESS | TBD | 0 | 8 bits | The node's willingness to |
| | | | | be selected as MPR; |
| | | | | unused bits (based on the |
| | | | | maximum willingness value |
| | | | | WILL_ALWAYS) are RESERVED |
| | | | | and SHOULD be set to zero |
+-------------+------+---------+--------+---------------------------+
Table 1
A node's willingness to be selected as MPR ranges from WILL_NEVER
(indicating that a node MUST NOT be selected as MPR by any node) to
WILL_ALWAYS (indicating that a node MUST always be selected as MPR).
If a node does not advertise a Willingness TLV in HELLO messages,
then the node MUST be assumed to have a willingness of WILL_DEFAULT.
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8.1.2. HELLO Message Address Block TLVs
In a HELLO message, a node MAY include MPR address block TLV(s) as
specified in Table 2.
+------+------+---------+--------+-------+
| Name | Type | Subtype | Length | Value |
+------+------+---------+--------+-------+
| MPR | TBD | 0 | 0 bits | None |
+------+------+---------+--------+-------+
Table 2
8.2. TC Messages
A TC message MUST contain:
o A message TLV with Type == CONT_SEQ_NUM, as specified in
Section 8.2.1.
o A message TLV with Type == VALIDITY_TIME, as specified in [2].
o A first address block (the Local Address Block) containing all of
the node's interface addresses. This is similar to the Local
Interface Block included in HELLO messages as specified in [4],
however in a TC message these addresses MUST be included in the
same order in all copies of a given TC message, regardless of
which OLSRv2 interface it is transmitted on, and no OTHER_IF
address block TLVs are required.
o Except when they would be empty, or when including a message TLV
with Type == INCOMPLETE (in which case the TC message does not
satisfy the necessary transmission constraints defined by
TC_INTERVAL and T_HOLD_TIME), address block(s) (Advertised Address
Blocks) containing addresses in the Advertised Address Set and
selected 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 A message TLV with Type == INTERVAL_TIME, as specified in [2].
o A message TLV with Type == INCOMPLETE, as specified in
Section 8.2.1.
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8.2.1. TC Message TLVs
In a TC message, a node MUST include a CONT_SEQ_NUM message TLV, and
MAY contain an INCOMPLETE message TLV, as specified in Table 3. A
node MUST NOT include more than one CONT_SEQ_NUM message TLV or
INCOMPLETE message TLV.
+--------------+------+---------+--------+--------------------------+
| Name | Type | Subtype | Length | Value |
+--------------+------+---------+--------+--------------------------+
| CONT_SEQ_NUM | TBD | 0 | 8 bits | The ANSN contained in |
| | | | | the Advertised Neighbor |
| | | | | Set |
| | | | | |
| INCOMPLETE | TBD | 0 | 0 bits | None |
+--------------+------+---------+--------+--------------------------+
Table 3
8.2.2. TC Message Address Block TLVs
In a TC message, a node MAY include GATEWAY address block TLV(s) as
specified in Table 4.
+---------+------+---------+--------+-------------------------------+
| Name | Type | Subtype | Length | Value |
+---------+------+---------+--------+-------------------------------+
| GATEWAY | TBD | 0 | 8 bits | Number of hops to attached |
| | | | | network |
+---------+------+---------+--------+-------------------------------+
Table 4
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9. HELLO Message Generation
An OLSRv2 HELLO message is composed as defined in [4], with the
following additions:
o A message TLV with Type == WILLINGNESS and Value == the node's
willingness to act as an MPR, MAY be included.
o For each address which is included in the message with an
associated TLV with Type == LINK_STATUS and Value == SYMMETRIC,
and is of an MPR (i.e. the address is in the
N_neighbor_iface_addr_list of a Neighbor Tuple with N_mpr ==
true), an address block TLV with Type == MPR MUST be included;
this TLV MUST be associated with the same copy of the address as
is the TLV with Type == LINK_STATUS.
o For each address which is included in the message and is not
associated with a TLV with Type == LINK_STATUS and Value ==
SYMMETRIC, or is not of an MPR (i.e. the address is not in the
N_neighbor_iface_addr_list of a Neighbor Tuple with N_mpr ==
true), an address block TLV with Type == MPR MUST NOT be
associated wit this address.
o For each Local Attached Tuple with AL_dist == 0, a node MAY
include AL_net_addr in the Local Interface Block of the message,
with an associated TLV with Type == OTHER_IF.
9.1. HELLO Message: Transmission
HELLO messages are included in packets as specified in [1]. These
packets may contain other messages, including TC messages.
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10. HELLO Message Processing
Subsequent to the processing of HELLO messages, as specified in [4],
the node MUST identify the Neighbor Tuple which was created or
updated by the processing specified in [4] (the "current Neighbor
Tuple") and update N_willingness as described in Section 10.1 and
N_mpr_selector as described in Section 10.2.
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 ==
WILLINGNESS then N_willingness is set to the value of that TLV;
2. otherwise, N_willingness is set to WILL_DEFAULT.
10.2. Updating MPR Selectors
N_mpr_selector is updated as follows:
1. If a node finds one of its local OLSRv2 interface addresses with
an associated TLV with Type == MPR in the HELLO message
(indicating that the originator node has selected the receiving
node as an MPR), then N_mpr_selector in the current Neighbor
Tuple is set true.
2. Otherwise, if a node finds one of its own interface addresses
with an associated TLV with Type == LINK_STATUS and Value ==
SYMMETRIC in the HELLO message, then N_mpr_selector in the
current Neighbor Tuple is set false.
10.3. Symmetric 1-Hop and 2-Hop Neighborhood Changes
A node MUST also perform the following:
1. If N_symmetric of a Neighbor Tuple changes from true to false,
then N_mpr_selector of that Neighbor Tuple MUST be set false.
2. The set of MPRs of a node 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;
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* 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 node 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 node is recalculated, this MUST be as
described in Section 13. 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.
An additional HELLO message MAY be sent when the node's set of MPRs
changes, in addition to the cases specified in [4], and subject to
the same constraints.
