/ Dynamic chains / variable, given by static chain
: for additional IP headers : (includes no SN)
--- --- --- --- --- --- --- ---
Note that the list of dynamic chains for the additional IP headers in
compressed packets do not have a sequence number at the end of the
chain, as SN is present within compressed base headers.
3.7. The CONTEXT_MEMORY Feedback Option
The CONTEXT_MEMORY option informs the compressor that the
decompressor does not have sufficient memory resources to handle the
context of the packet stream, as the stream is currently compressed.
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| Opt Type = 9 | Opt Len = 0 |
+---+---+---+---+---+---+---+---+
When receiving a CONTEXT_MEMORY option, the compressor SHOULD take
actions to compress the packet stream in a way that requires less
decompressor memory resources, or stop compressing the packet stream.
4. Security Considerations
The security considerations of [RFC-3095] apply equally to this
document, without exceptions or additions.
5. IANA Considerations
ROHC profile identifier 0x0004 has been reserved by the IANA for the
profile defined in this document.
6. Acknowledgements
The authors would like to thank Carsten Bormann, Fredrik Lindstrom,
Tommy Lundemo, and especially the committed document reviewers
Kristofer Sandlund and Mark West, for valuable input and review.
7. Normative References
[RFC-791] Postel, J., "Internet Protocol", RFC 791, September 1981.
[RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC-2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC-3095] Bormann, C., Burmeister, C., Degermark, M., Fukushima,
H., Hannu, H., Jonsson, L-E., Hakenberg, R., Koren, T.,
Le, K., Liu, Z., Martensson, A., Miyazaki, A., Svanbro,
K., Wiebke, T., Yoshimura, T. and H. Zheng, "Robust
Header Compression (ROHC)", RFC 3095, July 2001.
[PROTOCOL] "Assigned Internet Protocol Numbers", IANA registry at:
http://www.iana.org/assignments/protocol-numbers
Appendix A. Detailed Procedures for Canceling Mode Transitions
The profiles defined in [RFC-3095] operate using different modes of
compression: Unidirectional (U-Mode), Bi-directional Optimistic
(O-Mode), and Bi-directional Reliable (R-Mode). Compression always
starts in the U-Mode, and mode transitions can only be initiated by
the decompressor [RFC-3095, section 5.6.]. A mode transition can be
requested once a packet has reached the decompressor by sending
feedback indicating the desired mode.
With reference to the parameters C_TRANS, C_MODE, D_TRANS, and D_MODE
defined in [RFC-3095, section 5.6.1.], the following sub-sections
describe the resulting procedures when a compressor declines a mode
transition request from the decompressor as described in section 3.4.
A.1. Transition from Optimistic to Reliable Mode
When the decompressor initiates a mode transition from Optimistic to
Reliable mode, the cancellation of the transition procedure is as
follows:
Compressor Decompressor
----------------------------------------------
| |
| ACK(R)/NACK(R) +-<-<-<-| D_TRANS = I
| +-<-<-<-<-<-<-<-+ |
C_TRANS = P |-<-<-<-+ |
C_MODE = O | |
|->->->-+ IR/IR-DYN/UOR-2(SN,C) |
| +->->->->->->->-+ |
|->-.. +->->->-| D_TRANS = P
|->-.. | D_MODE = O
| ACK(SN,O) +-<-<-<-|
| +-<-<-<-<-<-<-<-+ |
C_TRANS = D |-<-<-<-+ |
| |
|->->->-+ UO-0, UO-1* |
| +->->->->->->->-+ |
| +->->->-| D_TRANS = D
The compressor must not send packet types 1 or 0 when C_TRANS is P,
i.e., not until it has received an ACK for a UOR-2, IR-DYN, or IR
packet sent with the mode transition parameter set to C. When the
decompressor receives a UOR-2, IR-DYN, or IR packet sent with the
mode transition parameter set to C, it must keep the value D_MODE as
O and set D_TRANS to P. When the decompressor receives packet types
0 or 1, after having ACKed a UOR-2, IR-DYN, or IR packet, it sets
D_TRANS to D.
