RFC 3095 (rfc3095) - Page 2 of 168
RObust Header Compression (ROHC): Framework and four profiles: RTP, UDP, ESP, and uncompressed
Alternative Format: Original Text Document
RFC 3095 Robust Header Compression July 2001
This is done in a framework designed to be extensible. For example,
a scheme for compressing TCP/IP headers will be simple to add, and is
in development. Headers specific to Mobile IPv4 are not subject to
special treatment, but are expected to be compressed sufficiently
well by the provided methods for compression of sequences of
extension headers and tunneling headers. For the most part, the same
will apply to work in progress on Mobile IPv6, but future work might
be required to handle some extension headers, when a standards track
Mobile IPv6 has been completed.
Table of Contents
1. Introduction....................................................6
2. Terminology.....................................................8
2.1. Acronyms.....................................................13
3. Background.....................................................14
3.1. Header compression fundamentals..............................14
3.2. Existing header compression schemes..........................14
3.3. Requirements on a new header compression scheme..............16
3.4. Classification of header fields..............................17
4. Header compression framework...................................18
4.1. Operating assumptions........................................18
4.2. Dynamicity...................................................19
4.3. Compression and decompression states.........................21
4.3.1. Compressor states..........................................21
4.3.1.1. Initialization and Refresh (IR) State....................22
4.3.1.2. First Order (FO) State...................................22
4.3.1.3. Second Order (SO) State..................................22
4.3.2. Decompressor states........................................23
4.4. Modes of operation...........................................23
4.4.1. Unidirectional mode -- U-mode..............................24
4.4.2. Bidirectional Optimistic mode -- O-mode....................25
4.4.3. Bidirectional Reliable mode -- R-mode......................25
4.5. Encoding methods.............................................25
4.5.1. Least Significant Bits (LSB) encoding .....................25
4.5.2. Window-based LSB encoding (W-LSB encoding).................28
4.5.3. Scaled RTP Timestamp encoding .............................28
4.5.4. Timer-based compression of RTP Timestamp...................31
4.5.5. Offset IP-ID encoding......................................34
4.5.6. Self-describing variable-length values ....................35
4.5.7. Encoded values across several fields in compressed headers 36
4.6. Errors caused by residual errors.............................36
4.7. Impairment considerations....................................37
5. The protocol...................................................39
5.1. Data structures..............................................39
5.1.1. Per-channel parameters.....................................39
5.1.2. Per-context parameters, profiles...........................40
5.1.3. Contexts and context identifiers ..........................41
Bormann, et al. Standards Track