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11. TC Message Generation
A node with one or more OLSRv2 interfaces, and with a non-empty
Advertised Neighbor Set or which acts as a gateway to an attached
network which is to be advertised in the MANET by this node, MUST
generate TC messages. A node with an empty Advertised Neighbor Set
and which is not acting as such a gateway SHOULD also generate
"empty" TC messages for a period A_HOLD_TIME after it last generated
a non-empty TC message. TC messages (non-empty and empty) are
generated according to the following:
1. The message hop count MUST be set to zero.
2. The message hop limit MAY be set to any positive value, this
SHOULD be at least two. A node MAY:
* use the same hop limit TC_HOP_LIMIT in all TC messages, this
MUST be at least equal to the network diameter in hops; OR
* use different values of the hop limit TC_HOP_LIMIT in TC
messages, this MUST regularly include messages with hop limit
as defined above, other, lower, hop limits SHOULD use a
regular pattern with a regular message interval at any given
number of hops distance.
3. The message MUST contain a message TLV with Type == CONT_SEQ_NUM
and Value == ANSN from the Advertised Neighbor Set.
4. The message MUST contain a message TLV with Type ==
VALIDITY_TIME, as specified in [2]. 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,
then this TLV MUST specify times which vary with the number of
hops distance appropriate to the chosen pattern of TC message hop
limits, these times SHOULD be appropriate multiples of
T_HOLD_TIME.
5. The message MAY contain a message TLV with Type == INTERVAL_TIME,
as specified in [2]. 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, these
times SHOULD be appropriate multiples of TC_INTERVAL.
6. The message MUST contain the addresses of all of its interfaces
in its first address block (the "Local Address Block"). Note
that the TC message generated on all OLSRv2 interfaces MUST be
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identical (including having identical message sequence number)
and hence these addresses are not ordered or otherwise identified
according to the interface on which the TC message is
transmitted.
7. The message MUST contain, in address blocks other than its first
("Advertised Address Blocks"):
1. A_neighbor_iface_addr from each Advertised Neighbor Tuple;
2. AL_net_addr from each Local Attached Neighbor Tuple with
AL_dist > 0, each associated with a TLV with Type == GATEWAY
and Value == AL_dist.
8. The message MAY contain, in address blocks other than its first:
1. AL_net_addr from each Local Attached Neighbor Tuple with
AL_dist == 0, each associated with a TLV with Type == GATEWAY
and Value == 0.
11.1. TC Message: Transmission
TC messages are generated and transmitted periodically on all OLSRv2
interfaces, with a default interval between two consecutive TC
emissions by the same node 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 node MAY send a
complete TC message, and if so MAY re-start its TC message schedule.
Alternatively a node MAY send only new content in its address blocks
(with appropriate associated TLVs) in which case it MUST include a
message TLV with Type == INCOMPLETE, and MUST NOT re-start its TC
message schedule. This TC message MUST include its usual message
TLVs. Note that a node cannot report removal of advertised content
using an incomplete TC message.
When sending a TC message in response to a change of contents, a node
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
node 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 [3]. The values
of MAXJITTER used SHOULD be:
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o TP_MAXJITTER for periodic TC message generation;
o TT_MAXJITTER for triggered TC message generation.
TC messages are included in packets as specified in [1]. 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 7.4.
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12. TC Message Processing
When according to Section 7.3 a TC message is to be processed
according to its type, this means that:
o if the message does not contain a message TLV with Type ==
INCOMPLETE, then processing according to Section 12.1 and then
according to Section 12.2 is carried out;
o if the message contains a message TLV with Type == INCOMPLETE,
then only processing according to Section 12.1 is carried out.
For all processing purposes, "ANSN" is defined as being the value of
the message TLV with Type == CONT_SEQ_NUM in the TC message. If a TC
message has no such TLV then it MUST NOT be processed.
12.1. Initial TC Message Processing
For the purposes of this section, note the following:
o "validity time" is calculated from the VALIDITY_TIME message TLV
in the TC message according to the specification in [2];
o "originator address" refers to the originator address in the TC
message header;
o "Local Address Block" refers to the Local Address Block (i.e. the
first address block) in the TC message;
o "sending address list" refers to the list of addresses in the
Local Address Block.
o "Advertised Address Block" refers to an Advertised Address Block
(i.e. the an address block other than the first address block) in
the TC message;
o comparisons of sequence numbers are carried out as specified in
Section 17.
The TC message is processed as follows:
1. the Advertising Remote Node Set is updated according to
Section 12.1.1; 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 12.1.2;
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3. the Attached Network Set is updated according to Section 12.1.3.
12.1.1. Populating the Advertising Remote Node Set
The node MUST update its Advertising Remote Node Set as follows:
1. If there is an Advertising Remote Node 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 Node Tuple such that:
+ AR_orig_addr == originator address;
then create an Advertising Remote Node Tuple with:
+ AR_orig_addr = originator address.
2. This Advertising Remote Node Tuple (existing or new, the
"current tuple") is then modified as follows:
+ AR_seq_number = ANSN;
+ AR_time = current time + validity time.
+ AR_iface_addr_list = sending address list
3. for each other Advertising Remote Node Tuple (with a
different AR_orig_addr, the "other tuple") whose
AR_iface_addr_list contains any address in the
AR_iface_addr_list of the current tuple:
1. remove all Topology Tuples with T_orig_addr ==
AR_orig_addr of the other tuple;
2. remove all Attached Network Tuples with AN_orig_addr ==
AR_orig_addr of the other tuple;
3. remove the other tuple.
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12.1.2. Populating the Topology Set
The node MUST update its Topology Set as follows:
1. For each address (henceforth advertised address) in an Advertised
Address Block which does not have an associated TLV with Type ==
GATEWAY:
1. If there is no Topology Tuple such that:
+ T_dest_iface_addr == advertised address; AND
+ T_orig_addr == originator address
then create a new Topology Tuple with:
+ T_dest_iface_addr = advertised address;
+ T_orig_addr = originator address.
2. This Topology Tuple (existing or new) is then modified as
follows:
+ T_seq_number = ANSN;
+ T_time = current time + validity time.
