IPHC, PPP Internet Protocol Header Compression

Description Glossary RFCs Publications Obsolete RFCs


Protocol suite: PPP.
Type:PPP Network Control Protocol.
PPP Protocol:

RFC 2509:

The IP Header Compression (IPHC) may be used for compression of both IPv4 and IPv6 datagrams or packets encapsulated with multiple IP headers. IPHC is also capable of compressing both TCP and UDP transport protocol headers. The IP/UDP/RTP header compression defined in [RFC 2508] fits within the framework defined by IPHC so that it may also be applied to both IPv4 and IPv6 packets.

In order to establish compression of IP datagrams sent over a PPP link each end of the link must agree on a set of configuration parameters for the compression. The process of negotiating link parameters for network layer protocols is handled in PPP by a family of network control protocols (NCPs). Since there are separate NCPs for IPv4 and IPv6, this document defines configuration options to be used in both NCPs to negotiate parameters for the compression scheme.

IPHC relies on the link layer's ability to indicate the types of datagrams carried in the link layer frames. In this document nine new types for the PPP Data Link Layer Protocol Field are defined along with their meaning.

In general, header compression schemes that use delta encoding of compressed packets require that the lower layer does not reorder packets between compressor and decompressor. IPHC uses delta encoding of compressed packets for TCP and RTP. The IPHC specification includes methods that allow link layers that may reorder packets to be used with IPHC. Since PPP does not reorder packets these mechanisms are disabled by default. When using reordering mechanisms such as multiclass multilink PPP, care must be taken so that packets that share the same compression context are not reordered.

Packet Header:

IPHC Configuration Options:

0001 02 03 04 05 06 07 08 09 10 11 12 13 14 15
Option Length
Data :::

Option. 8 bits.

12RTP-Compression Suboption. RFC 2509
2 >= 14 IP Header Compression. RFC 2509

Length. 8 bits.

Data. Variable length.


[RFC 1144] Compressing TCP/IP Headers for Low-Speed Serial Links.

[RFC 1332] The PPP Internet Protocol Control Protocol (IPCP).

[RFC 1661] The Point-to-Point Protocol (PPP).

[RFC 1889] RTP: A Transport Protocol for Real-Time Applications.

[RFC 2472] IP Version 6 over PPP.

[RFC 2507] IP Header Compression.

[RFC 2508] Compressing IP/UDP/RTP Headers for Low-Speed Serial Links.

[RFC 2509] IP Header Compression over PPP.

Obsoleted RFCs:

[RFC 1172] The Point-to-Point Protocol (PPP) Initial Configuration Options.

[RFC 2023] IP Version 6 over PPP.

Description Glossary RFCs Publications Obsolete RFCs