Mobile Ad hoc Networking (MANET) T. Clausen
Internet-Draft LIX, Ecole Polytechnique, France
Intended status: Standards Track C. Dearlove
Expires: December 8, 2008 BAE Systems Advanced Technology
Centre
P. Jacquet
Project Hipercom, INRIA
The OLSRv2 Design Team
MANET Working Group
June 6, 2008
The Optimized Link State Routing Protocol version 2
draft-ietf-manet-olsrv2-06
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Abstract
This document describes version 2 of the Optimized Link State Routing
(OLSRv2) protocol. The protocol embodies an optimization of the
classical link state algorithm tailored to the requirements of a
Mobile Ad hoc NETwork (MANET).
The key optimization in OLSRv2 is that of multipoint relays (MPRs),
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 flood 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 best in this context.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Applicability Statement . . . . . . . . . . . . . . . . . . . 8
4. Protocol Overview and Functioning . . . . . . . . . . . . . . 10
5. Protocol Parameters and Constants . . . . . . . . . . . . . . 13
5.1. Local History Times . . . . . . . . . . . . . . . . . . . 13
5.2. Message Intervals . . . . . . . . . . . . . . . . . . . . 14
5.3. Advertised Information Validity Times . . . . . . . . . . 14
5.4. Received Message Validity Times . . . . . . . . . . . . . 15
5.5. Jitter . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.6. Hop Limit Parameter . . . . . . . . . . . . . . . . . . . 16
5.7. Willingness . . . . . . . . . . . . . . . . . . . . . . . 17
5.8. Parameter Change Constraints . . . . . . . . . . . . . . . 17
6. Information Bases . . . . . . . . . . . . . . . . . . . . . . 19
6.1. Local Information Base . . . . . . . . . . . . . . . . . . 19
6.1.1. Originator Set . . . . . . . . . . . . . . . . . . . . 19
6.1.2. Local Attached Network Set . . . . . . . . . . . . . . 20
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6.2. Node Information Base . . . . . . . . . . . . . . . . . . 20
6.3. Topology Information Base . . . . . . . . . . . . . . . . 21
6.3.1. Advertised Neighbor Set . . . . . . . . . . . . . . . 21
6.3.2. Advertising Remote Node Set . . . . . . . . . . . . . 21
6.3.3. Topology Set . . . . . . . . . . . . . . . . . . . . . 22
6.3.4. Attached Network Set . . . . . . . . . . . . . . . . . 22
6.3.5. Routing Set . . . . . . . . . . . . . . . . . . . . . 23
6.4. Processing and Forwarding Information Base . . . . . . . . 23
6.4.1. Received Set . . . . . . . . . . . . . . . . . . . . . 24
6.4.2. Processed Set . . . . . . . . . . . . . . . . . . . . 24
6.4.3. Forwarded Set . . . . . . . . . . . . . . . . . . . . 24
6.4.4. Relay Set . . . . . . . . . . . . . . . . . . . . . . 25
7. Packet Processing and Message Forwarding . . . . . . . . . . . 26
7.1. Actions when Receiving an OLSRv2 Packet . . . . . . . . . 26
7.2. Actions when Receiving an OLSRv2 Message . . . . . . . . . 26
7.3. Message Considered for Processing . . . . . . . . . . . . 27
7.4. Message Considered for Forwarding . . . . . . . . . . . . 28
8. Packets and Messages . . . . . . . . . . . . . . . . . . . . . 31
8.1. HELLO Messages . . . . . . . . . . . . . . . . . . . . . . 31
8.1.1. HELLO Message TLVs . . . . . . . . . . . . . . . . . . 32
8.1.2. HELLO Message Address Block TLVs . . . . . . . . . . . 32
8.2. TC Messages . . . . . . . . . . . . . . . . . . . . . . . 32
8.2.1. TC Message TLVs . . . . . . . . . . . . . . . . . . . 34
8.2.2. TC Message Address Block TLVs . . . . . . . . . . . . 34
9. HELLO Message Generation . . . . . . . . . . . . . . . . . . . 35
9.1. HELLO Message: Transmission . . . . . . . . . . . . . . . 35
10. HELLO Message Processing . . . . . . . . . . . . . . . . . . . 36
10.1. Updating Willingness . . . . . . . . . . . . . . . . . . . 36
10.2. Updating MPR Selectors . . . . . . . . . . . . . . . . . . 36
10.3. Symmetric 1-Hop and 2-Hop Neighborhood Changes . . . . . . 36
11. TC Message Generation . . . . . . . . . . . . . . . . . . . . 38
11.1. TC Message: Transmission . . . . . . . . . . . . . . . . . 39
12. TC Message Processing . . . . . . . . . . . . . . . . . . . . 40
12.1. Initial TC Message Processing . . . . . . . . . . . . . . 40
12.1.1. Populating the Advertising Remote Node Set . . . . . . 41
12.1.2. Populating the Topology Set . . . . . . . . . . . . . 42
12.1.3. Populating the Attached Network Set . . . . . . . . . 42
12.2. Completing TC Message Processing . . . . . . . . . . . . . 43
12.2.1. Purging the Topology Set . . . . . . . . . . . . . . . 43
12.2.2. Purging the Attached Network Set . . . . . . . . . . . 43
13. Information Base Changes . . . . . . . . . . . . . . . . . . . 44
14. Selecting MPRs . . . . . . . . . . . . . . . . . . . . . . . . 45
15. Populating Derived Sets . . . . . . . . . . . . . . . . . . . 47
15.1. Populating the Relay Set . . . . . . . . . . . . . . . . . 47
15.2. Populating the Advertised Neighbor Set . . . . . . . . . . 47
16. Routing Set Calculation . . . . . . . . . . . . . . . . . . . 48
16.1. Network Topology Graph . . . . . . . . . . . . . . . . . . 48
16.2. Populating the Routing Set . . . . . . . . . . . . . . . . 49
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16.3. Routing Set Updates . . . . . . . . . . . . . . . . . . . 50
17. Proposed Values for Parameters and Constants . . . . . . . . . 51
17.1. Local History Time Parameters . . . . . . . . . . . . . . 51
17.2. Message Interval Parameters . . . . . . . . . . . . . . . 51
17.3. Advertised Information Validity Time Parameters . . . . . 51
17.4. Received Message Validity Time Parameters . . . . . . . . 51
17.5. Jitter Time Parameters . . . . . . . . . . . . . . . . . . 51
17.6. Hop Limit Parameter . . . . . . . . . . . . . . . . . . . 51
17.7. Willingness Parameter and Constants . . . . . . . . . . . 52
18. Sequence Numbers . . . . . . . . . . . . . . . . . . . . . . . 53
19. Security Considerations . . . . . . . . . . . . . . . . . . . 54
19.1. Confidentiality . . . . . . . . . . . . . . . . . . . . . 54
19.2. Integrity . . . . . . . . . . . . . . . . . . . . . . . . 54
19.3. Interaction with External Routing Domains . . . . . . . . 55
20. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 57
20.1. Message Types . . . . . . . . . . . . . . . . . . . . . . 57
20.2. TLV Types . . . . . . . . . . . . . . . . . . . . . . . . 57
21. References . . . . . . . . . . . . . . . . . . . . . . . . . . 59
21.1. Normative References . . . . . . . . . . . . . . . . . . . 59
21.2. Informative References . . . . . . . . . . . . . . . . . . 59
Appendix A. Node Configuration . . . . . . . . . . . . . . . . . 61
Appendix B. Example Algorithm for Calculating MPRs . . . . . . . 62
B.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 62
B.2. MPR Selection Algorithm for each OLSRv2 Interface . . . . 63
Appendix C. Example Algorithm for Calculating the Routing Set . . 64
C.1. Add Local Symmetric Links . . . . . . . . . . . . . . . . 64
C.2. Add Remote Symmetric Links . . . . . . . . . . . . . . . . 65
C.3. Add Attached Networks . . . . . . . . . . . . . . . . . . 66
Appendix D. Example Message Layout . . . . . . . . . . . . . . . 67
Appendix E. Constraints . . . . . . . . . . . . . . . . . . . . . 69
Appendix F. Flow and Congestion Control . . . . . . . . . . . . . 73
Appendix G. Contributors . . . . . . . . . . . . . . . . . . . . 74
Appendix H. Acknowledgements . . . . . . . . . . . . . . . . . . 75
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1. Introduction
The Optimized Link State Routing protocol version 2 (OLSRv2) is an
update to OLSRv1 as published in [RFC3626]. Compared to RFC3626,
OLSRv2 retains the same basic mechanisms and algorithms, while
providing a more flexible signaling framework and some simplification
of the messages being exchanged. Also, OLSRv2 accommodates either
IPv4 and IPv6 addresses in a compact manner.