12.1.3. Populating the Attached Network Set
The node MUST update its Attached Network Set as follows:
1. For each address (henceforth network address) in an Advertised
Address Block which has an associated TLV with Type == GATEWAY:
1. If there is no Attached Network Tuple such that:
+ AN_net_addr == network address; AND
+ AN_orig_addr == originator address
then create a new Attached Network Tuple with:
+ AN_net_addr = network address;
+ AN_orig_addr = originator address
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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.
12.2. Completing TC Message Processing
The TC message is processed as follows:
1. the Topology Set is updated according to Section 12.2.1;
2. the Attached Network Set is updated according to Section 12.2.2.
12.2.1. Purging the Topology Set
The Topology Set MUST be updated as follows:
Any Topology Tuples with:
o T_orig_addr == originator address; AND
o T_seq_number < ANSN
MUST be removed.
12.2.2. Purging the Attached Network Set
The Attached Network Set MUST be updated as follows:
1. Any Attached Network Tuples with:
* AN_orig_addr == originator address; AND
* AN_seq_number < ANSN
MUST be removed.
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13. Selecting MPRs
Each node MUST select, from among its symmetric 1-hop neighbors, a
subset of nodes as MPRs. MPRs are used to flood control messages
from a node into the network while reducing the number of
retransmissions that will occur in a region. Thus, the concept of
MPR 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 node 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 and recorded,
the MPR relationship is one of nodes, not interfaces. Nodes MAY
select their MPRs by any process which satisfies the conditions which
follow. Nodes can freely interoperate whether they use the same or
different MPR selection algorithms.
For each OLSRv2 interface a node MUST select a set of MPRs which have
the property that none of them have willingness WILL_NEVER, and that
if the node successfully sends a message on that OLSRv2 interface,
and that message is then successfully forwarded by all of the
selected MPRs, that all symmetric strict 2-hop neighbors of the node
by 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 symmetric 1-hop neighbors of a node which do not have
willingness WILL_NEVER is a (maximal) valid set of MPRs. A node
SHOULD NOT select a symmetric 1-hop neighbor with willingness not
equal to 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 node with no symmetric 1-hop neighbors with willingness
WILL_ALWAYS and no symmetric strict 2-hop neighbors SHOULD NOT select
any MPRs.
A node 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 node MAY select its MPRs independently from the MPR
selection by other nodes, or it MAY, for example, give preference to
nodes that either are, or are not, already selected as MPRs by other
nodes.
The set of MPRs for each OLSRv2 interface can be selected using
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information from the Link Set and 2-Hop Set of that OLSRv2 interface,
and the Neighbor Set of the node (specifically the N_willingness
elements). The selection of MPRs (overall, not per OLSRv2 interface)
is recorded in the Neighbor Set of the node (using the N_mpr
elements). A selected MPR MUST be in the node's symmetric 1-hop
neighborhood (i.e. the corresponding N_symmetric == true) and MUST
not have the corresponding N_willingness == WILL_NEVER.
A node 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 node's
MPRs when there is a change to any of the node'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 node'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.
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14. Populating Derived Sets
The Relay Sets and the Advertised Neighbor Set of a node 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 nodes
recorded in the Neighbor Set.
14.1. 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. It MUST contain only
addresses of OLSRv2 interfaces with which this OLSRv2 interface has a
symmetric link. It MUST include all such addresses of all such
OLSRv2 interfaces of nodes which are MPR selectors of this node. The
Relay Set for an OLSRv2 interface of this node is thus created by:
1. For each Link Tuple in the Link Set for this OLSRv2 interface
with L_status == SYMMETRIC, and the corresponding Neighbor Tuple
with N_neighbor_iface_addr_list containing
L_neighbor_iface_addr_list:
1. All addresses from L_neighbor_iface_addr_list MUST be
included in the Relay Set of this OLSRv2 interface if
N_mpr_selector == true, and otherwise MAY be so included.
14.2. Populating the Advertised Neighbor Set
The Advertised Neighbor Set of a node contains all interface
addresses of those symmetric 1-hop neighbors to which the node
advertises a link in its TC messages. This set MUST at least contain
all addresses in all MPR selector of this node. The Advertised
Neighbor Set for this node is thus created by:
1. For each Neighbor Tuple with N_symmetric == true:
1. All addresses from N_neighbor_iface_addr_list MUST be
included in the Advertised Neighbor Set if N_mpr_selector ==
true, and otherwise MAY be so included.
Whenever address(es) are added to or removed from the Advertised
Neighbor Set, its ANSN MUST be incremented.
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15. Routing Set Calculation
The Routing Set of a node is populated with Routing Tuples that
represent paths from that node to all destinations in the network.
These paths are calculated based on the Network Topology Graph, which
is constructed from information in the information repositories,
obtained via HELLO and TC message exchange.
15.1. Network Topology Graph
The Network Topology Graph is formed from information taken from the
node's Link Sets, Neighbor Set, Topology Set and Attached Network
Set. The Network Topology Graph SHOULD also use information taken
from the node's 2-Hop Sets. The Network Topology Graph forms that
node'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 node, 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 node's Link Sets, which has L_status ==
SYMMETRIC, AND;
* the Neighbor Tuple with Y in its N_neighbor_iface_addr_list has
N_willingness not equal to WILL_NEVER, AND;
* Z is the N2_2hop_iface_addr of a 2-Hop Tuple in the 2-Hop Set
corresponding to the OLSRv2 interface of the chosen Link Set.
o Advertised symmetric links - all arcs U -> V such that there
exists a Topology Tuple and a corresponding Advertising Remote
Node Tuple (i.e. with AR_orig_addr == T_orig_addr) with:
* U is in the AR_iface_addr_list of the Advertising Remote Node
Tuple, AND;
* V is the T_dest_iface_addr of the Topology Tuple.
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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
node's Link Sets, which has L_status == SYMMETRIC, AND;
* W and Y are included in the same N_neighbor_iface_addr_list
(i.e. the one in the Neighbor Tuple whose
N_neighbor_iface_addr_list contains the
L_neighbor_iface_addr_list that includes Y).
o Attached network addresses - all arcs U -> T such that there
exists an Attached Network Tuple and a corresponding Advertising
Remote Node Tuple (i.e. with AR_orig_addr == AN_orig_addr) with:
* U is in the AR_iface_addr_list of the Advertising Remote Node
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.