A.2. Transition from Unidirectional to Reliable Mode
The cancellation of a transition from Unidirectional to Reliable mode
follows the same procedure as defined in section 4.2 above.
A.3. Transition from Reliable to Optimistic Mode
When the decompressor initiates a mode transition from Reliable to
Optimistic mode, the cancellation of the transition procedure is
described as follows:
Compressor Decompressor
----------------------------------------------
| |
| ACK(O)/NACK(O) +-<-<-<-| D_TRANS = I
| +-<-<-<-<-<-<-<-+ |
C_TRANS = P |-<-<-<-+ |
C_MODE = R | |
|->->->-+ IR/IR-DYN/UOR-2(SN,C) |
| +->->->->->->->-+ |
|->-.. +->->->-| D_MODE = R
|->-.. |
| ACK(SN,R) +-<-<-<-|
| +-<-<-<-<-<-<-<-+ |
C_TRANS = D |-<-<-<-+ |
| |
|->->->-+ R-0, R-1* |
| +->->->->->->->-+ |
| +->->->-| D_TRANS = D
| |
The compressor must not send packet types 1 or 0 when C_TRANS is P,
i.e., not until it has received an ACK for a UOR-2, IR-DYN, or IR
packet sent with the mode transition parameter set to C. When the
decompressor receives a UOR-2, IR-DYN, or IR packet sent with the
mode transition parameter set to C, it must keep the value D_MODE as
R. When the decompressor receives packet types 0 or 1, after having
ACKed a UOR-2, IR-DYN, or IR packet, it sets D_TRANS to D.
A.4. Transition Back to Unidirectional Mode
When the decompressor initiates a mode transition from Reliable or
Optimistic mode back to Unidirectional mode, the cancellation of the
transition procedure is as follows:
Compressor Decompressor
----------------------------------------------
| |
| ACK(U)/NACK(U) +-<-<-<-| D_TRANS = I
| +-<-<-<-<-<-<-<-+ |
C_TRANS = P |-<-<-<-+ |
C_MODE = O/R| |
|->->->-+ IR/IR-DYN/UOR-2(SN,C) |
| +->->->->->->->-+ |
|->-.. +->->->-|
|->-.. |
| ACK(SN,O/R) +-<-<-<-|
| +-<-<-<-<-<-<-<-+ |
C_TRANS = D |-<-<-<-+ |
| R-0, R-1* or |
|->->->-+ UO-0, UO-1* |
| +->->->->->->->-+ |
| +->->->-| D_TRANS = D
D_MODE = O/R
When the decompressor receives a UOR-2, IR-DYN, or IR packet sent
with the mode transition parameter set to C, it must keep the value
D_MODE to the bi-directional mode already in use (either O- or R-
mode). After ACKing the first UOR-2(C), IR-DYN(C), or IR(C), the
decompressor MUST continue to send feedback with the Mode parameter
set to the bi-directional mode in use (either O- or R-mode) until it
receives packet types 0 or 1. When the decompressor receives packet
types 0 or 1, after having ACKed a UOR-2, IR-DYN, or IR packet, it
sets D_TRANS to D.
Authors’ Addresses
Lars-Erik Jonsson
Ericsson AB
Box 920
SE-971 28 Lulea, Sweden
Phone: +46 8 404 29 61
Fax: +46 920 996 21
EMail: lars-erik.jonsson@ericsson.com
Ghyslain Pelletier
Ericsson AB
Box 920
SE-971 28 Lulea, Sweden
Phone: +46 8 404 29 43
Fax: +46 920 996 21
EMail: ghyslain.pelletier@ericsson.com
Full Copyright Statement
Copyright (C) The Internet Society (2004). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at ietf-
ipr@ietf.org.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.