The Need For Header Compression
In streaming applications, the overhead of IP, UDP, and RTP is 40 bytes for IPv4, or 60 bytes for IPv6. For VoIP this corresponds to around 60% of the total amount of data sent. Such large overheads may 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.
ROHC compresses these 40 bytes or 60 bytes of overhead typically into only 1 or 3 bytes by placing a compressor before the link that has limited capacity, and a decompressor after that link. The compressor converts the large overhead to only a few bytes, while the decompressor does the opposite.
The ROHC compression scheme differs from other compression schemes such as IETF RFC 1144 and RFC 2508 by the fact that it performs well over links where the packet loss rate is high, such as wireless links.
Read more about this topic: Robust Header Compression
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