Mobile Ad hoc Networking (MANET) T. Clausen
Internet-Draft LIX, Ecole Polytechnique, France
Expires: August 5, 2007 C. Dearlove
BAE Systems Advanced Technology
Centre
P. Jacquet
Project Hipercom, INRIA
The OLSRv2 Design Team
MANET Working Group
February 2007
The Optimized Link State Routing Protocol version 2
draft-ietf-manet-olsrv2-03
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Abstract
This document describes version 2 of the Optimized Link State Routing
(OLSRv2) protocol for mobile ad hoc networks. The protocol embodies
an optimization of the classical link state algorithm tailored to the
requirements of a mobile ad hoc network (MANET).
The key optimization of OLSRv2 is that of multipoint relays,
providing an efficient mechanism for network-wide broadcast of link
state information (i.e. reducing the cost of performing a network-
wide link state broadcast). A secondary optimization is that OLSRv2
employs partial link state information: each node maintains
information about all destinations, but only a subset of links.
Consequently, only selected nodes diffuse link state advertisements
(thus reducing the number of network-wide link state broadcasts) and
these advertisements contain only a subset of links (thus reducing
the size of network-wide link state broadcasts). The partial link
state information thus obtained still allows each OLSRv2 node to at
all times maintain optimal (in terms of number of hops) routes to all
destinations in the network.
OLSRv2 imposes minimum requirements on the network by not requiring
sequenced or reliable transmission of control traffic. Furthermore,
the only interaction between OLSRv2 and the IP stack is routing table
management.
OLSRv2 is particularly suitable for large and dense networks as the
technique of MPRs works well in this context.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7
3. Applicability Statement . . . . . . . . . . . . . . . . . . . 8
4. Protocol Overview and Functioning . . . . . . . . . . . . . . 9
5. Local Information Base . . . . . . . . . . . . . . . . . . . . 11
5.1. Local Attached Network Set . . . . . . . . . . . . . . . . 11
6. Processing and Forwarding Repositories . . . . . . . . . . . . 12
6.1. Received Set . . . . . . . . . . . . . . . . . . . . . . . 12
6.2. Processed Set . . . . . . . . . . . . . . . . . . . . . . 12
6.3. Forwarded Set . . . . . . . . . . . . . . . . . . . . . . 13
6.4. Relay Set . . . . . . . . . . . . . . . . . . . . . . . . 13
7. Packet Processing and Message Forwarding . . . . . . . . . . . 14
7.1. Actions when Receiving an OLSRv2 Packet . . . . . . . . . 14
7.2. Actions when Receiving an OLSRv2 Message . . . . . . . . . 14
7.3. Message Considered for Processing . . . . . . . . . . . . 15
7.4. Message Considered for Forwarding . . . . . . . . . . . . 15
8. Information Repositories . . . . . . . . . . . . . . . . . . . 18
8.1. Neighborhood Information Base . . . . . . . . . . . . . . 18
8.1.1. Link Set . . . . . . . . . . . . . . . . . . . . . . . 18
8.1.2. MPR Set . . . . . . . . . . . . . . . . . . . . . . . 18
8.1.3. MPR Selector Set . . . . . . . . . . . . . . . . . . . 19
8.2. Topology Information Base . . . . . . . . . . . . . . . . 19
8.2.1. Advertised Neighbor Set . . . . . . . . . . . . . . . 19
8.2.2. ANSN History Set . . . . . . . . . . . . . . . . . . . 20
8.2.3. Topology Set . . . . . . . . . . . . . . . . . . . . . 20
8.2.4. Attached Network Set . . . . . . . . . . . . . . . . . 20
8.2.5. Routing Set . . . . . . . . . . . . . . . . . . . . . 21
9. Control Message Structures . . . . . . . . . . . . . . . . . . 22
9.1. HELLO Messages . . . . . . . . . . . . . . . . . . . . . . 22
9.1.1. HELLO Message TLVs . . . . . . . . . . . . . . . . . . 23
9.1.2. HELLO Message Address Block TLVs . . . . . . . . . . . 23
9.2. TC Messages . . . . . . . . . . . . . . . . . . . . . . . 24
9.2.1. TC Message TLVs . . . . . . . . . . . . . . . . . . . 24
9.2.2. TC Message Address Block TLVs . . . . . . . . . . . . 25
10. HELLO Message Generation . . . . . . . . . . . . . . . . . . . 26
10.1. HELLO Message: Transmission . . . . . . . . . . . . . . . 26
11. HELLO Message Processing . . . . . . . . . . . . . . . . . . . 27
11.1. Populating the MPR Selector Set . . . . . . . . . . . . . 27
11.2. Symmetric Neighborhood and 2-Hop Neighborhood Changes . . 28
12. TC Message Generation . . . . . . . . . . . . . . . . . . . . 29
12.1. TC Message: Transmission . . . . . . . . . . . . . . . . . 30
13. TC Message Processing . . . . . . . . . . . . . . . . . . . . 32
13.1. Initial TC Message Processing . . . . . . . . . . . . . . 32
13.1.1. Populating the ANSN History Set . . . . . . . . . . . 32
13.1.2. Populating the Topology Set . . . . . . . . . . . . . 33
13.1.3. Populating the Attached Network Set . . . . . . . . . 34
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13.2. Completing TC Message Processing . . . . . . . . . . . . . 34
13.2.1. Purging the Topology Set . . . . . . . . . . . . . . . 35
13.2.2. Purging the Attached Network Set . . . . . . . . . . . 35
14. Populating the MPR Set . . . . . . . . . . . . . . . . . . . . 36
15. Populating Derived Sets . . . . . . . . . . . . . . . . . . . 37
15.1. Populating the Relay Set . . . . . . . . . . . . . . . . . 37
15.2. Populating the Advertised Neighbor Set . . . . . . . . . . 37
16. Routing Table Calculation . . . . . . . . . . . . . . . . . . 38
17. Proposed Values for Constants . . . . . . . . . . . . . . . . 42
17.1. Neighborhood Discovery Constants . . . . . . . . . . . . . 42
17.2. Message Intervals . . . . . . . . . . . . . . . . . . . . 42
17.3. Holding Times . . . . . . . . . . . . . . . . . . . . . . 42
17.4. Jitter Times . . . . . . . . . . . . . . . . . . . . . . . 42
17.5. Willingness . . . . . . . . . . . . . . . . . . . . . . . 42
18. Sequence Numbers . . . . . . . . . . . . . . . . . . . . . . . 43
19. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 44
19.1. Message Types . . . . . . . . . . . . . . . . . . . . . . 44
19.2. TLV Types . . . . . . . . . . . . . . . . . . . . . . . . 44
20. References . . . . . . . . . . . . . . . . . . . . . . . . . . 46
20.1. Normative References . . . . . . . . . . . . . . . . . . . 46
20.2. Informative References . . . . . . . . . . . . . . . . . . 46
Appendix A. Node Configuration . . . . . . . . . . . . . . . . . 47
Appendix B. Protocol and Port Number . . . . . . . . . . . . . . 48
Appendix C. Example Heuristic for Calculating MPRs . . . . . . . 49
Appendix D. Packet and Message Layout . . . . . . . . . . . . . 52
Appendix D.1. Packet and Message Options . . . . . . . . . . . . . 52
Appendix D.2. Example HELLO Message . . . . . . . . . . . . . . . 54
Appendix D.3. Example TC Message . . . . . . . . . . . . . . . . . 55
Appendix E. Time TLVs . . . . . . . . . . . . . . . . . . . . . 58
E.1. Representing Time . . . . . . . . . . . . . . . . . . . . 58
E.2. General Time TLV Structure . . . . . . . . . . . . . . . . 58
E.3. Message TLVs . . . . . . . . . . . . . . . . . . . . . . . 60
E.3.1. VALIDITY_TIME TLV . . . . . . . . . . . . . . . . . . 60
E.3.2. INTERVAL_TIME TLV . . . . . . . . . . . . . . . . . . 60
Appendix F. Message Jitter . . . . . . . . . . . . . . . . . . . 61
F.1. Jitter . . . . . . . . . . . . . . . . . . . . . . . . . . 61
F.1.1. Periodic message generation . . . . . . . . . . . . . 61
F.1.2. Externally triggered message generation . . . . . . . 62
F.1.3. Message forwarding . . . . . . . . . . . . . . . . . . 63
F.1.4. Maximum Jitter Determination . . . . . . . . . . . . . 64
Appendix G. Security Considerations . . . . . . . . . . . . . . 65
Appendix G.1. Confidentiality . . . . . . . . . . . . . . . . . . 65
Appendix G.2. Integrity . . . . . . . . . . . . . . . . . . . . . 65
Appendix G.3. Interaction with External Routing Domains . . . . . 66
Appendix G.4. Node Identity . . . . . . . . . . . . . . . . . . . 67
Appendix H. Flow and Congestion Control . . . . . . . . . . . . 68
Appendix I. Contributors . . . . . . . . . . . . . . . . . . . . 69
Appendix J. Acknowledgements . . . . . . . . . . . . . . . . . . 70
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Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 71
Intellectual Property and Copyright Statements . . . . . . . . . . 72
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1. Introduction
The Optimized Link State Routing protocol version 2 (OLSRv2) is an
update to OLSRv1 as published in RFC3626 [1]. Compared to RFC3626,
OLSRv2 retains the same basic mechanisms and algorithms, while
providing a more flexible signaling framework and some simplification
of the messages being exchanged. Also, OLSRv2 accommodates both IPv4
and IPv6 addresses in a compact manner.
OLSRv2 is developed for mobile ad hoc networks. It operates as a
table driven, proactive protocol, i.e. it exchanges topology
information with other nodes in the network regularly. Each node
selects a set of its neighbor nodes as "MultiPoint Relays" (MPRs).
Control traffic may be diffused through the network using hop by hop
forwarding; a node only needs to forward control traffic directly
received from its MPR selectors (nodes which have selected it as an
MPR). MPRs thus provide an efficient mechanism for diffusing control
traffic by reducing the number of transmissions required.
Nodes selected as MPRs also have a special responsibility when
declaring link state information in the network. A sufficient
requirement for OLSRv2 to provide shortest path routes to all
destinations is that nodes declare link state information for their
MPR selectors, if any. Additional available link state information
may be transmitted, e.g. for redundancy. Thus, as well as being used
to facilitate efficient flooding, MPRs are also allow the reduction
of the number and size of link state messages. MPRs are also thus
used as intermediate nodes in multi-hop route calculations.
A node selects MPRs from among its one hop neighbors connected by
"symmetric", i.e. bi-directional, links. Therefore, selecting routes
through MPRs automatically avoids the problems associated with data
packet transfer over uni-directional links (such as the problem of
not getting link layer acknowledgments at each hop, for link layers
employing this technique).
