Mobile Ad hoc Networking (MANET) T. Clausen
Internet-Draft LIX, Ecole Polytechnique
Intended status: Standards Track C. Dearlove
Expires: September 10, 2009 BAE Systems ATC
J. Dean
Naval Research Laboratory
The OLSRv2 Design Team
MANET Working Group
March 9, 2009
MANET Neighborhood Discovery Protocol (NHDP)
draft-ietf-manet-nhdp-08
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Copyright Notice
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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 . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Applicability Statement . . . . . . . . . . . . . . . . . . . 9
3.1. Usage in Other Protocols . . . . . . . . . . . . . . . . . 10
4. Protocol Overview and Functioning . . . . . . . . . . . . . . 10
4.1. Routers and Interfaces . . . . . . . . . . . . . . . . . . 11
4.2. Information Base Overview . . . . . . . . . . . . . . . . 12
4.2.1. Local Information Base . . . . . . . . . . . . . . . . 12
4.2.2. Interface Information Bases . . . . . . . . . . . . . 13
4.2.3. Neighbor Information Base . . . . . . . . . . . . . . 14
4.3. Signaling Overview . . . . . . . . . . . . . . . . . . . . 14
4.3.1. HELLO Message Generation . . . . . . . . . . . . . . . 15
4.3.2. HELLO Message Content . . . . . . . . . . . . . . . . 15
4.3.3. HELLO Message Processing . . . . . . . . . . . . . . . 16
4.4. Link Quality . . . . . . . . . . . . . . . . . . . . . . . 17
5. Protocol Parameters and Constants . . . . . . . . . . . . . . 17
5.1. Interface Parameters . . . . . . . . . . . . . . . . . . . 18
5.1.1. Message Intervals . . . . . . . . . . . . . . . . . . 18
5.1.2. Information Validity Times . . . . . . . . . . . . . . 19
5.1.3. Link Quality . . . . . . . . . . . . . . . . . . . . . 20
5.1.4. Jitter . . . . . . . . . . . . . . . . . . . . . . . . 21
5.2. Router Parameters . . . . . . . . . . . . . . . . . . . . 21
5.2.1. Information Validity Time . . . . . . . . . . . . . . 21
5.3. Parameter Change Constraints . . . . . . . . . . . . . . . 21
5.4. Constants . . . . . . . . . . . . . . . . . . . . . . . . 23
6. Local Information Base . . . . . . . . . . . . . . . . . . . . 23
6.1. Local Interface Set . . . . . . . . . . . . . . . . . . . 23
6.2. Removed Interface Address Set . . . . . . . . . . . . . . 23
7. Interface Information Base . . . . . . . . . . . . . . . . . . 24
7.1. Link Set . . . . . . . . . . . . . . . . . . . . . . . . . 24
7.2. 2-Hop Set . . . . . . . . . . . . . . . . . . . . . . . . 25
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8. Neighbor Information Base . . . . . . . . . . . . . . . . . . 26
8.1. Neighbor Set . . . . . . . . . . . . . . . . . . . . . . . 26
8.2. Lost Neighbor Set . . . . . . . . . . . . . . . . . . . . 26
9. Local Information Base Changes . . . . . . . . . . . . . . . . 27
9.1. Adding an Interface . . . . . . . . . . . . . . . . . . . 27
9.2. Removing an Interface . . . . . . . . . . . . . . . . . . 27
9.3. Adding an Address to an Interface . . . . . . . . . . . . 28
9.4. Removing an Address from an Interface . . . . . . . . . . 29
10. Packets and Messages . . . . . . . . . . . . . . . . . . . . . 29
10.1. HELLO Messages . . . . . . . . . . . . . . . . . . . . . . 30
10.1.1. Address Blocks . . . . . . . . . . . . . . . . . . . . 31
11. HELLO Message Generation . . . . . . . . . . . . . . . . . . . 32
11.1. HELLO Message Specification . . . . . . . . . . . . . . . 32
11.2. HELLO Message Transmission . . . . . . . . . . . . . . . . 34
11.2.1. HELLO Message Jitter . . . . . . . . . . . . . . . . . 34
12. HELLO Message Processing . . . . . . . . . . . . . . . . . . . 35
12.1. Invalid Message . . . . . . . . . . . . . . . . . . . . . 35
12.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 36
12.3. Updating the Neighbor Set . . . . . . . . . . . . . . . . 37
12.4. Updating the Lost Neighbor Set . . . . . . . . . . . . . . 38
12.5. Updating the Link Set . . . . . . . . . . . . . . . . . . 39
12.6. Updating the 2-Hop Set . . . . . . . . . . . . . . . . . . 40
13. Other Information Base Changes . . . . . . . . . . . . . . . . 41
13.1. Link Tuple Symmetric . . . . . . . . . . . . . . . . . . . 42
13.2. Link Tuple Not Symmetric . . . . . . . . . . . . . . . . . 43
13.3. Link Tuple Heard Timeout . . . . . . . . . . . . . . . . . 43
14. Link Quality . . . . . . . . . . . . . . . . . . . . . . . . . 44
14.1. Deployment Without Link Quality . . . . . . . . . . . . . 44
14.2. Basic Principles of Link Quality . . . . . . . . . . . . . 45
14.3. When Link Quality Changes . . . . . . . . . . . . . . . . 46
14.4. Updating Link Quality . . . . . . . . . . . . . . . . . . 46
15. Proposed Values for Parameters and Constants . . . . . . . . . 47
15.1. Message Interval Interface Parameters . . . . . . . . . . 47
15.2. Information Validity Time Interface Parameters . . . . . . 47
15.3. Information Validity Time Router Parameters . . . . . . . 47
15.4. Link Quality Interface Parameters . . . . . . . . . . . . 47
15.5. Jitter Interface Parameters . . . . . . . . . . . . . . . 48
15.6. Constants . . . . . . . . . . . . . . . . . . . . . . . . 48
16. Security Considerations . . . . . . . . . . . . . . . . . . . 48
16.1. Invalid HELLO messages . . . . . . . . . . . . . . . . . . 48
16.2. Authentication, Integrity and Confidentiality
Suggestions . . . . . . . . . . . . . . . . . . . . . . . 50
17. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 50
17.1. Expert Review: Evaluation Guidelines . . . . . . . . . . . 50
17.2. Message Types . . . . . . . . . . . . . . . . . . . . . . 50
17.3. Message-Type-specific TLV Type Registries . . . . . . . . 51
17.4. Address Block TLV Types . . . . . . . . . . . . . . . . . 51
17.5. LINK_STATUS and OTHER_NEIGHB Values . . . . . . . . . . . 52
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18. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 53
19. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 53
20. References . . . . . . . . . . . . . . . . . . . . . . . . . . 54
20.1. Normative References . . . . . . . . . . . . . . . . . . . 54
20.2. Informative References . . . . . . . . . . . . . . . . . . 54
Appendix A. Address Block TLV Combinations . . . . . . . . . . . 54
Appendix B. Constraints . . . . . . . . . . . . . . . . . . . . . 55
Appendix C. HELLO Message Example . . . . . . . . . . . . . . . . 58
Appendix D. Flow and Congestion Control . . . . . . . . . . . . . 60
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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 router can determine
the presence of, and connectivity to, its 1-hop and symmetric 2-hop
neighbors. Messages are defined as instances of the specification
[RFC5444].
