Description:

IPPCP header:

Next header. 8 bits.
Stores the IPv4 Protocol field or the IPv6 Next Header field of the original IP header.

Flags. 8 bits.
Cleared to zero.

CPI, Compression parameter index. 16 bits.
(RFC 2393) The CPI is stored in network order. The values 0 - 63 define well-known compression algorithms, which require no additional information, and are used for manual setup. The values themselves are identical to IPCOMP Transform identifiers as defined in RFC 2407. Consult RFC 2407 for an initial set of defined values and for instructions on how to assign new values. The values 64-255 are reserved for future use. The values 256-61439 are negotiated between the two nodes in definition of an IPComp Association, as defined in section 4. Note: When negotiating one of the well-known algorithms, the nodes MAY select a CPI in the pre-defined range 0-63. The values 61440-65535 are for private use among mutually consenting parties. Both nodes participating can select a CPI value independently of each other and there is no relationships between the two separately chosen CPIs. The outbound IPComp header MUST use the CPI value chosen by the decompressing node. The CPI in combination with the destination IP address uniquely identifies the compression algorithm characteristics for the datagram.

Data. Variable length.

Glossary:

RFCs:

[RFC 2394] IP Payload Compression Using DEFLATE.

[RFC 2395] IP Payload Compression Using LZS.

[RFC 3051] IP Payload Compression Using ITU-T V.44 Packet Method.

[RFC 3173] IP Payload Compression Protocol (IPComp).

• Obsoletes: RFC 2393.

Obsolete RFCs:

[RFC 2393] IP Payload Compression Protocol (IPComp).

• Obsoleted by: RFC 3173.