Mobile Ad hoc Networking (MANET) T. Clausen
Internet-Draft LIX, Ecole Polytechnique, France
Intended status: Standards Track C. Dearlove
Expires: September 11, 2008 BAE Systems Advanced Technology
Centre
J. Dean
Naval Research Laboratory
The OLSRv2 Design Team
MANET Working Group
March 10, 2008
MANET Neighborhood Discovery Protocol (NHDP)
draft-ietf-manet-nhdp-06
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Abstract
This document describes a 1-hop and symmetric 2-hop neighborhood
discovery protocol (NHDP) for mobile ad hoc networks (MANETs).
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Applicability Statement . . . . . . . . . . . . . . . . . . . 7
4. Protocol Overview and Functioning . . . . . . . . . . . . . . 8
4.1. Nodes and Interfaces . . . . . . . . . . . . . . . . . . . 9
4.2. Information Base Overview . . . . . . . . . . . . . . . . 9
4.2.1. Local Information Base . . . . . . . . . . . . . . . . 9
4.2.2. Interface Information Bases . . . . . . . . . . . . . 10
4.2.3. Node Information Base . . . . . . . . . . . . . . . . 10
4.3. Signaling Overview . . . . . . . . . . . . . . . . . . . . 11
4.3.1. HELLO Message Generation . . . . . . . . . . . . . . . 11
4.3.2. HELLO Message Content . . . . . . . . . . . . . . . . 11
4.3.3. HELLO Message Processing . . . . . . . . . . . . . . . 12
4.4. Link Quality . . . . . . . . . . . . . . . . . . . . . . . 13
5. Protocol Parameters and Constants . . . . . . . . . . . . . . 14
5.1. Interface Parameters . . . . . . . . . . . . . . . . . . . 14
5.1.1. Message Intervals . . . . . . . . . . . . . . . . . . 14
5.1.2. Information Validity Times . . . . . . . . . . . . . . 15
5.1.3. Link Quality . . . . . . . . . . . . . . . . . . . . . 16
5.1.4. Jitter . . . . . . . . . . . . . . . . . . . . . . . . 17
5.2. Node Parameters . . . . . . . . . . . . . . . . . . . . . 17
5.2.1. Information Validity Time . . . . . . . . . . . . . . 17
5.3. Parameter Change Constraints . . . . . . . . . . . . . . . 17
5.4. Constants . . . . . . . . . . . . . . . . . . . . . . . . 19
6. Local Information Base . . . . . . . . . . . . . . . . . . . . 20
6.1. Local Interface Set . . . . . . . . . . . . . . . . . . . 20
6.2. Removed Interface Address Set . . . . . . . . . . . . . . 20
7. Interface Information Base . . . . . . . . . . . . . . . . . . 21
7.1. Link Set . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.2. 2-Hop Set . . . . . . . . . . . . . . . . . . . . . . . . 22
8. Node Information Base . . . . . . . . . . . . . . . . . . . . 23
8.1. Neighbor Set . . . . . . . . . . . . . . . . . . . . . . . 23
8.2. Lost Neighbor Set . . . . . . . . . . . . . . . . . . . . 23
9. Local Information Base Changes . . . . . . . . . . . . . . . . 24
9.1. Adding an Interface . . . . . . . . . . . . . . . . . . . 24
9.2. Removing an Interface . . . . . . . . . . . . . . . . . . 24
9.3. Adding an Address to an Interface . . . . . . . . . . . . 25
9.4. Removing an Address from an Interface . . . . . . . . . . 26
10. Packets and Messages . . . . . . . . . . . . . . . . . . . . . 27
10.1. HELLO Messages . . . . . . . . . . . . . . . . . . . . . . 27
10.1.1. Address Blocks . . . . . . . . . . . . . . . . . . . . 28
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11. HELLO Message Generation . . . . . . . . . . . . . . . . . . . 30
11.1. HELLO Message Specification . . . . . . . . . . . . . . . 30
11.2. HELLO Message Transmission . . . . . . . . . . . . . . . . 32
11.2.1. HELLO Message Jitter . . . . . . . . . . . . . . . . . 32
12. HELLO Message Processing . . . . . . . . . . . . . . . . . . . 33
12.1. Updating the Neighbor Set . . . . . . . . . . . . . . . . 34
12.2. Updating the Lost Neighbor Set . . . . . . . . . . . . . . 35
12.3. Updating the Link Set . . . . . . . . . . . . . . . . . . 35
12.4. Updating the 2-Hop Set . . . . . . . . . . . . . . . . . . 37
13. Other Information Base Changes . . . . . . . . . . . . . . . . 39
13.1. Link Tuple Not Symmetric . . . . . . . . . . . . . . . . . 39
13.2. Link Tuple Symmetric . . . . . . . . . . . . . . . . . . . 40
13.3. Link Tuple Heard Timeout . . . . . . . . . . . . . . . . . 41
14. Link Quality . . . . . . . . . . . . . . . . . . . . . . . . . 42
14.1. Deployment Without Link Quality . . . . . . . . . . . . . 42
14.2. Basic Principles of Link Quality . . . . . . . . . . . . . 42
14.3. When Link Quality Changes . . . . . . . . . . . . . . . . 43
14.4. Updating Link Quality . . . . . . . . . . . . . . . . . . 44
15. Proposed Values for Parameters and Constants . . . . . . . . . 45
15.1. Message Interval Interface Parameters . . . . . . . . . . 45
15.2. Information Validity Time Interface Parameters . . . . . . 45
15.3. Information Validity Time Node Parameters . . . . . . . . 45
15.4. Link Quality Interface Parameters . . . . . . . . . . . . 45
15.5. Jitter Interface Parameters . . . . . . . . . . . . . . . 45
15.6. Constants . . . . . . . . . . . . . . . . . . . . . . . . 46
16. Security Considerations . . . . . . . . . . . . . . . . . . . 47
16.1. Invalid HELLO messages . . . . . . . . . . . . . . . . . . 47
17. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 49
17.1. Message Types . . . . . . . . . . . . . . . . . . . . . . 49
17.2. TLV Types . . . . . . . . . . . . . . . . . . . . . . . . 49
17.3. LINK_STATUS and OTHER_NEIGHB Values . . . . . . . . . . . 50
18. References . . . . . . . . . . . . . . . . . . . . . . . . . . 51
18.1. Normative References . . . . . . . . . . . . . . . . . . . 51
18.2. Informative References . . . . . . . . . . . . . . . . . . 51
Appendix A. Address Block TLV Combinations . . . . . . . . . . . 52
Appendix B. HELLO Message Example . . . . . . . . . . . . . . . . 53
Appendix C. Constraints . . . . . . . . . . . . . . . . . . . . . 56
Appendix D. Flow and Congestion Control . . . . . . . . . . . . . 59
Appendix E. Contributors . . . . . . . . . . . . . . . . . . . . 60
Appendix F. Acknowledgements . . . . . . . . . . . . . . . . . . 61
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1. Introduction
This document describes a neighborhood discovery protocol (NHDP) for
a mobile ad hoc network (MANET) [RFC2501]. This protocol uses an
exchange of HELLO messages in order that each node can determine the
presence and status of its 1-hop and symmetric 2-hop neighbors.
Messages are defined as instances of the specification [packetbb].
This neighborhood information is recorded in the form of Information
Bases. These may be used by other protocols, such as MANET routing
protocols, for determining local connectivity and node configuration.
This protocol is designed to maintain this information in the
presence of a dynamic network topology.
This protocol makes no assumptions about the underlying link layer,
other than support of link local broadcast or multicast. Link layer
information may be used if available and applicable.
This protocol is based on the neighborhood discovery process
contained in the Optimized Link State Routing Protocol (OLSR)
[RFC3626].
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2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [RFC2119].
The terms "packet", "message", "address", "address block", "TLV", and
"TLV block" in this document are to be interpreted as described in
[packetbb].
Additionally, this document uses the following terminology:
Node - A MANET router which implements this neighborhood discovery
protocol.
Interface - A network device, configured and assigned one or more IP
addresses.
Address - An address, as recorded in the Information Bases specified
by this protocol, and included in HELLO messages generated by this
protocol, may be either an address or an address prefix. These
can be represented as a single address object in a HELLO message,
as defined by [packetbb]. An address so represented is considered
to have a prefix length equal to its length (in bits) when
considered as an address object, and a similar convention is used
in the Information Bases specified by this protocol. Two
addresses (address objects) are considered equal only if their
prefix lengths are also equal.
MANET interface - An interface participating in a MANET and using
this neighborhood discovery protocol. A node may have several
MANET interfaces.
Heard - A MANET interface of node X is considered heard on a MANET
interface of a node Y if the latter can receive traffic from the
former.
Link - A pair of MANET interfaces from two different nodes, where at
least one interface is heard by the other.
Symmetric link - A link where both MANET interfaces are heard by the
other.
1-hop neighbor - A node X is a 1-hop neighbor of a node Y if a MANET
interface of node X is heard by a MANET interface of node Y.
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Symmetric 1-hop neighbor - A node X is a symmetric 1-hop neighbor of
a node Y if a symmetric link exists between a MANET interface on
node X and a MANET interface on node Y.
Symmetric 2-hop neighbor - A node X is a symmetric 2-hop neighbor of
a node Y if node X is a symmetric 1-hop neighbor of a symmetric
1-hop neighbor of node Y, but is not node Y itself.
1-hop neighborhood - The 1-hop neighborhood of a node X is the set
of the 1-hop neighbors of node X.
Symmetric 1-hop neighborhood - The symmetric 1-hop neighborhood of a
node X is the set of the symmetric 1-hop neighbors of node X.
Symmetric 2-hop neighborhood - The symmetric 2-hop neighborhood of a
node X is the set of the symmetric 2-hop neighbors of node X.
(This may include nodes in the 1-hop neighborhood, or even in the
symmetric 1-hop neighborhood, of node X.)
