draft-ietf-manet-timetlv-07.txt   draft-ietf-manet-timetlv-08.txt 
Mobile Ad hoc Networking (MANET) T. Clausen Mobile Ad hoc Networking (MANET) T. Clausen
Internet-Draft LIX, Ecole Polytechnique, France Internet-Draft LIX, Ecole Polytechnique, France
Intended status: Standards Track C. Dearlove Intended status: Standards Track C. Dearlove
Expires: March 20, 2009 BAE Systems Advanced Technology Expires: March 30, 2009 BAE Systems Advanced Technology
Centre Centre
September 16, 2008 September 26, 2008
Representing multi-value time in MANETs Representing multi-value time in MANETs
draft-ietf-manet-timetlv-07 draft-ietf-manet-timetlv-08
Status of This Memo Status of This Memo
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Abstract Abstract
This document describes a general and flexible TLV (type-length-value This document describes a general and flexible TLV (type-length-value
structure) for representing time using the generalized MANET packet/ structure) for representing time-values, such as an interval or a
message format. It defines two message and two address block TLVs duration, using the generalized MANET packet/message format. It
for representing validity and interval times for MANET routing defines two message and two address block TLVs for representing
protocols. validity and interval times for MANET routing protocols.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Motivation and Rationale . . . . . . . . . . . . . . . . . 3 1.1. Motivation and Rationale . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Applicability Statement . . . . . . . . . . . . . . . . . . . 5 3. Applicability Statement . . . . . . . . . . . . . . . . . . . 6
4. Protocol Overview and Functioning . . . . . . . . . . . . . . 5 4. Protocol Overview and Functioning . . . . . . . . . . . . . . 6
5. Representing Time . . . . . . . . . . . . . . . . . . . . . . 5 5. Representing Time . . . . . . . . . . . . . . . . . . . . . . 6
6. General Time TLV Structure . . . . . . . . . . . . . . . . . . 6 6. General Time TLV Structure . . . . . . . . . . . . . . . . . . 7
6.1. Single-value Time TLVs . . . . . . . . . . . . . . . . . . 7 6.1. Single-value Time TLVs . . . . . . . . . . . . . . . . . . 8
6.2. Multi-value Time TLVs . . . . . . . . . . . . . . . . . . 8 6.2. Multi-value Time TLVs . . . . . . . . . . . . . . . . . . 9
7. Message TLVs . . . . . . . . . . . . . . . . . . . . . . . . . 9 7. Message TLVs . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. INTERVAL_TIME TLV . . . . . . . . . . . . . . . . . . . . 9 7.1. INTERVAL_TIME TLV . . . . . . . . . . . . . . . . . . . . 10
7.2. VALIDITY_TIME TLV . . . . . . . . . . . . . . . . . . . . 9 7.2. VALIDITY_TIME TLV . . . . . . . . . . . . . . . . . . . . 10
8. Address Block TLVs . . . . . . . . . . . . . . . . . . . . . . 9 8. Address Block TLVs . . . . . . . . . . . . . . . . . . . . . . 10
8.1. INTERVAL_TIME TLV . . . . . . . . . . . . . . . . . . . . 9 8.1. INTERVAL_TIME TLV . . . . . . . . . . . . . . . . . . . . 10
8.2. VALIDITY_TIME TLV . . . . . . . . . . . . . . . . . . . . 10 8.2. VALIDITY_TIME TLV . . . . . . . . . . . . . . . . . . . . 11
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
9.1. Expert Review: Evaluation Guidelines . . . . . . . . . . . 10 9.1. Expert Review: Evaluation Guidelines . . . . . . . . . . . 11
9.2. Message TLV Types . . . . . . . . . . . . . . . . . . . . 11 9.2. Message TLV Types . . . . . . . . . . . . . . . . . . . . 12
9.3. Address Block TLV Types . . . . . . . . . . . . . . . . . 11 9.3. Address Block TLV Types . . . . . . . . . . . . . . . . . 12
10. Security Considerations . . . . . . . . . . . . . . . . . . . 12 10. Security Considerations . . . . . . . . . . . . . . . . . . . 13
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
11.1. Normative References . . . . . . . . . . . . . . . . . . . 12 11.1. Normative References . . . . . . . . . . . . . . . . . . . 13
11.2. Informative References . . . . . . . . . . . . . . . . . . 12 11.2. Informative References . . . . . . . . . . . . . . . . . . 13
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 12 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 13
1. Introduction 1. Introduction
The generalized packet/message format [packetbb] specifies a The generalized packet/message format [packetbb] specifies a
signaling format which MANET routing protocols can employ for signaling format which MANET routing protocols can employ for
exchanging protocol information. This format presents the ability to exchanging protocol information. This format presents the ability to
express and associate attributes to packets, messages or addresses, express and associate attributes to packets, messages or addresses,
by way of a general TLV (type-length-value) mechanism. by way of a general TLV (type-length-value) mechanism.
