Design Considerations for Protocol Extensions
draft-iab-extension-recs-14

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Internet Architecture Board                                 B. Carpenter
Internet-Draft                                             B. Aboba (ed)
Intended Status: Informational                               S. Cheshire
Expires: December 10, 2012                                   9 June 2012

             Design Considerations for Protocol Extensions
                      draft-iab-extension-recs-14

Abstract

   This document discusses architectural issues related to the
   extensibility of Internet protocols, with a focus on design
   considerations.  It is intended to assist designers of both base
   protocols and extensions.  Case studies are included.  A companion
   document, RFC 4775/BCP 125, discusses procedures issues relating to
   the extensibility of IETF protocols.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
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   This Internet-Draft will expire on December 10, 2012.

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Copyright Notice

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Table of Contents

1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
  1.1   Requirements Language  . . . . . . . . . . . . . . . . . .  5
2.  Routine and Major Extensions . . . . . . . . . . . . . . . . .  5
  2.1   What Constitutes a Major Extension?  . . . . . . . . . . .  5
  2.2   When is an Extension Routine?  . . . . . . . . . . . . . .  7
3.  Architectural Principles . . . . . . . . . . . . . . . . . . .  8
  3.1   Limited Extensibility  . . . . . . . . . . . . . . . . . .  8
  3.2   Design for Global Interoperability . . . . . . . . . . . .  9
  3.3   Architectural Compatibility  . . . . . . . . . . . . . . . 13
  3.4   Protocol Variations  . . . . . . . . . . . . . . . . . . . 14
  3.5   Testability  . . . . . . . . . . . . . . . . . . . . . . . 16
  3.6   Parameter Parameter Registration . . . . . . . . . . . . . 17
  3.7   Extensions to Critical Protocols . . . . . . . . . . . . . 18
4.  Considerations for the Base Protocol . . . . . . . . . . . . . 18
  4.1   Version Numbers  . . . . . . . . . . . . . . . . . . . . . 19
  4.2   Reserved Fields  . . . . . . . . . . . . . . . . . . . . . 23
  4.3   Encoding Formats . . . . . . . . . . . . . . . . . . . . . 23
  4.4   Parameter Space Design . . . . . . . . . . . . . . . . . . 24
  4.5   Cryptographic Agility  . . . . . . . . . . . . . . . . . . 26
  4.6   Transport  . . . . . . . . . . . . . . . . . . . . . . . . 27
  4.7   Handling of Unknown Extensions . . . . . . . . . . . . . . 28
5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 29
6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 29
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