Constant - A constant is a numerical value which MUST be the same
for all MANET interfaces of all nodes in the MANET, at all times.
Interface parameter - An interface parameter is a boolean or
numerical value, specified separately for each MANET interface of
each node. A node MAY change interface parameter values at any
time, subject to some constraints.
Node parameter - A node parameter is a boolean or numerical value,
specified for each node. A node MAY change node parameter values
at any time, subject to some constraints.
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3. Applicability Statement
This protocol:
o Is applicable to networks, especially wireless networks, in which
unknown neighbors (i.e. other nodes with which direct
communication can be established) can be reached by local
broadcast or multicast packets.
o Is designed to work in networks with a dynamic topology, and in
which messages may be lost, such as due to collisions in wireless
networks.
o Supports nodes that each have one or more participating MANET
interfaces. The set of a node's interfaces may change over time.
Each interface may have one or more interface addresses, and these
may also be dynamically changing.
o Can use the link local multicast address and either the "manet"
UDP port or the "manet" IP protocol number specified in
[manet-iana].
o Uses the packet and message formats specified in [packetbb]. Such
packets may contain messages specified by this protocol as well as
other protocols.
o Specifies signaling using HELLO messages. The necessary contents
of these messages are defined in this specification, and may be
extended using the TLV mechanisms described in [packetbb].
o Can use relevant link layer information if it is available.
o Provides each node with local topology information up to two hops
away. This information is made available to other protocols, of
which this protocol may be a part, in Information Bases defined in
this specification.
o Is designed to work in a completely distributed manner, and does
not depend on any central entity.
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4. Protocol Overview and Functioning
The objective of this protocol is, for each node:
o To identify other nodes with which bidirectional links can be
established (symmetric 1-hop neighbors).
o To agree on the status of such links with the corresponding
symmetric 1-hop neighbor.
o To find the node's symmetric 2-hop neighbors.
o To record this information in Information Bases that can be used
by other protocols, of which this neighborhood discovery protocol
may be a part.
These objectives are achieved using local (one hop) signaling that:
o Advertises the presence of a node and its interfaces.
o Discovers links with adjacent nodes.
o Performs bidirectionality checks on the discovered links.
o Advertises discovered links, and whether each is symmetric, to its
1-hop neighbors, and hence discovers symmetric 2-hop neighbors.
This specification defines, in turn:
o Parameters and constants used by the protocol. Parameters used by
this protocol may be, where appropriate, specific to a MANET
interface. This protocol allows all parameters to be changed
dynamically.
o The Information Bases describing local interfaces, discovered
links and their status, current and former 1-hop neighbors, and
symmetric 2-hop neighbors.
o The format of the HELLO message that is used for local signaling.
o The generation of HELLO messages from some of the information in
the Information Bases.
o The updating of the Information Bases according to received HELLO
messages and other events.
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4.1. Nodes and Interfaces
In order for a node to participate in a MANET, it MUST have at least
one, and possibly more, MANET interfaces. Each MANET interface:
o Is characterized by a set of interface parameters, defining the
behavior of this MANET interface. Each MANET interface MAY be
individually parameterized.
o Has an Interface Information Base, recording information regarding
links to this MANET interface and symmetric 2-hop neighbors which
can be reached through such links.
o Generates and processes HELLO messages, according to the interface
parameters for that MANET interface.
In addition to a set of MANET interfaces as described above, each
node has:
o A Local Information Base, containing the addresses of the
interfaces (MANET and non-MANET) of this node. The contents of
this Information Base are not changed by signaling.
o A Node Information Base, recording information regarding current
and recently lost 1-hop neighbors of this node.
A node may have both MANET interfaces and non-MANET interfaces.
Interfaces of both of these types are recorded in a node's Local
Information Base, which is used, but not updated, by the signaling of
this protocol.
4.2. Information Base Overview
Each node maintains the Information Bases described in the following
sections. These are used for describing the protocol in this
document. An implementation of this protocol MAY maintain this
information in the indicated form, or in any other organization which
offers access to this information. In particular note that it is not
necessary to remove Tuples from Sets at the exact time indicated,
only to behave as if the Tuples were removed at that time.
4.2.1. Local Information Base
Each node maintains a Local Information Base, which contains:
o The Local Interface Set, which consists of Local Interface Tuples,
each of which records the addresses of an interface (MANET or non-
MANET) of the node.
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o The Removed Interface Address Set, which consists of Removed
Interface Address Tuples, each of which records a recently used
address of an interface (MANET or non-MANET) of the node.
4.2.2. Interface Information Bases
Each node maintains, for each of its MANET interfaces, an Interface
Information Base, which contains:
o A Link Set, which records information about current and recently
lost links between this interface and MANET interfaces of 1-hop
neighbors. The Link Set consists of Link Tuples, each of which
contains information about a single link. Recently lost links are
recorded so that they can be advertised in HELLO messages,
accelerating their removal from relevant 1-hop neighbors' Link
Sets. Link quality information, if used and available, is
recorded in Link Tuples and may indicate that links are treated as
lost.
o A 2-Hop Set, which records the existence of bidirectional links
between symmetric 1-hop neighbors of this MANET interface and
other nodes (symmetric 2-hop neighbors). The 2-Hop Set consists
of 2-Hop Tuples, each of which records an interface address of a
symmetric 2-hop neighbor, and all interface addresses of the
corresponding symmetric 1-hop neighbor. The 2-Hop Set is updated
by the signaling of this protocol, but is not itself reported in
that signaling.
4.2.3. Node Information Base
Each node maintains a Node Information Base, which contains:
o The Neighbor Set, which records 1-hop neighbors, each of which
must be currently heard, although this may be over a link with
insufficient link quality. The Neighbor Set consists of Neighbor
Tuples, each of which records all interface addresses (whether
directly linked or not) of a single 1-hop neighbor. Neighbor
Tuples are maintained as long as there are corresponding current
Link Tuples.
o The Lost Neighbor Set, which records recently lost symmetric 1-hop
neighbors. The Lost Neighbor Set consists of Lost Neighbor
Tuples, each of which records an interface address of such a
neighbor. These are recorded so that they can be advertised in
HELLO messages, accelerating their removal from other nodes' 2-Hop
Sets.
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4.3. Signaling Overview
This protocol contains a signaling mechanism for maintaining the
Interface Information Bases and the Node Information Base. If
information from the link layer, or any other source, is available
and appropriate, it may also be used to update these Information
Bases. Such updates are subject to the constraints specified in
Appendix C.
Signaling consists of a single type of message, known as a HELLO
message. Each node generates HELLO messages on each of its MANET
interfaces. Each HELLO message identifies that MANET interface, and
reports the other interfaces (MANET and non-MANET) of the node. Each
HELLO message includes information from the Link Set of the Interface
Information Base of the MANET interface, and from the Node
Information Base.
4.3.1. HELLO Message Generation
HELLO messages are generated by a node for each of its MANET
interfaces, and MAY be sent:
o Proactively, at a regular interval, known as HELLO_INTERVAL.
HELLO_INTERVAL may be fixed, or may be dynamic. For example
HELLO_INTERVAL may be backed off due to congestion or network
stability.
o As a response to a change in the node itself, or its 1-hop
neighborhood, for example on first becoming active or in response
to a new, broken, or changed status link.
o In a combination of these proactive and responsive mechanisms.
Jittering of HELLO message generation and transmission, as described
in Section 11.2, SHOULD be used if appropriate.
HELLO messages are generated independently on each MANET interface of
a node. HELLO messages MAY be scheduled independently for each MANET
interface, or, interface parameters permitting, using the same
schedule for all MANET interfaces of a node.
4.3.2. HELLO Message Content
Each HELLO message sent over a MANET interface need not contain all
of the information appropriate to that MANET interface, however:
o A HELLO message MUST contain all of the addresses in the Local
Interface Set of the node to which the MANET interface belongs.
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o Within every time interval of length REFRESH_INTERVAL, the HELLO
messages sent on each MANET interface of a node MUST collectively
include:
* All of the relevant information in the Link Set of the
Interface Information Base of that MANET interface.
* All of the relevant information in the Node Information Base of
that node.
This applies to otherwise purely responsive nodes as well as to
proactive nodes. In either case it means that all information
appropriate to that MANET interface will have always been
transmitted, in one or more HELLO messages, since the time
REFRESH_INTERVAL ago.
o A HELLO message MUST include a VALIDITY_TIME message TLV that
indicates the length of time for which the message content is to
be considered valid, and included in the receiving node's
Interface Information Base.
o A periodically generated HELLO message SHOULD include an
INTERVAL_TIME message TLV that indicates the current value of
HELLO_INTERVAL for that MANET interface, i.e. the period within
which a further HELLO message is guaranteed to be sent on that
MANET interface.
o Additional information may be added by a protocol using this
protocol using the TLV mechanisms described in [packetbb]. For
example, if multipoint relays (MPRs) are to be calculated
similarly to as in OLSR [RFC3626] and signaled to neighbors, then
this information may be added to HELLO messages using an address
block TLV.
4.3.3. HELLO Message Processing
All HELLO messages received by a node are used to update:
o The Interface Information Base for the MANET interface on which
that HELLO message is received.
o The Node Information Base.
Specifically:
o The node ensures that there is a single Neighbor Tuple
corresponding to the originator of that HELLO message.
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o If a Link Tuple corresponding to the link on which that HELLO
message was received exists, then its duration is extended,
otherwise such a Link Tuple is created. If the HELLO message
indicates that the receiving MANET interface has been heard, then
the link is considered symmetric, or its duration as symmetric is
extended. If the HELLO message indicates that the receiving MANET
interface is lost, then the link is no longer considered
symmetric. In this case one or more Lost Neighbor Tuples may be
created.
o If the link on which the HELLO message is received is symmetric,
then any symmetrically advertised neighbors in the HELLO message
are added to the 2-Hop Set for the receiving interface, or if
already present, the durations of the corresponding 2-Hop Tuples
are extended.