15.2. 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 15.1, each path will have as its first
arc a local symmetric link X -> Y. There will be a path for each
terminating Y, Z, V, W and T which can be connected to local OLSRv2
interface address X using the indicated arcs. The corresponding
Routing Tuple for this path will have:
o R_dest_addr = the terminating Y, Z, V, W or T;
o R_next_iface_addr = the first arc's Y;
o R_dist = the total hop count of the path;
o R_local_iface_addr = the first arc's X.
An example algorithm for calculating the Routing Set of a node is
given in Appendix C.
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15.3. 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 node, 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 Topology Set of the node.
o The Attached Network Set of the node.
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.
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16. Proposed Values for Parameters and Constants
OLSRv2 uses all parameters and constants defined in [4] and
additional parameters and constants defined in this document. All
but one (RX_HOLD_TIME) of these additional parameters are node
parameters as defined in [4]. These proposed values of the
additional parameters are appropriate to the case where all
parameters (including those defined in [4]) have a single value.
Proposed values for parameters defined in [4] are given in that
document.
16.1. Message Interval Parameters
o TC_INTERVAL = 5 seconds
o TC_MIN_INTERVAL = TC_INTERVAL/4
16.2. Advertised Information Validity Time Parameters
o T_HOLD_TIME = 3 x TC_INTERVAL
o A_HOLD_TIME = T_HOLD_TIME
16.3. Received Message Validity Time Parameters
o RX_HOLD_TIME = 30 seconds
o P_HOLD_TIME = 30 seconds
o F_HOLD_TIME = 30 seconds
16.4. Jitter Time Parameters
o TP_MAXJITTER = HP_MAXJITTER
o TT_MAXJITTER = HT_MAXJITTER
o F_MAXJITTER = TT_MAXJITTER
16.5. Hop Limit Parameter
o TC_HOP_LIMIT = 255
16.6. Willingness Parameter and Constants
o WILLINGNESS = WILL_DEFAULT
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o WILL_NEVER = 0
o WILL_DEFAULT = 3
o WILL_ALWAYS = 7
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17. Sequence Numbers
Sequence numbers are used in OLSRv2 with the purpose of discarding
"old" information, i.e. messages received out of order. However with
a limited number of bits for representing sequence numbers, wrap-
around (that the sequence number is incremented from the maximum
possible value to zero) will occur. To prevent this from interfering
with the operation of OLSRv2, the following MUST be observed when
determining the ordering of sequence numbers.
The term MAXVALUE designates in the following one more than the
largest possible value for a sequence number. For a 16 bit sequence
number (as are those defined in this specification) MAXVALUE is
65536.
The sequence number S1 is said to be "greater than" the sequence
number S2 if:
o S1 > S2 AND S1 - S2 < MAXVALUE/2 OR
o S2 > S1 AND S2 - S1 > MAXVALUE/2
When sequence numbers S1 and S2 differ by MAXVALUE/2 their ordering
cannot be determined. In this case, which should not occur, either
ordering may be assumed.
Thus when comparing two messages, it is possible - even in the
presence of wrap-around - to determine which message contains the
most recent information.
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18. IANA Considerations
18.1. Message Types
OLSRv2 defines one message type, which must be allocated from the
"Assigned Message Types" repository of [1].
+------+-------+--------------------------------------+
| Name | Value | Description |
+------+-------+--------------------------------------+
| TC | TBD | Topology Control (global signaling) |
+------+-------+--------------------------------------+
Table 5
18.2. TLV Types
OLSRv2 defines three message TLV types, which must be allocated from
the "Assigned message TLV Types" repository of [1].
+--------------+------+---------+-----------------------------------+
| Name | Type | Subtype | Description |
+--------------+------+---------+-----------------------------------+
| WILLINGNESS | TBD | 0 | Specifies the originating node's |
| | | | willingness to act as a relay and |
| | | | to partake in network formation |
| | | | |
| | TBD | 1-255 | RESERVED |
| | | | |
| CONT_SEQ_NUM | TBD | 0 | Specifies a content sequence |
| | | | number for this message |
| | | | |
| | TBD | 1-255 | RESERVED |
| | | | |
| INCOMPLETE | TBD | 0 | Specifies that this message is |
| | | | incomplete |
| | | | |
| | TBD | 1-255 | RESERVED |
+--------------+------+---------+-----------------------------------+
Table 6
Subtypes indicated as RESERVED may be allocated by standards action,
as specified in [7].
OLSRv2 defines two Address Block TLV types, which must be allocated
from the "Assigned address block TLV Types" repository of [1].
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+---------+------+---------+----------------------------------------+
| Name | Type | Subtype | Description |
+---------+------+---------+----------------------------------------+
| MPR | TBD | 0 | Specifies that a given address is of a |
| | | | node selected as an MPR |
| | | | |
| | TBD | 1-255 | RESERVED |
| | | | |
| GATEWAY | TBD | 0 | Specifies that a given address is |
| | | | reached via a gateway on the |
| | | | originating node |
| | | | |
| | TBD | 1-255 | RESERVED |
+---------+------+---------+----------------------------------------+
Table 7
Subtypes indicated as RESERVED may be allocated by standards action,
as specified in [7].
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19. References
19.1. Normative References
[1] Clausen, T., Dean, J., Dearlove, C., and C. Adjih, "Generalized
MANET Packet/Message Format", work in
progress draft-ietf-manet-packetbb-08.txt, July 2007.
[2] Clausen, T. and C. Dearlove, "Representing multi-value time in
MANETs", Work In Progress draft-ietf-manet-timetlv-01.txt,
June 2007.
[3] Clausen, T., Dearlove, C., and B. Adamson, "Jitter
considerations in MANETs", Work In
Progress draft-ietf-manet-jitter-01.txt, June 2007.
[4] Clausen, T., Dean, J., and C. Dearlove, "MANET Neighborhood
Discovery Protocol (NHDP)", work in
progress draft-ietf-manet-nhdp-04.txt, June 2007.
[5] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, BCP 14, March 1997.