OLSRv2 is developed for mobile ad hoc networks. It operates as a
table driven, proactive protocol, i.e. it exchanges topology
information with other nodes in the network regularly. Each node
selects a set of its neighbor nodes as "MultiPoint Relays" (MPRs).
Control traffic may be flooded through the network using hop by hop
forwarding, but where a node only needs to forward control traffic
directly received from its MPR selectors (nodes which have selected
it as an MPR). This mechanism, denoted "MPR flooding", provides an
efficient mechanism for information distribution within the MANET by
reducing the number of transmissions required.
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 (lowest hop count) 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 MPR flooding, use of MPRs
allows the reduction of the number and size of link state messages,
and MPRs are used as intermediate nodes in multi-hop routes.
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 [packetbb],
[timetlv], [RFC5148] and [nhdp] for wider use.) Likewise, OLSRv2
makes no assumptions about the underlying link layer. However,
OLSRv2 may use link layer information and notifications when
available and applicable, as described in [nhdp].
OLSRv2, as OLSRv1, inherits its concept of forwarding and relaying
from HIPERLAN (a MAC layer protocol) which is standardized by ETSI
[HIPERLAN], [HIPERLAN2].
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2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
MANET specific terminology is to be interpreted as described in
[packetbb] and [nhdp].
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. Note that all
references to MANET interfaces in [nhdp] refer to OLSRv2
interfaces when using [nhdp] as part of OLSRv2.
Address - An address, as recorded in the Information Bases specified
by this protocol, and included in HELLO and TC messages generated
by this protocol, may be either an address or an address prefix.
These can be represented as a single address object in a HELLO or
TC message, as defined by [packetbb]. An address so represented
is considered to have a prefix length equal to its length (in
bits) when considered as an address object, and a similar
convention is used in the Information Bases specified by this
protocol. Two addresses (address objects) are considered equal
only if their prefix lengths are also equal.
Willingness - The willingness of a node is a numerical value between
WILL_NEVER and WILL_ALWAYS (both inclusive), which represents the
node's willingness to be selected as an MPR.
Willing symmetric 1-hop neighbor - A symmetric 1-hop neighbor of
this node which has willingness not equal to WILL_NEVER.
Symmetric strict 2-hop neighbor - A symmetric 2-hop neighbor of this
node which is not a symmetric 1-hop neighbor of this node, and is
a symmetric 1-hop neighbor of a willing symmetric 1-hop neighbor
of this node.
Symmetric strict 2-hop neighbor through OLSRv2 interface I - A
symmetric strict 2-hop neighbor of this node which is a symmetric
1-hop neighbor of a willing symmetric 1-hop neighbor of this node
by a symmetric link including OLSRv2 interface I. This node MAY
elect to consider only information received over OLSRv2 interface
I in making this determination.
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Symmetric strict 2-hop neighborhood - The set of the symmetric
strict 2-hop neighbors of a 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.
MPR flooding - The optimized MANET-wide information distribution
mechanism, employed by this protocol, in which a message is
relayed by only a reduced subset of the nodes in the network.
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3. Applicability Statement
OLSRv2 is a proactive routing protocol for mobile ad hoc networks
(MANETs) [RFC2501]. The larger and more dense a network, the more
optimization can be achieved by using MPRs compared to the classic
link state algorithm. OLSRv2 enables hop-by-hop routing, i.e. each
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 [nhdp], 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 [packetbb] 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 [packetbb], 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 [nhdp]. This neighborhood discovery protocol serves to
ensure that each OLSRv2 node has available continuously updated
Information Bases describing the node's 1-hop and symmetric 2-hop
neighbors. This neighborhood discovery protocol, which also uses
[packetbb], is extended in this document by the addition of MPR
information.
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
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address for each interface that it has which participates in the
MANET.
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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 Unacknowledged transmission of all control messages; control
messages are sent periodically, but may also be sent in response
to changes in the local neighborhood.
o MPR flooding for MANET-wide link state information distribution.
o Partial topology maintenance - each node knows only a subset of
the links in the network, sufficient for a minimum hop route to
all destinations.
The MPR flooding and partial topology maintenance are based on the
concept of MultiPoint Relays (MPRs), selected independently by nodes
based on the symmetric 1-hop and 2-hop neighbor information
maintained using [nhdp].
Using the message exchange format [packetbb] and the neighborhood
discovery protocol [nhdp], OLSRv2 also contains the following main
components:
o A TLV, to be included within the HELLO messages of [nhdp],
allowing a node to signal MPR selection.
o The optimized mechanism for MANET-wide information distribution,
denoted "MPR flooding".
o A specification of MANET-wide signaling, denoted TC (Topology
Control) messages. TC messages in OLSRv2 serve to:
* inject link state information into the entire MANET;
* inject addresses of hosts and networks for which they may serve
as a gateway into the entire network.
TC messages are emitted periodically, thereby allowing nodes to
continuously track changes in the network. Incomplete TC messages
may be used to report additions to advertised information without
repeating unchanged information. Some TC messages may be MPR
flooded over only part of the network, allowing a node to ensure
that nearer nodes are kept more up to date than distant nodes,
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such as is used in Fisheye State Routing [FSR] and Fuzzy Sighted
Link State routing [FSLS].
Each node in the network selects a set of MPRs. The MPRs of a node X
may be any subset of node X's willing symmetric 1-hop neighbors, 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 an MPR, its MPR
selectors.
As long as the condition above is satisfied, any algorithm selecting
MPRs is acceptable in terms of implementation interoperability.
However if smaller sets of MPRs are selected then the greater the
efficiency gains that are possible. An analysis and examples of MPR
selection algorithms is given in [MPR].
A node may independently determine and advertise its willingness to
be selected as an MPR. A node may advertise that it always should be
selected as an MPR or that it should never be selected as an MPR. In
the latter case, the node will neither relay control messages, nor
will that node be included as an intermediate node in any routing
table calculations. Use of variable willingness is most effective in
dense networks.
In OLSRv2, actual efficiency gains are based on the sizes of each
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 outdated link state
information.
OLSRv2 is designed to work in a completely distributed manner and
does not depend on any central entity. The protocol does not require
reliable transmission of control messages; each 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 [RFC5148].
OLSRv2 does not require sequenced delivery of messages. Each TC
message contains a sequence number which is incremented for each
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message. Thus the recipient of a TC message can, if required, easily
identify which information is more recent - even if messages have
been re-ordered while in transmission.
OLSRv2 only interacts with IP through routing table management.
OLSRv2 sends its control messages as described in [packetbb] and
[nhdp].