OLSRv2 is developed to work independently from other protocols.
(Parts of OLSRv2 have been published separately as [3] and [4] for
wider use.) Likewise, OLSRv2 makes no assumptions about the
underlying link layer. However, OLSRv2 may use link layer
information and notifications when available and applicable, as
described in [4].
OLSRv2, as OLSRv1, inherits its concept of forwarding and relaying
from HIPERLAN (a MAC layer protocol) which is standardized by ETSI
[6], [7].
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2. Terminology
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [2].
MANET specific terminology is to be interpreted as described in [3]
and [4].
Additionally, this document uses the following terminology:
Node - A MANET router which implements the Optimized Link State
Routing protocol version 2 as specified in this document.
OLSRv2 interface - A MANET interface, running OLSRv2.
Symmetric strict 2-hop neighbor - A symmetric 2-hop neighbor which
is not a symmetric 1-hop neighbor and is not a 2-hop neighbor only
through a symmetric 1-hop neighbor with willingness WILL_NEVER.
Symmetric strict 2-hop neighborhood - The set of the symmetric
strict 2-hop neighbors of a node.
Multipoint relay (MPR) - A node which is selected by its symmetric
1-hop neighbor, node X, to "re-transmit" all the broadcast
messages that it receives from node X, provided that the message
is not a duplicate, and that the hop limit field of the message is
greater than one.
MPR selector - A node which has selected its symmetric 1-hop
neighbor, node X, as one of its MPRs is an MPR selector of node X.
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3. Applicability Statement
OLSRv2 is a proactive routing protocol for mobile ad hoc networks
(MANETs). 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 situation since
routes are maintained for all known destinations at all times. Also,
since routes are maintained continuously, traffic is subject to no
delays due to buffering or to route discovery.
OLSRv2 supports nodes which have multiple interfaces which
participate in the MANET using OLSRv2. As described in [4], each
OLSRv2 interface may have one or more network addresses (which may
have prefix lengths). OLSRv2, additionally, supports nodes which
have non-OLSRv2 interfaces which can serve as gateways towards other
networks.
OLSRv2 uses the format specified in [3] 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 [3], while still allowing nodes not
supporting that extension to forward messages including the extension
and process messages ignoring the extension.
The OLSRv2 neighborhood discovery protocol using HELLO messages is
specified in [4]; note that all references to MANET interfaces in [4]
refer to OLSRv2 interfaces when using [4] as part of OLSRv2. This
neighborhood discovery protocol serves to ensure that each OLSRv2
node has available continuously updated information repositories
describing the node's 1-hop and symmetric 2-hop neighbors. This
neighborhood discovery protocol, which also uses [3], is extended in
this document by the addition of MPR information.
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4. Protocol Overview and Functioning
OLSRv2 is a proactive routing protocol for mobile ad hoc networks.
The protocol inherits the stability of a link state algorithm and has
the advantage of having routes immediately available when needed due
to its proactive nature. OLSRv2 is an optimization of the classical
link state protocol, tailored for mobile ad hoc networks. The main
tailoring and optimizations of OLSRv2 are:
o periodic, unacknowledged transmission of all control messages;
o optimized flooding for global link state information diffusion;
o partial topology maintenance - each node knows only a subset of
the links in the network, sufficient for a minimum hop route to
all destinations.
The optimized flooding and partial topology maintenance are based on
the concept on MultiPoint Relays (MPRs), selected independently by
nodes based on the symmetric 1-hop and 2-hop neighbor information
maintained using [4].
Using the message exchange format [3] and the neighborhood discovery
protocol [4], OLSRv2 also contains the following main components:
o A TLV, to be included within the HELLO messages of [4], allowing a
node to signal MPR selection.
o An optimized flooding mechanism for global information exchange,
denoted "MPR flooding".
o A specification of global signaling, denoted TC (Topology Control)
messages. TC messages in OLSRv2 serve to:
* inject link state information into the entire network;
* inject addresses of hosts and networks for which they may serve
as a gateway into the entire network.
TC messages are emitted periodically, thereby allowing nodes to
continuously track global changes in the network. Incomplete TC
messages may be used to report additions to advertised information
without repeating unchanged information. Some TC messages may be
flooded over only part of the network, allowing a node to ensure
that nearer nodes are kept more up to date than distant nodes.
Each node in the network selects an MPR Set. The MPR Set of a node X
may be any subset of its symmetric 1-hop neighborhood such that every
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node in the symmetric strict 2-hop neighborhood of node X has a
symmetric link to a node in the MPR Set of node X. The MPR Set of a
node may thus be said to "cover" the node's symmetric strict 2-hop
neighborhood. Each node also maintains information about the set of
symmetric 1-hop neighbors that have selected it as MPR. This set is
called the MPR Selector Set of the node.
Note that as long as the condition above is satisfied, any algorithm
selecting MPR Sets is acceptable in terms of implementation
interoperability. However if smaller MPR Sets are selected then the
greater the efficiency gains that are possible. Note that [8] gives
an analysis and example of MPR selection algorithms.
In OLSRv2, actual efficiency gains are based on the sizes of each
node's Relay Set, the set of symmetric 1-hop neighbors for which it
is to relay broadcast traffic, and its Advertised Neighbor Set, the
set of symmetric 1-hop neighbors for which it is to advertise link
state information into the network in TC messages. Each of these
sets MUST contain all the nodes in the MPR Selector Set and MAY
contain additional nodes. If the Advertised Neighbor Set is empty,
TC messages are not generated by that node, unless needed for gateway
reporting, or for a short period to accelerate the removal of
unwanted links.
OLSRv2 is designed to work in a completely distributed manner and
does not depend on any central entity. The protocol does not require
reliable transmission of control messages: each node sends control
messages periodically, and can therefore sustain a reasonable loss of
some such messages. Such losses may occur frequently in radio
networks due to collisions or other transmission problems. OLSRv2
may use "jitter", randomized adjustments to message transmission
times, to reduce the incidence of collisions.
OLSRv2 does not require sequenced delivery of messages. Each control
message contains a sequence number which is incremented for each
message. Thus the recipient of a control message can, if required,
easily identify which information is more recent - even if messages
have been re-ordered while in transmission.
OLSRv2 does not require any changes to the format of IP packets, any
existing IP stack can be used as is: OLSRv2 only interacts with
routing table management. OLSR sends its control messages using UDP.
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5. Local Information Base
A node maintains a Local Information Base that records information
about its OLSRv2 interfaces, and its non-OLSRv2 interfaces that can
serve as gateways to other networks. The former is maintained using
a Local Interface Set, as described in [4]. The latter is maintained
using a Local Attached Network Set. All addresses in the Local
Information Base have an associated prefix length; if an address
otherwise does not have a prefix length then it is set equal to the
address length. Two addresses are considered equal if and only if
their associated prefix lengths are also equal.
The Local Information Base is not modified by this protocol. This
protocol may respond to changes of this Local Information Base which
MUST reflect corresponding changes in the node's status. It is not
the responsibility of OLSRv2 to maintain routes to networks recorded
in the Local Attached Network Set in that node.
5.1. Local Attached Network Set
A node's Local Attached Network Set records its local non-OLSRv2
interfaces. that can act as gateways to other networks. 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 with AL_dist == 0 MUST be local to this node and
MUST NOT be attached to any other node. Attached networks with
AL_dist > 0 MAY be attached to other nodes.
Attached networks with AL_dist > 0 MUST be advertised in TC messages
generated by this node, this may result in the node originating TC
messages when it has no other reason to do so. Attached networks
with AL_dist == 0 MAY be advertised in HELLO messages (which causes
the MPRs of this node to advertise them in their TC messages) or MAY
be advertised in TC messages; they MUST be advertised in one type of
message and SHOULD NOT be advertised in both. If a node is sending
TC messages for any other reason, then advertising attached networks
in TC messages is more efficient. A node MAY decide which form of
advertisement to use depending on its circumstances.
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6. Processing and Forwarding Repositories
The following data structures are employed in order to ensure that a
message is processed at most once and is forwarded at most once per
interface of a node.
6.1. Received Set
A node's Received Sets, one per OLSRv2 interface, each record the
signatures of messages which have been received over that interface.
Each consists of Received Tuples:
(RX_type, RX_orig_addr, RX_seq_number, RX_time)
where:
RX_type is the received message type, or zero if the received
message sequence number is not type-specific;
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.
6.2. 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.
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6.3. Forwarded Set
A node's Forwarded Set records signatures of messages which have been
processed by the node. It consists of Forwarded Tuples:
(F_type, F_orig_addr, F_seq_number, F_time)
where:
F_type is the forwarded message type, or zero if the forwarded
message sequence number is not type-specific;
F_orig_addr is the originator address of the forwarded message;
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. Relay Set
A node's Relay Set records the neighbor interface addresses for which
it is to relay flooded messages. It consists of Relay Tuples:
(RY_iface_addr)
where:
RY_iface_addr is the address of a neighbor interface for which the
node SHOULD relay flooded messages. This MUST include a prefix
length.
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7. Packet Processing and Message Forwarding
On receiving a packet, as defined in [3], a node examines the packet
header and each of the message headers. If the message type is known
to the node, the message is processed locally according to the
specifications for that message type. The message is also
independently evaluated for forwarding.
7.1. Actions when Receiving an OLSRv2 Packet
On receiving a packet, a node MUST perform the following tasks:
1. The packet MAY be fully parsed on reception, or the packet and
its messages MAY be parsed only as required. (It is possible to
parse the packet header, or determine its absence, without
parsing any messages. It is possible to divide the packet into
messages without even fully parsing their headers. It is
possible to determine whether a message is to be forwarded, and
to forward it, without parsing its body. It is possible to
determine whether a message is to be processed without parsing
its body.)
2. If parsing fails at any point the relevant entity (packet or
message) MUST be silently discarded, other parts of the packet
(up to the whole packet) MAY be silently discarded;
3. Otherwise if the packet header is present and it contains a
packet TLV block, then each TLV in it is processed according to
its type if recognized, otherwise the TLV is ignored;
4. Otherwise each message in the packet, if any, is treated
according to Section 7.2.
7.2. Actions when Receiving an OLSRv2 Message
A node MUST perform the following tasks for each received OLSRv2
message:
1. If the received OLSRv2 message header cannot be correctly parsed
according to the specification in [3], or if the node recognizes
from the originator address of the message that the message is
one which the receiving node itself originated, then the message
MUST be silently discarded;
2. Otherwise:
1. If the received message is of a known type then the message
is considered for processing according to Section 7.3, AND;
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2. If for the received message (<hop-limit> + <hop-count>) > 1,
then the message is considered for forwarding according to
Section 7.4.
