< draft-irtf-dtnrg-sdnv-04.txt   draft-irtf-dtnrg-sdnv-05.txt >
Network Working Group W. Eddy Network Working Group W. Eddy
Internet-Draft MTI Systems Internet-Draft MTI Systems
Intended status: Informational November 19, 2009 Intended status: Informational December 21, 2009
Expires: May 23, 2010 Expires: June 24, 2010
Using Self-Delimiting Numeric Values in Protocols Using Self-Delimiting Numeric Values in Protocols
draft-irtf-dtnrg-sdnv-04 draft-irtf-dtnrg-sdnv-05
Abstract Abstract
Self-Delimiting Numeric Values (SDNVs) have recently been introduced Self-Delimiting Numeric Values (SDNVs) have recently been introduced
as a field type in proposed Delay-Tolerant Networking protocols. as a field type in proposed Delay-Tolerant Networking protocols.
SDNVs encode an arbitrary-length non-negative integer or arbitrary- SDNVs encode an arbitrary-length non-negative integer or arbitrary-
length bit-string with minimum overhead. They are intended to length bit-string with minimum overhead. They are intended to
provide protocol flexibility without sacrificing economy, and to provide protocol flexibility without sacrificing economy, and to
assist in future-proofing protocols under development. This document assist in future-proofing protocols under development. This document
describes formats and algorithms for SDNV encoding and decoding, describes formats and algorithms for SDNV encoding and decoding,
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on May 23, 2010. This Internet-Draft will expire on June 24, 2010.
Copyright Notice Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
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This document is a product of the Internet Research Task Force (IRTF) This document is a product of the Internet Research Task Force (IRTF)
Delay-Tolerant Networking (DTN) Research Group (DTNRG). The document Delay-Tolerant Networking (DTN) Research Group (DTNRG). The document
has received review and support within the DTNRG, as discussed in the has received review and support within the DTNRG, as discussed in the
Acknowledgements section of this document. Acknowledgements section of this document.
This document begins by describing a common problem encountered in This document begins by describing a common problem encountered in
network protocol engineering. It then provides some background on network protocol engineering. It then provides some background on
the Self-Delimiting Numeric Values (SDNVs) proposed for use in DTN the Self-Delimiting Numeric Values (SDNVs) proposed for use in DTN
protocols, and motivates their potential applicability in other protocols, and motivates their potential applicability in other
networking protocols. The DTNRG has created SDNVs to meet the networking protocols. One example of SDNVs being used outside of the
challenges it attempts to solve, and it has been noted that SDNVs DTN protocols is in Hixie's Web Socket protocol
closely resemble certain constructs within ASN.1 and even older ITU [I-D.hixie-thewebsocketprotocol], which includes a binary frame
protocols, so the problems are not new or unique to DTN. length indicator field identical to an SDNV. The DTNRG has created
SDNVs to meet the challenges it attempts to solve, and it has been
noted that SDNVs closely resemble certain constructs within ASN.1 and
even older ITU protocols, so the problems are not new or unique to
DTN. SDNVs focus strictly on numeric values or bitstrings, while
other mechanisms have been developed for encoding more complex data
structures, such as ASN.1 encoding rules, and Haverty's MSDTP
[RFC0713]. Because of this focus, SDNVs are can be quickly
implemented with only a small amount of code.
SDNVs are tersely defined in both the bundle protocol [RFC5050] and SDNVs are tersely defined in both the bundle protocol [RFC5050] and
LTP [RFC5326] specifications, due to the flow of document production LTP [RFC5326] specifications, due to the flow of document production
in the DTNRG. This document clarifies and further explains the in the DTNRG. This document clarifies and further explains the
motivations and engineering decisions behind SDNVs. motivations and engineering decisions behind SDNVs.