In all cases the processing takes account of unexpected and erroneous
information in the HELLO message, maintaining the constraints
specified in Appendix C.
4.4. Link Quality
Some links in a MANET may be marginal, e.g. due to adverse wireless
propagation. In order to avoid using such marginal links, a link
quality is associated with each link in the Link Set, and links with
insufficient link quality are considered lost. Modifying the link
quality of a link is OPTIONAL. If link quality is not to be modified
it MUST be set to indicate an always usable quality link. Link
quality information is only used locally, it is not used in
signaling, and nodes may interoperate whether they are using the
same, different, or no, link quality information.
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5. Protocol Parameters and Constants
The parameters and constants used in this specification are described
in this section.
5.1. Interface Parameters
The interface parameters used by this specification may be classified
into the following four categories:
o Message intervals
o Information validity times
o Link quality
o Jitter
These are detailed in the following sections.
Different MANET interfaces (on the same or on different nodes) MAY
employ different interface parameter values, and may change their
interface parameter values dynamically, subject to the constraints
given in this section. A particular case is where all MANET
interfaces on all MANET nodes within a given MANET employ the same
set of interface parameter values.
5.1.1. Message Intervals
The following interface parameters regulate HELLO message
transmissions over a given MANET interface.
HELLO messages serve two principal functions:
o To advertise this node's own addresses to its 1-hop neighbors.
The frequency of these advertisements is regulated by the
interface parameters HELLO_INTERVAL and HELLO_MIN_INTERVAL.
o To advertise this node's knowledge of each of its 1-hop neighbors.
The frequency of the advertisement of each such neighbor is
regulated by the interface parameter REFRESH_INTERVAL.
Specifically, these parameters are as follows:
HELLO_INTERVAL - is the maximum time between the transmission of two
successive HELLO messages on this MANET interface. If using
periodic transmission of HELLO messages, these SHOULD be at a
separation of HELLO_INTERVAL, possibly modified by jitter as
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specified in [RFC5148].
HELLO_MIN_INTERVAL - is the minimum interval between transmission of
two successive HELLO messages, on this MANET interface. (This
minimum interval MAY be modified by jitter, as defined in
[RFC5148].)
REFRESH_INTERVAL - is the maximum interval between advertisements in
a HELLO message of each 1-hop neighbor address and its status. In
all intervals of length REFRESH_INTERVAL, a node MUST include all
1-hop neighbor information which it is specified as sending in at
least one HELLO message on this MANET interface.
The following constraints apply to these interface parameters:
o HELLO_INTERVAL > 0
o HELLO_MIN_INTERVAL >= 0
o HELLO_INTERVAL >= HELLO_MIN_INTERVAL
o REFRESH_INTERVAL >= HELLO_INTERVAL
o If INTERVAL_TIME message TLVs as defined in [timetlv] are included
in HELLO messages, then HELLO_INTERVAL MUST be representable as
described in [timetlv].
If REFRESH_INTERVAL > HELLO_INTERVAL, then a node may distribute its
neighbor advertisements between HELLO messages in any manner, subject
to the constraints above.
For a node to employ this protocol in a purely responsive manner on a
MANET interface, REFRESH_INTERVAL and HELLO_INTERVAL SHOULD both be
set to a value such that a responsive HELLO message is always
expected in a shorter period than this value.
5.1.2. Information Validity Times
The following interface parameters manage the validity time of link
information:
L_HOLD_TIME - is the period of advertisement, on this MANET
interface, of former 1-hop neighbor addresses as lost in HELLO
messages, allowing recipients of these HELLO messages to
accelerate removal of information from their Link Sets.
L_HOLD_TIME can be set to zero if accelerated information removal
is not required.
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H_HOLD_TIME - is used as the value in the VALIDITY_TIME message TLV
included in all HELLO messages on this MANET interface.
The following constraints apply to these interface parameters:
o L_HOLD_TIME >= 0
o H_HOLD_TIME >= REFRESH_INTERVAL
o If HELLO messages can be lost then both SHOULD be significantly
greater than REFRESH_INTERVAL.
o H_HOLD_TIME MUST be representable as described in [timetlv].
5.1.3. Link Quality
The following interface parameters manage the usage of link quality
(see Section 4.4):
HYST_ACCEPT - is the link quality threshold at or above which a link
becomes usable, if it was not already so.
HYST_REJECT - is the link quality threshold below which a link
becomes unusable, if it was not already so.
INITIAL_QUALITY - is the initial quality of a newly identified link.
INITIAL_PENDING - if true, then a newly identified link is
considered pending, and is not usable until the link quality has
reached or exceeded the HYST_ACCEPT threshold.
The following constraints apply to these interface parameters:
o 0 <= HYST_REJECT <= HYST_ACCEPT <= 1
o 0 <= INITIAL_QUALITY <= 1.
o If link quality is not updated, then INITIAL_QUALITY >=
HYST_ACCEPT.
o If INITIAL_QUALITY >= HYST_ACCEPT, then INITIAL_PENDING == false.
o If INITIAL_QUALITY < HYST_REJECT, then INITIAL_PENDING == true.
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5.1.4. Jitter
If jitter, as defined in [RFC5148], is used then these parameters are
as follows:
HP_MAXJITTER - represents the value of MAXJITTER used in [RFC5148]
for periodically generated HELLO messages on this MANET interface.
HT_MAXJITTER - represents the value of MAXJITTER used in [RFC5148]
for externally triggered HELLO messages on this MANET interface.
For constraints on these interface parameters see [RFC5148].
5.2. Node Parameters
The two node parameters defined by this specification are in the
category of information validity time.
5.2.1. Information Validity Time
The following node parameter manages the validity time of lost
symmetric 1-hop neighbor information:
N_HOLD_TIME - is used as the period during which former 1-hop
neighbor addresses are advertised as lost in HELLO messages,
allowing recipients of these HELLO messages to accelerate removal
of information from their 2-Hop Sets. N_HOLD_TIME can be set to
zero if accelerated information removal is not required.
I_HOLD_TIME - is the period for which a recently used local
interface address is recorded.
The following constraints applies to these node parameters:
o N_HOLD_TIME >= 0
o I_HOLD_TIME >= 0
5.3. Parameter Change Constraints
This section presents guidelines, applicable if protocol parameters
are changed dynamically.
HELLO_INTERVAL
* If the HELLO_INTERVAL for a MANET interface increases, then the
next HELLO message on this MANET interface MUST be generated
according to the previous, shorter, HELLO_INTERVAL. Additional
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subsequent HELLO messages MAY be generated according to the
previous, shorter, HELLO_INTERVAL (but MUST include times
according to current parameters).
* If the HELLO_INTERVAL for a MANET interface decreases, then the
following HELLO messages on this MANET interface MUST be
generated according to this current, shorter, HELLO_INTERVAL.
REFRESH_INTERVAL
* If the REFRESH_INTERVAL for a MANET interface increases, then
the content of subsequent HELLO messages must be organized such
that the specification of the old value of REFRESH_INTERVAL is
satisfied for a further period equal to the old value of
REFRESH_INTERVAL.
* If the REFRESH_INTERVAL for a MANET interface decreases, then
it MAY be necessary to reschedule HELLO message generation on
that MANET interface, in order that the specification of
REFRESH_INTERVAL is satisfied from the time of change.
HYST_ACCEPT and HYST_REJECT
* If HYST_ACCEPT or HYST_REJECT changes, then the appropriate
actions for link quality change, as specified in Section 14.3
MUST be taken.
L_HOLD_TIME
* If L_HOLD_TIME changes, then L_time for all relevant Link
Tuples MUST be changed.
N_HOLD_TIME
* If N_HOLD_TIME changes, then NL_time for all relevant Lost
Neighbor Tuples MUST be changed.
HP_MAXJITTER
* If HP_MAXJITTER changes, then the periodic HELLO message
schedule on this MANET interface MAY be changed.
HT_MAXJITTER
* If HT_MAXJITTER changes, then externally triggered HELLO
messages on this MANET interface MAY be rescheduled.
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5.4. Constants
The constant C (time granularity) is used as specified in [timetlv].
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6. Local Information Base
A node maintains a Local Information Base that records information
about its interfaces (MANET and non-MANET). Each interface MUST have
at least one address, and MAY have more than one address.
The Local Information Base is not modified by signaling. If a node's
interface configuration changes, then the Local Information Base MUST
reflect these changes. This MAY also result in signaling to
advertise these changes.
6.1. Local Interface Set
A node's Local Interface Set records its local interfaces. It
consists of Local Interface Tuples, one per interface:
(I_local_iface_addr_list, I_manet)
where:
I_local_iface_addr_list is an unordered list of the addresses of
this interface.
I_manet is a boolean flag, describing if this interface is a MANET
interface.
6.2. Removed Interface Address Set
A node's Removed Interface Address Set records addresses which were
recently local interface addresses. If a node's interface addresses
are immutable then this set is always empty and MAY be omitted. It
consists of Removed Interface Address Tuples, one per address:
(IR_local_iface_addr, IR_time)
where:
IR_local_iface_addr is a recently used address of an interface of
this node.
IR_time specifies when this Tuple expires and MUST be removed.
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7. Interface Information Base
A node maintains an Interface Information Base for each of its MANET
interfaces. This records information about links to that MANET
interface and symmetric 2-hop neighbors which can be reached in two
hops using those links as the first hop. The Interface Information
Base includes the Link Set and the 2-Hop Set.
A MANET interface address can be present as of both a 1-hop neighbor
and a symmetric 2-hop neighbor. This allows the node with this MANET
interface address to be immediately considered as a symmetric 2-hop
neighbor if it fails to be a symmetric 1-hop neighbor.