1-hop and symmetric 2-hop neighborhood information is recorded in the
form of Information Bases. These may be used by other protocols,
such as MANET routing protocols, which require information regarding
the local network connectivity. This protocol is designed to
maintain the information in these Information Bases even in the
presence of a dynamic network topology and wireless ad hoc network
interface characteristics.
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].
1.1. Motivation
MANETs differ from more traditional wired and infrastructure based
wireless networks, due to their envisioned applicability also over
more challenging network interfaces (e.g. wireless, lossy, broadcast
interfaces with moderate and shared bandwidth, hidden and exposed
terminals and interference from other network interfaces and the
environment) and in more challenging topological conditions (e.g.
rapid and unpredictable mobility, dynamic and non-predetermined
network membership). An approach, often taken by MANET routing
protocols, is to collect local topological information up to 2 hops,
in order to, for example, optimize their flooding performance within
the MANET.
Due to the properties of wireless transmissions, communication
between two network interfaces on neighboring routers may not be
bidirectional; even if router A is able to receive a packets from
router B, the converse is not guaranteed to be true. Furthermore,
because of the localized nature of wireless broadcast communication,
neighboring routers within the same communications channel may have
different sets of neighbors. If router A is able to exchange packets
with router B and router B is able to exchange packets with router C
on the same interface, this does not guarantee that router A and
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router C can exchange packets directly.
Routers in a MANET may have multiple heterogeneous interfaces
participating in the same MANET routing protocol, each of which with
the characteristics described above. Between the same pair of
routers, more than one distinct communications channel (link) may
therefore exist, each with different properties.
For MANET routing protocols to correctly identify candidate links for
inclusion in a routing path, the existence and, in many cases,
bidirectionality of such distinct links between a router and its
neighbors must be established and monitored.
The set of neighbor routers of a given MANET router may be
continuously changing, often due to router mobility or a changing
physical environment in which the MANET is located. There are
typically no signals from lower layers which would enable an IP
routing protocol to detect and, as appropriate, react to such
changes. Such changes are can often take place on a short timescale,
such as of the order of seconds, requiring MANET routing protocols to
act rapidly to ensure suitable convergence properties.
MANET routing protocols, for example [RFC3626] and [RFC5449], often
employ relay set reductions in order to conserve network capacity
when maintaining network-wide topological information, with
calculation of these reduced relay sets employing up to two hop
information.
The neighborhood discovery protocol specified in this document
provides continued tracking of neighborhood changes, continued
bidirectionality tracking of links between neighbors, and local
topological information up to two hops. Combined, this allows a
MANET routing protocol access to information describing link
establishment/disappearance, and provides the necessary topological
information for reduced relay set selection and other purposes.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
All terms introduced in [RFC5444], including "packet", "message",
"Address Block", "TLV Block" and "TLV", are to be interpreted as
described there.
Additionally, this document uses the following terminology:
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Router - A MANET router which implements this neighborhood discovery
protocol.
Interface - A network device, configured and assigned one or more IP
addresses.
Address - An IPv4 or IPv6 address, as recorded in the Information
Bases specified by this protocol, and included in messages
generated by this protocol, may be either an address or an address
prefix. The exception to this is addresses described as
originator addresses; these must be simple addresses without a
prefix length. Non-originator addresses can be represented as a
single address object in a message, as defined by [RFC5444]. 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 router may have several
MANET interfaces.
Heard - A MANET interface of router X is considered heard on a MANET
interface of a router Y if the latter can receive traffic from the
former.
Link - A pair of MANET interfaces from two different routers, 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 router X is a 1-hop neighbor of a router Y if a
MANET interface of router X is heard by a MANET interface of
router Y.
Symmetric 1-hop neighbor - A router X is a symmetric 1-hop neighbor
of a router Y if a symmetric link exists between a MANET interface
on router X and a MANET interface on router Y.
Symmetric 2-hop neighbor - A router X is a symmetric 2-hop neighbor
of a router Y if router X is a symmetric 1-hop neighbor of a
symmetric 1-hop neighbor of router Y, but is not router Y itself.
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1-hop neighborhood - The 1-hop neighborhood of a router X is the set
of the 1-hop neighbors of router X.
Symmetric 1-hop neighborhood - The symmetric 1-hop neighborhood of a
router X is the set of the symmetric 1-hop neighbors of router X.
Symmetric 2-hop neighborhood - The symmetric 2-hop neighborhood of a
router X is the set of the symmetric 2-hop neighbors of router X.
(This may include routers in the 1-hop neighborhood, or even in
the symmetric 1-hop neighborhood, of router X.)
Constant - A constant is a numerical value which MUST be the same
for all MANET interfaces of all routers 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 router. A router MAY change interface parameter values at
any time, subject to some constraints.
Router parameter - A router parameter is a boolean or numerical
value, specified for each router, and not specific to an
interface. A router MAY change router parameter values at any
time, subject to some constraints.
Furthermore, this document uses the following notational conventions:
X contains y, or y is contained in X, is an unordered list
membership operator, returning true if the unordered list X
includes the element y, and returning false otherwise.
X contains Y, or Y is contained in X, is an unordered list inclusion
operator, returning true if the unordered list X contains all
elements y which are contained in Y, and returning false
otherwise.
a := b is an assignment operator, whereby the left side (a) is
assigned the value of the right side (b). a and b may be values,
addresses, or unordered lists (they must be of the same type).
c = d is a comparison operator, returning true if the value of the
left side (c) is equal to the value of the right side (d). c and d
may be values, addresses, or unordered lists (they must be of the
same type). If c and d are unordered lists, then they are
considered to be equal if they contain the same set of elements,
regardless of the order in which they are recorded in either list
(in which case c is contains d, and d contains c).
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e != f is a comparison operator, returning true where (e = f) would
have returned false, and returning false where (e = f) would have
returned true.