7.3. Message Considered for Processing
If a message (the "current message") is considered for processing,
the following tasks MUST be performed:
1. If an entry exists in the Processed Set where:
* P_type == the message type of the current message, or 0 if the
typedep bit in the message semantics octet (in the message
header) of the current message is cleared ('0'), AND;
* P_orig_addr == the originator address of the current message,
AND;
* P_seq_number == the message sequence number of the current
message.
then the current message MUST NOT be processed.
2. Otherwise:
1. Create an entry in the Processed Set with:
+ P_type = the message type of the current message, or 0 if
the typedep bit in the message semantics octet (in the
message header) of the current message is cleared ('0');
+ P_orig_addr = originator address of the current message;
+ P_seq_number = sequence number of the current message;
+ P_time = current time + P_HOLD_TIME.
2. Process the 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 or of an unknown message type,
then it MUST use the following algorithm. A message type not defined
in this document MAY 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.)
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If a message is considered for forwarding according to this
algorithm, the following tasks MUST be performed:
1. If the sending interface (as indicated by the source interface of
the IP datagram containing the message) does not match (taking
into account any address prefix of) any N_neighbor_iface_addr in
any Symmetric Neighbor Tuple, then the message MUST be silently
discarded.
2. Otherwise:
1. If an entry exists in the Received Set for the receiving
interface, where:
+ RX_type == the message type, or 0 if the typedep bit in
the message semantics octet (in the message header) is
cleared ('0'), AND;
+ RX_orig_addr == the originator address of the received
message, AND;
+ RX_seq_number == the sequence number of the received
message.
then the message MUST be silently discarded.
2. Otherwise:
1. Create an entry in the Received Set for the receiving
interface with:
- RX_type = the message type, or 0 if the typedep bit in
the message semantics octet (in the message header) is
cleared ('0');
- RX_orig_addr = originator address of the message;
- RX_seq_number = sequence number of the message;
- RX_time = current time + RX_HOLD_TIME.
2. If an entry exists in the Forwarded Set where:
- F_type == the message type, or 0 if the typedep bit in
the message semantics octet (in the message header) is
cleared ('0');
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- F_orig_addr == the originator address of the received
message, AND;
- F_seq_number == the sequence number of the received
message.
then the message MUST be silently discarded.
3. Otherwise if a Relay Tuple exists whose RY_iface_addr
matches (taking into account any address prefix) the
sending interface (as indicated by the source interface
of the IP datagram containing the message):
1. Create an entry in the Forwarded Set with:
o F_type = the message type, or 0 if the typedep bit
in the message semantics octet (in the message
header) is cleared ('0');
o F_orig_addr = originator address of the message;
o F_seq_number = sequence number of the message;
o F_time = current time + F_HOLD_TIME.
2. The message header is modified as follows:
o Decrement <hop-limit> in the message header by 1;
o Increment <hop-count> in the message header by 1;
3. Transmit the message on all OLSRv2 interfaces of the
node.
Messages are retransmitted in the format specified by [3] with the
ALL-MANET-NEIGHBORS address (see [4]) as destination IP address.
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8. Information Repositories
The purpose of OLSRv2 is to determine the Routing Set, which may be
used to update IP's Routing Table, providing "next hop" routing
information for IP datagrams. In order to accomplish this, OLSRv2
uses a number of protocol sets: the Neighborhood Information Base,
provided by [4], is in OLSRv2 augmented by information allowing MPR
selection and signaling. Additionally, OLSRv2 specifies a Topology
Information Base, which describes the information used for and
acquired through TC message exchange - in other words: the Topology
Information Base represents the network topology graph as seen from
each node.
Addresses (other than originator addresses) recorded in the
Neighborhood Information Base and the Topology Information Base MUST
all be recorded with prefix lengths, in order to allow comparison
with addresses received in HELLO and TC messages.
8.1. Neighborhood Information Base
The Neighborhood Information Base stores information about links
between local interfaces and interfaces on adjacent nodes. In
addition to the sets described in [4], OLSRv2 adds an element to each
Link Tuple to allow a node to record the willingness of a 1-hop
neighbor node to be selected as an MPR. Also, OLSRv2 adds an MPR Set
and an MPR Selector Set to the Neighborhood Information Base. The
MPR Set is used by a node to record which of its symmetric 1-hop
neighbors are selected as MPRs, and the MPR Selector Set is used by a
node to record which of its symmetric 1-hop neighbors have selected
it as MPR. Thus, in addition to what is specified in [4], the MPR
Set is used when generating HELLO messages, and the MPR Selector Set
is populated when processing HELLO messages.
8.1.1. Link Set
Link Tuples are as specified in [4], augmented with:
L_willingness is the node's willingness to be selected as an MPR;
8.1.2. MPR Set
A node's MPR Set contains OLSRv2 interface addresses with which the
node has a symmetric link and which are of 1-hop symmetric neighbors
which the node has selected as MPRs:
(MP_neighbor_iface_addr)
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8.1.3. MPR Selector Set
A node's MPR Selector Set records the nodes which have selected this
node as an MPR. It consists of MPR Selector Tuples:
(MS_neighbor_iface_addr, MS_time)
where:
MS_neighbor_iface_addr is an OLSRv2 interface address with which
this node has a symmetric link and which is of a 1-hop symmetric
neighbor which has selected this node as an MPR;
MS_time specifies the time at which this Tuple expires and MUST be
removed.
8.2. Topology Information Base
The Topology Information Base stores information, required for the
generation and processing of TC messages. The Advertised Neighbor
Set contains OLSRv2 interface addresses of symmetric 1-hop neighbors
which are to be reported in TC messages. The Topology Set and
Attached Network Set both record information received through TC
messages. Thus the Advertised Neighbor Set is used for generating TC
messages, while the Topology Set and Attached Network Set are
populated when processing TC messages.
Additionally, a Routing Set is maintained, derived from the
information recorded in the Neighborhood Information Base, Topology
Set and Attached Network Set.
8.2.1. Advertised Neighbor Set
A node's Advertised Neighbor Set contains OLSRv2 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.
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8.2.2. ANSN History Set
A node's ANSN History Set records information about the freshness of
the topology information received from each other node. It consists
of ANSN History Tuples:
(AH_orig_addr, AH_seq_number, AH_time)
where:
AH_orig_addr is the originator address of a received TC message,
note that this does not include a prefix length;
AH_seq_number is the highest ANSN in any TC message received which
originated from AH_orig_addr;
AH_time is the time at which this Tuple expires and MUST be removed.
8.2.3. Topology Set
A node's Topology Set records topology information about the network.
It consists of Topology Tuples:
(T_dest_iface_addr, T_last_iface_addr, T_seq_number, T_time)
where:
T_dest_iface_addr is an OLSRv2 interface address of a destination
node, which may be reached in one hop from the node with the
OLSRv2 interface address T_last_iface_addr;
T_last_iface_addr is, conversely, an OLSRv2 interface address of a
node which is the last hop on a path towards the node with OLSRv2
interface address T_dest_iface_addr.
T_seq_number is the highest received ANSN associated with the
information contained in this Topology Tuple;
T_time specifies the time at which this Tuple expires and MUST be
removed.
8.2.4. 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_gw_iface_addr, AN_dist, AN_seq_number, AN_time)
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where:
AN_net_addr is the network address of an attached network, which may
be reached via the node with the OLSRv2 interface address
AN_gw_iface_addr;
AN_gw_iface_addr is the address of an OLSRv2 interface of a node
which can act as gateway to the network with address AN_net_addr;
AN_dist is the number of hops to the network with address
AL_net_addr from the node with address AN_gw_iface_addr.
AN_seq_number is the highest received ANSN associated with the
information contained in this Attached Network Tuple;
AN_time specifies the time at which this Tuple expires and MUST be
removed.
8.2.5. 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 OLSRv2 interface of a destination node, or the network address
of an attached network;
R_next_iface_addr is the OLSRv2 interface address of the "next hop"
on the selected path to the destination;
R_dist is the number of hops on the selected path to the
destination;
R_local_iface_addr is the address of the local interface over which
a packet MUST be sent to reach the destination.
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9. Control Message Structures
Nodes using OLSRv2 exchange information through messages. One or
more messages sent by a node at the same time SHOULD be combined into
a single packet. These messages may have originated at the sending
node, or have originated at another node and are forwarded by the
sending node. Messages with different originators may be combined in
the same packet.
The packet and message format used by OLSRv2 is defined in [3].
However this specification contains some options which are not used
by OLSRv2. In particular (using the syntactical entities defined in
[3]):
o All OLSRv2 packets, not limited to those defined in this document,
include a <packet-header>.
o All OLSRv2 packets, not limited to those defined in this document,
have the pseqnum bit of <packet-semantics> cleared ('0'), i.e.
they include a packet sequence number.
o OLSRv2 packets MAY include packet TLVs, however OLSRv2 itself does
not specify any packet TLVs.
o All OLSRv2 messages, not limited to those defined in this
document, include a full <msg-header> and hence have the noorig
and nohops bits of <msg-semantics> cleared ('0').
o All OLSRv2 message defined in this document have the typedep bit
of <msg-semantics> cleared ('0').
Other options defined in [3] may be freely used, in particular any
other values of <packet-semantics>, <addr-semantics> or <tlv-
semantics> consistent with its specification.
The remainder of this section defines, within the framework of [3],
message types and TLVs specific to OLSRv2.
9.1. HELLO Messages
A HELLO message in OLSRv2 is generated as specified in [4].
Additionally, an OLSRv2 node:
o MUST include TLV(s) with Type == MPR associated with all OLSRv2
interface addresses included in the HELLO message with a TLV with
Type == LINK_STATUS and Value == SYMMETRIC if that address is also
included in the node's MPR Set (if there is more than one copy of
the address, this applies to the specific copy of the address to
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which the LINK_STATUS TLV is associated);
o MUST NOT include any TLVs with Type == MPR associated with any
other addresses;
o MAY include a message TLV with Type == WILLINGNESS, indicating the
node's willingness to be selected as an MPR.
9.1.1. HELLO Message TLVs
In a HELLO message, a node MAY include a WILLINGNESS message TLV as
specified in Table 1.
+----------------+------+-------------------+-----------------------+
| Name | Type | Length | Value |
+----------------+------+-------------------+-----------------------+
| WILLINGNESS | TBD | 8 bits | The node's |
| | | | willingness to be |
| | | | selected as MPR; |
| | | | unused bits (based on |
| | | | the maximum |
| | | | willingness value |
| | | | WILL_ALWAYS) are |
| | | | RESERVED and SHOULD |
| | | | be set to zero |
+----------------+------+-------------------+-----------------------+
Table 1
A node's willingness to be selected as MPR ranges from WILL_NEVER
(indicating that a node MUST NOT be selected as MPR by any node) to
WILL_ALWAYS (indicating that a node MUST always be selected as MPR).