This document specifies a general Time TLV structure, which can be This document specifies a general Time TLV structure, which can be
used by any MANET routing protocol that needs to express either used by any MANET routing protocol that needs to express either
single time-values or a set of time-values with each time-value single time-values or a set of time-values with each time-value
associated with a range of hop counts, as provided by the message associated with a range of hop counts, as provided by the message
header of [packetbb]. This allows a receiving node to determine a header of [packetbb]. This allows a receiving node to determine a
single time-value if either it knows its hop count from the single time-value if either it knows its hop count from the
originator node, or the Time TLV specifies a single time-value. originator node, or the Time TLV specifies a single time-value.
A time-value is, in this context, not an "absolute point in time",
but rather an interval or a duration. An instance of a Time TLV can,
therefore, express an interval or a duration such as "10 seconds".
This document also specifies two message TLV types, which use the TLV This document also specifies two message TLV types, which use the TLV
structure proposed. These TLV types are INTERVAL_TIME and structure proposed. These TLV types are INTERVAL_TIME and
VALIDITY_TIME, specifying respectively the maximum time before VALIDITY_TIME, specifying respectively the maximum time before
another message of the same type as this message from the same another message of the same type as this message from the same
originator should be received, and the duration for which the originator should be received, and the duration for which the
information in this message is valid after receipt. Note that, if information in this message is valid after receipt. Note that, if
both are present, then the latter will usually be greater than the both are present, then the latter will usually be greater than the
former in order to allow for possible message loss. former in order to allow for possible message loss.
This document also specifies two address block TLV types, which use This document also specifies two address block TLV types, which use
the TLV structure proposed. These TLV types are INTERVAL_TIME and the TLV structure proposed. These TLV types are INTERVAL_TIME and
VALIDITY_TIME, defined equivalently to the two message TLVs with the VALIDITY_TIME, defined equivalently to the two message TLVs with the
same names. same names.
1.1. Motivation and Rationale 1.1. Motivation and Rationale
The Time TLV structure, specified in this document, is intended to be
used as a component in a MANET routing protocol, e.g. to indicate the
expected spacing between successive transmissions of a given message
type, by including a Time TLV in transmitted messages.
Some MANET routing protocols may employ very short spacing for some
messages and very long spacing for others, or may change the message
transmission rate according to observed behavior. For example, if a
network is observed at some point in time to exhibit a highly dynamic
topology, a very short (sub-second) message spacing could be
appropriate, whereas if the network later is observed to stabilize,
multi-hour message spacing may become appropriate. Different MANET
routing protocols and different deployments of MANET routing
protocols may have different granularity requirement and bounds on
shortest and longest spacing between successive message
transmissions.
In addition, MANET routing protocol deployments typically use
bandwidth limited wireless network interfaces, and therefore prefer
to trade off computational complexity for a saving in the number of
bits transmitted. This is practical in this case, because the
intended usages of Time TLVs, including the specified examples of
message interval time and information validity time, do not require
high precision values of time.