3. Applicability Statement
This protocol:
o Provides each router with local topology information up to two
hops away.
o Makes this local topology information a available to MANET routing
protocols in Information Bases, which are defined in this
specification.
o May interact with other protocols, such as MANET routing
protocols, see Section 3.1.
o Is applicable to networks, especially wireless networks, in which
unknown neighbors (i.e. other routers with which direct link layer
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 routers that each have one or more participating MANET
interfaces. The set of a router'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 "LL-MANET-Routers", and
either the "manet" UDP port or the "manet" IP protocol number, all
as specified in [manet-iana].
o Uses the packet and message formats specified in [RFC5444]. 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 [RFC5444].
o Can use relevant link layer information if it is available.
o Is designed to work in a completely distributed manner, and does
not depend on any central entity.
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3.1. Usage in Other Protocols
Other protocols which use neighborhood discovery MAY need to interact
with this protocol. This protocol is designed to permit such
interactions, in particular:
o Through accessing, and possibly extending, the information in the
Local Information Base (Section 6), the Interface Information Base
(Section 7) and the Neighbor Information Base (Section 8). These
Information Bases record the interface configuration of the
router, as well as the local connectivity, up to two hops away.
All updates to the elements specified in this document are subject
to the constraints specified in Appendix B.
o Through accessing an outgoing HELLO message prior to it being
transmitted over any MANET interface, and to add information (e.g.
TLVs) as specified in [RFC5444]. This may, for example, be to
allow a security protocol, as suggested in Section 16, to add a
TLV containing a cryptographic signature to the message, or be to
allow inserting relay selection information into a HELLO message
by way of adding a TLV to an outgoing HELLO message prior to it
being transmitted.
o Through accessing an incoming HELLO message, and potentially
discard it prior to processing by this protocol. This may, for
example, allow a security protocol, as suggested in Section 16, to
perform verification of HELLO message signatures and prevent
processing of unverifiable HELLO messages by this protocol.
o Through accessing an incoming HELLO message after it has been
completely processed by this protocol. This may, in particular,
allow a protocol which has added information, such as relay
selection information by way of inclusion of appropriate TLVs,
access to such information after appropriate updates has been
recorded in the Information Bases in this protocol.
o Through requesting that a HELLO message be generated at a specific
time. In that case, HELLO message generation MUST still respect
the constraints in Appendix B.
4. Protocol Overview and Functioning
The objective of this protocol is, for each router:
o To identify other routers which can be heard, and those with which
bidirectional links can be established (symmetric 1-hop
neighbors).
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o To agree on the status of such links with the corresponding
symmetric 1-hop neighbor.
o To find the interface addresses of the router'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 router and its interfaces.
o Discovers links from neighboring routers.
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 specific
MANET interface, or to a MANET router. This protocol allows all
parameters to be changed dynamically, and to be set independently
for each MANET router or MANET interface, as appropriate.
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.
4.1. Routers and Interfaces
In order for a router to participate in a MANET, it MUST have at
least one, and possibly more, MANET interfaces. Each MANET
interface:
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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
router has:
o A Local Information Base, containing the addresses of the
interfaces (MANET and non-MANET) of this router. The contents of
this Information Base are not changed by signaling.
o A Neighbor Information Base, recording information regarding
current and recently lost 1-hop neighbors of this router.
A router may have both MANET interfaces and non-MANET interfaces.
Interfaces of both of these types are recorded in a router's Local
Information Base, which is used, but not updated, by the signaling of
this protocol.
4.2. Information Base Overview
Each router maintains the Information Bases described in the
following sections. These are used for describing the protocol in
this document. An implementation of this protocol MAY maintain this
information in the indicated form, or in any other organization which
offers access to this information. In particular note that it is not
necessary to remove Tuples from Sets at the exact time indicated,
only to behave as if the Tuples were removed at that time.
4.2.1. Local Information Base
Each router 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 router.
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 router.
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The Local Interface Set is used for generating HELLO messages,
specifically for determining which interface addresses are to be
included and identified through inclusion of an appropriate TLV as
being a "local interface" of the router at which the HELLO message is
generated. The Removed Interface Address Set is used to allow a
router to detect if a neighbor is advertising a formerly used
address, and to exclude this from inclusion in the Interface
Information Bases described below.
The Local Information Base is used for generating signaling, but is
not itself updated by signaling specified in this document. Updates
to the Local Information Base are due to changes of the router
configuration, and may be allowed to trigger signaling.
4.2.2. Interface Information Bases
Each router 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 (see Section 14), 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 routers (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.
The Link Set for a MANET interface is used for generating HELLO
messages. Specifically, the Link Set information is included to both
allow other routers to detect bidirectionality (if router A
advertises router B as heard in a HELLO message and router B receives
that HELLO message, then router B knows that bidirectional
communication is possible between routers A and B), and to populate
the 2-Hop Set (if router C receives a HELLO message from router B
advertising a bidirectional link to address A, then router C knows
that address A is reachable in two hops via router B).
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The Link Set for a MANET interface is itself updated upon receipt of
a HELLO message, including to record link bidirectionality as
indicated above.
The 2-Hop Set for a MANET interface is updated as indicated above,
and is not itself used in generating HELLO messages.
4.2.3. Neighbor Information Base
Each router maintains a Neighbor 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 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 routers'
2-Hop Sets.
The Neighbor Set is used for recording which interface addresses of
neighbor routers are associated to the same router, and for including
this when generating HELLO messages such that 2-Hop sets in other
neighboring routers may record this information. The Neighbor Set
can itself be updated on receipt of a HELLO message.
The Lost Neighbor Set is used for generating HELLO messages.
Specifically, the Lost Neighbor Set is used for determining which
addresses are to be included in a HELLO and identified through
inclusion of an appropriate TLV as being "lost", i.e. formerly, but
no longer, recorded as a symmetric neighbor. The Lost Neighbor Set
can itself be updated on receipt of a HELLO message.
4.3. Signaling Overview
This protocol contains a signaling mechanism for maintaining the
Interface Information Bases and the Neighbor 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 B.
Signaling consists of a single type of message, known as a HELLO
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message. Each router generates HELLO messages on each of its MANET
interfaces. HELLO messages are generated independently on each MANET
interface of a MANET router; the content of a given HELLO message
depends on the interface for which it has been generated.
Each HELLO message identifies the MANET interface for which it is
generated and over which it is transmitted. This allows its
recipients to identify from which MANET interface this HELLO message
has been received. Each HELLO message also reports the other
interfaces (MANET and non-MANET) of the router, which allows
recipients to associate a set of interface addresses with a single
neighbor. Finally, each HELLO message also includes information from
the Link Set of the Interface Information Base of the MANET
interface, and from the Neighbor Information Base. This serves to
allow detection of bidirectional communication between two MANET
routers and over a pair of MANET interfaces, as well as to determine
symmetric 2-hop neighborhood information.