If a node does not advertise a Willingness TLV in HELLO messages, the
node MUST be assumed to have a willingness of WILL_DEFAULT.
9.1.2. HELLO Message Address Block TLVs
In a HELLO message, a node MAY include MPR address block TLV(s) as
specified in Table 2.
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+----------------+------+-------------------+----------------------+
| Name | Type | Length | Value |
+----------------+------+-------------------+----------------------+
| MPR | TBD | 0 bits | None |
+----------------+------+-------------------+----------------------+
Table 2
9.2. TC Messages
A TC message MUST contain:
o A message TLV with Type == CONT_SEQ_NUM, as specified in
Section 9.2.1.
o A message TLV with Type == VALIDITY_TIME, as specified in
Appendix E.
o A first address block containing all of the node's OLSRv2
interface addresses. This is similar to the Local Interface Block
included in HELLO messages as specified in [4], however in a TC
message these addresses MUST be included in the same order in all
copies of a given TC message, regardless of which OLSRv2 interface
it is transmitted on, and no OTHER_IF address block TLVs are
required.
o Additional address block(s) containing all addresses in the
Advertised Address Set and selected addresses in the Local
Attached Network Set, the latter (only) with associated GATEWAY
address block TLV(s), as specified in Section 9.2.2.
A TC message MAY contain:
o A message TLV with Type == INTERVAL_TIME, as specified in
Appendix E.
o A message TLV with Type == INCOMPLETE, as specified in
Section 9.2.1.
9.2.1. TC Message TLVs
In a TC message, a node MUST include a CONT_SEQ_NUM message TLV, and
MAY contain an INCOMPLETE message TLV, as specified in Table 3.
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+----------------+------+-------------------+-----------------------+
| Name | Type | Length | Value |
+----------------+------+-------------------+-----------------------+
| CONT_SEQ_NUM | TBD | 8 bits | The ANSN contained in |
| | | | the Advertised |
| | | | Neighbor Set |
| | | | |
| INCOMPLETE | TBD | 0 bits | None |
+----------------+------+-------------------+-----------------------+
Table 3
9.2.2. TC Message Address Block TLVs
In a TC message, a node MAY include GATEWAY address block TLV(s) as
specified in Table 4.
+----------------+------+-------------------+-----------------------+
| Name | Type | Length | Value |
+----------------+------+-------------------+-----------------------+
| GATEWAY | TBD | 8 bits | Number of hops to |
| | | | attached network |
+----------------+------+-------------------+-----------------------+
Table 4
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10. HELLO Message Generation
An OLSRv2 HELLO message is composed as defined in [4], with the
following additions:
o A message TLV with Type == WILLINGNESS and Value == the node's
willingness to act as an MPR, MAY be included.
o For each address which is included in the message with an
associated TLV with Type == LINK_STATUS, and is of an MPR (i.e. is
an MP_neighbor_iface_addr), an address 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 address which is included in the message and is not of an MPR
(i.e. is not an MP_neighbor_iface_addr) or is not associated with
a TLV with Type == LINK_STATUS, an address TLV with Type == MPR
MUST NOT be included.
o For each Local Attached Tuple with AL_dist == 0, a node MAY
include AL_net_addr in the Local Interface Block of the message,
with an associated TLV with Type == OTHER_IF.
10.1. HELLO Message: Transmission
HELLO messages are included in packets as specified in [3]. These
packets may contain other messages, including TC messages.
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11. HELLO Message Processing
Subsequent to the processing of HELLO messages, as specified in [4],
the node MUST:
1. Determine the willingness of the originating node to be an MPR
by:
* if the HELLO message contains a message TLV with Type ==
WILLINGNESS then the willingness is the value of that TLV,
ignoring the reserved bits in that field;
* otherwise the willingness is WILL_DEFAULT.
2. Update each Link Tuple for which any address in its
L_neighbor_iface_addr_list is present in the Local Interface
Block of the HELLO message, with:
* L_willingness = the willingness of the originating node.
3. Update its MPR Selector Set, according to Section 11.1.
11.1. Populating the MPR Selector Set
On receiving a HELLO message:
1. If a node finds one of its 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), the MPR Selector Set MUST be updated as follows:
1. For each address, henceforth neighbor address, in the Local
Interface Block of the received HELLO message, where the
neighbor address is present as an N_neighbor_iface_addr in a
Symmetric Neighbor Tuple with N_STATUS == SYMMETRIC:
1. If there exists no MPR Selector Tuple with:
- MS_neighbor_iface_addr == neighbor address
then a new MPR Selector Tuple is created with:
- MS_neighbor_iface_addr = neighbor address
2. The MPR Selector Tuple (new or otherwise) with:
- MS_neighbor_iface_addr == neighbor address
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is then modified as follows:
- MS_time = current time + validity time
2. Otherwise if a node finds one of its own interface addresses with
an associated TLV with Type == LINK_STATUS and Value == SYMMETRIC
in the HELLO message, the MPR Selector Set MUST be updated as
follows:
1. All MPR Selector Tuples whose MS_neighbor_iface_addr is in
the Local Interface Block of the HELLO message are removed.
MPR Selector Tuples are also removed upon expiration of MS_time, or
upon symmetric link breakage as described in Section 11.2.
11.2. Symmetric Neighborhood and 2-Hop Neighborhood Changes
A node MUST also perform the following:
1. If a Link Tuple with L_STATUS == SYMMETRIC is removed, or its
L_STATUS changes from SYMMETRIC to HEARD or LOST, and for each
address in that Link Tuple's L_neighbor_iface_addr_list, if it is
an MS_neighbor_iface_addr of an MPR Selector Tuple, then that MPR
Selector Tuple MUST be removed.
2. If any of:
* a Link Tuple is added with L_STATUS == SYMMETRIC, OR;
* a Link Tuple with L_STATUS == SYMMETRIC is removed, or its
L_STATUS changes from SYMMETRIC to HEARD or LOST, or vice
versa, OR;
* a 2-Hop Neighbor Tuple is added or removed, OR;
* the Neighbor Address Association Set is changed such that the
subset of any NA_neighbor_iface_addr_list consisting of those
addresses which are in the L_neighbor_iface_addr_list of a
Link Tuple with L_STATUS == SYMMETRIC is changed, including
the cases of removal or addition of a Neighbor Address
Association Tuple containing any such addresses;
then the MPR Set MUST be recalculated.
An additional HELLO message MAY be sent when the MPR Set changes, in
addition to the cases specified in [4], and subject to the same
constraints.
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12. TC Message Generation
A node with one or more OLSRv2 interfaces, and with a non-empty
Advertised Neighbor Set or which acts as a gateway to an associated
network which is to be advertised in the MANET, MUST generate TC
messages. A node with an empty Advertised Neighbor Set and which is
not acting as such a gateway SHOULD also generate "empty" TC messages
for a period A_HOLD_TIME after it last generated a non-empty TC
message. TC messages (non-empty and empty) are generated according
to the following:
1. The message hop count MUST be set to zero.
2. The message hop limit MAY be set to any positive value, this
SHOULD be at least two. A node MAY:
* use the same hop limit in all TC messages, this MUST be at
least equal to the network diameter in hops, a value of 255 is
RECOMMENDED in this case; OR
* use different hop limits in TC messages, this MUST regularly
include messages with hop limit at least equal to the network
diameter, a value of 255 is RECOMMENDED for these messages;
other hop limits SHOULD use a regular pattern with a regular
interval at any given number of hops distance.
3. The message MUST contain a message TLV with Type == CONT_SEQ_NUM
and Value == ANSN from the Advertised Neighbor Set.
4. The message MUST contain a message TLV with Type ==
VALIDITY_TIME, as specified in Appendix E.2. If all TC messages
are sent with the same hop limit (usually 255) then this TLV MUST
have Value == T_HOLD_TIME. If TC messages are sent with
different hop limits, then this TLV MUST specify times which vary
with the number of hops distance appropriate to the chosen
pattern of TC message hop limits, these times SHOULD be
appropriate multiples of T_HOLD_TIME.
5. The message MAY contain a message TLV with Type == INTERVAL_TIME,
as specified in Appendix E.2. If all TC messages are sent with
the same hop limit (usually 255) then this TLV MUST have Value ==
TC_INTERVAL. If TC messages are sent with different hop limits,
then this TLV MUST specify times which vary with the number of
hops distance appropriate to the chosen pattern of TC message hop
limits, these times SHOULD be appropriate multiples of
TC_INTERVAL.
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6. The message MUST contain the addresses of all of its OLSRv2
interfaces in its first address block, note that the TC message
generated on all OLSRv2 interfaces MUST be identical (including
having identical message sequence number) and hence these
addresses are not ordered or otherwise identified according to
the interface on which the TC message is transmitted.
7. The message MUST contain, in address blocks other than its first:
1. A_neighbor_iface_addr from each Advertised Neighbor Tuple;
2. AL_net_addr from each Local Attached Neighbor Tuple with
AL_dist > 0, each associated with a TLV with Type == GATEWAY
and Value == AL_dist.
8. The message MAY contain, in address blocks other than its first:
1. AL_net_addr from each Local Attached Neighbor Tuple with
AL_dist == 0, each associated with a TLV with Type == GATEWAY
and Value == 0.
12.1. TC Message: Transmission
TC messages are generated and transmitted periodically on all OLSRv2
interfaces, with a default interval between two consecutive TC
emissions by the same node of TC_INTERVAL.
TC messages MAY be generated in response to a change of contents,
indicated by a change in ANSN. In this case a node MAY send a
complete TC message, and if so MAY re-start its TC message schedule.
Alternatively a node MAY send only new content in its address blocks
(with appropriate associated TLVs) in which case it MUST include a
message TLV with Type == INCOMPLETE, and MUST NOT re-start its TC
message schedule. This TC message MUST include its usual message
TLVs. Note that a node cannot report removal of advertised content
using an incomplete TC message.
When sending a TC message in response to a change of contents, a node
must respect a minimum interval of TC_MIN_INTERVAL between generated
TC messages. Sending an incomplete TC message MUST NOT cause the
interval between complete TC messages to be increased, and thus a
node MUST NOT send an incomplete TC message if within TC_MIN_INTERVAL
of the next scheduled complete TC message.