[6] Chakeres, I., "Internet Assigned Numbers Authority (IANA)
Allocations for the Mobile Ad hoc Networks (MANET) Working
Group", Work In Progress draft-ietf-manet-iana-05.txt,
June 2007.
[7] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", October 1998.
19.2. Informative References
[8] Clausen, T. and P. Jacquet, "The Optimized Link State Routing
Protocol", RFC 3626, October 2003.
[9] Atkins, D., Stallings, W., and P. Zimmermann, "PGP Message
Exchange Formats", RFC 1991, August 1996.
[10] ETSI, "ETSI STC-RES10 Committee. Radio equipment and systems:
HIPERLAN type 1, functional specifications ETS 300-652",
June 1996.
[11] Jacquet, P., Minet, P., Muhlethaler, P., and N. Rivierre,
"Increasing reliability in cable free radio LANs: Low level
forwarding in HIPERLAN.", 1996.
[12] Qayyum, A., Viennot, L., and A. Laouiti, "Multipoint relaying:
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An efficient technique for flooding in mobile wireless
networks.", 2001.
[13] Macker, J. and S. Corson, "Mobile Ad hoc Networking (MANET):
Routing Protocol Performance Issues and Evaluation
Considerations", RFC 2501, January 1999.
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Appendix A. Node Configuration
OLSRv2 does not make any assumption about node addresses, other than
that each node 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 nodes/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 nodes in the
existing routing domain.
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Appendix B. Example Algorithm for Calculating MPRs
The following specifies an algorithm which MAY be used to select
MPRs. MPRs are calculated per OLSRv2 interface, but then a single
set of MPRs is formed from the union of the MPRs for all OLSRv2
interfaces. A node'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 node 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 node, use the algorithm in
Appendix B.2. Note that this sets N_mpr = true for some Neighbor
Tuples, these nodes 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 node still satisfies the necessary
conditions, for all OLSRv2 interfaces, then that node MAY be
removed from the set of MPRs. This process MAY be repeated until
no MPRs are removed. Nodes MAY be considered in order of
increasing N_willingness.
Symmetric 1-hop neighbor nodes with N_willingness == WILL_NEVER MUST
NOT be selected as MPRs, and MUST be ignored in the following
algorithm, as MUST be symmetric 2-hop neighbor nodes which are also
symmetric 1-hop neighbor nodes (i.e. when considering 2-Hop Tuples,
ignore any 2-Hop Tuples whose N2_2hop_iface_addr is in the
N_neighbor_iface_addr_list of any Neighbor Tuple, or whose
N2_neighbor_iface_addr_list is included in the
N_neighbor_iface_addr_list of any Neighbor Tuple with N_willingness
== WILL_NEVER).
B.1. Terminology
The following terminology will be used when selecting MPRs for the
OLSRv2 interface I:
N(I) - The set of symmetric 1-hop neighbors which have a symmetric
link to I.
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N2(I) - The set of addresses of interfaces of a node with a
symmetric link to a node in N(I) (i.e. the set of
N2_2hop_iface_addr in 2-Hop Tuples in the 2-Hop Set for OLSRv2
interface I).
Connected to I via Y - An address A in D2(I) is connected to I via a
node Y in N(I) if A is an address of an interface of a symmetric
1-hop neighbor of Y (i.e. A is the N2_2hop_iface_addr in a 2-Hop
Tuple in the 2-Hop Set for OLSRv2 interface I, and whose
N2_neighbor_iface_addr_list is contained in the set of interface
addresses of Y).
D(Y, I) - For a node Y in N(I), the number of addresses in D2(I)
which are connected to I via Y.
R(Y, I): - For a node Y in N(I), the number of addresses in D2(I)
which are connected to I via Y, but are not connected to I via any
node 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 node Y in
N(I) such that A is connected to I via Y, select that node Y as
an MPR (i.e. set N_mpr = true in the Neighbor Tuple corresponding
to Y).
2. While there exists any node Y in N(I) with R(Y, I) > 0:
1. Select a node 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;
+ any choice.
2. Select Y as an MPR (i.e. set N_mpr = true in the Neighbor
Tuple corresponding to Y).
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Appendix C. Example Algorithm for Calculating the Routing Set
The following procedure is given as an example for calculating the
Routing Set using a variation of Dijkstra's algorithm. First all
Routing Tuples are removed, and then the procedures in the following
sections are applied in turn.
C.1. Add Local Symmetric Links
1. For each Local Interface Tuple in the Local Interface Set:
1. For each address A in I_local_iface_addr_list:
1. For each Link Tuple in the Link Set for this local
interface, with L_status == SYMMETRIC:
1. For each address, B, in that Link Tuple's
L_neighbor_iface_addr_list, add a new Routing Tuple
with:
o R_dest_addr = B;
o R_next_iface_addr = B;
o R_dist = 1;
o R_local_iface_addr = A.
2. For each Neighbor Tuple, for which there is an address B in
N_neighbor_iface_addr_list, for which there is a Routing Tuple
(the "previous Routing Tuple") with R_dest_addr == B:
1. For each address C in N_neighbor_iface_addr_list for which
there is no Routing Tuple with R_dest_addr == C, add a
Routing Tuple with:
+ R_dest_addr = C;
+ R_next_iface_addr = B;
+ R_dist = 1;
+ R_local_iface_addr = R_local_iface_addr of the previous
Routing Tuple.
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C.2. Add Remote Symmetric Links
The following procedure, which adds Routing Tuples for destination
nodes h+1 hops away, MUST be executed for each value of h, starting
with h = 1 and incrementing by 1 for each iteration. The execution
MUST stop if no new Routing Tuples are added in an iteration.
1. For each Topology Tuple, if:
* T_dest_iface_addr is not equal to R_dest_addr of any Routing
Tuple, AND;
* for the Advertising Remote Node Tuple with AR_orig_addr ==
T_orig_addr, there is an address in the AR_iface_addr_list
which is equal to the R_dest_addr of a Routing Tuple (the
"previous Routing Tuple") whose R_dist == h
then add a new Routing Tuple, with:
* R_dest_addr = T_dest_iface_addr;
* R_next_iface_addr = R_next_iface_addr of the previous Routing
Tuple;
* R_dist = h+1;
* R_local_iface_addr = R_local_iface_addr of the previous
Routing Tuple.