4.3.1. HELLO Message Generation
HELLO messages are generated by a router 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 router 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 MAY be scheduled independently for each MANET
interface, or, interface parameters permitting, using the same
schedule for all MANET interfaces of a router.
4.3.2. HELLO Message Content
Each HELLO message sent on 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 router to which the MANET interface belongs.
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o For each MANET interface, within every time interval of length
equal to the corresponding parameter REFRESH_INTERVAL, the HELLO
messages sent 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 Neighbor Information
Base of that router.
This applies to otherwise purely responsive routers as well as to
proactive routers. 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. Note that this rule applies at all times,
not just to times at which HELLO messages are sent. In
considering whether to include information in a HELLO message, the
sender MUST consider all times up to when it may send its next
HELLO message on that MANET interface.
o A HELLO message MUST include a VALIDITY_TIME Message TLV, as
specified in [timetlv], that indicates the length of time for
which the message content is to be considered valid, and is
therefore to be included in the receiving router's Interface
Information Base.
o A periodically generated HELLO message SHOULD include an
INTERVAL_TIME Message TLV, as specified in [timetlv], 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 [RFC5444]. For
example, if multipoint relays (MPRs) are to be calculated
similarly to as in [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 router are used to update:
o The Interface Information Base for the MANET interface on which
that HELLO message is received.
o The Neighbor Information Base.
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Specifically:
o The router ensures that there is a single Neighbor Tuple
corresponding to the originator of that HELLO message.
o If a Link Tuple corresponding to the link on which that HELLO
message was received exists, then the duration for which that Link
Tuple is kept 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 the
duration for which that Link Tuple is kept 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 neighbor addresses in the HELLO
message are added to the 2-Hop Set for the receiving interface, or
if already present, the duration for which the corresponding 2-Hop
Tuples are kept are extended.
In all cases the processing takes into account unexpected and
erroneous information in the HELLO message, maintaining the
constraints specified in Appendix B.
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 value is recorded with each link in the Link Set. A MANET
router considers links for which an insufficient link quality is
recorded to be lost. Modifying the recorded link quality of a link
in the Link Set 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 routers may interoperate whether they are using the
same, different, or no, link quality information. Link quality
information is thus not equivalent to a link metric.
5. Protocol Parameters and Constants
The parameters and constants used in this specification are described
in this section.
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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 routers) 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 routers 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 router's interface 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 router'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
specified in [RFC5148].
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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 router MUST include
all 1-hop neighbor information that 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 router may distribute
its neighbor advertisements between HELLO messages in any manner,
subject to the constraints above.
For a router 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.
If a router has more than one MANET interface, then, even if the
router configures different values of HELLO_INTERVAL on each
interface, the router SHOULD configure the same value of
HELLO_MIN_INTERVAL on all interfaces on which responsive HELLO
messages may be sent.
5.1.2. Information Validity Times
The following interface parameters manage the validity time of link
information:
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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 this information from their Link Sets.
L_HOLD_TIME MAY be set to zero, if accelerated information removal
is not required.
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 parameters 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 14):
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.
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o If INITIAL_QUALITY >= HYST_ACCEPT, then INITIAL_PENDING := false.
o If INITIAL_QUALITY < HYST_REJECT, then INITIAL_PENDING := true.
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. Router Parameters
The two router parameters defined by this specification are in the
category of information validity time.
5.2.1. Information Validity Time
The following router 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 this information from their 2-Hop Sets. N_HOLD_TIME MAY 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 router 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.
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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
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.
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HT_MAXJITTER
* If HT_MAXJITTER changes, then externally triggered HELLO
messages on this MANET interface MAY be rescheduled.
5.4. Constants
The constant C (time granularity) is used as specified in [timetlv].
6. Local Information Base
A router 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
router's interface configuration changes, then the Local Information
Base MUST reflect these changes. This MAY also result in signaling
to advertise these changes.
Interfaces and addresses MAY be excluded from the Local Information
Base, and hence from HELLO messages, if they are not to be used for
routing.
6.1. Local Interface Set
A router'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.
Local Interface Tuples are removed from the Local Interface Set only
when the routers' interface configuration changes, subject to
Section 9, i.e. they are not subject to timer-based expiration.
6.2. Removed Interface Address Set
A router's Removed Interface Address Set records addresses which were
recently local interface addresses. If a router's interface
addresses are immutable then this set is always empty and MAY be
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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 router.
IR_time specifies when this Tuple expires and MUST be removed.
7. Interface Information Base
A router 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 router 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.
An element which specifies a time is considered expired if the
current time is greater than or equal to that time. One such element
in most Tuples when expired indicates that the Tuple itself is
considered expired and MUST be removed when that element so
indicates. Tuples which do not have such a time element are removed
at other times as specified, for example a Neighbor Tuple is removed
when all corresponding Link Tuples have been removed.
7.1. Link Set
A router's Link Set records links from other routers 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;
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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.
L_status can take the values PENDING, HEARD, SYMMETRIC and LOST. The
values LOST, SYMMETRIC and HEARD are defined in Section 17.5. The
value PENDING is never used in a HELLO message, it is only used
locally by a router, and any value distinct from LOST, SYMMETRIC and
HEARD may be used.
L_status is defined by:
1. If L_pending = true, then L_status := PENDING;
2. otherwise, if L_lost = 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 router's 2-Hop Set records symmetric 2-hop neighbor interface
addresses, 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
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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.
8. Neighbor Information Base
Each router maintains a Neighbor Information Base that records
information about addresses of current and recently symmetric 1-hop
neighbors.
8.1. Neighbor Set
A router'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.
Neighbor Tuples are removed from the Neighbor Set only when
corresponding Link Tuples expire from the routers' Link Set, i.e.
Neighbor Tuples are not directly subject to timer-based expiration.
8.2. Lost Neighbor Set
A router's Lost Neighbor Set records addresses of all interfaces of
routers 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:
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(NL_neighbor_iface_addr, NL_time)
where:
NL_neighbor_iface_addr is an address of an interface of a router
which recently was a symmetric 1-hop neighbor of this router;
NL_time specifies when this Tuple expires and MUST be removed.
9. Local Information Base Changes
The Local Information Base MUST change to respond to changes in the
router's local interface configuration. The router MUST update its
Interface Information Base and Neighbor Information Base in response
to such changes. If any changes in the Interface Information Base or
the Neighbor Information Base satisfy any of the conditions described
in Section 13, then those changes must be applied immediately, unless
noted otherwise.
