< draft-ietf-rohc-context-replication-05.txt   draft-ietf-rohc-context-replication-06.txt >
Network Working Group Ghyslain Pelletier, Ericsson Network Working Group Ghyslain Pelletier, Ericsson
INTERNET-DRAFT INTERNET-DRAFT
Expires: March 2005 September 27, 2004 Expires: April 2005 October 5, 2004
RObust Header Compression (ROHC): RObust Header Compression (ROHC):
Context Replication for ROHC Profiles Context Replication for ROHC Profiles
<draft-ietf-rohc-context-replication-05.txt> <draft-ietf-rohc-context-replication-06.txt>
Status of this memo Status of this memo
By submitting this Internet-Draft, I (we) certify that any applicable By submitting this Internet-Draft, I (we) certify that any applicable
patent or other IPR claims of which I am (we are) aware have been patent or other IPR claims of which I am (we are) aware have been
disclosed, and any of which I (we) become aware will be disclosed, in disclosed, and any of which I (we) become aware will be disclosed, in
accordance with RFC 3668 (BCP 79). accordance with RFC 3668 (BCP 79).
By submitting this Internet-Draft, I (we) accept the provisions of By submitting this Internet-Draft, I (we) accept the provisions of
Section #3 of RFC 3667 (BCP 78). Section #3 of RFC 3667 (BCP 78).
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3. Context Replication for ROHC profiles............................4 3. Context Replication for ROHC profiles............................4
3.1. Robustness considerations...................................4 3.1. Robustness considerations...................................4
3.2. Replication of Control Fields...............................5 3.2. Replication of Control Fields...............................5
3.3. Compressor states and logic.................................5 3.3. Compressor states and logic.................................5
3.3.1. Context replication (CR) state.........................6 3.3.1. Context replication (CR) state.........................6
3.3.2. State machine with context replication.................6 3.3.2. State machine with context replication.................6
3.3.3. State transition logic.................................7 3.3.3. State transition logic.................................7
3.3.3.1. Selection of base context, upward transition......7 3.3.3.1. Selection of base context, upward transition......7
3.3.3.2. Optimistic approach, upward transition............8 3.3.3.2. Optimistic approach, upward transition............8
3.3.3.3. Optional acknowledgements (ACKs), upward transition 3.3.3.3. Optional acknowledgements (ACKs), upward transition
...........................................................9 ...........................................................8
3.3.3.4. Negative ACKs (NACKs), downward transition........9 3.3.3.4. Negative ACKs (NACKs), downward transition........9
3.4. Decompressor logic..........................................9 3.4. Decompressor logic..........................................9
3.4.1. Replication and context initialization.................9 3.4.1. Replication and context initialization.................9
3.4.2. Reconstruction and verification.......................10 3.4.2. Reconstruction and verification........................9
3.4.3. Actions upon failure..................................10 3.4.3. Actions upon failure..................................10
3.4.4. Feedback logic........................................10 3.4.4. Feedback logic........................................10
3.5. Packet Formats.............................................11 3.5. Packet Formats.............................................10
3.5.1. CRCs in the IR-CR packet..............................11 3.5.1. CRCs in the IR-CR packet..............................11
3.5.1.1. 7-bit CRC........................................12 3.5.1.1. 7-bit CRC........................................12
3.5.1.2. 8-bit CRC........................................12 3.5.1.2. 8-bit CRC........................................12
3.5.2. General format of the IR-CR packet....................12 3.5.2. General format of the IR-CR packet....................12
3.5.3. Properties of the Base Context Identifier (BCID)......14 3.5.3. Properties of the Base Context Identifier (BCID)......14
4. Security Considerations.........................................14 4. Security Considerations.........................................14
5. Acknowledgments.................................................14 5. Acknowledgments.................................................14
6. Authors' Addresses..............................................15 6. Authors' Addresses..............................................14
7. References......................................................15 7. References......................................................15
7.1. Normative references.......................................15 7.1. Normative references.......................................15
7.2. Informative References.....................................15 7.2. Informative References.....................................15
Appendix A - General format of the IR-CR packet (informative)......16 Appendix A - General format of the IR-CR packet (informative)......16
Appendix B - Inter-profile context replication (informative).......17 Appendix B - Inter-profile context replication (informative).......17
1. Introduction 1. Introduction
There is often some redundancy between header fields of different There is often some redundancy between header fields of different
flows passing through the same compressor-decompressor pair. This flows passing through the same compressor-decompressor pair. This
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selecting a base context. selecting a base context.
In the case where feedback is not used by the decompressor, the In the case where feedback is not used by the decompressor, the
compressor may have to periodically transit back to the IR state. In compressor may have to periodically transit back to the IR state. In
such case, the same logic applies for the transition back to the such case, the same logic applies for the transition back to the
higher order state via the CR state: a base context previously higher order state via the CR state: a base context previously
acknowledged and suitable for replication must be re-selected. acknowledged and suitable for replication must be re-selected.
The criteria for whether an existing context is a suitable base The criteria for whether an existing context is a suitable base
context for replication for a new flow are left to implementations. context for replication for a new flow are left to implementations.
For simplicity, contexts with the same Source-IP and/or Destination-
IP may be considered as replicable contexts.
Whenever available, the compressor MAY also use the sequencing Whenever available, the compressor MAY also use the sequencing
information from the last acknowledgement received to determine what information from the last acknowledgement received to determine what
fields can be replicated, and not replicate any fields that have fields can be replicated, and not replicate any fields that have
changed significantly from the state corresponding to the changed significantly from the state corresponding to the
acknowledged packet. acknowledged packet.
3.3.3.2. Optimistic approach, upward transition 3.3.3.2. Optimistic approach, upward transition
Transition to a higher order state can be carried out according to Transition to a higher order state can be carried out according to
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the 8 LSBs given (see also [2]). the 8 LSBs given (see also [2]).
CRC: 8-bit CRC computed using the polynomial of section 3.5.1.2. CRC: 8-bit CRC computed using the polynomial of section 3.5.1.2.
Profile specific information: The contents of this part of the Profile specific information: The contents of this part of the
IR-CR packet are defined by the individual profiles. This IR-CR packet are defined by the individual profiles. This
information is interpreted according to the profile indicated information is interpreted according to the profile indicated
in the Profile field. It MUST include a 7-bit CRC over the in the Profile field. It MUST include a 7-bit CRC over the
original uncompressed header using the polynomial of section original uncompressed header using the polynomial of section
3.5.1.1. It also includes the static and dynamic subheader 3.5.1.1. It also includes the static and dynamic subheader
information used for replication. information used for replication; what header fields are
replicated along with their respective encoding methods is
thus outside the scope of this document.
Payload: The payload of the corresponding original packet, if any. Payload: The payload of the corresponding original packet, if any.
3.5.3. Properties of the Base Context Identifier (BCID) 3.5.3. Properties of the Base Context Identifier (BCID)
The Base CID within the packet format of the IR-CR may be assigned a The Base CID within the packet format of the IR-CR may be assigned a
different value than the context identifier associated to the new different value than the context identifier associated to the new
flow (i.e. BCID != CID); otherwise the base context is overwritten flow (i.e. BCID != CID); otherwise the base context is overwritten
with the new context by the replication process. with the new context by the replication process.
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Disclaimer of Validity Disclaimer of Validity
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
This Internet-Draft expires March 27, 2005. This Internet-Draft expires April 5, 2005.
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