The Time TLV structure, specified in this document, caters to these
characteristics by:
o encoding time-values, such as an interval or a duration, in an 8
bit field; while
o allowing these time-values to range from "very small" (e.g. 1/1024
second) to "very long" (e.g. 45 days); and
o allowing a MANET routing protocol, or a deployment, to parametrize
this (e.g. to attain finer granularity at the expense of a lower
upper bound) through a single parameter, C.
The parameter C must be the same for all MANET routers in the same
deployment.
The TLV mechanism as specified in [packetbb] allows associating a The TLV mechanism as specified in [packetbb] allows associating a
"value" to either a packet, a message or to addresses. The data "value" to either a packet, a message or to addresses. The data
structure for doing so - the TLV - is identical in each of the three structure for doing so - the TLV - is identical in each of the three
cases, however the TLV's position in a received packet allows cases, however the TLV's position in a received packet allows
determining if that TLV is a "packet TLV" (it appears in the packet determining if that TLV is a "packet TLV" (it appears in the packet
header, before any messages), a "message TLV" (it appears in the TLV header, before any messages), a "message TLV" (it appears in the TLV
block immediately following a message header) or an "address block block immediately following a message header) or an "address block
TLV" (it appears in the TLV block immediately following an address TLV" (it appears in the TLV block immediately following an address
block). block).
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6. General Time TLV Structure 6. General Time TLV Structure
The following data structure allows the representation of a single The following data structure allows the representation of a single
time-value, or of a default time-value plus pairs of (time-values, time-value, or of a default time-value plus pairs of (time-values,
hop counts) for when hop count dependent time-values are required. hop counts) for when hop count dependent time-values are required.
The time-values are represented as time-codes as defined in The time-values are represented as time-codes as defined in
Section 5. This <time-data> data structure is specified, using the Section 5. This <time-data> data structure is specified, using the
regular expression syntax of [packetbb], by: regular expression syntax of [packetbb], by:
<time-data> = (<time-code><hop count>)*<time-code> <time-data> = (<time-code><hop-count>)*<time-code>
where: where:
<time-code> is an 8 bit unsigned integer field containing a time- <time-code> is an 8 bit unsigned integer field containing a time-
code as defined in Section 5. code as defined in Section 5.
<hop count> is an 8 bit unsigned integer field specifying a hop <hop-count> is an 8 bit unsigned integer field specifying a hop
count from the message originator. count from the message originator.
A <time-data> structure thus consists of an odd number of octets; A <time-data> structure thus consists of an odd number of octets;
with a repetition factor of n for the (time, hop count) pairs in the with a repetition factor of n for the (time, hop count) pairs in the
regular expression syntax, it contains 2n+1 octets. On reception, n regular expression syntax, it contains 2n+1 octets. On reception, n
is determined from the length. is determined from the length.
A <time-data> field may be thus represented by: A <time-data> field may be thus represented by:
<t_1><d_1><t_2><d_2> ... <t_i><d_i> ... <t_n><d_n><t_default> <t_1><d_1><t_2><d_2> ... <t_i><d_i> ... <t_n><d_n><t_default>
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11. References 11. References
11.1. Normative References 11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, BCP 14, March 1997. Requirement Levels", RFC 2119, BCP 14, March 1997.
[packetbb] Clausen, T., Dearlove, C., Dean, J., and C. Adjih, [packetbb] Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
"Generalized MANET Packet/Message Format", "Generalized MANET Packet/Message Format",
draft-ietf-manet-packetbb-15.txt (work in progress), draft-ietf-manet-packetbb-16.txt (work in progress),
September 2008. September 2008.
11.2. Informative References 11.2. Informative References
[RFC3626] Clausen, T. and P. Jacquet, "The Optimized Link State [RFC3626] Clausen, T. and P. Jacquet, "The Optimized Link State
Routing Protocol", RFC 3626, October 2003. Routing Protocol", RFC 3626, October 2003.
Appendix A. Acknowledgements Appendix A. Acknowledgements
The authors would like to thank Brian Adamson and Justin Dean (both The authors would like to thank Brian Adamson and Justin Dean (both
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