A router MAY transmit HELLO messages in response to these changes.
9.1. Adding an Interface
If an interface is added to the router 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 router, then this MUST result in
changes to the Local Information Base and to the Neighbor 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;
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* 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;
2. All Neighbor Tuples for which none of the addresses in its
N_neighbor_iface_addr_list are contained in any
L_neighbor_iface_addr_list in any remaining Link Set, are
removed.
If a router removes the Local Interface Tuple that contains the
interface address which is used to define the router's originator
address, as defined in [RFC5444], then the router MAY change
originator address. If this interface address may now be used by
another router (e.g. if the address was taken from a prefix no longer
delegated to this router, or if the address was assigned with an
expiration timer, and not renewed before expiration) then this router
MUST change originator address.
If the removed interface is the last MANET interface of the router,
then there will be no remaining Interface Information Bases, and the
router 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 any removed
Neighbor Tuple
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are removed; apply Section 13.2, but not Section 13.3.
3. Any Lost Neighbor Tuples whose NL_neighbor_iface_addr = the added
address, are removed.
4. Any 2-Hop Tuples whose N2_2hop_iface_addr = the added address,
are removed.
After adding the address and making these changes, a HELLO message
MAY be sent on all MANET interfaces.
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 router removes the interface address that is used to define the
router's originator address, as defined in [RFC5444], then the router
MAY change originator address. If this interface address may now be
used by another router then this router MUST change originator
address.
After removing the address and making these changes, a HELLO message
MAY be sent on all MANET interfaces.
10. Packets and Messages
The packet and message format used by this protocol is defined in
[RFC5444], which is used with the following considerations:
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o This protocol specifies one Message Type, the HELLO message.
o A HELLO message MAY use any combination of Message Header options.
o HELLO messages MUST NOT be forwarded.
o HELLO messages MAY be included in multi-message packets as
specified in [RFC5444].
o Received HELLO messages MUST be parsed in accordance with
[RFC5444]. A HELLO message which is not in conformance with
[RFC5444] MUST be discarded. A HELLO message may also be
discarded for other reasons, see Section 12.1.
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,
an Address Block TLV with Type = LINK_STATUS, are to be considered
as referring to an Address Block 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:
o Other Message TLVs.
o One or more Address Blocks, each with an associated Address Block
TLV Block, which MAY contain other Address Block TLVs.
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10.1.1. Address Blocks
All addresses in a router'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 from being included in an Address Block, provided that
this address is included as the sending address of the IP datagram in
which the HELLO message is included. All addresses of the router's
interfaces included in an Address Block MUST be associated with an
Address Block TLV with Type = LOCAL_IF, as defined in Table 1.
+----------+---------+----------------------------------------------+
| Name | Value | Description |
| | Length | |
+----------+---------+----------------------------------------------+
| LOCAL_IF | 1 octet | Specifies that the address is an address |
| | | associated with the interface on which the |
| | | message was sent (THIS_IF) or another |
| | | interface of the sending router (OTHER_IF). |
+----------+---------+----------------------------------------------+
Table 1: LOCAL_IF TLV definition
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.
+--------------+---------+------------------------------------------+
| Name | Value | Description |
| | Length | |
+--------------+---------+------------------------------------------+
| LINK_STATUS | 1 octet | Specifies the status of the link from |
| | | the indicated address (LOST, SYMMETRIC |
| | | or HEARD). |
| OTHER_NEIGHB | 1 octet | Specifies that the address is |
| | | (SYMMETRIC) or was (LOST) of an |
| | | interface of a symmetric 1-hop neighbor |
| | | of the router transmitting the HELLO |
| | | message. |
+--------------+---------+------------------------------------------+
Table 2: LINK_STATUS and OTHER_NEIGHB TLV definition
An Address Block TLV with Type = LINK_STATUS and Value = SYMMETRIC or
Value = LOST also performs the function of an Address Block TLV with
Type = OTHER_NEIGHB and the same value. The latter SHOULD NOT also
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be included. If an Address Block TLV with Type = LINK_STATUS and
Value = SYMMETRIC is combined with an Address Block 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 Address Block TLVs specified in this
specification.
11. HELLO Message Generation
Each MANET interface MUST generate HELLO messages according to the
specification in this section. HELLO messages are generated for each
HELLO interface independently. 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, provided that this address is
included as the sending address of the IP datagram in which the
HELLO message is included.
All such included addresses MUST be associated with an Address Block
TLV included with Type := LOCAL_IF and Value according to the
following:
o If the address is an address of the sending interface, then Value
:= THIS_IF.
o Otherwise, Value := OTHER_IF.
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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, other
than those from Link Tuples with L_status = PENDING.
o Other addresses of symmetric 1-hop neighbors from the Neighbor Set
of this router's Neighbor 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.)
o Other addresses of previously symmetric 1-hop neighbors from the
Lost Neighbor Set of this router's Neighbor 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
Address Block TLVs, respecting the parameter REFRESH_INTERVAL for
each association for each MANET interface. Specifically:
1. For each address (henceforth linked address) which is contained
in an L_neighbor_iface_addr_list of a Link Tuple in the Link Set
for this MANET interface, for which L_status != PENDING, include
the linked address with an associated Address Block TLV with:
* Type := LINK_STATUS; AND
* Value := L_status.
2. For each address (henceforth neighbor address) which is contained
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 Address Block TLV with Type = LINK_STATUS and Value
= SYMMETRIC, include the neighbor address with an associated
Address Block 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 Address Block TLV with:
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* Type := OTHER_NEIGHB; AND
* Value := LOST.
If any such addresses have been added since the last HELLO message
was sent on this MANET interface, or if their status (as indicated by
these TLVs and the values they associate with that address) have
changed since that address was last reported on this MANET interface,
then that address, and the indicated TLVs, MUST be included in the
HELLO message.
If a 1-hop neighbor address is specified with more than one
associated Address Block TLV, then these Address Block TLVs MAY be
independently included or excluded from each HELLO message. Each
such Address Block 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.
Address Block TLVs associated with the same address included in the
same HELLO message MAY be applied to the same or different copies of
that address.
11.2. HELLO Message Transmission
HELLO messages are transmitted in the packet/message format specified
by [RFC5444] 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:
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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, as
described in [RFC5148]. In this case HP_MAXJITTER MUST NOT be
greater than HELLO_MIN_INTERVAL.
12. HELLO Message Processing
On receiving a HELLO message, a router MUST first check if the
message is invalid for processing by this router, as defined in
Section 12.1. Otherwise the receiving router MUST update its
appropriate Interface Information Base and its Neighbor Information
Base as specified in Section 12.3 to Section 12.6. These updates
MUST be performed in the order in which they are presented in this
specification. If any changes satisfy any of the conditions
described in Section 13 then the indicated consequences MUST be
applied immediately, unless noted otherwise.