7.1. Link Set
A node's Link Set records links from other nodes which are, or
recently were, 1-hop neighbors. It consists of Link Tuples, each
representing a single link:
(L_neighbor_iface_addr_list, L_HEARD_time, L_SYM_time,
L_quality, L_pending, L_lost, L_time)
where:
L_neighbor_iface_addr_list is an unordered list of the addresses of
the MANET interface of the 1-hop neighbor;
L_HEARD_time is the time until which the MANET interface of the
1-hop neighbor would be considered heard if not considering link
quality;
L_SYM_time is the time until which the link to the 1-hop neighbor
would be considered symmetric if not considering link quality;
L_quality is a dimensionless number between 0 (inclusive) and 1
(inclusive) describing the quality of a link; a greater value of
L_quality indicating a higher quality link;
L_pending is a boolean flag, describing if a link is considered
pending (i.e. a candidate, but not yet established, link);
L_lost is a boolean flag, describing if a link is considered lost
due to link quality;
L_time specifies when this Tuple expires and MUST be removed.
The status of the link, as obtained through HELLO message exchange,
and also taking link quality into account is denoted L_status.
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L_status can take the values PENDING, HEARD, SYMMETRIC and LOST. The
values LOST, SYMMETRIC and HEARD are defined in Section 17.3. The
value PENDING is never used in a message, it is only used locally by
a node, and any value distinct from LOST, SYMMETRIC and HEARD may be
used.
L_status is defined by:
1. If L_pending is true, then L_status = PENDING;
2. otherwise, if L_lost is true, then L_status = LOST;
3. otherwise, if L_SYM_time is not expired, then L_status =
SYMMETRIC;
4. otherwise, if L_HEARD_time is not expired, then L_status = HEARD;
5. otherwise, L_status = LOST.
7.2. 2-Hop Set
A node's 2-Hop Set records symmetric 2-hop neighbors, and the
symmetric links to symmetric 1-hop neighbors through which the
symmetric 2-hop neighbors can be reached. It consists of 2-Hop
Tuples, each representing a single interface address of a symmetric
2-hop neighbor, and a single MANET interface of a symmetric 1-hop
neighbor.
(N2_neighbor_iface_addr_list, N2_2hop_iface_addr, N2_time)
where:
N2_neighbor_iface_addr_list is an unordered list of the addresses of
the MANET interface of the symmetric 1-hop neighbor from which
this information was received;
N2_2hop_iface_addr is an address of an interface of a symmetric
2-hop neighbor which has a symmetric link (using any MANET
interface) to the indicated symmetric 1-hop neighbor;
N2_time specifies when this Tuple expires and MUST be removed.
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8. Node Information Base
Each node maintains a Node Information Base that records information
about addresses of current and recently symmetric 1-hop neighbors.
8.1. Neighbor Set
A node's Neighbor Set records all interface addresses of each 1-hop
neighbor. It consists of Neighbor Tuples, each representing a single
1-hop neighbor:
(N_neighbor_iface_addr_list, N_symmetric)
where:
N_neighbor_iface_addr_list is an unordered list of the interface
addresses of a 1-hop neighbor;
N_symmetric is a boolean flag, describing if this is a symmetric
1-hop neighbor.
8.2. Lost Neighbor Set
A node's Lost Neighbor Set records addresses of all interfaces of
nodes which recently were symmetric 1-hop neighbors, but are now
advertised as lost. It consists of Lost Neighbor Tuples, each
representing a single such address:
(NL_neighbor_iface_addr, NL_time)
where:
NL_neighbor_iface_addr is an address of an interface of a node which
recently was a symmetric 1-hop neighbor of this node;
NL_time specifies when this Tuple expires and MUST be removed.
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9. Local Information Base Changes
The Local Information Base MUST change to respond to changes in the
node's local interface configuration. The node MUST update its
Interface and Node Information Bases in response to such changes. If
any changes in the Interface and Node Information Bases satisfy any
of the conditions described in Section 13, then those changes must be
applied immediately, unless noted otherwise.
A node MAY transmit HELLO messages in response to these changes.
9.1. Adding an Interface
If an interface is added to the node then this is indicated by the
addition of a Local Interface Tuple to the Local Interface Set. If
the new interface is a MANET interface then an initially empty
Interface Information Base MUST be created for this new MANET
interface. The actions in Section 9.3 MUST be taken for each address
of this added interface. A HELLO message MAY be sent on all MANET
interfaces, it SHOULD be sent on the new interface if it is a MANET
interface. If using scheduled messages, then a message schedule MUST
be established on a new MANET interface.
9.2. Removing an Interface
If an interface is removed from the node, then this MUST result in
changes to the Local Information Base and the Node Information Base
as follows:
1. Identify the Local Interface Tuple that corresponds to the
interface to be removed.
2. For each address (henceforth removed address) in the
I_local_iface_addr_list of that Local Interface Tuple, create a
Removed Interface Address Tuple with:
* IR_local_iface_addr = removed address;
* IR_time = current time + I_HOLD_TIME.
3. Remove that Local Interface Tuple from the Local Interface Set.
4. If the interface to be removed is a MANET interface (i.e. with
I_manet == true) then:
1. Remove the Interface Information Base for that MANET
interface;
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2. All Neighbor Tuples for which none of the addresses in its
N_neighbor_iface_addr_list are found in any
L_neighbor_iface_addr_list in any remaining Link Set, are
removed.
If a node removes the Local Interface Tuple that contains the
interface address that is used to define the node's originator
address, as defined in [packetbb], then the node MAY change
originator address.
If the removed interface is the last MANET interface of the node,
then there will be no remaining Interface Information Bases, and the
node will longer participate in this protocol.
After removing the interface and making these changes, a HELLO
message MAY be sent on all remaining MANET interfaces.
9.3. Adding an Address to an Interface
If an address is added to an interface then this is indicated by the
addition of an address to the appropriate I_local_iface_addr_list.
The following changes MUST be made to the Information Bases:
1. The Neighbor Tuples, if any, whose N_neighbor_iface_addr_list
contains the added address, are removed.
2. Any Link Tuples, in any Link Set, whose
L_neighbor_iface_addr_list contains:
* the added address; OR
* any address in the N_neighbor_iface_addr_list of the removed
Neighbor Tuples, if any
are removed; apply Section 13.1, but not Section 13.3.
3. Any Lost Neighbor Tuples whose NL_neighbor_iface_addr is the
added address, are removed.
4. Any 2-Hop Tuples whose N2_2hop_iface_addr is the added address,
are removed.
After adding the address and making these changes, a HELLO message
MAY be sent on all MANET interfaces.
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9.4. Removing an Address from an Interface
If an address (henceforth removed address) is removed from an
interface then:
1. Identify the Local Interface Tuple that corresponds to the
interface to be removed.
2. If this is the only address of that interface (the only address
in the corresponding I_local_iface_addr_list) then remove that
interface as specified in Section 9.2.
3. Otherwise:
1. Remove the removed address from this I_local_iface_addr_list.
2. Create a Removed Interface Address Tuple with:
+ IR_local_iface_addr = removed address;
+ IR_time = current time + I_HOLD_TIME.
If a node removes the interface address that is used to define the
node's originator address, as defined in [packetbb], then the node
MAY change originator address.
After removing the address and making these changes, a HELLO message
MAY be sent on all MANET interfaces.
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10. Packets and Messages
The packet and message format used by this protocol is defined in
[packetbb], which is used with the following considerations:
o This protocol specifies one message type, the HELLO message.
o HELLO message header options MAY be used as specified by a
protocol which uses this neighborhood discovery protocol.
o HELLO messages MUST NOT be forwarded.
o HELLO messages MAY be included in multi-message packets as
specified in [packetbb].
o Packet header options MAY be used as specified by a protocol which
uses this neighborhood discovery protocol.
o Received HELLO messages MUST be parsed in accordance with
[packetbb]. A HELLO message which is not in conformance with
[packetbb] MUST be discarded.
o This protocol specifies three address block TLVs. It also uses
two message TLVs defined in [timetlv]. These five TLV types are
all defined only with Type Extension == 0. TLVs of other types,
and of these types but without Type Extension == 0, are ignored by
this protocol. All references in this protocol to, for example, a
TLV with Type == LINK_STATUS, are to be considered as referring to
a TLV with Type == LINK_STATUS and Type Extension == 0.
10.1. HELLO Messages
A HELLO message MUST contain:
o A VALIDITY_TIME message TLV as specified in [timetlv],
representing H_HOLD_TIME for the transmitting MANET interface.
The options included in [timetlv] for representing zero and
infinite times MUST NOT be used.
A HELLO message which is transmitted periodically SHOULD contain, and
otherwise MAY contain:
o An INTERVAL_TIME message TLV as specified in [timetlv],
representing HELLO_INTERVAL for the transmitting MANET interface.
The options included in [timetlv] for representing zero and
infinite times MUST NOT be used.
A HELLO message MAY contain:
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o One or more address blocks, each with an associated TLV block.
o Other message TLVs.
10.1.1. Address Blocks
All addresses in a node's Local Interface Set (i.e. in any
I_local_iface_addr_list) MUST be included in the address blocks in
all generated HELLO messages with the following exception. If the
MANET interface on which the HELLO message is to be sent has a single
interface address with maximum prefix length then that address MAY be
omitted. All addresses of the node's interfaces included in an
address block MUST be associated with a TLV with Type == LOCAL_IF, as
defined in Table 1.
+----------+--------+-----------------------------------------------+
| Name | Value | Description |
| | Length | |
+----------+--------+-----------------------------------------------+
| LOCAL_IF | 1 | Specifies that the address is an address |
| | octet | associated with the interface on which the |
| | | message was sent (THIS_IF), another interface |
| | | of the sending node (OTHER_IF), or an |
| | | unspecified interface of the sending node |
| | | (UNSPEC_IF). |
+----------+--------+-----------------------------------------------+
Table 1
Note that the value UNSPEC_IF is not used by this protocol. It is
provided for an expected alternative use of this TLV.