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5. Protocol Parameters and Constants
The parameters and constants used in this specification are those
defined in [nhdp] plus those defined in this section. The separation
in [nhdp] into interface parameters, node parameters and constants is
also used in OLSRv2, however all but one (RX_HOLD_TIME) of the
parameters added by OLSRv2 are node parameters. Parameters may be
classified into the following categories:
o Local history times
o Message intervals
o Advertised information validity times
o Received message validity times
o Jitter times
o Hop limits
o Willingness
In addition, constants for particular cases of a node's willingness
to be an MPR are defined. These parameters and constants are
detailed in the following sections. As for the parameters in [nhdp],
parameters defined in this document may be changed dynamically by a
node, and need not be the same on different nodes, even in the same
MANET, or on different interfaces of the same node (for interface
parameters).
5.1. Local History Times
The following parameter manages the time for which local information
is retained:
O_HOLD_TIME - is used to define the time for which a recently used
and replaced originator address is used to recognize the node's
own messages.
The following constraint applies to this parameter:
o O_HOLD_TIME >= 0
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5.2. 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 the parameter
TC_INTERVAL, and a smaller value of the parameter TC_MIN_INTERVAL, TC
messages may more often be transmitted in response to changes in a
highly dynamic network. However because a 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 [RFC5148].
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 specified in [RFC5148].)
The following constraints apply to these parameters:
o TC_INTERVAL > 0
o TC_MIN_INTERVAL >= 0
o TC_INTERVAL >= TC_MIN_INTERVAL
o If INTERVAL_TIME TLVs as defined in [timetlv] are included in TC
messages, then TC_INTERVAL MUST be representable as described in
[timetlv].
5.3. Advertised Information Validity Times
The following 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 (see Section 5.6) is
used then this will be the only value in that TLV.
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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 T_HOLD_TIME >= TC_INTERVAL
o If TC messages can be lost, then both T_HOLD_TIME and A_HOLD_TIME
SHOULD be significantly greater than TC_INTERVAL; a value >= 3 x
TC_INTERVAL is RECOMMENDED.
o T_HOLD_TIME MUST be representable as described in [timetlv].
5.4. Received Message Validity Times
The following parameters manage the validity time of recorded
received message information:
RX_HOLD_TIME - is an interface parameter, and is the period after
receipt of a message by the appropriate OLSRv2 interface of this
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
difference in time that a message may take to traverse the MANET,
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taking into account any message forwarding jitter as well as
propagation, queuing, and processing delays.
5.5. Jitter
If jitter, as defined in [RFC5148], is used then these parameters are
as follows:
TP_MAXJITTER - represents the value of MAXJITTER used in [RFC5148]
for periodically generated TC messages sent by this node.
TT_MAXJITTER - represents the value of MAXJITTER used in [RFC5148]
for externally triggered TC messages sent by this node.
F_MAXJITTER - represents the default value of MAXJITTER used in
[RFC5148] 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 [RFC5148].
5.6. Hop Limit Parameter
The parameter TC_HOP_LIMIT is the hop limit set in each TC message.
TC_HOP_LIMIT MAY be a single fixed value, or MAY be different in TC
messages sent by the same node. However each other node, at any hop
count distance, SHOULD see a regular pattern of TC messages, in order
that meaningful values of INTERVAL_TIME and VALIDITY_TIME TLVs at
each hop count distance can be included as defined in [timetlv].
Thus the pattern of TC_HOP_LIMIT SHOULD be defined to have this
property. For example the repeating pattern (255 4 4) satisfies this
property (having period TC_INTERVAL at hop counts up to 4, inclusive,
and 3 x TC_INTERVAL at hop counts greater than 4), but the repeating
pattern (255 255 4 4) does not satisfy this property because at hop
counts greater than 4, message intervals are alternately TC_INTERVAL
and 3 x TC_INTERVAL.
The following constraints apply to this parameter:
o The maximum value of TC_HOP_LIMIT >= the network diameter in hops,
a value of 255 is RECOMMENDED.
o All values of TC_HOP_LIMIT >= 2.
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5.7. 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 5.7. (Use of WILLINGNESS == WILL_DEFAULT
allows a node to avoid including an MPR_WILLING 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.)
The following constraints apply to this parameter:
o WILLINGNESS >= WILL_NEVER
o WILLINGNESS <= WILL_ALWAYS
5.8. Parameter Change Constraints
This section presents guidelines, applicable if protocol parameters
are changed dynamically.
O_HOLD_TIME
* If O_HOLD_TIME for a node changes, then O_time for all
Originator Tuples MAY be changed.
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.
* If the TC_INTERVAL for a node decreases, then the following TC
messages from this node MUST be generated according to the
current, shorter, TC_INTERVAL.
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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
values with its largest value.
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6. Information Bases
Each node maintains the Information Bases described in the following
sections. These are used for describing the protocol in this
document. An implementation of this protocol MAY maintain this
information in the indicated form, or in any other organization which
offers access to this information. In particular note that it is not
necessary to remove Tuples from Sets at the exact time indicated,
only to behave as if the Tuples were removed at that time.
The purpose of OLSRv2 is to determine the Routing Set, which may be
used to update IP's Routing Table, providing "next hop" routing
information for IP datagrams. OLSRv2 maintains the following
Information Bases:
Local Information Base - as defined in [nhdp], extended by the
addition of an Originator Set, defined in Section 6.1.1 and a
Local Attached Network Set, defined in Section 6.1.2.
Interface Information Bases - as defined in [nhdp], one Interface
Information Base for each OLSRv2 interface.
Node Information Base - as defined in [nhdp], extended by the
addition of three elements to each Neighbor Tuple, as defined in
Section 6.2.
Topology Information Base - this Information Base is specific to
OLSRv2, and is defined in Section 6.3.
Processing and Forwarding Information Base - this Information Base
is specific to OLSRv2, and is defined in Section 6.4.
The ordering of sequence numbers, when considering which is the
greater, is as defined in Section 18.
6.1. Local Information Base
The Local Information Base as defined in [nhdp] is extended by the
addition of an Originator Set, defined in Section 6.1.1, and a Local
Attached Network Set, defined in Section 6.1.2.
6.1.1. Originator Set
A node's Originator Set records addresses that were recently
originator addresses. If a node's originator address is immutable
then this set is always empty and MAY be omitted. It consists of
Originator Tuples:
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(O_orig_addr, O_time)
where:
O_orig_addr is a recently used originator address;
O_time specifies the time at which this Tuple expires and MUST be
removed.
6.1.2. Local Attached Network Set
A 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:
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 local to this node SHOULD be treated as local non-
MANET interfaces, and added to the Local Interface Set, as specified
in [nhdp], rather than being added to the Local Attached Network Set.
An attached network MAY also be attached to other nodes.
It is not the responsibility of OLSRv2 to maintain routes from this
node to networks recorded in the Local Attached Network Set.
6.2. Node Information Base
Each Neighbor Tuple in the Neighbor Set, defined in [nhdp], 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;
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N_mpr is a boolean flag, describing if this 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 information 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 Advertising Remote Node Set, the Topology Set and the
Attached Network Set record information received in TC messages.
Additionally, a Routing Set is maintained, derived from the
information recorded in the Neighborhood Information Base, Topology
Set, Attached Network Set and Advertising Remote 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;
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AR_seq_number is the greatest ANSN in any TC message received which
originated from the node with originator address AR_orig_addr
(i.e. which contributed to the information contained in this
Tuple);
AR_iface_addr_list is an unordered 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:
(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 ANSN in any TC message received which
originated from the node with originator address T_orig_addr (i.e.
which contributed to the information contained in this Tuple);
T_time specifies the time at which this Tuple expires and MUST be
removed.