All message processing, including determination of whether a message
is invalid, considers only TLVs with Type Extension = 0. TLVs with
any other type extension are ignored. All references to, for
example, a TLV with Type = LINK_STATUS refer to a TLV with Type =
LINK_STATUS and Type Extension = 0.
12.1. Invalid Message
A received HELLO message is invalid for processing by this router if
any of the following conditions are true.
o The message has a <msg-hop-limit> field in its <msg-header> with a
value other than one. (Note that the message need not have a
<msg-hop-limit> field.)
o The message has a <msg-hop-count> field in its <msg-header> with a
value other than zero. (Note that the message need not have a
<msg-hop-count> field.)
o The message does not have a Message TLV with Type = VALIDITY_TIME
in its Message TLV Block.
o The message has more than one Message TLV with Type =
VALIDITY_TIME in its Message TLV Block, and these Message TLVs
indicate different validity times, as specified by [timetlv].
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o The message has any Address Block TLV(s) with Type = LOCAL_IF and
any single value v such that v != THIS_IF and v!= OTHER_IF.
o Any address (including different copies of an address, in the same
or different Address Blocks) is associated with more than one
value by one or more Address Block TLV(s) with Type = LOCAL_IF.
o Any address (the local address) associated with an Address Block
TLV with Type = LOCAL_IF is one of the receiving router's current
or recently used interface addresses (i.e. the local address is
contained in any I_local_iface_addr_list in the Local Interface
Set or the local address = any IR_local_iface_addr in the Removed
Interface Address Set).
o The message has any Address Block TLV(s) with Type = LINK_STATUS
with any single value v such that v != LOST, v != SYMMETRIC, and
v!= HEARD.
o Any address (including different copies of an address, in the same
or different Address Blocks) is associated with more than one
value by one or more Address Block TLVs with Type = LINK_STATUS.
o The message has any Address Block TLV(s) with Type = OTHER_NEIGHB
with any single value v such that v!= LOST and v!= SYMMETRIC.
o Any address (including different copies of an address, in the same
or different Address Blocks) is associated with more than one
value by one or more Address Block TLVs with Type = OTHER_NEIGHB.
An invalid message MUST be silently discarded, without updating the
router's Information Bases. A router MAY recognize additional
reasons for identifying that a message is badly formed, and discard
such messages.
12.2. Definitions
For the purpose of this section, note the following definitions:
o "validity time" is calculated from the Message TLV with Type =
VALIDITY_TIME of the HELLO message as specified in [timetlv].
(Note that, as specified by Section 12.1, there must be such a
Message TLV, and if there is more than one, they must indicate the
same validity time.) 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
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o "Sending Address List" is the list of the addresses contained in
the HELLO message with an associated Address Block 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
Address Block 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 router 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.
12.3. Updating the Neighbor Set
On receiving a HELLO message, the router 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 matching Neighbor Tuple's N_neighbor_iface_addr_list
!= Neighbor Address List, then:
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1. For each address (henceforth removed address) which is
contained in that N_neighbor_iface_addr_list, but is not
contained 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
contained 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.
2. Replace the matching Neighbor Tuples by a single Neighbor
Tuple with:
+ N_neighbor_iface_addr_list := Neighbor Address List;
+ N_symmetric := false
12.4. Updating the Lost Neighbor Set
On receiving a HELLO message, a router MUST update its Lost Neighbor
Set:
1. For each address (henceforth lost address) which is contained 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.
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12.5. Updating the Link Set
On receiving a HELLO message, a router 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 13.2, 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 13.2, 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;
* 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 router 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 an Address Block TLV with Type =
LINK_STATUS and with Value = HEARD or Value = SYMMETRIC
then:
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- L_SYM_time := current time + validity time.
2. Otherwise if any receiving address in the HELLO message
is associated with an Address Block 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 L_status = 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 L_status = SYMMETRIC, then:
+ L_time := max(L_time, L_HEARD_time + L_HOLD_TIME).
12.6. Updating the 2-Hop Set
On receiving a HELLO message a router 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 whose 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, where:
+ 2-hop address is not contained in the Neighbor Address
List;
+ 2-hop address is not contained in any
I_local_iface_addr_list; AND
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+ 2-hop address != any IR_local_iface_addr
4. If 2-hop address has an associated Address Block 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.
5. Otherwise if the 2-hop address has an Address Block TLV
with:
- Type = LINK_STATUS and Value = LOST or Value = HEARD;
OR
- Type = OTHER_NEIGHB and Value =o LOST;
then remove all 2-Hop Tuples with:
- N2_neighbor_iface_addr_list contains one or more
addresses in the Sending Address List; AND
- N2_2hop_iface_addr = 2-hop address.
13. Other Information Base Changes
The Interface and Neighbor 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).
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Events which cause changes in the Information Bases are:
o A Link Tuple's L_status changes to symmetric.
o A Link Tuple's L_status changes from symmetric, or the Link Tuple
is removed.
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.
If a Link Tuple is removed, or if L_status changes from symmetric and
L_HEARD_time expires, then Section 13.2 MUST be performed before
Section 13.3 for that Link Tuple.
A router MAY report updated information in response to any of these
changes in HELLO message(s), subject to the constraints in
Section 11.
A router 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 L_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 Symmetric
If, for any Link Tuple which does not have L_status = SYMMETRIC:
o L_status := 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 contains
L_neighbor_iface_addr_list, set:
* N_symmetric := true.
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2. Remove all Lost Neighbor Tuples whose NL_neighbor_iface_addr is
contained in that N_neighbor_iface_addr_list.
13.2. 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:
* 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
where:
+ L_neighbor_iface_addr_list is 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.
13.3. Link Tuple Heard Timeout
If, for any Link Tuple:
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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 where:
* L_neighbor_iface_addr_list is contained in
N_neighbor_iface_addr_list; AND
* L_HEARD_time is not expired;
then remove the Neighbor Tuple.
14. Link Quality
Link quality is a mechanism whereby a router 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.
Link quality information for a link is generated (e.g. through access
to signal to noise ratio, packet loss rate, or other information from
the link layer) and used only locally, i.e. is not included in
signaling, and routers may interoperate whether they are using the
same, different, or no, link quality information.
For deployments where no link quality is used, the considerations in
Section 14.1 apply. For deployments where 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.
