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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The RFC defines a generic compression mechanism. Any explicit references within that referenced document should also be listed:. The packet type is able to carry variable-length feedback information.
In the Full Context state: What differs is the decompression and feedback logic. Contexts and context identifiers Associated with each compressed flow is a context, which is the state compressor and decompressor maintain in order to correctly compress or decompress the headers of the packet stream. All RFCs always remain available on-line.
Operation in Unidirectional mode 5. In order to handle potential decompression errors, the compressor sends periodic refreshes of the stream context to the decompressor.
The decompressor might be able to detect this situation and avoid context damage by using a local clock. Relationship with other existing or emerging documents:.
It is impossible to know for certain which of these is the actual cause. Comments on Iietf and corresponding changes are accommodated through the existing standardization process. If a feedback channel is available, however, the decompressor MAY send an acknowledgment of successful decompression with the mode parameter set to U send an ACK U.
If another algorithm is used, it MUST have at least as high ierf rate of correct repairs as the one in 5. If RTP Timestamp and IP Identification fields are not included in the received header, they are supposed to be calculated from the sequence number.
The context table is indexed using the CID which is sent along with compressed headers and feedback information. The compressor converts the large overhead to only a few bytes, while the decompressor does the opposite.
The O-mode aims to maximize compression efficiency and aims for sparse usage of the jetf channel. Iet the header generated in b.
In Initialization and Refresh IR state, the compressor has just been created or reset, and full packet headers are sent.
Headers of packets transferred using packet type 2 can be used as references for subsequent decompression. Current information, if any, about IPR issues:. Several compression profiles are available, including the following:. Rgc parameters, profiles Per-context parameters are established with IR headers see section 5.
When CRC checks fail only occasionally, assume residual errors in the current header and simply discard the packet. In this state, the 8-bit ROHC header contains three fields:.
In this situation, the decompressor will detect the incorrect decompression of the following packet with high probability, but it does not know the reason for the failure.
All segment header packets for one reconstructed unit have 30095 be sent consecutively on a channel, i. Optional reference to a channel in the reverse direction.
If the decompressed header generated in d. Maximum reconstructed reception unit. Redundant information is transmitted in the first packets only. Repair of incorrect SN updates The CRC can fail to detect residual errors in the compressed header because of its limited length, i.
If decompression of any of the three headers fails, the iftf MUST discard that header and the previously generated headers, and act according to rules a through c of section 5. In the Static Context state: Data compression Internet Standards.
This part of the IR packet is defined by individual profiles. In First-Order FO state, the compressor has detected and stored the static fields such as IP addresses and port numbers on both sides of the connection. The following steps is an outline of initial decompressor processing which upon reception of a ROHC istf can determine its contents. The procedure for finding the size of the feedback data is as follows: Other for any supplementary information: If provided, this parameter indicates which channel any feedback sent on this channel refers to see 5.
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