More than one Topology Tuple may be usable to select the next hop
R_next_iface_addr for reaching the address R_dest_addr. When h
== 1, ties should be broken such that nodes with greater
willingness are preferred, and between nodes of equal
willingness, MPR selectors are preferred over non-MPR selectors.
2. After the above iteration has completed, if h == 1, for each
2-Hop Neighbor Tuple where:
* N2_2hop_iface_addr is not equal to R_dest_addr of any Routing
Tuple, AND;
* The Neighbor Tuple whose N_neighbor_iface_addr_list contains
N2_neighbor_iface_addr_list has N_willingness not equal to
WILL_NEVER
select a Routing Tuple (the "previous Routing Tuple") whose
R_dest_addr is contained in N2_neighbor_iface_addr_list, and add
a new Routing Tuple with:
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* R_dest_addr = N2_2hop_iface_addr;
* R_next_iface_addr = R_next_iface_addr of the previous Routing
Tuple;
* R_dist = 2;
* R_local_iface_addr = R_local_iface_addr of the previous
Routing Tuple.
C.3. Add Attached Networks
1. For each Attached Network Tuple, if for the Advertising Remote
Node Tuple with AR_orig_addr == AN_orig_addr, there is an address
in the AR_iface_addr_list which is equal to the R_dest_addr of a
Routing Tuple (the "previous Routing Tuple"), then:
1. If there is no Routing Tuple with R_dest_addr == AN_net_addr,
then add a new Routing Tuple with:
+ R_dest_addr = AN_net_addr;
+ R_next_iface_addr = R_next_iface_addr of the previous
Routing Tuple;
+ R_dist = (R_dist of the previous Routing Tuple) + AN_dist;
+ R_local_iface_addr = R_local_iface_addr of the previous
Routing Tuple.
2. Otherwise if the Routing Tuple with R_dest_addr ==
AN_net_addr (the "current Routing Tuple") has R_dist >
(R_dist of the previous Routing Tuple) + AN_dist, then modify
the current Routing Tuple by:
+ R_next_iface_addr = R_next_iface_addr of the previous
Routing Tuple;
+ R_dist = (R_dist of the previous Routing Tuple) + AN_dist;
+ R_local_iface_addr = R_local_iface_addr of the previous
Routing Tuple.
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Appendix D. Packet and Message Layout
This appendix illustrates the translation from the abstract
descriptions of packets employed in the protocol specification, and
the bit-layout packets actually exchanged between the nodes.
Appendix D.1. Packet and Message Options
The basic layout of an OLSRv2 packet is as described in [1]. However
the following points should be noted.
In the following figures, reserved bits marked Reserved or Resv MUST
be cleared ('0'). Octets indicated as Padding are optional and MAY
be omitted; if not omitted they SHOULD be used to pad to a 32 bit
boundary and MUST all be zero.
OLSRv2 uses only packets with a packet header including a packet
sequence number, either with or without a packet TLV block. Thus all
OLSRv2 packets have the layout of either
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 0| Reserved |0|0| Packet Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Message + Padding |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: ... :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Message + Padding |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
or
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 0| Reserved |1|0| Packet Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Packet TLV Block |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Message + Padding |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: ... :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Message + Padding |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
OLSRv2 uses only messages with a complete message header. Thus all
OLSRv2 messages, plus padding if any, have the following layout.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Type | Rsv |N|0|0|0|0| Message Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Originator Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hop Limit | Hop Count | Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Message Body |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In standard OLSRv2 messages (HELLO and TC) the type dependent
sequence number bit marked N MUST be cleared ('0').
The layouts of the message body, address block, TLV block and TLV are
as in [1], allowing all options. Standard (HELLO and TC) messages
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contain a first address block which contains local interface address
information, all other address blocks contain neighbor interface
address information (or, for a TC message, address information for
which it is a gateway) specific to the message type.
Appendix D.2. Example HELLO Message
An example HELLO message, using IPv4 (four octet) addresses is as
follows. The overall message length is 58 octets. The message has a
hop limit of 1 and a hop count of 0, as sent by its originator.
The message has a message TLV block with content length 12 octets
containing three message TLVs. These TLVs represent message validity
time, message interval time and willingness. Each uses a TLV with
semantics value 8, indicating no start and stop indexes are included,
and each has a value length of 1 octet.
The first address block contains 1 local interface address. The
semantics octet 2 indicates it has no tail section. It has head
length 4, this is equal to the address length, it thus has no mid
section. This address block has no TLVs (TLV block content length is
0 octets).
The second, and last, address block includes 4 neighbor interface
addresses. The semantics octet 2 indicates they have no tail
section. The addresses have head length 3 octets, thus each mid
section is of length one octet. The following address TLV block
(content length 11 octets) includes two TLVs.
The first of these TLVs reports the link status of all four neighbors
in a single multivalue TLV, the first two addresses are HEARD, the
last two addresses are SYMMETRIC. The TLV semantics octet value of
40 indicates, in addition to that this is a multivalue TLV, that no
start index and stop index are included, hence values for all
addresses are included. The TLV value length of 4 octets indicates
one octet per value per address.
The second of these TLVs indicates that the last address (start index
3, stop index 3) is an MPR. This TLV has no value, or value length,
fields, as indicated by its semantics octet being equal to 4.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HELLO |0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 0 0 0 1 1 1 0 1 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Originator Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1|0 0 0 0 0 0 0 0| Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0| VALIDITY_TIME |0 0 0 0 1 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1| Value | INTERVAL_TIME |0 0 0 0 1 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1| Value | WILLINGNESS |0 0 0 0 1 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1| Value |0 0 0 0 0 0 0 1|0 0 0 0 0 0 1 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 1 0 0| Head |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Head (cont) |0 0 0 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 0|0 0 0 0 0 0 1 1| Head |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Head (cont) | Mid | Mid | Mid |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mid |0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 1| LINK_STATUS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 1 0 1 0 0 0|0 0 0 0 0 1 0 0| HEARD | HEARD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SYMMETRIC | SYMMETRIC | MPR |0 0 0 0 0 1 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 1 1|0 0 0 0 0 0 1 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Appendix D.3. Example TC Message
An example TC message, using IPv4 (four octet) addresses, is as
follows. The overall message length is 67 octets.