6.3.4. Attached Network Set
A 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;
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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 ANSN in any TC message received which
originated from the node with originator address AN_orig_addr
(i.e. which contributed to the information contained in this
Tuple);
AN_time specifies the time at which this Tuple expires and MUST be
removed.
6.3.5. Routing Set
A 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 OLSRv2 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 OLSRv2 interface of a node, using MPR
flooding.
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6.4.1. Received Set
A node has a Received Set per local OLSRv2 interface. Each Received
Set records the signatures of messages which have been received over
that OLSRv2 interface. Each consists of Received Tuples:
(RX_type, RX_orig_addr, RX_seq_number, RX_time)
where:
RX_type is the received message type, or zero if the received
message sequence number is not type-specific;
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)
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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;
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 has a Relay Set per local OLSRv2 interface. Each Relay Set
records the OLSRv2 interface addresses of symmetric 1-hop neighbors,
such that the node is to forward messages received from those
neighbors' OLSRv2 interfaces, on that local OLSRv2 interface, if not
otherwise excluded from forwarding that message (e.g. by it having
been previously forwarded):
{RY_neighbor_iface_addr}
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7. Packet Processing and Message Forwarding
On receiving a packet, as defined in [packetbb], 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 specification 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 fully parsing the message 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:
1. 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.
2. 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 [packetbb], or if the node recognizes from the
originator address of the message that the message is one which
the receiving node itself originated (i.e. is the current
originator address of the node, or is an O_orig_addr in an
Originator Tuple) then the message MUST be silently discarded.
2. Otherwise:
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1. If the message is a HELLO message, then the message is
processed according to Section 10.
2. Otherwise:
1. Define the "dependent message type" of the message to
equal the message type if the mistypedep bit of the
message semantics octet in the message header is set
('1'), or to equal 0 otherwise.
2. If the message is of a known type, including being a TC
message, then the message is considered for processing
according to Section 7.3, AND;
3. If for the message:
- <hop-limit> is present and <hop-limit> > 1, AND;
- <hop-count> is not present or <hop-count> < 255
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 dependent message type of the current message,
AND;
* P_orig_addr == the originator address of the current message,
AND;
* P_seq_number == the message sequence number of the current
message;
then the current message MUST NOT be processed.
2. Otherwise:
1. Create a Processed Tuple with:
+ P_type = the dependent message type of the current
message;
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+ 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.
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) 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 dependent message type of the current
message, AND;
+ RX_orig_addr == the originator address of the current
message, AND;
+ RX_seq_number == the sequence number of the current
message;
then the current message MUST be silently discarded.
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2. Otherwise:
1. Create a Received Tuple in the Received Set for the
receiving interface with:
- RX_type = the dependent message type of the current
message;
- RX_orig_addr = originator address of the current
message;
- RX_seq_number = sequence number of the current
message;
- RX_time = current time + RX_HOLD_TIME.
2. If a Forwarded Tuple exists with:
- F_type == the dependent message type of the current
message, AND;
- F_orig_addr == the originator address of the current
message, AND;
- F_seq_number == the sequence number of the current
message.
then the current message MUST be silently discarded.
3. Otherwise if the sending interface address matches
(taking account of any address prefix) an
RY_neighbor_iface_addr in the Relay Set for the receiving
interface, then:
1. Create a Forwarded Tuple with:
o F_type = the dependent message type of the current
message;
o F_orig_addr = originator address of the current
message;
o F_seq_number = sequence number of the current
message;
o F_time = current time + F_HOLD_TIME.
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2. The message header of the current message is modified
by:
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 [RFC5148]. The value of
MAXJITTER used in jittering a forwarded message MAY
be based on information in that message (in
particular any INTERVAL_TIME or VALIDITY_TIME TLVs in
that message) or otherwise SHOULD be with a maximum
delay of F_MAXJITTER. A node MAY modify the jitter
applied to a message in order to more efficiently
combine messages in packets, as long as the maximum
jitter is not exceeded.
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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 originating nodes MAY be
combined in the same packet. Messages from other protocols defined
using [packetbb] MAY be combined in the same packet.
The packet and message format used by OLSRv2 is defined in
[packetbb], where:
o OLSRv2 packets MAY include packet TLVs, however OLSRv2 itself does
not specify any packet TLVs.
o All references in this specification to TLVs that do not indicate
a type extension, assume Type Extension == 0. TLVs in processed
messages with a type extension which is neither zero as so
assumed, nor a specifically indicated non-zero type extension, are
ignored.
Other options defined in [packetbb] may be freely used, in particular
any other values of <pkt-semantics>, <msg-semantics>, <addr-
semantics> or <tlv-semantics> consistent with their specifications.
The remainder of this section defines, within the framework of
[packetbb], message types and TLVs specific to OLSRv2.
8.1. HELLO Messages
A HELLO message in OLSRv2 is generated as specified in [nhdp].
Additionally, an OLSRv2 node:
o MUST include TLV(s) with Type == MPR associated with all OLSRv2
interface addresses that:
* are included in the HELLO message associated with a TLV with
Type == LINK_STATUS and Value == SYMMETRIC; AND
* are included in a Neighbor Tuple with N_mpr == true.
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.
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o MAY include a message TLV with Type == MPR_WILLING, indicating the
node's willingness to be selected as an MPR.
8.1.1. HELLO Message TLVs
In a HELLO message, a node MUST include an MPR_WILLING message TLV as
specified in Table 1, unless WILLINGNESS == WILL_DEFAULT (in which
case it MAY be included). A node MUST NOT include more than one
MPR_WILLING message TLV.
+-------------+--------+--------------------------------------------+
| Type | Value | Value |
| | Length | |
+-------------+--------+--------------------------------------------+
| MPR_WILLING | 8 bits | Node parameter WILLINGNESS; unused bits |
| | | (based on the maximum willingness value |
| | | WILL_ALWAYS) are RESERVED and SHOULD be |
| | | set to zero. |
+-------------+--------+--------------------------------------------+
Table 1
If a node does not advertise an MPR_WILLING TLV in a HELLO message,
then the node MUST be assumed to have WILLINGNESS equal to
WILL_DEFAULT.
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.
+------+--------------+-------+
| Type | Value Length | Value |
+------+--------------+-------+
| MPR | 0 bits | None. |
+------+--------------+-------+
Table 2
8.2. TC Messages
A TC message MUST contain:
o <msg-orig-addr>, <msg-seq-num> and <msg-hop-limit> elements in its
message header, as specified in [packetbb].
o A <msg-hop-count> element in its message header if the message
contains either a VALIDITY_TIME or an INTERVAL_TIME TLV indicating
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more than one time value according to distance.
o A single message TLV with Type == CONT_SEQ_NUM, and Type Extension
== COMPLETE or Type Extension == INCOMPLETE, as specified in
Section 8.2.1 (for complete and incomplete TC messages,
respectively).
o A message TLV with Type == VALIDITY_TIME, as specified in
[timetlv]. The options included in [timetlv] for representing
zero and infinite times MUST NOT be used.
o All of the node's interface addresses. These MUST be included in
the message's address blocks, unless:
* the node has a single interface, with a single interface
address with maximum prefix length, and
* that address is the node's originator address.
In this exceptional case, the address will be included as the
message's originator address, and MAY be omitted from the
message's address blocks.
o TLV(s) with Type == LOCAL_IF and Value == UNSPEC_IF associated
with all of the node's interface addresses.
o If the TC message is complete, all addresses in the Advertised
Address Set and all addresses in the Local Attached Network Set,
the latter (only) with associated GATEWAY address block TLV(s), as
specified in Section 8.2.2.
A TC message SHOULD have the mistypedep bit of <msg-semantics>, as
defined in [packetbb], cleared ('0').