Address blocks MAY contain current or recently lost 1-hop neighbors'
interface addresses, each of which is associated with address block
TLVs as described in Table 2.
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+--------------+--------+-------------------------------------------+
| Name | Value | Description |
| | Length | |
+--------------+--------+-------------------------------------------+
| LINK_STATUS | 1 | Specifies the status of the link from the |
| | octet | indicated address (LOST, SYMMETRIC or |
| | | HEARD). |
| | | |
| OTHER_NEIGHB | 1 | Specifies that the address is (SYMMETRIC) |
| | octet | or was (LOST) of an interface of a |
| | | symmetric 1-hop neighbor of the node |
| | | transmitting the HELLO message. |
+--------------+--------+-------------------------------------------+
Table 2
A TLV with Type == LINK_STATUS and (Value == SYMMETRIC or Value ==
LOST) also performs the function of a TLV with Type == OTHER_NEIGHB
and the same value. The latter SHOULD NOT also be included. If a
TLV with Type == LINK_STATUS and Value == SYMMETRIC is combined with
a TLV with Type == OTHER_NEIGHB and Value == LOST then the latter
MUST be ignored, and SHOULD NOT be included. See Appendix A.
Other addresses MAY be included in address blocks, but MUST NOT be
associated with any of the TLVs specified in this section.
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11. HELLO Message Generation
Each MANET interface MUST generate HELLO messages according to the
specification in this section. HELLO message generation and
scheduling MUST be according to the interface parameters for that
MANET interface and MAY be independent for each MANET interface or,
interface parameters permitting, MANET interfaces MAY use the same
schedule.
If transmitting periodic HELLO messages then, following a HELLO
message transmission on a MANET interface, another HELLO message MUST
be transmitted on the same MANET interface after an interval not
greater than HELLO_INTERVAL. Two successive HELLO message
transmissions on the same MANET interface MUST be separated by at
least HELLO_MIN_INTERVAL, except as noted in Section 11.2.1.
11.1. HELLO Message Specification
HELLO messages are generated independently on each MANET interface.
All addresses in any I_local_iface_addr_list MUST be included, except
that:
o If the interface on which the HELLO message is to be sent has a
single interface address with maximum prefix length then that
interface address MAY be omitted.
All such included addresses MUST be associated with a TLV with Type
== LOCAL_IF and value according to the following:
o If the address is of the sending interface, then Value == THIS_IF.
o Otherwise, Value == OTHER_IF.
The following addresses of current or former 1-hop neighbors MAY be
included in any HELLO message:
o Addresses of MANET interfaces of 1-hop neighbors from the Link Set
of the Interface Information Base for this MANET interface.
o Other addresses of symmetric 1-hop neighbors from the Neighbor Set
of this node's Node Information Base.
o Addresses of MANET interfaces of previously symmetric or heard
1-hop neighbors connected on this MANET interface from the Link
Set of the Interface Information Base for this MANET interface.
(These are advertised for a period equal to this interface's
L_HOLD_TIME after loss.)
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o Other addresses of previously symmetric 1-hop neighbors from the
Lost Neighbor Set of this node's Node Information Base. (These
are advertised for a period equal to N_HOLD_TIME after loss.)
Each such address MUST be associated with one or more appropriate
TLVs, respecting the parameter REFRESH_INTERVAL for each association
for each MANET interface. Specifically:
1. For each address (henceforth linked address) which appears in a
Link Tuple in the Link Set for this MANET interface, for which
L_status does not equal PENDING, include the linked address with
an associated TLV with:
* Type = LINK_STATUS; AND
* Value = L_status.
2. For each address (henceforth neighbor address) which appears in
an N_neighbor_iface_addr_list in a Neighbor Tuple with
N_symmetric == true, and which has not already been included with
an associated TLV with (Type == LINK_STATUS and Value ==
SYMMETRIC), include the neighbor address with an associated TLV
with:
* Type = OTHER_NEIGHB; AND
* Value = SYMMETRIC.
3. For each Lost Neighbor Tuple whose NL_neighbor_iface_addr
(henceforth lost address) has not already been included, include
the lost address with an associated TLV with:
* Type = OTHER_NEIGHB; AND
* Value = LOST.
If a 1-hop neighbor address is specified with more than one
associated TLV, then these TLVs MAY be independently included or
excluded from each HELLO message. Each such TLV MUST be included
associated with that address in a HELLO message sent on that MANET
interface in every interval of length equal to that MANET interface's
parameter REFRESH_INTERVAL. TLVs associated with the same address
included in the same HELLO message MAY be applied to the same or
different copies of that address.
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11.2. HELLO Message Transmission
HELLO messages are transmitted in the packet/message format specified
by [packetbb] using the "LL-MANET-Routers" multicast address
specified by [manet-iana] as destination IP address, using either the
"manet" UDP port, or the "manet" IP protocol number specified in
[manet-iana].
11.2.1. HELLO Message Jitter
HELLO messages MAY be sent using periodic message generation or
externally triggered message generation. If using data link and
physical layers which are subject to packet loss due to collisions,
HELLO messages SHOULD be jittered as described in [RFC5148].
Internally triggered message generation (such as due to a change in
local interfaces) MAY be treated as if externally generated message
generation, or MAY be not jittered.
HELLO messages MUST NOT be forwarded, and thus message forwarding
jitter does not apply to HELLO messages.
Each form of jitter described in [RFC5148] requires a parameter
MAXJITTER. These interface parameters may be dynamic, and are
specified by:
o For periodic message generation: HP_MAXJITTER.
o For externally triggered message generation: HT_MAXJITTER.
When HELLO message generation is delayed in order that a HELLO
message is not sent within HELLO_MIN_INTERVAL of the previous HELLO
message on the same MANET interface, then HELLO_MIN_INTERVAL SHOULD
be reduced by jitter, with maximum reduction HP_MAXJITTER. In this
case HP_MAXJITTER MUST NOT be greater than HELLO_MIN_INTERVAL.
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12. HELLO Message Processing
On receiving a HELLO message, a node MUST first check if any address
associated with a TLV with Type == LOCAL_IF is one of the receiving
node's current or recently used interface addresses (i.e. is in any
I_local_iface_addr_list in the Local Interface Set or is equal to any
IR_local_iface_addr in the Removed Interface Address Set). If so
then the HELLO message MUST be discarded.
Otherwise the receiving node MUST update its appropriate Interface
Information Base and its Node Information Base according to this
section. Section 12.1 to Section 12.4 MUST be performed in the order
presented. If any changes satisfy any of the conditions described in
Section 13 then the indicated consequences MUST be applied
immediately, unless noted otherwise.
For the purpose of this section, note the following definitions:
o "validity time" is calculated from the VALIDITY_TIME message TLV
of the HELLO message as specified in [timetlv]. All information
in the HELLO message has the same validity time.
o "Receiving Address List" is the I_local_iface_addr_list
corresponding to the MANET interface on which the HELLO message
was received
o "Sending Address List" is the list of the addresses contained in
the HELLO message with an associated TLV with Type == LOCAL_IF and
Value == THIS_IF. If the Sending Address List is otherwise empty,
then the Sending Address List contains a single address (with
maximum prefix length) equal to the sending address of the IP
datagram in which the HELLO message was included.
o "Neighbor Address List" is the Sending Address List, plus the
addresses contained in the HELLO message with an associated TLV
with Type == LOCAL_IF and Value == OTHER_IF.
o EXPIRED indicates that a timer is set to a value clearly preceding
the current time (e.g. current time - 1).
o "Removed Address List" is a list of addresses created by this
HELLO message processing which were formerly reported as local by
the node originating the HELLO message, but which are not included
in the Neighbor Address List. This list is initialized as empty.
o "Lost Address List" is a subset of the Removed Address List
containing addresses which were formerly considered as symmetric.
This list is initialized as empty.
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12.1. Updating the Neighbor Set
On receiving a HELLO message, the node MUST update its Neighbor Set
and populate the Removed Address List and Lost Address List:
1. Find all Neighbor Tuples (hereafter matching Neighbor Tuples)
where:
* N_neighbor_iface_addr_list contains at least one address in
the Neighbor Address List.
2. If there are no matching Neighbor Tuples, then:
1. Create a new Neighbor Tuple with:
+ N_neighbor_iface_addr_list = Neighbor Address List;
+ N_symmetric = false.
3. If there is one matching Neighbor Tuple, then:
1. If the N_neighbor_iface_addr_list of the matching Neighbor
Tuple is not equal to the Neighbor Address List, then:
1. For each address (henceforth removed address) which is in
the N_neighbor_iface_addr_list, but not in the Neighbor
Address List:
1. Add the removed address to the Removed Address List.
2. If N_symmetric == true, then add the removed address
to the Lost Address List.
2. Update the matching Neighbor Tuple by:
- N_neighbor_iface_addr_list = Neighbor Address List.
4. If there are two or more matching Neighbor Tuples, then:
1. For each address (henceforth removed address) which is in the
N_neighbor_iface_addr_list of any of the matching Neighbor
Tuples:
1. Add the removed address to the Removed Address List.
2. If N_symmetric == true, then add the removed address to
the Lost Address List.
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2. Replace the matching Neighbor Tuples by a single Neighbor
Tuple with:
+ N_neighbor_iface_addr_list = Neighbor Address List;
+ N_symmetric = false
12.2. Updating the Lost Neighbor Set
On receiving a HELLO message, a node MUST update its Lost Neighbor
Set:
1. For each address (henceforth lost address) in the Lost Address
List, if no Lost Neighbor Tuple with NL_neighbor_iface_addr ==
lost address exists, then add a Lost Neighbor Tuple with:
* NL_neighbor_iface_addr = lost address;
* NL_time = current time + N_HOLD_TIME.
12.3. Updating the Link Set
On receiving a HELLO message, a node MUST update its Link Set for the
MANET interface on which the HELLO message is received:
1. Remove all addresses in the Removed Address List from the
L_neighbor_iface_addr_list of all Link Tuples.
