The ROHC framework, along with a set of compression profiles, was initially defined in RFC To improve and simplify the ROHC specifications, this. Canonical URL: ; File formats: Plain Text PDF Discuss this RFC: Send questions or comments to [email protected] Robust Header Compression (ROHC) is a standardized method to compress the IP, UDP, The ROHC compression scheme differs from other compression schemes, such as IETF RFC and RFC , by the fact that it performs According to RFC , the ROHC scheme has three modes of operation, as follows.
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IR This packet ietr communicates the static part of the context, i. When a CRC mismatch is caused by residual bit errors in the current header case 1 abovethe decompressor should stay in its current state to avoid unnecessary loss of subsequent packets.
The packet type is able to carry variable-length feedback information.
If MRRU is negotiated to be 0, no segment headers are allowed on the channel. This classification takes advantage of inter-packet redundancy. ROHC segmentation Some link layers may provide a much more efficient service if the set of different packet sizes to be transported is kept small.
Feedback logic O-mode The feedback logic defines what feedback to send due to different events when operating in the various states.
Robust Header Compression – Wikipedia
References within the referenced RFC are listed under item 8. All RFCs always remain available on-line. Framework and four profiles: The link layer may, however, be limited in the size rcf packets it can offer in this efficient mode, or it may be desirable to request only a limited largest size.
The decompressor does not attempt to decompress headers at all in the No Context and Static Context states unless sufficient information is included in the packet itself. Current information, if any, about IPR issues: Compressor states and logic U-mode Below is the state machine for the compressor dfc Unidirectional mode.
ITU-T work programme
Note that this size includes the CRC. In the IR packet, ief profile identifier is abbreviated to the 8 least significant bits.
This means that the compressor transits to a higher compression state when it is fairly confident that the decompressor has received enough information to correctly decompress packets sent according to the higher compression state.
Please help improve this article by adding citations to reliable sources. It is not intended to replace link layer iet functions; these SHOULD be used whenever available and efficient for the task at hand.
Set of nonnegative integers, each integer indicating a profile supported by the decompressor. Comments on RFCs and corresponding changes are accommodated through the existing standardization process.
RFC – part 3 of 7
If decompression may not be performed the packet is discarded, unless the optional delayed decompression mechanism is used, see section 6.
When 30095 decompressor has determined the size of the feedback data field, it removes the feedback type octet and the Size field if present and hands the rest to the same-side associated compressor. Clear description of the referenced document: Feedback in Unidirectional mode To improve performance for the Unidirectional mode over a link that does have a feedback channel, the iftf MAY send an acknowledgment when decompression succeeds.
In summary, ROHC segmentation should be used with a relatively low frequency in the packet flow.
The optimistic approach principle and transitions occasioned by the need for updates work in the same way as described in chapter 5. It jetf carries a CID.
It can typically also refresh parts of the context. Thus the type needs to be reserved at the framework level. Such large overheads rcc be tolerable in local wired links where capacity is often not an issue, but are excessive for wide area networks and wireless systems where bandwidth is scarce. Feedback is described in section 5. The IP Identifier usually increases by the same delta as the sequence 30995 and the timestamp by the same delta times a fixed value.
Data structures The ROHC protocol is based on a number of parameters that form part of the negotiated channel state and the per-context state.
The incorrect decompressed header will then update the context. In Initialization and Refresh IR state, the compressor has just been created or reset, and full packet headers are sent. If defined by a “ROHC over X” document, per-channel negotiation can be used to pre-establish state information for a context e.
If decompression of the third packet using the new context also succeeds, the context repair is deemed successful and this and subsequent decompressed packets 33095 delivered to the upper layers. A type 0 packet carries a packet header compressed according to a fixed pattern, rvc type 1, 2 and IR-DYN packets are used when this pattern is broken.
Need for updates, downward transition In addition to the downward state transitions carried out due to periodic timeouts, the compressor must also immediately transit back to the FO state when the header to be compressed does not conform to the established pattern.