A TC message MAY contain:
o If the TC message is incomplete, any addresses in the Advertised
Address Set and any addresses in the Local Attached Network Set,
the latter (only) with associated GATEWAY address block TLV(s), as
specified in Section 8.2.2.
o A message TLV with Type == INTERVAL_TIME, as specified in
[timetlv]. The options included in [timetlv] for representing
zero and infinite times MUST NOT be used.
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8.2.1. TC Message TLVs
In a TC message, a node MUST include a single CONT_SEQ_NUM message
TLV, as specified in Table 3, and with Type Extension == COMPLETE or
Type Extension == INCOMPLETE, according to whether the TC message is
complete or incomplete.
+--------------+------------+---------------------------------------+
| Type | Value | Value |
| | Length | |
+--------------+------------+---------------------------------------+
| CONT_SEQ_NUM | 8 bits | The ANSN contained in the Advertised |
| | | Neighbor Set. |
+--------------+------------+---------------------------------------+
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.
+---------+--------------+-------------------------------------+
| Type | Value Length | Value |
+---------+--------------+-------------------------------------+
| GATEWAY | 8 bits | Number of hops to attached network. |
+---------+--------------+-------------------------------------+
Table 4
GATEWAY address block TLV(s) MUST be associated with all attached
network addresses, and MUST NOT be associated with any other
addresses.
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9. HELLO Message Generation
An OLSRv2 HELLO message is composed and generated as defined in
[nhdp], with the following additions:
o A message TLV with Type == MPR_WILLING and Value == the node
parameter WILLINGNESS MUST be included, unless WILLINGNESS ==
WILL_DEFAULT (in which case it MAY be included).
o For each address which is included in the message with an
associated TLV with Type == LINK_STATUS and Value == SYMMETRIC,
and is of an MPR (i.e. the address is in the
N_neighbor_iface_addr_list of a Neighbor Tuple with N_mpr ==
true), 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 with any copy of this address.
o An additional HELLO message MAY be sent when the node's set of
MPRs changes, in addition to the cases specified in [nhdp], and
subject to the same constraints.
9.1. HELLO Message: Transmission
HELLO messages are included in packets as specified in [packetbb].
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
[nhdp], the node MUST identify the Neighbor Tuple which was created
or updated by the processing specified in [nhdp] (the "current
Neighbor Tuple") and update N_willingness as described in
Section 10.1 and N_mpr_selector as described in Section 10.2.
Following these, the node MUST also perform the processing defined in
Section 10.3.
10.1. Updating Willingness
N_willingness in the current Neighbor Tuple is updated as follows:
1. If the HELLO message contains a message TLV with Type ==
MPR_WILLING then N_willingness 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 any 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 any 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;
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* a Link Tuple with L_status == SYMMETRIC changes to having
L_status == HEARD or L_status == LOST, OR;
* a Link Tuple with L_status == HEARD or L_status == LOST
changes to having L_status == SYMMETRIC, OR;
* a 2-Hop Tuple is added or removed, OR;
* the N_willingness of a Neighbor Tuple with N_symmetric == true
changes from WILL_NEVER to any other value, OR;
* the N_willingness of a Neighbor Tuple with N_symmetric == true
and N_mpr == true changes to WILL_NEVER from any other value,
OR;
* the N_willingness of a Neighbor Tuple with N_symmetric == true
and N_mpr == false changes to WILL_ALWAYS from any other
value.
3. Otherwise the set of MPRs of a 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 14. Before that calculation, the N_mpr of all
Neighbor Tuples are set false. After that calculation the N_mpr of
all Neighbor Tuples representing symmetric 1-hop neighbors which are
chosen as MPRs, are set true.
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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 a non-empty Local Attached Network Set
MUST generate TC messages. A node with an empty Advertised Neighbor
Set and empty Local Attached Network Set SHOULD also generate "empty"
TC messages for a period A_HOLD_TIME after it last generated a non-
empty TC message. TC messages (non-empty and empty) are generated
according to the following:
1. The message hop count, if included, MUST be set to zero.
2. The message hop limit MUST be set to a value greater than 1. A
node MAY use the same hop limit TC_HOP_LIMIT in all TC messages,
or use different values of the hop limit TC_HOP_LIMIT in TC
messages, see Section 5.6.
3. The message MUST contain a message TLV with Type == CONT_SEQ_NUM
and Value == ANSN from the Advertised Neighbor Set. If the TC
message is complete then this message TLV MUST have Type
Extension == COMPLETE, otherwise it MUST have Type Extension ==
INCOMPLETE.
4. The message MUST contain a message TLV with Type ==
VALIDITY_TIME, as specified in [timetlv]. If all TC messages are
sent with the same hop limit then this TLV MUST have Value ==
T_HOLD_TIME. If TC messages are sent with different hop limits
(more than one value of TC_HOP_LIMIT) then this TLV MUST specify
times which vary with the number of hops distance appropriate to
the chosen pattern of TC message hop limits, as specified in
[timetlv], these times SHOULD be appropriate multiples of
T_HOLD_TIME.
5. The message MAY contain a message TLV with Type == INTERVAL_TIME,
as specified in [timetlv]. If all TC messages are sent with the
same hop limit then this TLV MUST have Value == TC_INTERVAL. If
TC messages are sent with different hop limits, then this TLV
MUST specify times which vary with the number of hops distance
appropriate to the chosen pattern of TC message hop limits, as
specified in [timetlv], these times SHOULD be appropriate
multiples of TC_INTERVAL.
6. Unless the node has a single interface, with a single interface
address with maximum prefix length, and that address is the
node's originator address, the message MUST contain all of the
node's interface addresses (i.e. all addresses in an
I_local_iface_addr_list) in its address blocks.
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7. All addresses of the node's interfaces that are included in an
address block MUST be associated with a TLV with Type == LOCAL_IF
and Value == UNSPEC_IF.
8. A complete message MUST include, and an incomplete message MAY
include, in its address blocks:
1. Each A_neighbor_iface_addr from the Advertised Neighbor Set;
2. AL_net_addr from each Local Attached Neighbor Tuple, each
associated with a TLV with Type == GATEWAY and Value ==
AL_dist.
11.1. TC Message: Transmission
Complete TC messages are generated and transmitted periodically on
all OLSRv2 interfaces, with a default interval between two
consecutive TC transmissions by the same 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 an incomplete TC message with at least
the new content in its address blocks. 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 [RFC5148]. The
values of MAXJITTER used SHOULD be:
o TP_MAXJITTER for periodic TC message generation;
o TT_MAXJITTER for responsive TC message generation.
TC messages are included in packets as specified in [packetbb].
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 any address associated with a TLV with Type == LOCAL_IF is one
of the receiving node's current or recently used interface
addresses (i.e. is in any I_local_iface_addr_list in the Local
Interface Set or is equal to any IR_local_iface_addr in the
Removed Interface Address Set), then the TC message MUST be
discarded.
o If the TC message does not contain exactly one message TLV with
Type == CONT_SEQ_NUM and Type Extension == COMPLETE or Type
Extension == INCOMPLETE, then the TC message MUST be discarded.
o If the TC message contains a message TLV with Type == CONT_SEQ_NUM
and Type Extension == COMPLETE, then processing according to
Section 12.1 and then according to Section 12.2 is carried out.
o If the TC message contains a message TLV with Type == CONT_SEQ_NUM
and Type Extension == INCOMPLETE, then only processing according
to Section 12.1 is carried out.
12.1. Initial TC Message Processing
For the purposes of this section:
o "originator address" refers to the originator address in the TC
message header.
o "validity time" is calculated from the VALIDITY_TIME message TLV
in the TC message according to the specification in [timetlv].