14.1. Deployment Without Link Quality
In order for a router to not employ link quality, the router MUST
define:
o INITIAL_PENDING := false;
o INITIAL_QUALITY >= HYST_REJECT (there is no reason not to define
INITIAL_QUALITY := 1).
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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, on the value of parameter
INITIAL_PENDING). 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 router 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.
* Otherwise this is such that L_quality >= HYST_REJECT. To
ensure this, a router MUST NOT define INITIAL_PENDING = false
and INITIAL_QUALITY < HYST_REJECT. (A router 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 router sets L_pending := 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.
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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 != 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.
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 router 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
packet acknowledgement reception and loss information.
o Receipt or loss of control packets. If control packets include a
sequential packet sequence number, as defined in [RFC5444], then
link quality can be updated when a control packet is received,
whether or not it contains a HELLO message. The link quality may
then, for example, be based on whether the last N out of M control
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packets on the link were received, or may use a "leaky integrator"
tracking packet reception and loss.
o Receipt or loss of HELLO messages. If the maximum interval
between HELLO messages is known (such as by inclusion in HELLO
messages of a Message TLV with Type := INTERVAL_TIME, as defined
in [timetlv]) then the loss of HELLO messages can be determined
without the need to receive a later 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.
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 Router 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
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o INITIAL_QUALITY := 1
o INITIAL_PENDING := false
15.5. Jitter Interface Parameters
o HP_MAXJITTER := HELLO_INTERVAL/4
o HT_MAXJITTER := HP_MAXJITTER
15.6. Constants
o C := 1/1024 second
16. Security Considerations
The objective of this protocol is to allow each router in the network
to acquire information describing its 1-hop and symmetric 2-hop
neighborhoods. This is acquired through message exchange between
neighboring routers. The information is made available through the
Interface Information Bases and Neighbor Information Base, describing
the router'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 a router for some reason, whether malice or malfunction, injects
invalid HELLO messages, incorrect information may be recorded in
other routers' Information Bases. The protocol specification does,
however, prevent inconsistent information from being injected in the
protocol sets through the constraints in Appendix B. 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, in
Section 16.1. In addition, in Section 16.2, the security suggestions
in [RFC5444] are considered for applicability.
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,
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LINK_STATUS and OTHER_NEIGHB Address Block TLVs that causes problems.
A router may provide false information about its own identity:
* The HELLO message may contain addresses with an associated
LOCAL_IF Address Block TLV which do not correspond to addresses
of interfaces of the router transmitting the HELLO message.
* The HELLO message may omit addresses, or their associated
LOCAL_IF Address Block TLV, of interfaces of the router
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 Address
Block TLV value associated with one or more local interface
addresses, indicating incorrectly whether they are associated
with the MANET interface over which the HELLO message is
transmitted.
A router may provide false information about the identity of other
routers:
* A present LINK_STATUS Address Block 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 Address Block 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 Address Block TLV may, incorrectly,
identify an address as being of a router which is or was in the
sending router's symmetric 1-hop neighborhood;
* A consistently absent OTHER_NEIGHB Address Block TLV may,
incorrectly, fail to identify an address as being of a router
which is or was in the sending router's symmetric 1-hop
neighborhood;
* The value of a LINK_STATUS Address Block TLV may incorrectly
indicate the status (LOST, SYMMETRIC or HEARD) of the link from
a 1-hop neighbor.
* The value of an OTHER_NEIGHB Address Block TLV may incorrectly
indicate the status (LOST or SYMMETRIC) of a symmetric 1-hop
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neighbor.
16.2. Authentication, Integrity and Confidentiality Suggestions
The security mechanisms suggested in [RFC5444] with respect to
authentication and integrity can be applied to this neighborhood
discovery protocol, with the following additional considerations:
o As HELLO messages MUST NOT be forwarded, the fields <msg-hop-
count> and <msg-hop-limit> are either omitted, or will always have
the values of 0 and 1, respectively.
o Consequently, a cryptographic signature can be calculated based on
the entire HELLO message, including its Message Header, and
included in a Message TLV of an appropriate type.
o As HELLO messages MUST NOT be forwarded, and in case hop-by-hop
packet level authentication and integrity is ensured by including
an appropriate Packet TLV containing a cryptographic signature
across the entire packet, inclusion of an additional Message TLV
containing a cryptographic signature for the HELLO Message may not
be necessary.
The security mechanisms suggested in [RFC5444] with respect to
confidentiality can be directly applied to this neighborhood
discovery protocol.
17. IANA Considerations
This specification defines one Message Type, which must be allocated
from the "Message Types" repository of [RFC5444], and three Address
Block TLV Types, which must be allocated from the "Message TLV Types"
repository of [RFC5444].
17.1. Expert Review: Evaluation Guidelines
For the registries where an Expert Review is required, the designated
expert SHOULD take the same general recommendations into
consideration as are specified by [RFC5444].
17.2. Message Types
This specification defines one Message Type, to be allocated from the
0-223 range of the "Message Types" namespace defined in [RFC5444], as
specified in Table 3.
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+-------+------+-----------------+
| Name | Type | Description |
+-------+------+-----------------+
| HELLO | TBD1 | Local signaling |
+-------+------+-----------------+
Table 3: Message Type assignment
17.3. Message-Type-specific TLV Type Registries
IANA is requested to create a registry for Message-Type-specific
Message TLVs for HELLO messages, in accordance with Section 6.4 of
[RFC5444], and with initial assignments and allocation policies as
specified in Table 4.
+---------+-------------+-------------------+
| Type | Description | Allocation Policy |
+---------+-------------+-------------------+
| 128-223 | Unassigned | Expert Review |
+---------+-------------+-------------------+
Table 4: HELLO Message-Type-specific Message TLV Types
IANA is requested to create a registry for Message-Type-specific
Address Block TLVs for HELLO messages, in accordance with Section 6.5
of [RFC5444], and with initial assignments and allocation policies as
specified in Table 5.
+---------+-------------+-------------------+
| Type | Description | Allocation Policy |
+---------+-------------+-------------------+
| 128-223 | Unassigned | Expert Review |
+---------+-------------+-------------------+
Table 5: HELLO Message-Type-specific Address Block TLV Types
17.4. Address Block TLV Types
This specification defines three Address Block TLV Types, which must
be allocated from the "Address Block TLV Types" namespace defined in
[RFC5444]. IANA are requested to make allocations in the 0-127 range
for these types. This will create three new type extension
registries with assignments as specified in Table 6, Table 7 and
Table 8. Specifications of these Address Block TLVs are in
Section 10.1.1, with value constants defined in Section 17.5.
