RFC 3173 (rfc3173) - Page 2 of 13

IP Payload Compression Protocol (IPComp)

RFC 3173            IP Payload Compression Protocol       September 2001


   This document defines the IP payload compression protocol (IPComp),
   the IPComp packet structure, the IPComp Association (IPCA), and
   several methods to negotiate the IPCA.

   Other documents shall specify how a specific compression algorithm
   can be used with the IP payload compression protocol.  Such
   algorithms are beyond the scope of this document.

1.1. Specification of Requirements

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC 2119].

2. Compression Process

   The compression processing of IP datagrams has two phases:
   compressing of outbound IP datagrams ("compression") and
   decompressing of inbound datagrams ("decompression").  The
   compression processing MUST be lossless, ensuring that the IP
   datagram, after being compressed and decompressed, is identical to
   the original IP datagram.

   Each IP datagram is compressed and decompressed by itself without any
   relation to other datagrams ("stateless compression"), as IP
   datagrams may arrive out of order or not arrive at all.  Each
   compressed IP datagram encapsulates a single IP payload.

   Processing of inbound IP datagrams MUST support both compressed and
   non-compressed IP datagrams, in order to meet the non-expansion
   policy requirements, as defined in section 2.2.

   The compression of outbound IP datagrams MUST be done before any IP
   security processing, such as encryption and authentication, and
   before any fragmentation of the IP datagram.  In addition, in IP
   version 6 [RFC 2460], the compression of outbound IP datagrams MUST be
   done before the addition of either a Hop-by-Hop Options header or a
   Routing Header, since both carry information that must be examined
   and processed by possibly every node along a packet's delivery path,
   and therefore MUST be sent in the original form.

   Similarly, the decompression of inbound IP datagrams MUST be done
   after the reassembly of the IP datagrams, and after the completion of
   all IP security processing, such as authentication and decryption.







Shacham, et al.             Standards Track