All information in the TC message has the same validity time.
o "ANSN" is defined as being the value of the message TLV with Type
== CONT_SEQ_NUM.
o "sending address list" refers to the list of addresses in all
address blocks which have associated TLV(s) with Type == LOCAL_IF
and Value == UNSPEC_IF. If the sending address list is otherwise
empty, then the message's originator address is added to the
sending address list, with maximum prefix length.
o Comparisons of sequence numbers are carried out as specified in
Section 18.
The TC message is processed as follows:
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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.
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;
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2. remove all Attached Network Tuples with AN_orig_addr ==
AR_orig_addr of the other tuple;
3. remove the other tuple.
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 address
block which does not have an associated TLV with Type ==
LOCAL_IF, or an associated TLV with Type == GATEWAY:
1. If there is no Topology Tuple such that:
+ T_dest_iface_addr == advertised address; AND
+ T_orig_addr == originator address
then create a new Topology Tuple with:
+ T_dest_iface_addr = advertised address;
+ T_orig_addr = originator address.
2. This Topology Tuple (existing or new) is then modified as
follows:
+ T_seq_number = ANSN;
+ 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 address block
which does not have an associated TLV with Type == LOCAL_IF, and
does have an associated TLV with Type == GATEWAY:
1. If there is no Attached Network Tuple such that:
+ AN_net_addr == network address; AND
+ AN_orig_addr == originator address
then create a new Attached Network Tuple with:
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+ AN_net_addr = network address;
+ AN_orig_addr = originator address
2. This Attached Network Tuple (existing or new) is then
modified as follows:
+ AN_dist = the value of the associated GATEWAY TLV;
+ AN_seq_number = ANSN;
+ AN_time = current time + validity time.
12.2. 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:
1. Any Topology Tuples with:
* T_orig_addr == originator address; AND
* 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. Information Base Changes
1. The Originator Set in the Local Information Base MUST be updated
when the node changes originator address. If there is no
Originator Tuple with:
* O_orig_addr == old originator address
then create an Originator Tuple with:
* O_orig_addr = old originator address
This Originator Tuple (existing or new) is then modified as
follows:
* O_time = current time + O_HOLD_TIME
2. The Topology Information Base MUST be changed when an Advertising
Remote Node Tuple expires (AR_time is reached). The following
changes are required before the Advertising Remote Node Tuple is
removed:
1. All Topology Tuples with:
+ T_orig_addr == AR_orig_addr of the Advertising Remote Node
Tuple
are removed.
2. All Attached Network Tuples with:
+ AN_orig_addr == AR_orig_addr of the Advertising Remote
Node Tuple
are removed.
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14. Selecting MPRs
Each node MUST select, from among its willing 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 flooding is an optimization of a classical flooding mechanism.
MPRs MAY also be used to reduce the shared topology information in
the network. Consequently, while it is not essential that the set of
MPRs is minimal, keeping the number of MPRs small ensures that the
overhead of OLSRv2 is kept at a minimum.
A 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, the recorded
and used 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. This set
MUST have the properties that:
o All of the selected MPRs are willing symmetric 1-hop neighbors,
AND;
o If the selecting node sends a message on that OLSRv2 interface,
and that message is successfully forwarded by all of the selected
MPRs for that interface, then all symmetric strict 2-hop neighbors
of the selecting node through that OLSRv2 interface will receive
that message on a symmetric link.
Note that it is always possible to select a valid set of MPRs. The
set of all willing symmetric 1-hop neighbors of a node is a (maximal)
valid set of MPRs for that node. However 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 with 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
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nodes.
When selecting MPRs for each OLSRv2 interface independently, this MAY
be done using information from the Link Set and 2-Hop Set of that
OLSRv2 interface, and the Neighbor Set of the 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 a willing symmetric 1-hop neighbor (i.e. the
corresponding N_symmetric == true, and the corresponding
N_willingness is not equal to 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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15. 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.
15.1. Populating the Relay Set
The Relay Set for an OLSRv2 interface contains the set of OLSRv2
interface addresses of those symmetric 1-hop neighbors for which this
OLSRv2 interface is to relay broadcast traffic. This set MUST
contain only addresses of OLSRv2 interfaces with which this OLSRv2
interface has a symmetric link. This set MUST include all such
addresses of all such OLSRv2 interfaces of 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.
15.2. 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 include 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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16. 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 Bases, obtained
via HELLO and TC message exchange.
16.1. Network Topology Graph
The Network Topology Graph is formed from information from the node's
Link Sets, Neighbor Set, Topology Set and Attached Network Set. The
Network Topology Graph SHOULD also use information 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.
16.2. Populating the Routing Set
The Routing Set MUST contain the shortest paths for all destinations
from all local OLSRv2 interfaces using the Network Topology Graph.
This calculation MAY use any algorithm, including any means of
choosing between paths of equal length.
Using the notation of Section 16.1, each path will have as its first
arc a local symmetric link X -> Y. There will be a path for each
terminating Y, Z, V, W and T which can be connected to local OLSRv2
interface address X using the indicated arcs. The corresponding
Routing Tuple for this path will have:
o R_dest_addr = the terminating Y, Z, V, W or T;
o R_next_iface_addr = the first arc's Y;
o R_dist = the total hop count of the path;
o R_local_iface_addr = the first arc's X.
An example algorithm for calculating the Routing Set of a node is
given in Appendix C.
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16.3. Routing Set Updates
The Routing Set MUST be updated when changes in the Neighborhood
Information Base or the Topology Information Base indicate a change
of the known symmetric links and/or attached networks in the MANET.
It is sufficient to consider only changes which affect at least one
of:
o The Link Set of any OLSRv2 interface, and to consider only Link
Tuples which have, or just had, L_status == SYMMETRIC (including
removal of such Link Tuples).
o The Neighbor Set of the 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 Advertising Remote Node Set of the node.
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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17. Proposed Values for Parameters and Constants
OLSRv2 uses all parameters and constants defined in [nhdp] and
additional parameters and constants defined in this document. All
but one (RX_HOLD_TIME) of these additional parameters are node
parameters as defined in [nhdp]. These proposed values of the
additional parameters are appropriate to the case where all
parameters (including those defined in [nhdp]) have a single value.
Proposed values for parameters defined in [nhdp] are given in that
document.
17.1. Local History Time Parameters
o O_HOLD_TIME = 30 seconds
17.2. Message Interval Parameters
o TC_INTERVAL = 5 seconds
o TC_MIN_INTERVAL = TC_INTERVAL/4
17.3. Advertised Information Validity Time Parameters
o T_HOLD_TIME = 3 x TC_INTERVAL
o A_HOLD_TIME = T_HOLD_TIME
17.4. Received Message Validity Time Parameters
o RX_HOLD_TIME = 30 seconds
o P_HOLD_TIME = 30 seconds
o F_HOLD_TIME = 30 seconds
17.5. Jitter Time Parameters
o TP_MAXJITTER = HP_MAXJITTER
o TT_MAXJITTER = HT_MAXJITTER
o F_MAXJITTER = TT_MAXJITTER
17.6. Hop Limit Parameter
o TC_HOP_LIMIT = 255
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17.7. Willingness Parameter and Constants
o WILLINGNESS = WILL_DEFAULT
o WILL_NEVER = 0
o WILL_DEFAULT = 3
o WILL_ALWAYS = 7
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18. Sequence Numbers
Sequence numbers are used in OLSRv2 with the purpose of discarding
"old" information, i.e. messages received out of order. However with
a limited number of bits for representing sequence numbers, wrap-
around (that the sequence number is incremented from the maximum
possible value to zero) will occur. To prevent this from interfering
with the operation of OLSRv2, the following MUST be observed when
determining the ordering of sequence numbers.