2. Remove all Link Tuples whose L_neighbor_iface_addr_list is now
empty; apply Section 13.1, but not Section 13.3.
3. Find all Link Tuples (hereafter matching Link Tuples) where:
* L_neighbor_iface_addr_list contains one or more addresses in
the Sending Address List.
4. If there is more than one matching Link Tuple, then remove them
all; apply Section 13.1, but not Section 13.3.
5. If no matching Link Tuples remain, then create a new matching
Link Tuple with:
* L_neighbor_iface_addr_list = empty;
* L_HEARD_time = EXPIRED;
* L_SYM_time = EXPIRED;
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* L_quality = INITIAL_QUALITY;
* L_pending = INITIAL_PENDING;
* L_lost = false;
* L_time = current time + validity time.
6. The matching Link Tuple, existing or new, is then modified as
follows:
1. If the node finds any address (henceforth receiving address)
in the Receiving Address List in an address block in the
HELLO message, then the Link Tuple is modified as follows:
1. If any receiving address in the HELLO message is
associated with a TLV with Type == LINK_STATUS and (Value
== HEARD or Value == SYMMETRIC) then:
- L_SYM_time = current time + validity time.
2. Otherwise if any receiving address in the HELLO message
is associated with a TLV with Type == LINK_STATUS and
Value == LOST then:
1. if L_SYM_time has not expired, then:
1. L_SYM_time = EXPIRED.
2. if L_status == HEARD or SYMMETRIC, then:
* L_time = current time + L_HOLD_TIME.
2. L_neighbor_iface_addr_list = Sending Address List.
3. L_HEARD_time = max(current time + validity time, L_SYM_time).
4. If L_status == PENDING, then:
+ L_time = max(L_time, L_HEARD_time).
5. Otherwise if L_status == HEARD or SYMMETRIC, then:
+ L_time = max(L_time, L_HEARD_time + L_HOLD_TIME).
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12.4. Updating the 2-Hop Set
On receiving a HELLO message a node MUST update its 2-Hop Set for the
MANET interface on which the HELLO message was received:
1. Remove all addresses in the Removed Address List from the
N2_neighbor_iface_addr_list of all 2-Hop Tuples.
2. If the Link Tuple with L_neighbor_iface_addr_list == Sending
Address List has L_status == SYMMETRIC then:
1. For each address (henceforth 2-hop address) in an address
block of the HELLO message, which is not in the Neighbor
Address List, in any I_local_iface_addr_list, or equal to any
IR_local_iface_addr:
1. If the 2-hop address has an associated TLV with:
- Type == LINK_STATUS and Value == SYMMETRIC; OR
- Type == OTHER_NEIGHB and Value == SYMMETRIC,
then, if there is no 2-Hop Tuple such that:
- N2_neighbor_iface_addr_list contains one or more
addresses in the Sending Address List; AND
- N2_2hop_iface_addr == 2-hop address.
then create a 2-Hop Neighbor Tuple with:
- N2_2hop_iface_addr = 2-hop address.
This 2-Hop Tuple (existing or new) is then modified as
follows:
- N2_neighbor_iface_addr_list = Sending Address List;
- N2_time = current time + validity time.
2. Otherwise if the 2-hop address has a TLV with:
- Type == LINK_STATUS and (Value == LOST or Value ==
HEARD); OR
- Type == OTHER_NEIGHB and Value == LOST;
then remove all 2-Hop Tuples with:
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- N2_neighbor_iface_addr_list contains one or more
addresses in the Sending Address List; AND
- N2_2hop_iface_addr == 2-hop address.
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13. Other Information Base Changes
The Interface and Node Information Bases MUST be changed when some
events occur. These events may result from HELLO message processing,
or may be otherwise generated (e.g. expiry of timers or link quality
changes).
Events which cause changes in the Information Bases are:
o A Link Tuple's state changes from symmetric, or the Link Tuple is
removed.
o A Link Tuple's state changes to symmetric.
o A Link Tuple's L_HEARD_time expires, or the Link Tuple is removed.
o Local interface address changes, as specified in Section 9.
o Link quality changes, as specified in Section 14.
A node MAY report updated information in response to any of these
changes in HELLO message(s), subject to the constraints in
Section 11.
A node which transmits HELLO messages in response to such changes
SHOULD transmit a HELLO message:
o On all MANET interfaces, if the Neighbor Set changes such as to
indicate the change in symmetry of any 1-hop neighbors (including
addition or removal of symmetric 1-hop neighbors).
o Otherwise, on all those MANET interfaces whose Link Set changes
such as to indicate a change in status of any 1-hop neighbors
(including the addition or removal of any 1-hop neighbors, other
than those considered pending).
13.1. Link Tuple Not Symmetric
If for any Link Tuple with L_status == SYMMETRIC:
o L_status changes to any other value; OR
o the Link Tuple is removed;
then:
1. All 2-Hop Tuples for the same MANET interface with:
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* N2_neighbor_iface_addr_list contains one or more addresses in
L_neighbor_iface_addr_list;
are removed.
2. For the Neighbor Tuple whose N_neighbor_iface_addr_list contains
L_neighbor_iface_addr_list:
1. If there are no remaining Link Tuples for any MANET interface
with:
+ L_neighbor_iface_addr_list contained in
N_neighbor_iface_addr_list; AND
+ L_status == SYMMETRIC;
then modify the Neighbor Tuple by:
1. N_symmetric = false.
2. For each address (henceforth neighbor address) in
N_neighbor_iface_addr_list, add a Lost Neighbor Tuple
with:
- NL_neighbor_iface_addr = neighbor address;
- NL_time = current time + N_HOLD_TIME.
13.2. Link Tuple Symmetric
If, for any Link Tuple which does not have L_status == SYMMETRIC:
o L_status changes to SYMMETRIC;
(this includes a newly created Link Tuple which is immediately
updated to have L_status == SYMMETRIC) then:
1. For the Neighbor Tuple whose N_neighbor_iface_addr_list includes
L_neighbor_iface_addr_list, set:
* N_symmetric = true.
2. Remove all Lost Neighbor Tuples whose NL_neighbor_iface_addr is
included in that N_neighbor_iface_addr_list.
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13.3. Link Tuple Heard Timeout
If, for any Link Tuple:
o L_HEARD_time expires; OR
o the Link Tuple is removed;
then:
1. For the Neighbor Tuple whose N_neighbor_iface_addr_list contains
L_neighbor_iface_addr_list, if no Link Tuples for any MANET
interface remain with:
* L_neighbor_iface_addr_list contained in
N_neighbor_iface_addr_list; AND
* L_HEARD_time is not expired;
then remove the Neighbor Tuple.
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14. Link Quality
Link quality is a mechanism whereby a node MAY take considerations
other than message exchange into account for determining when a link
is and is not a candidate for being considered as HEARD or SYMMETRIC.
For deployments where no link quality is used, the considerations in
Section 14.1 apply. For deployments were link quality is used, the
general principles of link quality usage are described in
Section 14.2. Section 14.3 and Section 14.4 detail link quality
functioning.
Link quality is used only locally by a node, and nodes may fully
interoperate whether they are using the same, different or no link
quality methods.
14.1. Deployment Without Link Quality
In order for a node to not employ link quality, the node MUST define:
o INITIAL_PENDING = false;
o INITIAL_QUALITY >= HYST_REJECT (there is no reason not to define
INITIAL_QUALITY = 1).
14.2. Basic Principles of Link Quality
To enable link quality usage, the L_quality value of a Link Tuple is
used in conjunction with two thresholds, HYST_ACCEPT and HYST_REJECT,
to set the flags L_pending and L_lost of that Link Tuple. Based on
these flags, the link status to advertise for that Link Tuple is
determined as described in Section 7.1.
The use of two thresholds implements link hysteresis, whereby a link
which has HYST_REJECT <= L_quality < HYST_ACCEPT may be either
accepted or rejected (depending on which threshold it has most
recently crossed, or if neither the value of INITIAL_QUALITY). With
appropriate values of these parameters, this prevents over-rapid
changes of link status.
The basic principles of link quality usage are as follows:
o A node does not advertise a neighbor interface in any state until
L_quality is acceptable:
* If INITIAL_PENDING == true, then this is such that L_quality >=
HYST_ACCEPT.
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* Otherwise this is such that L_quality >= HYST_REJECT. To
ensure this, a node MUST NOT define INITIAL_PENDING == false
and INITIAL_QUALITY < HYST_REJECT. (A node also MUST NOT
define INITIAL_PENDING == true and INITIAL_QUALITY >=
HYST_ACCEPT.)
* A link which is not yet advertised has L_pending == true.
o Once L_quality >= HYST_ACCEPT, the L_pending flag is set false,
indicating that the link can be advertised.
o A link for which L_pending == false is advertised until its
L_quality drops below HYST_REJECT.
o If a link has L_pending == false and L_quality < HYST_REJECT, the
link is LOST and is advertised as such. This link is not
reconsidered as a candidate HEARD or SYMMETRIC link until
L_quality >= HYST_ACCEPT.
o A link which has an acceptable quality may be advertised as HEARD,
SYMMETRIC or LOST according to the exchange of HELLO messages.
14.3. When Link Quality Changes
If L_quality for a link changes, then the following actions MUST be
taken:
1. If L_quality >= HYST_ACCEPT then the corresponding Link Tuple is
modified by:
1. L_pending = false.
2. L_lost = false.
3. If L_status == HEARD or L_status == SYMMETRIC, then:
+ L_time = max(L_time, L_HEARD_time + L_HOLD_TIME)
2. If L_status is not equal to PENDING, and L_quality < HYST_REJECT
then the corresponding Link Tuple is modified by:
1. If L_lost == false, then:
+ L_lost = true
+ L_time = min(L_time, current time + L_HOLD_TIME)
Any appropriate action indicted in Section 13 MUST also be taken.