The generation of TC messages, whether scheduled or triggered by a
change of contents, and the forwarding of TC messages, MAY be
jittered as described in Appendix F. The values of MAXJITTER used
SHOULD be:
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o TP_MAXJITTER for periodic TC message generation;
o TT_MAXJITTER for triggered TC message generation;
o TF_MAXJITTER for TC message forwarding;
TC messages are included in packets as specified in [3]. 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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13. TC Message Processing
When according to Section 7.3 a TC message is to be processed
according to its type, this means that:
o if the message does not contain a message TLV with Type ==
INCOMPLETE, then processing according to Section 13.1 and then
according to Section 13.2 is carried out;
o if the message contains a message TLV with Type == INCOMPLETE,
then only processing according to Section 13.1 is carried out.
For all processing purposes, "ANSN" is defined as being the value of
the message TLV with Type == CONT_SEQ_NUM in the TC message. If a TC
message has no such TLV then it MUST NOT be processed.
13.1. Initial TC Message Processing
For the purposes of this section, note the following:
o "validity time" is calculated from the VALIDITY_TIME message TLV
in the TC message according to the specification in Appendix E.2;
o "originator address" refers to the originator address in the TC
message header;
o comparisons of sequence numbers are carried out as specified in
Section 18.
The TC message is processed as follows:
1. the ANSN History Set is updated according to Section 13.1.1; 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 13.1.2;
3. the Attached Network Set is updated according to Section 13.1.3.
13.1.1. Populating the ANSN History Set
The node MUST update its ANSN History Set as follows:
1. If there is an ANSN History Tuple with:
* AH_orig_addr == originator address; AND
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* AH_seq_number > ANSN
then the TC message MUST be discarded.
2. Otherwise
1. If there is no ANSN History Tuple such that:
+ AH_orig_addr == originator address;
then create a new ANSN History Tuple with:
+ AH_orig_addr = originator address.
2. This ANSN History Tuple (existing or new) is then modified as
follows:
+ AH_seq_number = ANSN;
+ AH_time = current time + validity time.
13.1.2. Populating the Topology Set
The node MUST update its Topology Set as follows:
1. For each address, henceforth local address, in the first address
block in the TC message:
1. For each address, henceforth advertised address, in an
address block other than the first in the TC message, and
which does not have an associated TLV with Type == GATEWAY:
1. If there is no Topology Tuple such that:
- T_dest_iface_addr == advertised address; AND
- T_last_iface_addr == local address
then create a new Topology Tuple with:
- T_dest_iface_addr = advertised address;
- T_last_iface_addr = local address.
2. This Topology Tuple (existing or new) is then modified as
follows:
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- T_seq_number = ANSN;
- T_time = current time + validity time.
13.1.3. Populating the Attached Network Set
The node MUST update its Attached Network Set as follows:
1. For each address, henceforth gateway address, in the first
address block in the TC message:
1. For each address, henceforth network address, in an address
block other than the first in the TC message, and which has
an associated TLV with Type == GATEWAY:
1. If there is no Attached Network Tuple such that:
- AN_net_addr == network address; AND
- AN_gw_iface_addr == gateway address
then create a new Attached Network Tuple with:
- AN_net_addr = network address;
- AN_gw_iface_addr = gateway 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.
13.2. Completing TC Message Processing
The TC message is processed as follows:
1. the Topology Set is updated according to Section 13.2.1;
2. the Attached Network Set is updated according to Section 13.2.2.
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13.2.1. Purging the Topology Set
The Topology Set MUST be updated as follows:
1. for each address, henceforth local address, in the first address
block of the TC message, all Topology Tuples with:
* T_last_iface_addr == local address; AND
* T_seq_number < ANSN
MUST be removed.
13.2.2. Purging the Attached Network Set
The Attached Network Set MUST be updated as follows:
1. for each address, henceforth local address, in the first address
block of the TC message, all Attached Network Tuples with:
* AN_gw_iface_addr == local address; AND
* AN_seq_number < ANSN
MUST be removed.
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14. Populating the MPR Set
Each node MUST select, from among its symmetric 1-hop neighbors, a
subset of nodes as MPRs. This subset MUST be selected such that a
message transmitted by the node, and retransmitted by all its MPRs,
will be received by all of its symmetric strict 2-hop neighbors.
Each node selects its MPR Set individually, utilizing the information
in the Symmetric Neighbor Set, the 2-Hop Neighbor Set and the
Neighborhood Address Association Set. Initially these sets will be
empty, as will be the MPR Set. A node SHOULD recalculate its MPR Set
when a relevant change is made to the Symmetric Neighbor Set, the
2-Hop Neighbor Set or the Neighborhood Address Association Set.
More specifically, a node MUST calculate MPRs per interface, the
union of the MPR Sets of each interface make up the MPR Set for the
node. All OLSRv2 interfaces of nodes selected as MPRs with which the
node has a symmetric link MUST be added to the MPR Set. Also
symmetric 1-hop neighbor nodes with willingness WILL_NEVER (as
recorded in the Link Set) MUST NOT be considered as MPRs.
MPRs are used to flood control messages from a node into the network
while reducing the number of retransmissions that will occur in a
region. Thus, the concept of MPR is an optimization of a classical
flooding mechanism. While it is not essential that the MPR Set is
minimal, it is essential that all symmetric strict 2-hop neighbors
can be reached through the selected MPR nodes. A node MUST select an
MPR Set such that any strict 2-hop neighbor is "covered" by at least
one MPR node. A node MAY select additional MPRs beyond the minimum
set. Keeping the MPR Set small ensures that the overhead of OLSRv2
is kept at a minimum.
Appendix C contains an example heuristic for selecting MPRs.
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15. Populating Derived Sets
The Relay Set and the Advertised Neighbor Set of OLSRv2 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 the MPR Selector Set.
15.1. Populating the Relay Set
The Relay Set contains the set of OLSRv2 interface addresses of those
symmetric 1-hop neighbors for which a node is supposed to relay
broadcast traffic. This set MUST at least contain all addresses in
the MPR Selector Set (i.e. all MS_neighbor_iface_addr). This set MAY
contain additional symmetric 1-hop neighbor OLSRv2 interface
addresses.
15.2. Populating the Advertised Neighbor Set
The Advertised Neighbor Set contains the set of OLSRv2 interface
addresses of those 1-hop neighbors to which a node advertises a
symmetric link in TC messages. This set MUST at least contain all
addresses in the MPR Selector Set (i.e. all MS_neighbor_iface_addr).
This set MAY contain additional symmetric 1-hop neighbor OLSRv2
interface addresses.
Whenever an address is added to or removed from the Advertised
Neighbor Set, the ANSN MUST be incremented.
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16. Routing Table Calculation
The Routing Set is updated when a change (an entry appearing or
disappearing, or changing between SYMMETRIC and LOST) is detected in:
o the Link Set, OR;
o the Neighbor Address Association Set, OR;
o the 2-Hop Neighbor Set, OR;
o the Topology Set, OR;
o the Attached Network Set.
Note that some changes to these sets do not necessitate a change to
the Routing Set, in particular changes to the Link Set which do not
involve Link Tuples with L_STATUS == SYMMETRIC (either before or
after the change), and similar changes to the Neighbor Address
Association Set. A node MAY avoid updating the Routing Set in such
cases.
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 routing table as appropriate.
To construct the Routing Set of node X, a shortest path algorithm is
run on the directed graph containing
o the arcs X -> Y where there exists a Link Tuple with Y in the
L_neighbor_iface_addr_list and L_STATUS == SYMMETRIC (i.e. Y is a
symmetric 1-hop neighbor of X), AND;
o the arcs Y -> Z where Y is added as above and the Link Tuple with
Y in its L_neighbor_iface_addr_list has L_willingness not equal to
WILL_NEVER, and there exists a 2-Hop Neighbor Tuple with Y as
N2_neighbor_iface_addr and Z as N2_2hop_iface_addr (i.e. Z is a
symmetric 2-hop neighbor of Z through Y, which does not have
willingness WILL_NEVER), AND;
o the arcs U -> V, where there exists a Topology Tuple with U as
T_last_iface_addr and V as T_dest_iface_addr (i.e. this is an
advertised link in the network).
The graph is complemented with:
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o arcs Y -> W where there exists a Link Tuple with Y in its
L_neighbor_iface_addr_list and L_STATUS == SYMMETRIC and a
Neighborhood Address Association Tuple with Y and W both contained
in its NA_neighbor_iface_addr_list (i.e. Y and W are both
addresses of the same symmetric 1-hop neighbor), AND;
o arcs U -> T where there exists an Attached Network Tuple with U as
AN_net_addr and T as AN_gw_iface_addr (i.e. U is a gateway to
network T).
The following procedure is given as an example for calculating the
Routing Set using a variation of Dijkstra's algorithm. Thus:
1. All Routing Tuples are removed.
2. For each Link Tuple with L_STATUS == SYMMETRIC, and for each
address (henceforth neighbor address) in that Link Tuple's
L_neighbor_iface_addr_list, a new Routing Tuple is added with:
* R_dest_addr = neighbor address;
* R_next_iface_addr = neighbor address;
* R_dist = 1;
* R_local_iface_addr = neighbor address.
3. For each Neighbor Address Association Tuple, for which two
addresses A1 and A2 are in NA_neighbor_iface_addr_list where:
* there is a Routing Tuple with:
+ R_dest_addr == A1
* and there is no Routing Tuple with:
+ R_dest_addr == A2
then a Routing Tuple is added with:
* R_dest_addr = A2;
* R_next_iface_addr = R_next_iface_addr of the Routing Tuple in
which R_dest_addr == A1;
* R_dist = 1;
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* R_local_iface_addr = R_local_iface_addr of the Routing Tuple
in which R_dest_addr == A1.
4. 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=2 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;
+ T_last_iface_addr is equal to R_dest_addr of a Routing
Tuple whose R_dist == h;
then a new Routing Tuple MUST be added, with:
+ R_dest_addr = T_dest_iface_addr;
+ R_next_iface_addr = R_next_iface_addr of the Routing Tuple
whose R_dest_addr == T_last_iface_addr;
+ R_dist = h+1;
+ R_local_iface_addr = R_local_iface_addr of the Routing
Tuple whose R_dest_addr == T_last_iface_addr.
Several Topology Tuples may be used to select a next hop
R_next_iface_addr for reaching the address R_dest_addr. When
h == 1, ties should be broken such that nodes with highest
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;
+ N2_neighbor_iface_addr has a willingness (i.e. the
L_willingness of the Link Tuple whose
L_neighbor_iface_addr_list contains
N2_neighbor_iface_addr) which is not equal to WILL_NEVER;
a Routing Tuple is added with:
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+ R_dest_addr = N2_2hop_iface_addr of the 2-Hop Neighbor
Tuple;
+ R_next_iface_addr = R_next_iface_addr of the Routing Tuple
in which R_dest_addr == N2_neighbor_iface_addr;
+ R_dist = 2;
+ R_local_iface_addr = R_local_iface_addr of the Routing
Tuple in which R_dest_addr == N2_neighbor_iface_addr.