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+----------+------+-----------+-------------------------------------+
| Name | Type | Type | Description |
| | | extension | |
+----------+------+-----------+-------------------------------------+
| LOCAL_IF | TBD2 | 0 | Specifies that the address is |
| | | | associated with a local interface |
| | | | of the sending router |
| | | 1-255 | Expert Review |
+----------+------+-----------+-------------------------------------+
Table 6: Address Block TLV Type assignment: LOCAL_IF
+-------------+------+-----------+----------------------------------+
| Name | Type | Type | Description |
| | | extension | |
+-------------+------+-----------+----------------------------------+
| LINK_STATUS | TBD3 | 0 | Specifies the status of the link |
| | | | from the indicated address |
| | | | (LOST, SYMMETRIC or HEARD) |
| | | 1-255 | Expert Review |
+-------------+------+-----------+----------------------------------+
Table 7: Address Block TLV Type assignment: LINK_STATUS
+--------------+------+-----------+---------------------------------+
| Name | Type | Type | Description |
| | | extension | |
+--------------+------+-----------+---------------------------------+
| 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 |
| | | | router transmitting the message |
| | | 1-255 | Expert Review |
+--------------+------+-----------+---------------------------------+
Table 8: Address Block TLV Type assignment: OTHER_NEIGHB
17.5. LINK_STATUS and OTHER_NEIGHB Values
The values which the LOCAL_IF Address Block TLV can use are the
following:
o THIS_IF := 0
o OTHER_IF := 1
The values which the LINK_STATUS Address Block TLV can use are the
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following:
o LOST := 0
o SYMMETRIC := 1
o HEARD := 2
The values which the OTHER_NEIGHB Address Block TLV can use are the
following:
o LOST := 0
o SYMMETRIC := 1
18. 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 ATC, UK,
<chris.dearlove@baesystems.com>
o Philippe Jacquet, INRIA, France, <Philippe.Jacquet@inria.fr>
19. 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 (listed alphabetically): Alan Cullen
(BAE Systems), Ulrich Herberg (LIX), Satoh Hiroki (Hitachi) Joe
Macker (NRL), Charles E. Perkins (WiChorus), Laurent Viennot (INRIA),
and the entire IETF MANET working group.
20. References
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20.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, BCP 14, March 1997.
[RFC5148] Clausen, T., Dearlove, C., and B. Adamson, "Jitter
considerations in MANETs", RFC 5148, February 2008.
[RFC5444] Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
"Generalized MANET Packet/Message Format", RFC 5444,
February 2009.
[timetlv] Clausen, T. and C. Dearlove, "Representing multi-value
time in MANETs", Work In
Progress draft-ietf-manet-timetlv-08.txt,
September 2008.
[manet-iana] Chakeres, I., "IANA Allocations for MANET Protocols",
Work In Progress draft-ietf-manet-iana-07.txt,
November 2007.
20.2. Informative References
[RFC2501] Macker, J. and S. Corson, "Mobile Ad hoc Networking
(MANET): Routing Protocol Performance Issues and
Evaluation Considerations", RFC 2501, January 1999.
[RFC3626] Clausen, T. and P. Jacquet, "The Optimized Link State
Routing Protocol", RFC 3626, October 2003.
[RFC5449] Clausen, T., Baccelli, E., Nguyen, D., and P. Jacquet,
"OSPF Multipoint Relay (MPR) Extension for Ad Hoc
Networks", RFC 5449, February 2009.
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 Address Block TLVs. These Address Block TLVs may
have Type = LINK_STATUS or Type = OTHER_NEIGHB, or both. Address
Block TLVs with Type = LINK_STATUS may have three possible values
(Value = HEARD, Value = SYMMETRIC or Value = LOST), and Address Block
TLVs of TYPE = OTHER_NEIGHB may have two possible values (Value =
SYMMETRIC or Value = LOST). When both Address Block TLVs are
associated with the same address only certain combinations of these
Address Block TLV values are necessary, and are the only combinations
generated by the algorithm in Section 11. These combinations are
indicated in Table 9.
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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. The cell labeled with "No*" is actually inconsistent, it
is handled by ignoring the Address Block TLV with Type =
OTHER_NEIGHB.
+----------------+----------------+----------------+----------------+
| | 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 9: LINK_STATUS and OTHER_NEIGHB TLV combinations
Appendix B. Constraints
Any process which updates the Local Information Base or the Neighbor
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:
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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).
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.
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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 is = 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 is = 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
= 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
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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.
Appendix C. HELLO Message Example
An example HELLO message, transmitted by an originator router with a
single MANET interface, is as follows.
The message has full Message Header (four bit flags field value is
15). Its four bit Message Address Length field has value 3 and hence
addresses in the message have length four octets, here being IPv4
addresses. The message is as transmitted 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 Message TLV with flags octet value 16,
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
flags octet value 128 indicates an address Head but no address Tail,
and no address prefixes. The Head Length of 3 octets indicates
address Mid sections of one octet each (Mid 0 to Mid 4).
The following Address Block TLV Block (content length 14 octets)
includes two Address Block TLVs. The first is a LOCAL_IF Address
Block TLV which (with flags octet value 80) indicates that a single
address, with index 0 (i.e. Head:Mid 0) is the single local
interface address of this router (the 1 octet value THIS_IF indicates
that this address is of this interface). The second is a LINK_STATUS
Address Block TLV which (with flags octet value 48) specifies the
link status values of all reported neighbors in a single multivalue
Address Block TLV which covers the addresses with indexes 1 to 4.
The Address Block TLV value length of 4 octets indicates one octet
per value per address. The last four addresses have associated link
status, the first and second HEARD, the third SYMMETRIC, and the
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 |1 1 1 1 0 0 1 1|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 1 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 0 0 1|0 1 1 0 0 1 0 0| INTERVAL_TIME |0 0 0 1 0 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|1 0 0 0 0 0 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|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 1 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 1 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 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 TLV 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 1 1|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 1 0 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|1 0 0 0 0 0 0 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 0 1 0 1 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0 0 1 0 0| HEARD | HEARD | SYMMETRIC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LOST |
+-+-+-+-+-+-+-+-+
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 router's 1-hop neighborhood. HELLO messages MUST NOT be
forwarded.
A router 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 router in the
network employing this protocol.
A router 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 router in the network
employing this protocol.
Authors' Addresses
Thomas Heide Clausen
LIX, Ecole Polytechnique
Phone: +33 6 6058 9349
EMail: T.Clausen@computer.org
URI: http://www.ThomasClausen.org/
Clausen, et al. Expires September 10, 2009 [Page 60]
Internet-Draft MANET-NHDP March 2009
Christopher Dearlove
BAE Systems ATC
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
Clausen, et al. Expires September 10, 2009 [Page 61]