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If L_quality for a link is updated based on HELLO message reception,
or on reception of a packet including a HELLO message, then L_quality
MUST be updated prior to the HELLO message processing described in
Section 12. (If the receipt of the HELLO message, or the packet
containing it, creates the Link Tuple then the Link Tuple MUST be
created with the appropriately updated L_quality value, rather than
with L_quality = INITIAL_QUALITY.)
14.4. Updating Link Quality
A node MAY update link quality based on any information available to
it. Particular cases that MAY be used include:
o Information from the link layer, such as signal to noise ratio or
acknowledgement reception and loss information.
o Receipt or loss of packets. If packets include a packet sequence
number as defined in [packetbb], then packets on a link SHOULD
have sequential packet sequence numbers, whether or not they
include HELLO messages. Link quality can be updated when a packet
is received based on, for example, whether the last N out of M
packets on the link were received, or a "leaky integrator"
tracking packets.
o Receipt or loss of HELLO messages. If the maximum interval
between HELLO messages is known (such as by inclusion of a message
TLV with Type == INTERVAL_TIME, as defined in [timetlv], in HELLO
messages) then the loss of HELLO messages can be determined
without the need to receive a HELLO message. Note that if this
case is combined with the previous case then care must be taken to
avoid "double counting" a lost HELLO message in a lost packet.
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15. Proposed Values for Parameters and Constants
This section lists the parameters and constants used in the
specification of the protocol, and proposed values of each which may
be used when a single value of each is used.
15.1. Message Interval Interface Parameters
o HELLO_INTERVAL = 2 seconds
o HELLO_MIN_INTERVAL = HELLO_INTERVAL/4
o REFRESH_INTERVAL = HELLO_INTERVAL
15.2. Information Validity Time Interface Parameters
o H_HOLD_TIME = 3 x REFRESH_INTERVAL
o L_HOLD_TIME = H_HOLD_TIME
15.3. Information Validity Time Node Parameters
o N_HOLD_TIME = L_HOLD_TIME
o I_HOLD_TIME = N_HOLD_TIME
15.4. Link Quality Interface Parameters
If link quality is changed, then parameter values will depend on the
link quality process. If link quality is not changed, then:
o HYST_ACCEPT = 1
o HYST_REJECT = 0
o INITIAL_QUALITY = 1
o INITIAL_PENDING = false
15.5. Jitter Interface Parameters
o HP_MAXJITTER = HELLO_INTERVAL/4
o HT_MAXJITTER = HP_MAXJITTER
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15.6. Constants
o C = 1/1024 second
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16. Security Considerations
The objective of this protocol is to allow each node in the network
to acquire information describing its 1-hop and symmetric 2-hop
neighborhoods. This is acquired through message exchange between
neighboring nodes. The information is made available through the
Interface Information Bases and Node Information Base, describing the
node's 1-hop neighborhood and symmetric 2-hop neighborhood.
Under normal circumstances, the information recorded in these
Information Bases is correct - i.e. corresponds to the actual network
topology, apart from any changes which have not (yet) been tracked by
the HELLO message exchanges.
If some node for some reason, malice or malfunction, injects invalid
HELLO messages, incorrect information may be recorded in the
Information Bases. The protocol specification does, however, prevent
inconsistent information from being injected in the protocol sets
through the constraints in Appendix C. The exact consequence of
information inexactness depends on the use of these Information
Bases, and should be reflected in the specification of protocols
which use information provided by NHDP.
This section, therefore, only outlines the ways in which correctly
formed, but still invalid, HELLO messages may appear.
16.1. Invalid HELLO messages
A correctly formed, but still invalid, HELLO message may take any of
the following forms. Note that a present or absent address in an
address block, does not in and by itself cause a problem. It is the
presence, absence, or incorrectness of associated LOCAL_IF,
LINK_STATUS and OTHER_NEIGHB TLVs that causes problems.
A node may provide false information about its own identity:
* The HELLO message may contain addresses with an associated
LOCAL_IF TLV which do not correspond to addresses of interfaces
of the node transmitting the HELLO message.
* The HELLO message may omit addresses, or their associated
LOCAL_IF TLV, of interfaces of the local node transmitting the
HELLO message (other than the allowed omission of the only
local interface address of the MANET interface over which the
HELLO message is transmitted, if that is the case).
* The HELLO message may incorrectly specify the LOCAL_IF TLV
value associated with one or more local interface addresses,
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indicating incorrectly whether they are associated with the
MANET interface over which the HELLO message is transmitted.
A node may provide false information about the identity of other
nodes:
* A present LINK_STATUS TLV may, incorrectly, identify an address
as being of a MANET interface which is or was heard on the
MANET interface over which the HELLO message is transmitted.
* A consistently absent LINK_STATUS TLV may, incorrectly, fail to
identify an address as being of a MANET interface which is or
was heard on the MANET interface over which the HELLO message
is transmitted.
* A present OTHER_NEIGHB TLV may, incorrectly, identify an
address as being of a node which is or was in the sending
node's symmetric 1-hop neighborhood;
* A consistently absent OTHER_NEIGHB TLV may, incorrectly, fail
to identify an address as being of a node which is or was in
the sending node's symmetric 1-hop neighborhood;
* The value of a LINK_STATUS TLV may incorrectly indicate the
status (LOST, SYMMETRIC or HEARD) of the link from a 1-hop
neighbor.
* The value of an OTHER_NEIGHB TLV may incorrectly indicate the
status (LOST or SYMMETRIC) of a symmetric 1-hop neighbor.
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17. IANA Considerations
17.1. Message Types
This specification defines one message type, which must be allocated
from the "Assigned Message Types" repository of [packetbb] with
assignment as specified in Table 3.
+-------+------+------------------+
| Name | Type | Description |
+-------+------+------------------+
| HELLO | TBD1 | Local signaling. |
+-------+------+------------------+
Table 3
17.2. TLV Types
This specification defines three address block TLV types, which must
be allocated from the "Assigned Address Block TLV Types" repository
of [packetbb] with assignments as specified in Table 4.
+--------------+------+-----------+---------------------------------+
| Name | Type | Type | Description |
| | | extension | |
+--------------+------+-----------+---------------------------------+
| LOCAL_IF | TBD2 | 0 | Specifies that the address is |
| | | | associated with a local |
| | | | interface of the sending node. |
| | | | |
| | | 1-255 | RESERVED |
| | | | |
| LINK_STATUS | TBD3 | 0 | Specifies the status of the |
| | | | link from the indicated address |
| | | | (LOST, SYMMETRIC or HEARD). |
| | | | |
| | | 1-255 | RESERVED |
| | | | |
| OTHER_NEIGHB | TBD4 | 0 | Specifies that the address is |
| | | | (SYMMETRIC) or recently was |
| | | | (LOST) of an interface of a |
| | | | symmetric 1-hop neighbor of the |
| | | | node transmitting the message. |
| | | | |
| | | 1-255 | RESERVED |
+--------------+------+-----------+---------------------------------+
Table 4
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Type extensions indicated as RESERVED may be allocated by standards
action, as specified in [RFC2434].
17.3. LINK_STATUS and OTHER_NEIGHB Values
The values which the LOCAL_IF TLV can use are the following:
o UNSPEC_IF = 0
o THIS_IF = 1
o OTHER_IF = 2
The values which the LINK_STATUS TLV can use are the following:
o LOST = 0
o SYMMETRIC = 1
o HEARD = 2
The values which the OTHER_NEIGHB TLV can use are the following:
o LOST = 0
o SYMMETRIC = 1
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18. References
18.1. Normative References
[packetbb] Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
"Generalized MANET Packet/Message Format", Work In
Progress draft-ietf-manet-packetbb-12.txt, March 2008.
[manet-iana] Chakeres, I., "IANA Allocations for MANET Protocols",
Work In Progress draft-ietf-manet-iana-07.txt,
November 2007.
[timetlv] Clausen, T. and C. Dearlove, "Representing multi-value
time in MANETs", Work In
Progress draft-ietf-manet-timetlv-04.txt,
November 2007.
[RFC5148] Clausen, T., Dearlove, C., and B. Adamson, "Jitter
considerations in MANETs", RFC 5148, February 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, BCP 14, March 1997.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing
an IANA Considerations Section in RFCs", RFC 2434,
BCP 26, October 1998.
18.2. Informative References
[RFC3626] Clausen, T. and P. Jacquet, "The Optimized Link State
Routing Protocol", RFC 3626, October 2003.
[RFC2501] Macker, J. and S. Corson, "Mobile Ad hoc Networking
(MANET): Routing Protocol Performance Issues and
Evaluation Considerations", RFC 2501, January 1999.
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Appendix A. Address Block TLV Combinations
The algorithm for generating HELLO messages in Section 11 specifies
which 1-hop addresses may be included in the address blocks, and with
which associated TLVs. These TLVs may have Type == LINK_STATUS or
Type == OTHER_NEIGHB, or both. TLVs with Type == LINK_STATUS may
have three possible values (Value == HEARD, Value == SYMMETRIC or
Value == LOST), and TLVs of TYPE == OTHER_NEIGHB may have two
possible values (Value == SYMMETRIC or Value == LOST). When both
TLVs are associated with the same address only certain combinations
of these TLV values are necessary, and are the only combinations
generated by the algorithm in Section 11. These combinations are
indicated in Table 5.
Cells labeled with "Yes" indicate the possible combinations which are
generated by the algorithm in Section 11. Cells labeled with "No"
indicate combinations not generated by the algorithm in Section 11,
but which are correctly parsed and interpreted by the algorithm in
Section 12.