5. For each Attached Network Tuple, if
* AN_net_addr is not equal to R_dest_addr of any Routing Tuple,
AND;
* AN_gw_iface_addr is equal to R_dest_addr of a Routing Tuple;
then a new Routing Tuple MUST be added, with:
* R_dest_addr = AN_net_addr;
* R_next_iface_addr = R_next_iface_addr of the Routing Tuple
whose R_dest_addr == AN_gw_iface_addr;
* R_dist = (R_dist of the Routing Tuple whose R_dest_addr ==
AN_gw_iface_addr) + AN_dist;
* R_local_iface_addr = R_local_iface_addr of the Routing Tuple
whose R_dest_addr == AN_gw_iface_addr.
If more than one Attached Network Tuple has the same AN_net_addr,
then more than one Routing Tuple MUST NOT be added, and the added
Routing Tuple MUST have minimum R_dist.
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17. Proposed Values for Constants
This section list the values for the constants used in the
description of the protocol. These proposed values are appropriate
to the case where all TC messages are sent with the same hop limit
(usually 255).
17.1. Neighborhood Discovery Constants
The constants HELLO_INTERVAL, REFRESH_INTERVAL, HELLO_MIN_INTERVAL,
H_HOLD_TIME, L_HOLD_TIME, N_HOLD_TIME, HP_MAXJITTER, HT_MAXJITTER and
C are used as in [4].
17.2. Message Intervals
o TC_INTERVAL = 5 seconds
o TC_MIN_INTERVAL = TC_INTERVAL/4
17.3. Holding Times
o T_HOLD_TIME = 3 x TC_INTERVAL
o A_HOLD_TIME = T_HOLD_TIME
o P_HOLD_TIME = 30 seconds
o RX_HOLD_TIME = 30 seconds
o F_HOLD_TIME = 30 seconds
17.4. Jitter Times
o TP_MAXJITTER = HP_MAXJITTER
o TT_MAXJITTER = HT_MAXJITTER
o TF_MAXJITTER = TT_MAXJITTER
17.5. Willingness
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. IANA Considerations
19.1. Message Types
OLSRv2 defines one message type, which must be allocated from the
"Assigned Message Types" repository of [3].
+--------------------+-------+--------------------------------------+
| Mnemonic | Value | Description |
+--------------------+-------+--------------------------------------+
| TC | TBD | Topology Control (global signaling) |
+--------------------+-------+--------------------------------------+
Table 5
19.2. TLV Types
OLSRv2 defines three message TLV types, which must be allocated from
the "Assigned message TLV Types" repository of [3].
+--------------------+-------+--------------------------------------+
| Mnemonic | Value | Description |
+--------------------+-------+--------------------------------------+
| WILLINGNESS | TBD | Specifies the originating node's |
| | | willingness to act as a relay and to |
| | | partake in network formation |
| | | |
| CONT_SEQ_NUM | TBD | Specifies a content sequence number |
| | | for this message |
| | | |
| INCOMPLETE | TBD | Specifies that this message is |
| | | incomplete |
+--------------------+-------+--------------------------------------+
Table 6
OLSRv2 defines two Address Block TLV types, which must be allocated
from the "Assigned address block TLV Types" repository of [3].
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+--------------------+-------+--------------------------------------+
| Mnemonic | Value | Description |
+--------------------+-------+--------------------------------------+
| MPR | TBD | Specifies that a given address is |
| | | selected as MPR |
| | | |
| GATEWAY | TBD | Specifies that a given address is |
| | | reached via a gateway on the |
| | | originating node |
+--------------------+-------+--------------------------------------+
Table 7
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20. References
20.1. Normative References
[1] Clausen, T. and P. Jacquet, "The Optimized Link State Routing
Protocol", RFC 3626, October 2003.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, BCP 14, March 1997.
[3] Clausen, T., Dean, J., Dearlove, C., and C. Adjih, "Generalized
MANET Packet/Message Format", work in
progress draft-ietf-manet-packetbb-03.txt, January 2007.
[4] Clausen, T., Dean, J., and C. Dearlove, "MANET Neighborhood
Discovery Protocol (NHDP)", work in
progress draft-ietf-manet-nhdp-01.txt, February 2007.
20.2. Informative References
[5] Atkins, D., Stallings, W., and P. Zimmermann, "PGP Message
Exchange Formats", RFC 1991, August 1996.
[6] ETSI, "ETSI STC-RES10 Committee. Radio equipment and systems:
HIPERLAN type 1, functional specifications ETS 300-652",
June 1996.
[7] Jacquet, P., Minet, P., Muhlethaler, P., and N. Rivierre,
"Increasing reliability in cable free radio LANs: Low level
forwarding in HIPERLAN.", 1996.
[8] Qayyum, A., Viennot, L., and A. Laouiti, "Multipoint relaying:
An efficient technique for flooding in mobile wireless
networks.", 2001.
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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. Protocol and Port Number
Packets in OLSRv2 are communicated using UDP. Port 698 has been
assigned by IANA for exclusive usage by the OLSR (v1 and v2)
protocol.
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Appendix C. Example Heuristic for Calculating MPRs
The following specifies a proposed heuristic for selection of MPRs.
In graph theory terms, MPR computation is a "set cover" problem,
which is a difficult optimization problem, but for which an easy and
efficient heuristics exist: the so-called "Greedy Heuristic", a
variant of which is described here. In simple terms, MPR computation
constructs an MPR Set that enables a node to reach any symmetric
2-hop neighbors by relaying through an MPR node.
There are several peripheral issues that the algorithm needs to
address. The first one is that some nodes have some willingness
WILL_NEVER. The second one is that some nodes may have several
interfaces.
The algorithm hence can be summarized by:
o All 1-hop neighbor nodes with willingness equal to WILL_NEVER MUST
ignored in the following algorithm: they are not considered as
1-hop neighbors (hence not used as MPRs).
o Because link sensing is performed by interface, the local network
topology is best described in terms of links: hence the algorithm
is considering 1-hop neighbor OLSRv2 interfaces, and 2-hop
neighbor OLSRv2 interfaces (and their addresses). Additionally,
asymmetric links are ignored. This is reflected in the
definitions below.
o MPR computation is performed on each interface of the node: on
each interface I, the node MUST select some neighbor interfaces,
so that all 2-hop neighbor interfaces are reached.
From now on, MPR calculation will be described for one interface I on
the node, and the following terminology will be used in describing
the heuristics:
neighbor interface (of I) - An OLSRv2 interface of a 1-hop neighbor
to which there exist a symmetric link using interface I.
N - the set of such neighbor interfaces
2-hop neighbor interface (of I) An interface of a symmetric strict
2-hop neighbor which can be reached from a neighbor interface for
I.
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N2 - the set of such 2-hop neighbor interfaces
D(y): - the degree of a 1-hop neighbor interface y (where y is a
member of N), is defined as the number of symmetric neighbor
interfaces of node y which are in N2
MPR Set - the set of the neighbor interfaces selected as MPRs.
The proposed heuristic selects iteratively some interfaces from N as
MPRs in order to cover 2-hop neighbor interfaces from N2, as follows:
1. Start with an MPR Set made of all members of N with L_willingness
equal to WILL_ALWAYS
2. Calculate D(y), where y is a member of N, for all interfaces in
N.
3. Add to the MPR Set those interfaces in N, which are the *only*
nodes to provide reachability to an interface in N2. For
example, if interface B in N2 can be reached only through a
symmetric link to interface A in N, then add interface B to the
MPR Set. Remove the interfaces from N2 which are now covered by a
interface in the MPR Set.
4. While there exist interfaces in N2 which are not covered by at
least one interface in the MPR Set:
1. For each interface in N, calculate the reachability, i.e.,
the number of interfaces in N2 which are not yet covered by
at least one node in the MPR Set, and which are reachable
through this neighbor interface;
2. Select as an MPR the interface with highest L_willingness
among the interfaces in N with non-zero reachability. In
case of multiple choice select the interface which provides
reachability to the maximum number of interfaces in N2. In
case of multiple interfaces providing the same amount of
reachability, select the interface as MPR whose D(y) is
greater. Remove the interfaces from N2 which are now covered
by an interface in the MPR Set.
Other algorithms, as well as improvements over this algorithm, are
possible. For example:
o Assume that in a multiple interface scenario there exists more
than one link between nodes 'a' and 'b'. If node 'a' has selected
node 'b' as MPR for one of its interfaces, then node 'b' can be
selected as MPR with minimal performance loss by any other
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interfaces on node 'a'.
o In a multiple interface scenario MPRs are selected for each
interface of the selecting node, providing full coverage of all
2-hop nodes accessible through that interface. The overall MPR
Set is then the union of these sets. These sets do not however
have to be selected independently, if a node is selected as an MPR
for one interface it may be automatically added to the MPR
selection for other interfaces.
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Appendix D. Packet and Message Layout
This appendix illustrates the translation from the abstract
descriptions of packets employed in the protocol specification, and
the bit-layout packets actually exchanged between the nodes.
Appendix D.1. Packet and Message Options
The basic layout of an OLSRv2 packet is as described in [3]. However
the following points should be noted.
In the following figures, reserved bits marked Reserved or Resv MUST
be cleared ('0'). Octets indicated as Padding are optional and MAY
be omitted; if not omitted they SHOULD be used to pad to a 32 bit
boundary and MUST all be zero.
OLSRv2 uses only packets with a packet header including a packet
sequence number, either with or without a packet TLV block. Thus all
OLSRv2 packets have the layout of either
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 0| Reserved |0|0| Packet Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Message + Padding |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: ... :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Message + Padding |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
or
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 0| Reserved |1|0| Packet Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Packet TLV Block |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Message + Padding |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
: ... :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Message + Padding |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
OLSRv2 uses only messages with a complete message header. Thus all
OLSRv2 messages, plus padding if any, have the following layout.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Type | Resv |N|0|0| Message Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Originator Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hop Limit | Hop Count | Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Message Body |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In standard OLSRv2 messages (HELLO and TC) the type dependent
sequence number bit marked N MUST be cleared ('0').
The layouts of the message body, address block, TLV block and TLV are
as in [3], allowing all options. Standard (HELLO and TC) messages
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contain a first address block which contains local interface address
information, all other address blocks contain neighbor interface
address information (or for a TC message address information for
which it is a gateway) specific to the message type.
Appendix D.2. Example HELLO Message
An example HELLO message, using IPv4 (four octet) addresses is as
follows. The overall message length is 58 octets. The message has a
hop limit of 1 and a hop count of 0, as sent by its originator.