The term MAXVALUE designates in the following one more than the
largest possible value for a sequence number. For a 16 bit sequence
number (as are those defined in this specification) MAXVALUE is
65536.
The sequence number S1 is said to be "greater than" the sequence
number S2 if:
o S1 > S2 AND S1 - S2 < MAXVALUE/2 OR
o S2 > S1 AND S2 - S1 > MAXVALUE/2
When sequence numbers S1 and S2 differ by MAXVALUE/2 their ordering
cannot be determined. In this case, which should not occur, either
ordering may be assumed.
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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19. 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.
19.1. Confidentiality
Being a proactive protocol, OLSRv2 periodically MPR floods
topological information to all nodes in the network. Hence, if used
in an unprotected wireless network, the network topology is revealed
to anyone who listens to OLSRv2 control messages.
In situations where the confidentiality of the network topology is of
importance, regular cryptographic techniques, such as exchange of
OLSRv2 control traffic messages encrypted by PGP [RFC4880] or
encrypted by some shared secret key, can be applied to ensure that
control traffic can be read and interpreted by only those authorized
to do so.
19.2. 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 packets can
be established through employing IPsec authentication headers,
whereas authenticity of individual links (situations 1 and 3) require
additional security information to be distributed.
An important consideration is that all control messages in OLSRv2 are
transmitted either to all 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.
19.3. 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.
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20. IANA Considerations
20.1. Message Types
OLSRv2 defines one message type, which must be allocated from the
"Assigned Message Types" repository of [packetbb].
+------+------+-----------------------------------------+
| Name | Type | Description |
+------+------+-----------------------------------------+
| TC | TBD1 | Topology Control (MANET-wide signaling) |
+------+------+-----------------------------------------+
Table 5
20.2. TLV Types
OLSRv2 defines two message TLV types, which must be allocated from
the "Assigned message TLV Types" repository of [packetbb].
+--------------+------+----------------+----------------------------+
| Name | Type | Type extension | Description |
+--------------+------+----------------+----------------------------+
| MPR_WILLING | TBD2 | 0 | Specifies the originating |
| | | | node's willingness to act |
| | | | as a relay and to partake |
| | | | in network formation |
| | | | |
| | | 1-255 | RESERVED |
| | | | |
| CONT_SEQ_NUM | TBD3 | 0 (COMPLETE) | Specifies a content |
| | | | sequence number for this |
| | | | complete message |
| | | | |
| | | 1 (INCOMPLETE) | Specifies a content |
| | | | sequence number for this |
| | | | incomplete message |
| | | | |
| | | 2-255 | RESERVED |
+--------------+------+----------------+----------------------------+
Table 6
Type extensions indicated as RESERVED may be allocated by standards
action, as specified in [RFC2434].
OLSRv2 defines two Address Block TLV types, which must be allocated
from the "Assigned address block TLV Types" repository of [packetbb].
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+---------+------+-----------+--------------------------------------+
| Name | Type | Type | Description |
| | | extension | |
+---------+------+-----------+--------------------------------------+
| MPR | TBD4 | 0 | Specifies that a given address is of |
| | | | a node selected as an MPR |
| | | | |
| | | 1-255 | RESERVED |
| | | | |
| GATEWAY | TBD5 | 0 | Specifies that a given address is |
| | | | reached via a gateway on the |
| | | | originating node |
| | | | |
| | | 1-255 | RESERVED |
+---------+------+-----------+--------------------------------------+
Table 7
Type extensions indicated as RESERVED may be allocated by standards
action, as specified in [RFC2434].
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21. References
21.1. Normative References
[packetbb] Clausen, T., Dean, J., Dearlove, C., and C. Adjih,
"Generalized MANET Packet/Message Format", work in
progress draft-ietf-manet-packetbb-12.txt, March 2008.
[timetlv] Clausen, T. and C. Dearlove, "Representing multi-value
time in MANETs", Work In
Progress draft-ietf-manet-timetlv-04.txt, November 2007.
[RFC5148] Clausen, T., Dearlove, C., and B. Adamson, "Jitter
considerations in MANETs", RFC 5148, February 2008.
[nhdp] Clausen, T., Dean, J., and C. Dearlove, "MANET
Neighborhood Discovery Protocol (NHDP)", work in
progress draft-ietf-manet-nhdp-06.txt, March 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, BCP 14, March 1997.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 2434, BCP 26,
October 1998.
21.2. Informative References
[RFC3626] Clausen, T. and P. Jacquet, "The Optimized Link State
Routing Protocol", RFC 3626, October 2003.
[RFC4880] Callas, J., Donnerhacke, L., Finney, H., and R. Thayer,
"OpenPGP message format", RFC 4880, November 2007.
[HIPERLAN] ETSI, "ETSI STC-RES10 Committee. Radio equipment and
systems: HIPERLAN type 1, functional specifications ETS
300-652", June 1996.
[HIPERLAN2] Jacquet, P., Minet, P., Muhlethaler, P., and N.
Rivierre, "Increasing reliability in cable free radio
LANs: Low level forwarding in HIPERLAN.", 1996.
[MPR] Qayyum, A., Viennot, L., and A. Laouiti, "Multipoint
relaying: An efficient technique for flooding in mobile
wireless networks.", 2001.
[RFC2501] Macker, J. and S. Corson, "Mobile Ad hoc Networking
(MANET): Routing Protocol Performance Issues and
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Evaluation Considerations", RFC 2501, January 1999.
[FSR] Pei, G., Gerla, M., and T. Chen, "Fisheye state routing
in mobile ad hoc networks", 2000.
[FSLS] Santivanez, C., Ramanathan, R., and I. Stavrakakis,
"Making link-state routing scale for ad hoc networks",
2000.
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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. (As noted in Section 14 a node MAY improve on this, by
coordination between 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); this MAY be restricted to
considering only information received over I (in which case N2(I)
is the set of N2_2hop_iface_addr in 2-Hop Tuples in the 2-Hop Set
for OLSRv2 interface I).
Connected to I via Y - An address A in N2(I) is connected to I via a
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 N2(I)
which are connected to I via Y.
R(Y, I): - For a node Y in N(I), the number of addresses in N2(I)
which are connected to I via Y, but are not connected to I via any
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;
+ N_mpr_selector is equal to true, if possible, THEN;
+ any choice.
2. Select Y as an MPR (i.e. set N_mpr = true in the Neighbor
Tuple corresponding to Y).
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Appendix C. Example Algorithm for Calculating the Routing Set
The following procedure is given as an example for calculating the
Routing Set using a variation of Dijkstra's algorithm. First all
Routing Tuples are removed, and then the procedures in the following
sections are applied in turn.
C.1. Add Local Symmetric Links
1. For each Local Interface Tuple 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. 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.
More than one 2-Hop Neighbor Tuple may be usable to select the
next hop R_next_iface_addr for reaching the address R_dest_addr.
Ties should be broken such that nodes with greater willingness
are preferred, and between nodes of equal willingness, MPR
selectors are preferred over non-MPR selectors.
C.3. Add Attached Networks
1. For each Attached Network Tuple, if for the Advertising Remote
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. Example Message Layout
An example TC message, using IPv4 (four octet) addresses, is as
follows. The overall message length is 65 octets.
The message has semantics octet 30, and hence all required message
header fields. It has a message TLV block with content length 13
octets containing three TLVs. The first two TLVs are validity and
interval times for the message. The third TLV is the content
sequence number TLV used to carry the 2 octet ANSN, and (with default
type extension zero, i.e. COMPLETE) indicating that the TC message
is complete. Each TLV uses a TLV with semantics value 8, indicating
that it has a value, but no type extension or start and stop indexes.
The first two TLVs have a value length of 1 octet, the last has a
value length of 2 octets.
