Evaulation and implemenation of header compression algorithm ECRTP

This dissertation offers an assessment of Enhanced Compressed RealTime Protocol (ECRTP). ECRTP an extension to CRTP, is actually a header compression method for real time traffic. ECRTP makes use of the hop-by-hop redundancy in a stream of IP/UDP/RTP packets, were practically the identical header is sent repeatedly. The header and extra details are stored in a context at the compressor and decompressor. In case the context is synchronized, the compressor can deliver only the differences since the last header and decompressor has the ability to rebuild the header.

ECRTP was created to get rid of the down sides of CRTP. CRTP fails to work well over links with long round trip time that lose and reorder packets. ECRTP expands CRTP by duplicating context updates and also by delivering absolute values in addition to delta values when encoding monotonically increasing header fields to boost robustness. The idea is to insert a header checksum when UDP checksum is missing, to enhance error recovery and fail checks for the compression.

The evaluation of Enhanced Compressed RealTime Protocol ECRTP includes 2 portions, simulations and a theoretical investigation. With the outcomes of the simulations and the theory under consideration, weaknesses and strength are outlined and recommendations of improvement will be provided.

A potential error in the establishment of the repetition value in the decompressor was discovered. The error could be averted by transmitting the repetition value in the compressed header at the start of a session.

The study shows that Enhanced Compressed RealTime Protocol ECRTP deals with packet loss and large round trip times efficiently. ECRTP could be set up to take care of packet reordering by exclusive utilization of absolute encoding for monotonically increasing header fields, through the use of most often changing fields that isn’t secured by the checksum as context-defining fields. The checksum-protected RTP fields should, if altered between 2 consecutive headers, be incorporated into every packet rather than compressed on the assumption of in-order delivery. All the proposed adjustments will reduce the compression efficiency.

ECRTP is simulated along with a couple of other schemes; CRTP and ROHC. It is demonstrated that Robust header compression (ROHC) addresses reordering a lot better than anticipated. Particularly the least significant bit encoding exhibits encouraging results and the handling of CSRC list. And also the handling of the checksum-protected RTP fields indicate that ROHC with a few modifications may perhaps be built to take care of compression during reordering better than ECRTP.

Source: Luleå University of Technology

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