The message has a message TLV block with content length 12 octets
containing three message TLVs. These TLVs represent message validity
time, message interval time and willingness. Each uses a TLV with
semantics value 4, indicating no start and stop indexes are included,
and each has a value length of 1 octet.
The first address block contains 1 local interface address. The
semantics octet 2 indicates it has no tail section. It has head
length 4, this is equal to the address length, it thus has no mid
section. This address block has no TLVs (TLV block content length is
0 octets).
The second, and last, address block includes 4 neighbor interface
addresses. The semantics octet 2 indicates they have no tail
section. The addresses have head length 3 octets, thus each mid
section is of length one octet. The following address TLV block
(content length 11 octets) includes two TLVs.
The first of these TLVs reports the link status of all four neighbors
in a single multivalue TLV, the first two addresses are HEARD, the
last two addresses are SYMMETRIC. The TLV semantics octet value of
20 indicates, in addition to that this is a multivalue TLV, that no
start index and stop index are included, hence values for all
addresses are included. The TLV value length of 4 octets indicates
one octet per value per address.
The second of these TLVs indicates that the last address (start index
3, stop index 3) is an MPR. This TLV has no value, or value length,
fields, as indicated by its semantics octet being equal to 2.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| HELLO |0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 0 0 0 1 1 1 0 1 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Originator Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1|0 0 0 0 0 0 0 0| Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0| VALIDITY_TIME |0 0 0 0 0 1 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1| Value | INTERVAL_TIME |0 0 0 0 0 1 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1| Value | WILLINGNESS |0 0 0 0 0 1 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1| Value |0 0 0 0 0 0 0 1|0 0 0 0 0 0 1 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 1 0 0| Head |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Head (cont) |0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0|0 0 0 0 0 1 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 1 0|0 0 0 0 0 0 1 1| Head |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Head (cont) | Mid | Mid | Mid |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mid |0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 1| LINK_STATUS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1 0 1 0 0|0 0 0 0 0 1 0 0| HEARD | HEARD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SYMMETRIC | SYMMETRIC | MPR |0 0 0 0 0 0 1 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 1 1|0 0 0 0 0 0 1 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Appendix D.3. Example TC Message
An example TC message, using IPv4 (four octet) addresses, is as
follows. The overall message length is 67 octets.
The message has a message TLV block with content length 13 octets
containing three TLVs. The first two TLVs are validity and interval
times as for the HELLO message above. The third TLV is a content
sequence number TLV used to carry the 2 octet ANSN. The semantics
value is also 4.
The message has three address blocks. The first address block
contains 3 local interface addresses (with semantics octet 2, hence
no tail section, head length 2 octets, and hence mid sections with
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length two octets) and has no TLVs (TLV block content length 0
octets).
The other two address blocks contain neighbor interface addresses.
The first contains 3 addresses (semantics octet 2, no tail section,
head length 2 octets, hence mid sections length two octets) and has
no TLVs (TLV block content length 0 octets). The second contains 1
address, with semantics octet 4 indicating that the tail section,
length 2 octets, consists of zero valued octets (not included). The
following TLV block (content length 6 octets) includes two TLVs, the
first (semantics value 4 indicating no indexes are needed) indicates
that the address has a netmask, with length given by the value (of
length 1 octet) of 16. Thus this address is Head.0.0/16. The second
TLV indicates that the originating node is a gateway to this network,
at a given number of hops distance. The TLV semantics value of 4
indicates that no indexes are needed.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TC |0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Originator Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hop Limit | Hop Count | Message Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 1| VALIDITY_TIME |0 0 0 0 0 1 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1| Value | INTERVAL_TIME |0 0 0 0 0 1 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1| Value | CONT_SEQ_NUM |0 0 0 0 0 1 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 1 0| Value (ANSN) |0 0 0 0 0 0 1 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x02 |0 0 0 0 0 0 1 0| Head |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mid | Mid |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mid |0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 1 1| 0x02 |0 0 0 0 0 0 1 0| Head |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Head (cont) | Mid | Mid |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mid (cont) | Mid |0 0 0 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 1|0 0 0 0 0 1 0 0|0 0 0 0 0 0 1 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Head |0 0 0 0 0 0 1 0|0 0 0 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 1 1 1| PREFIX_LENGTH |0 0 0 0 0 1 0 0|0 0 0 0 0 0 0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1 0 0 0 0| GATEWAY |0 0 0 0 0 1 0 0| Number Hops |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Appendix E. Time TLVs
This appendix specifies a general time TLV structure for expressing
either single time values or a set of time values with each value
associated with a range of distances. Furthermore, using this
general time TLV structure, this document specifies the INTERVAL_TIME
and VALIDITY_TIME TLVs, which are used by OLSRv2.
E.1. Representing Time
This document specifies a TLV structure in which time values are each
represented in an 8 bit time code, one or more of which may be used
in a TLV's value field. Of these 8 bits, the least significant four
bits represent the mantissa (a), and the most significant four bits
represent the exponent (b), so that:
o time value = (1 + a/16) * 2^b * C
o time code = 16 * b + a
All nodes in the network MUST use the same value of C, which will be
specified in seconds, hence so will be all time values. Note that
ascending values of the time code represent ascending time values,
time values may thus be compared by comparison of time codes.
An algorithm for computing the time code representing the smallest
representable time value not less than the time value t is:
1. find the largest integer b such that t/C >= 2^b;
2. set a = 16 * (t / (C * 2^b) - 1), rounded up to the nearest
integer;
3. if a == 16 then set b = b + 1 and set a = 0;
4. if a and b are in the range 0 and 15 then the required time value
can be represented by the time code 16 * b + a, otherwise it can
not.
The minimum time value that can be represented in this manner is C.
The maximum time value that can be represented in this manner is
63488 * C.
E.2. General Time TLV Structure
A Time TLV may be a packet, message or address block TLV. If it is a
packet or message TLV then it must be a single value TLV as defined
in [3]; if it is an address block TLV then it may be single value or
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multivalue TLV. The specific Time TLVs specified in this document,
in Appendix E.3 are message, and hence single value, TLVs. Note that
even a single value Time TLV may contain a multiple octet <value>
field.
The purpose of a single value Time TLV is to allow a single time
value to be determined by a node receiving an entity containing the
Time TLV, based on its distance from the entity's originator. The
Time TLV may contain information that allows that time value to be a
function of distance, and thus different receiving nodes may
determine different time values. If a receiving node will not be
able to determine its distance from the originating node, then the
form of this Time TLV with a single time code in a <value> field (or
single value subfield) SHOULD be used.
The <value> field of a single value Time TLV is specified, using the
regular expression syntax of [3], by:
<value> = {<time><distance>}*<time>
where:
<time> is an 8 bit field containing a time code as defined in
Appendix E.1.
<distance> is an 8 bit field specifying a distance from the message
originator, in hops.
A single value <value> field thus consists of an odd number of
octets; with a repetition factor of n in the regular expression
syntax it contains 2n+1 octets, thus the <length> field of a single
value Time TLV, which MUST always be present, is given by:
o <length> = 2n+1
A single value <value> field may be thus represented by:
<t_1><d_1><t_2><d_2> ... <t_i><d_i> ... <t_n><d_n><t_default>
<d_1>, ... <d_n>, if present, MUST be a strictly increasing sequence.
Then, at the receiving node's distance from the originator node, the
time value indicated is that represented by the time code:
o <t_1>, if n > 0 and distance <= <d_1>;
o <t_i+1>, if n > 1 and <d_i> < distance <= <d_i+1> for some i such
that 1 <= i < n;
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o <t_default> otherwise, i.e. if n == 0 or distance > <d_n>.
In a multivalue Time TLV, each single value subfield of the
multivalue Time TLV is defined as above. Note that [3] requires that
each single value subfield has the same length (i.e. the same value
of n) but they need not use the same values of <d_1> to <d_n>.
E.3. Message TLVs
Two message TLVs are defined, for signaling message validity time
(VALIDITY_TIME) and message interval (INTERVAL_TIME).
E.3.1. VALIDITY_TIME TLV
A VALIDITY TIME TLV is a message TLV that defines the validity time
of the information carried in the message in which the TLV is
contained. After this time the receiving node MUST consider the
message content to no longer be valid (unless repeated in a later
message). The validity time of a message MAY be specified to depend
on the distance from its originator. (This is appropriate if
messages are sent with different hop limits, so that receiving nodes
at greater distances receive information less frequently and must
treat is as valid for longer.)
A VALIDITY_TIME TLV is an example of a Time TLV specified as in
Appendix E.1.
E.3.2. INTERVAL_TIME TLV
An INTERVAL_TIME TLV is a message TLV that defines the maximum time
before another message of the same type as this message from the same
originator should be received. This interval time MAY be specified
to depend on the distance from the originator. (This is appropriate
if messages are sent with different hop limits, so that receiving
nodes at greater distances have an increased interval time.)
An INTERVAL_TIME TLV is an example of a Time TLV specified as in
Appendix E.1.
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Appendix F. Message Jitter
Since NHDP employs periodic message transmission in order to detect
neighborhoods, and since NHDP is a building block for MANET routing
protocols employing other triggered or periodic message exchanges,
this appendix presents global concerns pertaining to jittering of
MANET control traffic.
F.1. Jitter
In order to prevent nodes in a MANET from simultaneous transmission,
whilst retaining the MANET characteristic of maximum node autonomy, a
randomization of the transmission time of packets by nodes, known as
jitter, MAY be employed. Three jitter mechanisms, which target
different aspects of this problem, MAY be employed, with the aim of
reducing the likelihood of simultaneous transmission, and, if it
occurs, preventing it from continuing.
Three cases exist:
o Periodic message generation;
o Externally triggered message generation;
o Message forwarding.
Each of these cases uses a parameter, denoted MAXJITTER, for the
maximum timing variation that it introduces. If more than one of
these cases is used by a protocol, it MAY use the same or a different
value of MAXJITTER for each case. It also MAY use the same or
different values of MAXJITTER according to message type, and under
different circumstances - in particular if other parameters (such as
message interval) vary.
Issues relating to the value of MAXJITTER are considered in
Appendix F.1.4.
F.1.1. Periodic message generation
When a node generates a message periodically, two successive messages
will be separated by a well-defined interval, denoted
MESSAGE_INTERVAL. A node MAY maintain more than one such interval,
e.g. for different message types or in different circumstances (such
as backing off transmissions to avoid congestion). Jitter MAY be
applied by reducing this delay by a random amount, so that the delay
between consecutive transmissions of a messages of the same type is
equal to (MESSAGE_INTERVAL - jitter), where jitter is the random
value.