+----------------+----------------+----------------+----------------+
| | Type == | Type == | Type == |
| | OTHER_NEIGHB | OTHER_NEIGHB, | OTHER_NEIGHB, |
| | (absent) | Value == | Value == LOST |
| | | SYMMETRIC | |
+----------------+----------------+----------------+----------------+
| Type == | No | Yes | Yes |
| LINK_STATUS | | | |
| (absent) | | | |
| | | | |
| Type == | Yes | Yes | Yes |
| LINK_STATUS, | | | |
| Value == HEARD | | | |
| | | | |
| Type == | Yes | No | No |
| LINK_STATUS, | | | |
| Value == | | | |
| SYMMETRIC | | | |
| | | | |
| Type == | Yes | Yes | No |
| LINK_STATUS, | | | |
| Value == LOST | | | |
+----------------+----------------+----------------+----------------+
Table 5
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Appendix B. HELLO Message Example
An example HELLO message, transmitted by an originator node with a
single MANET interface, is as follows. The message uses IPv4 (four
octet) addresses without specified prefix lengths. The message is
transmitted with a full message header other than version number
(message semantics octet is 30) with a hop limit of 1 and a hop count
of 0. The overall message length is 49 octets.
The message contains a message TLV block with content length 8 octets
containing two message TLVs, of types VALIDITY_TIME and
INTERVAL_TIME. Each uses a TLV with semantics value 8, indicating
that each has a value. Each has a value length of 1 octet; the
values included (0x64 and 0x58) are time codes representing the
default values of parameters H_HOLD_TIME and HELLO_INTERVAL,
respectively (6 seconds and 2 seconds) assuming the default value of
constant C (1/1024 second).
The message has a single address block containing 5 addresses. The
semantics octet value 1 indicates an address head but no address
tail. The head length of 3 octets indicates address mid sections of
one octet each (Mid 0 to Mid 4).
The following TLV block (content length 14 octets) includes two TLVs.
The first is a LOCAL_IF TLV which (with semantics value 10) indicates
that a single address, with index 0 (i.e. Head:Mid 0) is the single
local interface address of this node (the 1 octet value LOCAL_IF
indicates that this address is of this interface). The second is a
LINK_STATUS TLV which (with semantics octet 44) specifies the link
status values of all reported neighbors in a single multivalue TLV
which covers the addresses with indexes 1 to 4. The TLV value length
of 4 octets indicates one octet per value per address. The last four
addresses are first and second HEARD, third SYMMETRIC, and fourth
LOST.
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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 1 1 1 1 0|0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 0 0 0| VALIDITY_TIME |0 0 0 0 1 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1|0 1 1 0 0 1 0 0| INTERVAL_TIME |0 0 0 0 1 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1|0 1 0 1 1 0 0 0|0 0 0 0 0 1 0 1|0 0 0 0 0 0 0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 1 1| Head |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mid 0 | Mid 1 | Mid 2 | Mid 3 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mid 4 |0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 0| LOCAL_IF |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1 0 0 0 0|0 0 0 0 0 0 0 0|0 0 0 0 0 0 0 1| THIS_IF |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LINK_STATUS |0 0 1 0 1 1 0 0|0 0 0 0 0 0 0 1|0 0 0 0 0 1 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 1 0 0| HEARD | HEARD | SYMMETRIC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LOST |
+-+-+-+-+-+-+-+-+
Note that this example is for illustrative purposes. The essential
information can be conveyed, more efficiently (assuming that the
local interface address will be supplied by IP, and that the
INTERVAL_TIME is not needed) by the 29 octets:
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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 0 1 1 1 0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0| VALIDITY_TIME |0 0 0 0 1 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1|0 1 1 0 0 1 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mid 1 | Mid 2 | Mid 3 | Mid 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1| LINK_STATUS |0 0 1 0 1 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 1 0 0| HEARD | HEARD | SYMMETRIC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LOST |
+-+-+-+-+-+-+-+-+
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Appendix C. Constraints
Any process which updates the Local Information Base or the Node
Information Base MUST ensure that all constraints specified in this
appendix are maintained.
In each Local Interface Tuple:
o I_local_iface_addr_list MUST NOT be empty.
o I_local_iface_addr_list MUST NOT contain any duplicated addresses.
o I_local_iface_addr_list MUST NOT contain any address which is in
the I_local_iface_addr_list of any other Local Interface Tuple.
In each Removed Interface Address Tuple:
o IR_local_iface_addr MUST NOT contain any address which is in the
I_local_iface_addr_list of any Local Interface Tuple.
o IR_local_iface_addr MUST NOT equal the IR_local_iface_addr of any
other Removed Interface Address Tuple.
In each Link Tuple:
o L_neighbor_iface_addr_list MUST NOT be empty.
o L_neighbor_iface_addr_list MUST NOT contain any address which is
in the I_local_iface_addr_list of any Local Interface Tuple or the
IR_local_iface_addr of any Removed Interface Address Tuple.
o L_neighbor_iface_addr_list MUST NOT contain any duplicated
addresses.
o L_neighbor_iface_addr_list MUST NOT contain any address which is
in the L_neighbor_iface_addr_list of any other Link Tuple in the
same Link Set.
o If L_HEARD_time has not expired then there MUST be a Neighbor
Tuple whose N_neighbor_iface_addr_list contains
L_neighbor_iface_addr_list.
o L_HEARD_time MUST NOT be greater than L_time.
o L_SYM_time MUST NOT be greater than L_HEARD_time (unless both are
expired).
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o L_quality MUST NOT be less than 0 or greater than 1.
o If L_quality >= HYST_ACCEPT then L_pending MUST be false.
o If L_quality < HYST_REJECT then L_status MUST be PENDING or LOST.
o L_pending MUST NOT be set to true if it is currently false.
In each Neighbor Tuple:
o N_neighbor_iface_addr_list MUST NOT contain any address which is
in the I_local_iface_addr_list of any Local Interface Tuple or the
IR_local_iface_addr of any Removed Interface Address Tuple.
o N_neighbor_iface_addr_list MUST NOT contain any duplicated
addresses.
o N_neighbor_iface_addr_list MUST NOT contain any address which is
in the N_neighbor_iface_addr_list of any other Neighbor Tuple.
o If N_symmetric == true, then there MUST be one or more Link Tuples
with:
* L_neighbor_iface_addr_list contained in
N_neighbor_iface_addr_list; AND
* L_status == SYMMETRIC.
o If N_symmetric == false, then there MUST be one or more Link
Tuples with:
* L_neighbor_iface_addr_list contained in
N_neighbor_iface_addr_list.
All such Link Tuples MUST NOT have L_status == SYMMETRIC. At
least one such Link Tuple MUST have L_HEARD_time not expired.
In each Lost Neighbor Tuple:
o NL_neighbor_iface_addr MUST NOT be in the I_local_iface_addr_list
of any Local Interface Tuple or the IR_local_iface_addr of any
Removed Interface Address Tuple.
o NL_neighbor_iface_addr MUST NOT equal the NL_neighbor_iface_addr
of any other Lost Neighbor Tuple.
o NL_neighbor_iface_addr MUST NOT be in the
N_neighbor_iface_addr_list of any Neighbor Tuple with N_symmetric
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== true.
In each 2-Hop Tuple:
o There MUST be a Link Tuple associated with the same MANET
interface with:
* L_neighbor_iface_addr_list == N2_neighbor_iface_addr_list; AND
* L_status == SYMMETRIC.
o N2_2hop_iface_addr MUST NOT be in the I_local_iface_addr_list of
any Local Interface Tuple or the IR_local_iface_addr of any
Removed Interface Address Tuple.
o N2_2hop_iface_addr MUST NOT be the N2_2hop_iface_addr of any other
2-Hop Tuple in the same 2-Hop Set and with the same
N2_neighbor_iface_addr_list.
o N2_2hop_iface_addr MUST NOT be in the N2_neighbor_iface_addr_list
of the same 2-Hop Tuple.
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Appendix D. Flow and Congestion Control
This protocol specifies one message type, the HELLO message. The
maximum size of a HELLO message is proportional to the size of the
originating node's 1-hop neighborhood. HELLO messages MUST NOT be
forwarded.
A node MUST report its 1-hop neighborhood in HELLO messages on each
of its MANET interfaces at least each REFRESH_INTERVAL. This puts a
lower bound on the control traffic generated by each node in the
network employing this protocol.
A node MUST ensure that two successive HELLO messages sent on the
same MANET interface are separated by at least HELLO_MIN_INTERVAL.
(If using jitter then this may be reduced to a mean minimum value of
HELLO_MIN_INTERVAL - HP_MAXJITTER/2.) Thus, this puts an upper bound
on the control traffic generated by each node in the network
employing this protocol.
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Appendix E. Contributors
This specification is the result of the joint efforts of the
following contributors, listed alphabetically.
o Brian Adamson, NRL, USA, <adamson@itd.nrl.navy.mil>
o Cedric Adjih, INRIA, France, <Cedric.Adjih@inria.fr>
o Thomas Heide Clausen, LIX, France, <T.Clausen@computer.org>
o Justin Dean, NRL, USA, <jdean@itd.nrl.navy.mil>
o Christopher Dearlove, BAE Systems, UK,
<Chris.Dearlove@baesystems.com>
o Philippe Jacquet, INRIA, France, <Philippe.Jacquet@inria.fr>
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Appendix F. Acknowledgements
The authors would like to acknowledge the team behind OLSRv1,
specified in RFC3626 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: Joe Macker (NRL), Alan Cullen (BAE
Systems), and the entire IETF MANET working group.
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Authors' Addresses
Thomas Heide Clausen
LIX, Ecole Polytechnique, France
Phone: +33 6 6058 9349
EMail: T.Clausen@computer.org
URI: http://www.ThomasClausen.org/
Christopher Dearlove
BAE Systems Advanced Technology Centre
Phone: +44 1245 242194
EMail: chris.dearlove@baesystems.com
URI: http://www.baesystems.com/
Justin W. Dean
Naval Research Laboratory
Phone: +1 202 767 3397
EMail: jdean@itd.nrl.navy.mil
URI: http://pf.itd.nrl.navy.mil/
The OLSRv2 Design Team
MANET Working Group
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