1.1. Problems with Fixed Value Fields 1.1. Problems with Fixed Value Fields
Protocol designers commonly face an optimization problem in Protocol designers commonly face an optimization problem in
determining the proper size for header fields. There is a strong determining the proper size for header fields. There is a strong
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Scott Burleigh, Manikantan Ramadas, Michael Demmer, Stephen Farrell, Scott Burleigh, Manikantan Ramadas, Michael Demmer, Stephen Farrell,
and other members of the IRTF DTN Research Group contributed to the and other members of the IRTF DTN Research Group contributed to the
development and usage of SDNVs in DTN protocols. George Jones and development and usage of SDNVs in DTN protocols. George Jones and
Keith Scott from Mitre, Lloyd Wood, Gerardo Izquierdo, Joel Halpern, Keith Scott from Mitre, Lloyd Wood, Gerardo Izquierdo, Joel Halpern,
Peter TB Brett, Kevin Fall, and Elwyn Davies also contributed useful Peter TB Brett, Kevin Fall, and Elwyn Davies also contributed useful
comments on and criticisms of this document. DTNRG last call comments on and criticisms of this document. DTNRG last call
comments on the draft were sent to the mailing list by Lloyd Wood, comments on the draft were sent to the mailing list by Lloyd Wood,
Will Ivancic, Jim Wyllie, William Edwards, Hans Kruse, Janico Will Ivancic, Jim Wyllie, William Edwards, Hans Kruse, Janico
Greifenberg, Teemu Karkkainen, Stephen Farrell, and Scott Burleigh. Greifenberg, Teemu Karkkainen, Stephen Farrell, and Scott Burleigh.
Further constructive comments were incorporated from Dave Crocker.
Work on this document was performed at NASA's Glenn Research Center, Work on this document was performed at NASA's Glenn Research Center,
in support of the NASA Space Communications Architecture Working in support of the NASA Space Communications Architecture Working
Group (SCAWG), NASA's Earth Science Technology Office (ESTO), and the Group (SCAWG), NASA's Earth Science Technology Office (ESTO), and the
FAA/Eurocontrol Future Communications Study (FCS) in the 2005-2007 FAA/Eurocontrol Future Communications Study (FCS) in the 2005-2007
timeframe, while the editor was an employee of Verizon Federal timeframe, while the editor was an employee of Verizon Federal
Network Systems. Network Systems.
8. Informative References 8. Informative References
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Encoding Rules (DER)", ISO/IEC 8825-1:2002, 2002. Encoding Rules (DER)", ISO/IEC 8825-1:2002, 2002.
[BRF04] Burleigh, S., Ramadas, M., and S. Farrell, "Licklider [BRF04] Burleigh, S., Ramadas, M., and S. Farrell, "Licklider
Transmission Protocol", Transmission Protocol",
draft-irtf-dtnrg-ltp-00 (replaced), May 2004. draft-irtf-dtnrg-ltp-00 (replaced), May 2004.
[Hain05] Hain, T., "A Pragmatic Report on IPv4 Address Space [Hain05] Hain, T., "A Pragmatic Report on IPv4 Address Space
Consumption", Internet Protocol Journal Vol. 8, No. 3, Consumption", Internet Protocol Journal Vol. 8, No. 3,
September 2005. September 2005.
[I-D.hixie-thewebsocketprotocol]
Hickson, I., "The Web Socket protocol",
draft-hixie-thewebsocketprotocol-68 (work in progress),
December 2009.
[IEN21] Cerf, V. and J. Postel, "Specification of Internetwork [IEN21] Cerf, V. and J. Postel, "Specification of Internetwork
Transmission Control Program: TCP Version 3", Internet Transmission Control Program: TCP Version 3", Internet
Experimental Note 21, January 1978. Experimental Note 21, January 1978.
[RFC0713] Haverty, J., "MSDTP-Message Services Data Transmission
Protocol", RFC 713, April 1976.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981. September 1981.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, [RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, September 1981. RFC 793, September 1981.
[RFC1323] Jacobson, V., Braden, B., and D. Borman, "TCP Extensions [RFC1323] Jacobson, V., Braden, B., and D. Borman, "TCP Extensions
for High Performance", RFC 1323, May 1992. for High Performance", RFC 1323, May 1992.
[RFC2993] Hain, T., "Architectural Implications of NAT", RFC 2993, [RFC2993] Hain, T., "Architectural Implications of NAT", RFC 2993,
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