The message has two address blocks. The first address block contains
6 addresses, with semantics octet 1, hence with a head section, (with
length 2 octets) but no tail section, and hence mid sections with
length two octets. The following TLV block (content length 6 octets)
contains a single LOCAL_IF TLV (semantics value 12) indicating that
the first three addresses (indexes 0 to 2) are associated with the
value (length 1 octet) UNSPEC_IF, i.e. they are the originating
node's local interface addresses. The remaining three addresses have
no associated TLV, they are the interface addresses of advertised
neighbors.
The second address block contains 1 address, with semantics octet 13
indicating that there is a head section (with length 2 octets), that
the tail section (length 2 octets) consists of zero valued octets
(not included), and that there is a single prefix length, which is
16. The network address is thus Head.0.0/16. The following TLV
block (content length 8 octets) includes one TLV that indicates that
the originating node is a gateway to this network, at a given number
of hops distance (value length 1 octet). 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 1 1 1 1 0|0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Originator Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hop Limit | Hop Count | Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 1| 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 1 1 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1|0 0 0 0 0 0 1 0| Head |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mid | Mid |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mid | Mid |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mid | Mid |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0| LOCAL_IF |0 0 0 0 1 1 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 0|0 0 0 0 0 0 1 0|0 0 0 0 0 0 0 1| UNSPEC_IF |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1|0 0 0 0 1 1 0 1|0 0 0 0 0 0 1 0| Head |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Head (cont) |0 0 0 0 0 0 1 0|0 0 0 1 0 0 0 0|0 0 0 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 1 0 0| GATEWAY |0 0 0 0 1 0 0 0|0 0 0 0 0 0 0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 [nhdp].
In each Originator Tuple:
o O_orig_addr MUST NOT equal any other O_orig_addr.
o O_orig_addr MUST NOT equal this node's originator address.
In each Local Attached Network Tuple:
o AL_net_addr MUST NOT equal any other AL_net_addr.
o AL_net_addr MUST NOT be in the I_local_iface_addr_list of any
Local Interface Tuple or be equal to the IR_local_iface_addr of
any Removed Interface Address Tuple.
o AL_dist MUST NOT be less than zero.
In each Link Tuple:
o L_neighbor_iface_addr_list MUST NOT contain the AL_net_addr of any
Local Attached Network Tuple.
o If L_status == SYMMETRIC and the Neighbor Tuple whose
N_neighbor_iface_addr_list contains L_neighbor_iface_addr_list has
N_mpr_selector == true, then, for each address in this
L_neighbor_iface_addr_list, there MUST be an equal
RY_neighbor_iface_addr in the Relay Set associated with the same
OLSRv2 interface.
In each Neighbor Tuple:
o N_neighbor_iface_addr_list MUST NOT contain the AL_net_addr of any
Local Attached Network Tuple.
o If N_willingness MUST be in the range from WILL_NEVER to
WILL_ALWAYS, inclusive.
o If N_mpr == true, then N_symmetric MUST be true and N_willingness
MUST NOT equal WILL_NEVER.
o If N_symmetric == true and N_mpr == false, then N_willingness MUST
NOT equal WILL_ALWAYS.
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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:
o NL_neighbor_iface_addr MUST NOT equal the AL_net_addr of any Local
Attached Network Tuple.
In each 2-Hop Tuple:
o N2_2hop_iface_addr MUST NOT equal the AL_net_addr of any Local
Attached Network Tuple.
In each Received Tuple:
o RX_orig_addr MUST NOT equal this node's originator address or any
O_orig_addr.
o Each ordered triple (RX_type, RX_orig_addr, RX_seq_number) MUST
NOT equal the corresponding triple in any other Received Tuple in
the same Received Set.
In each Processed Tuple:
o P_orig_addr MUST NOT equal this node's originator address or any
O_orig_addr.
o Each ordered triple (P_type, P_orig_addr, P_seq_number) MUST NOT
equal the corresponding triple in any other Processed Tuple.
In each Forwarded Tuple:
o F_orig_addr MUST NOT equal this node's originator address or any
O_orig_addr.
o Each ordered triple (F_type, F_orig_addr, F_seq_number) MUST NOT
equal the corresponding triple in any other Forwarded Tuple.
In each Relay Tuple:
o RY_neighbor_iface_addr MUST NOT equal the RY_neighbor_iface_addr
in any other Relay Tuple in the same Relay Set.
o RY_neighbor_iface_addr MUST be in the L_neighbor_iface_addr_list
of a Link Tuple with L_status == SYMMETRIC.
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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 MUST NOT equal this node's originator address or any
O_orig_addr.
o AR_orig_addr MUST NOT equal the AR_orig_addr in any other ANSN
History Tuple.
o AR_iface_addr_list MUST NOT be empty.
o AR_iface_addr_list MUST NOT contain any duplicated addresses.
o AR_iface_addr_list MUST NOT contain any address which is in the
I_local_iface_addr_list of any Local Interface Tuple or be equal
to the IR_local_iface_addr of any Removed Interface Address Tuple.
o AR_iface_addr_list MUST NOT contain any address which is the
AL_net_addr of any Local Attached Network Tuple.
In each Topology Tuple:
o T_dest_iface_addr MUST NOT be in the I_local_iface_addr_list of
any Local Interface Tuple or be equal to the IR_local_iface_addr
of any Removed Interface Address Tuple.
o T_dest_iface_addr MUST NOT equal the AL_net_addr of any Local
Attached Network Tuple.
o There MUST be an Advertising Remote 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.
o The ordered pair (T_dest_iface_addr, T_orig_addr) MUST NOT equal
the corresponding pair in any other Topology Tuple.
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In each Attached Network Tuple:
o AN_net_addr MUST NOT be in the I_local_iface_addr_list of any
Local Interface Tuple or be equal to the IR_local_iface_addr of
any Removed Interface Address Tuple.
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. 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 [nhdp] 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 [nhdp].
Furthermore, MPR flooding greatly reduces signaling overhead from
from link state information dissemination in two ways. First, the
amount of link state information for a node to declare is reduced to
only contain that node's MPR selectors. This reduces the size of a
link state declaration as compared to declaring full link state
information. In particular some nodes may not need to declare any
such information. Second, using MPR flooding, the cost of
distributing link state information throughout the network is greatly
reduced, as compared to when using classic flooding, since only MPRs
need to forward link state declaration messages. In dense networks,
the reduction of control traffic can be of several orders of
magnitude compared to routing protocols using classical flooding
[MPR]. This feature naturally provides more bandwidth for useful
data traffic and pushes further the frontier of congestion.
Since the control traffic is continuous and periodic, it keeps the
quality of the links used in routing more stable. However, using
certain OLSRv2 options, some control messages (HELLO messages or TC
messages) may be intentionally sent in advance of their deadline in
order to increase the responsiveness of the protocol to topology
changes. This may cause a small, temporary, and local increase of
control traffic, however this is at all times bounded by the use of
minimum message intervals.
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Appendix G. 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 H. Acknowledgements
The authors would like to acknowledge the team behind OLSRv1,
specified in RFC3626, including Anis Laouiti (INT, Paris), Pascale
Minet (INRIA, France), Laurent Viennot (INRIA, France), and Amir
Qayyum (M.A. Jinnah University, Islamabad) for their contributions.
The authors would like to gratefully acknowledge the following people
for intense technical discussions, early reviews and comments on the
specification and its components: Li Li (CRC), Louise Lamont (CRC),
Joe Macker (NRL), Alan Cullen (BAE Systems), Khaldoun Al Agha (LRI),
Richard Ogier (SRI), Song-Yean Cho (LIX), Shubhranshu Singh (Samsung
AIT), Charles E. Perkins, 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 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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Full Copyright Statement
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