The message has a message TLV block with content length 13 octets
containing three TLVs. The first two TLVs are validity and interval
times as for the HELLO message above. The third TLV is a content
sequence number TLV used to carry the 2 octet ANSN. The semantics
value is also 8.
The message has three address blocks. The first address block
contains 3 local interface addresses (with semantics octet 2, hence
no tail section, head length 2 octets, and hence mid sections with
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length two octets) and has no TLVs (TLV block content length 0
octets).
The other two address blocks contain neighbor interface addresses.
The first contains 3 addresses (semantics octet 2, no tail section,
head length 2 octets, hence mid sections length two octets) and has
no TLVs (TLV block content length 0 octets). The second contains 1
address, with semantics octet 4 indicating that the tail section,
length 2 octets, consists of zero valued octets (not included). The
following TLV block (content length 6 octets) includes two TLVs, the
first (semantics value 8 indicating no indexes are needed) indicates
that the address has a netmask, with length given by the value (of
length 1 octet) of 16. Thus this address is Head.0.0/16. The second
TLV indicates that the originating node is a gateway to this network,
at a given number of hops distance. The TLV semantics value of 8
indicates that no indexes are needed.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TC |0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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| VALIDITY_TIME |0 0 0 0 1 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1| Value | INTERVAL_TIME |0 0 0 0 1 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1| Value | CONT_SEQ_NUM |0 0 0 0 1 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 1 0| Value (ANSN) |0 0 0 0 0 0 1 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x02 |0 0 0 0 0 0 1 0| Head |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mid | Mid |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mid |0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 1 1| 0x02 |0 0 0 0 0 0 1 0| Head |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Head (cont) | Mid | Mid |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mid (cont) | Mid |0 0 0 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 1|0 0 0 0 0 1 0 0|0 0 0 0 0 0 1 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Head |0 0 0 0 0 0 1 0|0 0 0 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 1 1 1| PREFIX_LENGTH |0 0 0 0 1 0 0 0|0 0 0 0 0 0 0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1 0 0 0 0| GATEWAY |0 0 0 0 1 0 0 0| Number Hops |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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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 [4].
In each Local Attached Network Tuple:
o AL_net_addr MUST NOT be in the I_local_iface_addr_list of any
Local Interface Tuple.
o AL_dist MUST NOT be less than zero.
In each Link Tuple:
o L_neighbor_iface_addr_list MUST NOT contain the AL_net_addr of any
Local Attached Network Tuple.
o If L_status == SYMMETRIC and the Neighbor Tuple whose
N_neighbor_iface_addr_list contains L_neighbor_iface_addr_list has
N_mpr_selector == true, then, for each address in this
L_neighbor_iface_addr_list, there MUST be an equal
RY_neighbor_iface_addr in the Relay Set associated with the same
OLSRv2 interface.
In each Neighbor Tuple:
o N_neighbor_iface_addr_list MUST NOT contain the AL_net_addr of any
Local Attached Network Tuple.
o If N_willingness MUST be in the range from WILL_NEVER to
WILL_ALWAYS, inclusive.
o If N_mpr == true, then N_symmetric MUST be true and N_willingness
MUST NOT equal WILL_NEVER.
o If N_symmetric == true and N_mpr == false, then N_willingness MUST
NOT equal WILL_ALWAYS.
o If N_mpr_selector == true, then N_symmetric MUST be true.
o If N_mpr_selector == true, then, for each address in this
N_neighbor_iface_addr_list, there MUST be an equal
A_neighbor_iface_addr in the Advertised Neighbor Set.
In each Lost Neighbor Tuple:
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o NL_neighbor_iface_addr MUST NOT equal the AL_net_addr of any Local
Attached Network Tuple.
In each 2-Hop Tuple:
o N2_2hop_iface_addr MUST NOT equal the AL_net_addr of any Local
Attached Network Tuple.
In each Received Tuple:
o RX_orig_addr SHOULD NOT be in the I_local_iface_addr_list of any
Local Interface Tuple.
o RX_orig_addr SHOULD NOT equal the AL_net_addr of any Local
Attached Network Tuple.
o Each ordered triple (RX_type, RX_orig_addr, RX_seq_number) SHOULD
NOT equal the corresponding triple in any other Received Tuple in
the same Received Set.
In each Processed Tuple:
o P_orig_addr SHOULD NOT be in the I_local_iface_addr_list of any
Local Interface Tuple.
o P_orig_addr SHOULD NOT equal the AL_net_addr of any Local Attached
Network Tuple.
o Each ordered triple (P_type, P_orig_addr, P_seq_number) SHOULD NOT
equal the corresponding triple in any other Processed Tuple.
In each Forwarded Tuple:
o F_orig_addr SHOULD NOT be in the I_local_iface_addr_list of any
Local Interface Tuple.
o F_orig_addr SHOULD NOT equal the AL_net_addr of any Local Attached
Network Tuple.
o Each ordered triple (F_type, F_orig_addr, F_seq_number) SHOULD NOT
equal the corresponding triple in any other Forwarded Tuple.
In each Relay Set:
o Each RY_neighbor_iface_addr SHOULD NOT equal any other
RY_neighbor_iface_addr.
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o Each RY_neighbor_iface_addr MUST be in the
L_neighbor_iface_addr_list of a Link Tuple with L_status ==
SYMMETRIC.
In the Advertised Neighbor Set:
o Each A_neighbor_iface_addr MUST NOT equal any other
A_neighbor_iface_addr.
o Each A_neighbor_iface_addr MUST be in the
N_neighbor_iface_addr_list of a Neighbor Tuple with N_symmetric ==
true.
In each Advertising Remote Node Tuple:
o AR_orig_addr SHOULD NOT be in the I_local_iface_addr_list of any
Local Interface Tuple.
o AR_orig_addr SHOULD NOT equal the AL_net_addr of any Local
Attached Network Tuple.
o Each AR_orig_addr MUST NOT equal the AR_orig_addr in any other
ANSN History Tuple.
o AR_iface_addr_list MUST NOT contain any address which is in the
I_local_iface_addr_list of any Local Interface Tuple.
o AR_iface_addr_list MUST NOT contain any address which is the
AL_net_addr of any Local Attached Network Tuple.