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Subtraction of the random value from the message interval ensures
that the message interval never exceeds MESSAGE_INTERVAL, and does
not adversely affect timeouts or other mechanisms which may be based
on message late arrival or failure to arrive. By basing the message
transmission time on the previous transmission time, rather than by
jittering a fixed clock, nodes can become completely desynchronized,
which minimizes their probability of repeated collisions. This is
particularly useful when combined with externally triggered message
generation and rescheduling.
The jitter value SHOULD be taken from a uniform distribution between
zero and MAXJITTER.
Note that a node will know its own MESSAGE_INTERVAL value and can
readily ensure that any MAXJITTER value used satisfies the conditions
in Appendix F.1.4.
F.1.2. Externally triggered message generation
An internal or external condition or event MAY trigger message
generation by a node. Depending upon the protocol, this condition
MAY trigger generation of a single message, initiation of a new
periodic message schedule, or rescheduling of existing periodic
messaging. Collision between externally triggered messages is made
more likely if more than one node is likely to respond to the same
event. To reduce this likelihood, an externally triggered message
MAY be jittered by delaying it by a random duration; an internally
triggered message MAY also be so jittered if appropriate. This delay
SHOULD be generated uniformly in an interval between zero and
MAXJITTER. If periodically transmitted messages are rescheduled,
then this SHOULD be based on this delayed time, with subsequent
messages treated as described in Appendix F.1.1.
When messages are triggered, whether or not they are also
periodically transmitted, a protocol MAY impose a minimum interval
between messages of the same type, denoted MESSAGE_MIN_INTERVAL. It
is however appropriate to also allow this interval to be reduced by
jitter, so that when a message is transmitted the next message is
allowed after a time (MESSAGE_MIN_INTERVAL - jitter), where jitter
SHOULD be generated uniformly in an interval between zero and
MAXJITTER (using a value of MAXJITTER appropriate to periodic message
transmission). This is because otherwise, when external triggers are
more frequent than MESSAGE_MIN_INTERVAL, it takes the role of
MESSAGE_INTERVAL and the arguments applying to jittering of the
latter also apply to the former. This also permits
MESSAGE_MIN_INTERVAL to equal MESSAGE_INTERVAL even when jitter is
used.
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F.1.3. Message forwarding
When a node forwards a message, it may be jittered by delaying it by
a random duration. This delay SHOULD be generated uniformly in an
interval between zero and MAXJITTER.
Unlike the cases of periodically generated and externally triggered
messages, a node is not automatically aware of the message
originator's value of MESSAGE_INTERVAL, which is required to select a
value of MAXJITTER which is known to be valid. This may require
prior agreement as to the value (or minimum value) of
MESSAGE_INTERVAL, may be by inclusion in the message of
MESSAGE_INTERVAL (the time until the next relevant message, rather
than the time since the last message) or be by any other protocol
specific mechanism, which may include estimation of the value of
MESSAGE_INTERVAL based on received message times.
For several possible reasons (differing parameters, message
rescheduling, extreme random values) a node may receive a message
while still waiting to forward an earlier message of the same type
originating from the same node. This is possible without jitter, but
may occur more often with it. The appropriate action to take is
protocol specific (typically to discard the earlier message or to
forward both, possible modifying timing to maintain message order).
In many cases, including [1] and protocols using the full
functionality of [3], messages are transmitted hop by hop in
potentially multi-message packets, and some or all of those messages
may need to be forwarded. For efficiency this should be in a single
packet, and hence the forwarding jitter of all messages received in a
single packet should be the same. (This also requires that a single
value of MAXJITTER is used in this case.) For this to have the
intended uniform distribution it is necessary to choose a single
random jitter for all messages. It is not appropriate to give each
message a random jitter and then to use the smallest of these jitter
values, as that produces a jitter with a non-uniform distribution and
a reduced mean value.
In addition, the protocol may permit messages received in different
packets to be combined, possibly also with locally generated messages
(periodically generated or triggered). However in this case the
purpose of the jitter will be accomplished by choosing any of the
independently scheduled times for these events as the single
forwarding time; this may have to be the earliest time to achieve all
constraints. This is because without combining messages, a
transmission was due at this time anyway.
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F.1.4. Maximum Jitter Determination
In considering how the maximum jitter (one or more instances of
parameter MAXJITTER) may be determined, the following points may be
noted:
o While jitter may resolve the problem of simultaneous
transmissions, the timing changes (in particular the delays) it
introduces will otherwise only have a negative impact on a well-
designed protocol. Thus MAXJITTER should always be minimized,
subject to acceptably achieving its intent.
o When messages are periodically generated, all of the following
that are relevant apply to each instance of MAXJITTER:
* it MUST NOT be greater than MESSAGE_INTERVAL/2;
* it SHOULD be significantly less than MESSAGE_INTERVAL;
* it MUST NOT be greater than MESSAGE_MIN_INTERVAL;
* it SHOULD NOT be greater than MESSAGE_MIN_INTERVAL/2.
o As well as the decision as to whether to use jitter being
dependent on the medium access control and lower layers, the
selection of the MAXJITTER parameter should be appropriate to
those mechanisms.
o As jitter is intended to reduce collisions, greater jitter, i.e.
an increased value of MAXJITTER, is appropriate when the chance of
collisions is greater. This is particularly the case with
increased node density, where node density should be considered
relative to (the square of) the interference range rather than
useful signal range.
o The choice of MAXJITTER used when forwarding messages may also
take into account the expected number of times that the message
may be sequentially forwarded, up to the network diameter in hops.
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Appendix G. Security Considerations
Currently, OLSRv2 does not specify any special security measures. As
a proactive routing protocol, OLSRv2 makes a target for various
attacks. The various possible vulnerabilities are discussed in this
section.
Appendix G.1. Confidentiality
Being a proactive protocol, OLSRv2 periodically diffuses topological
information. Hence, if used in an unprotected wireless network, the
network topology is revealed to anyone who listens to OLSRv2 control
messages.
In situations where the confidentiality of the network topology is of
importance, regular cryptographic techniques, such as exchange of
OLSRv2 control traffic messages encrypted by PGP [5] or encrypted by
some shared secret key, can be applied to ensure that control traffic
can be read and interpreted by only those authorized to do so.
Appendix G.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,
thereby allowing that "secured" and "unsecured" nodes can coexist in
the same network, if desired, or signatures and security information
may be transmitted within the OLSRv2 HELLO and TC messages, using the
TLV mechanism.
Specifically, the authenticity of entire OLSRv2 control messages can
be established through employing IPsec authentication headers,
whereas authenticity of individual links (situations 1 and 3) require
additional security information to be distributed.
An important consideration is, that all control messages in OLSRv2
are transmitted either to all nodes in the neighborhood (HELLO
messages) or broadcast to all nodes in the network (TC messages).
For example, a control message in OLSRv2 is always a point-to-
multipoint transmission. It is therefore important that the
authentication mechanism employed permits that any receiving node can
validate the authenticity of a message. As an analogy, given a block
of text, signed by a PGP private key, then anyone with the
corresponding public key can verify the authenticity of the text.
Appendix G.3. Interaction with External Routing Domains
OLSRv2 does, through the use of TC messages, provide a basic
mechanism for injecting external routing information to the OLSRv2
domain. Appendix A also specifies that routing information can be
extracted from the topology table or the routing table of OLSRv2 and,
potentially, injected into an external domain if the routing protocol
governing that domain permits.
Other than as described in Appendix A, when operating nodes,
connecting OLSRv2 to an external routing domain, care MUST be taken
not to allow potentially insecure and untrustworthy information to be
injected from the OLSRv2 domain to external routing domains. Care
MUST be taken to validate the correctness of information prior to it
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being injected as to avoid polluting routing tables with invalid
information.
A recommended way of extending connectivity from an existing routing
domain to an OLSRv2 routed MANET is to assign an IP prefix (under the
authority of the nodes/gateways connecting the MANET with the exiting
routing domain) exclusively to the OLSRv2 MANET area, and to
configure the gateways statically to advertise routes to that IP
sequence to nodes in the existing routing domain.
Appendix G.4. Node Identity
OLSRv2 does not make any assumption about node addresses, other than
that each node is assumed to have at least one a unique and routable
IP address for each interface that it has which participates in the
MANET.
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Appendix H. Flow and Congestion Control
Due to its proactive nature, the OLSRv2 protocol has a natural
control over the flow of its control traffic. Nodes transmit control
messages at predetermined rates specified and bounded by message
intervals.
OLSRv2 employs [4] for local signalling, embedding MPR selection
advertisement through a simple address block TLV, and node
willingness advertisement (if any) as a single message TLV. OLSRv2
local signalling, therefore, shares the characteristics and
constraints of [4].
Furthermore, the MPR optimization greatly constrains global
signalling overhead from link state diffusion in two ways. First,
the messages that advertise the topology need only contain MPR
selectors, reducing their size as compared to full link state.
Second, the cost of diffusing these messages throughout the network
is greatly reduced as compared to when using classic flooding, since
only MPRs need to forward broadcast messages. In dense networks, the
reduction of control traffic can be of several orders of magnitude
compared to routing protocols using classical flooding [8]. 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 I. 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, Hitachi Labs Europe, France,
<Emmanuel.Baccelli@inria.fr>
o Thomas Heide Clausen, PCRI, 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, <h-satoh@sdl.hitachi.co.jp>
o Philippe Jacquet, INRIA, France, <Philippe.Jacquet@inria.fr>
o Monden Kazuya, Hitachi SDL, Japan, <monden@sdl.hitachi.co.jp>
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 J. Acknowledgements
The authors would like to acknowledge the team behind OLSRv1,
specified in RFC3626, including Anis Laouiti, Pascale Minet, Laurent
Viennot (all at INRIA, France), and Amir Qayyum (Center for Advanced
Research in Engineering, Pakistan) for their contributions.
The authors would like to gratefully acknowledge the following people
for intense technical discussions, early reviews and comments on the
specification and its components: Li Li (CRC), Louise Lamont (CRC),
Joe Macker (NRL), Alan Cullen (BAE Systems), Philippe Jacquet
(INRIA), Khaldoun Al Agha (LRI), Richard Ogier (SRI), Song-Yean Cho
(Samsung Software Center), Shubhranshu Singh (Samsung AIT) 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.lix.polytechnique.fr/Labo/Thomas.Clausen/
Christopher M. Dearlove
BAE Systems Advanced Technology Centre
Phone: +44 1245 242194
Email: chris.dearlove@baesystems.com
URI: http://www.baesystems.com/ocs/sharedservices/atc/
Philippe Jacquet
Project Hipercom, INRIA
Phone: +33 1 3963 5263
Email: philippe.jacquet@inria.fr
URI: http://hipercom.inria.fr/test/Jacquet.htm
The OLSRv2 Design Team
MANET Working Group
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Clausen, et al. Expires August 5, 2007 [Page 72]
