[tsvwg][ips] TCP framing

["Douglas Otis" <dotis@sanlight.net>]

All,

Attached is a proposal to allow framing compatible with SCTP. It is very
small.

Doug

   Internet Draft                                     Douglas Otis
   Expires October 2001                                   SANlight
                                                    April 19, 2001

                      TCP Framing Header
                 draft-otis-tcp-framing-00.txt

   Status of this Memo


   This document is an Internet-Draft and is in full conformance 
   with all provisions of Section 10 of RFC2026 [1]. 

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   Abstract

   This document is to define a header structure suitable for
   implementing a framing structure that encapsulates SCTP (RFC 2960)
   within TCP (RFC 793).  This provides the following:

    - Frame Validation within Frame Header. 
    - Additional Frame Error Checking.
    - Both Fixed and Variable Length Framing.
    - Identifies Payloads and incorporates SCTP Conventions.



  draft-otis-tcp-framing-00.txt                              Page [2]

   Introduction

   This framing scheme is to incorporate SCTP within TCP.  SCTP is a 
   framing protocol unlike TCP and to create a natural transition to
   SCTP, this TCP framing scheme can be employed. 

   To allow a generic method of framing records within TCP byte streams,
   the following two constructs are used.  These are Fixed Interval and
   Variable Interval header placement.  In the Fixed Interval mode, the
   actual SCTP frame size is indicated in the Pseudo-Frame Length with
   the remainder padded to this fixed interval.  The Fixed Interval is
   set by the 32-bit byte length Fixed Interval parameter within the
   Initiation (INIT) Chunk as assigned by IANA.  In the Variable Interval
   mode, the Pseudo-Frame Length indicates the byte displacement to the
   next Modified SCTP Common Header.

   Modified SCTP Common Header Format

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Mode  | Ver   |         Pseudo-Frame Length in Bytes          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Verification Tag                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Checksum                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Mode field identifies the possible framing mechanisms used.
     0 = Fixed Interval Modified SCTP Common Header Placement
     1 = Variable Interval Modified SCTP Common Header Placement
     2 - 15 = Reserved.
   
   The Ver field identifies different levels of compatibility.  Presently
   this field is defined as 0.  Verification Tag and Checksum are
   defined within the SCTP specification.  The flow control schemes and
   physical framing is determined by TCP.  

   As an illustrative example for Fixed Interval Header Placement.
 
    | Ethernet Frame |   |         |      |      |        |
    |  Pseudo-Frame  |   Pseudo-Frame    |  Pseudo-Frame  |
    |xxxxxxxxxxx00000|xxxxxxxxxxxxxxxxxx0|xxxxxxxxxxxxxxxx|
    [Chunk|Chunk|----[ Chunk |   Chunk   [        | Chunk [...

   [ = Modified SCTP Common Header
   0 = Padding
   x = payload
   | = boundary

   The reasons for using either fixed or variable length modes and their
   interaction with Upper Layer Protocols are beyond the scope of this
   document.





  draft-otis-tcp-framing-00.txt                               Page [3]

   Author's Address: 

         Douglas Otis 
         SANlight Inc. 
         160 Saratoga Ave, #40 
         Santa Clara, CA 95051 
         Tel: (408) 260-1400 x2 
         dotis@sanlight.net 

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