In each Topology Tuple:
o T_dest_iface_addr MUST NOT be in the I_local_iface_addr_list of
any Local Interface Tuple.
o T_dest_iface_addr MUST NOT equal the AL_net_addr of any Local
Attached Network Tuple.
o There MUST be an Advertising Remote Node Tuple with AR_orig_addr
== T_orig_addr.
o T_dest_iface_addr MUST NOT be in the AR_iface_addr_list of the
Advertising Remote Node Tuple with AR_orig_addr == T_orig_addr.
o T_seq_number MUST NOT be greater than AR_seq_number of the
Advertising Remote Node Tuple with AR_orig_addr == T_orig_addr.
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o The ordered pair (T_dest_iface_addr, T_orig_addr) MUST NOT equal
the corresponding pair in any other Topology Tuple.
In each Attached Network Tuple:
o AN_net_addr MUST NOT be in the I_local_iface_addr_list of any
Local Interface Tuple.
o AN_net_addr MUST NOT equal the AL_net_addr of any Local Attached
Network Tuple.
o There MUST be an Advertising Remote Node Tuple with AR_orig_addr
== AN_orig_addr.
o AN_seq_number MUST NOT be greater than AR_seq_number of the
Advertising Remote Node 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.
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Appendix F. 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.
Appendix F.1. Confidentiality
Being a proactive protocol, OLSRv2 periodically diffuses topological
information. Hence, if used in an unprotected wireless network, the
network topology is revealed to anyone who listens to OLSRv2 control
messages.
In situations where the confidentiality of the network topology is of
importance, regular cryptographic techniques, such as exchange of
OLSRv2 control traffic messages encrypted by PGP [9] 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.
Appendix F.2. Integrity
In OLSRv2, each node is injecting topological information into the
network through transmitting HELLO messages and, for some nodes, TC
messages. If some nodes 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 node generates TC messages, advertising links to non-neighbor
nodes;
2. a node generates TC messages, pretending to be another node;
3. a node generates HELLO messages, advertising non-neighbor nodes;
4. a node generates HELLO messages, pretending to be another node;
5. a node forwards altered control messages;
6. a node does not forward control messages;
7. a node does not select multipoint relays correctly;
8. a node forwards broadcast control messages unaltered, but does
not forward unicast data traffic;
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9. a node "replays" previously recorded control traffic from another
node.
Authentication of the originator node 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 nodes from repeating old (and
correctly authenticated) information (situation 9) temporal
information is required, allowing a node to positively identify such
delayed messages.
In general, digital signatures and other required security
information may be transmitted as a separate OLSRv2 message type, or
signatures and security information may be transmitted within the
OLSRv2 HELLO and TC messages, using the TLV mechanism. Either option
permits that "secured" and "unsecured" nodes can coexist in the same
network, if desired,
Specifically, the authenticity of entire OLSRv2 control messages 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 nodes in the neighborhood (HELLO
messages) or broadcast to all nodes 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 node 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.
Appendix F.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 nodes
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
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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 nodes/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 nodes in the existing routing domain.
Appendix F.4. Node Identity
OLSRv2 does not make any assumption about node addresses, other than
that each node is assumed to have at least one a unique and routable
IP address for each interface that it has which participates in the
MANET.
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Appendix G. Flow and Congestion Control
Due to its proactive nature, the OLSRv2 protocol has a natural
control over the flow of its control traffic. Nodes transmit control
messages at predetermined rates specified and bounded by message
intervals.
OLSRv2 employs [4] for local signaling, embedding MPR selection
advertisement through a simple address block TLV, and node
willingness advertisement (if any) as a single message TLV. OLSRv2
local signaling, therefore, shares the characteristics and
constraints of [4].
Furthermore, the MPR optimization greatly constrains global signaling
overhead from link state diffusion in two ways. First, the messages
that advertise the topology need only contain MPR selectors, reducing
their size as compared to full link state. Second, the cost of
diffusing these messages throughout the network is greatly reduced as
compared to when using classic flooding, since only MPRs need to
forward broadcast messages. In dense networks, the reduction of
control traffic can be of several orders of magnitude compared to
routing protocols using classical flooding [12]. This feature
naturally provides more bandwidth for useful data traffic and pushes
further the frontier of congestion.
Since the control traffic is continuous and periodic, it keeps the
quality of the links used in routing more stable. However, using
certain OLSRv2 options, some control messages (HELLO messages or TC
messages) may be intentionally sent in advance of their deadline in
order to increase the responsiveness of the protocol to topology
changes. This may cause a small, temporary, and local increase of
control traffic, however this is at all times bounded by the use of
minimum message intervals.
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Appendix H. 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>
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Appendix I. Acknowledgements
The authors would like to acknowledge the team behind OLSRv1,
specified in RFC3626, including Anis Laouiti, Pascale Minet, Laurent
Viennot (all at INRIA, France), and Amir Qayyum (Center for Advanced
Research in Engineering, Pakistan) 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: Li Li (CRC), Louise Lamont (CRC),
Joe Macker (NRL), Alan Cullen (BAE Systems), Philippe Jacquet
(INRIA), Khaldoun Al Agha (LRI), Richard Ogier (SRI), Song-Yean Cho
(Samsung Software Center), Shubhranshu Singh (Samsung AIT), Charles
E. Perkins (Nokia) and the entire IETF MANET working group.
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Authors' Addresses
Thomas Heide Clausen
LIX, Ecole Polytechnique, France
Phone: +33 6 6058 9349
Email: T.Clausen@computer.org
URI: http://www.ThomasClausen.org/
Christopher M. Dearlove
BAE Systems Advanced Technology Centre
Phone: +44 1245 242194
Email: chris.dearlove@baesystems.com
URI: http://www.baesystems.com/
Philippe Jacquet
Project Hipercom, INRIA
Phone: +33 1 3963 5263
Email: philippe.jacquet@inria.fr
The OLSRv2 Design Team
MANET Working Group
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