Robust header compression for RTP header in a RTP profile over Ethernet
Loading...
Date
2009-06
Authors
Mehta, Mihir Jaykant
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Information on the internet is sent using packets and if the layered approach to the
internet is observed, one can understand that at every layer, there is a header belonging
to that layer is attached to the message. The packet that is built from a sender consists of
the original message with a number of headers attached to it. At the receiving end, these
headers containing relevant information about the packet are stripped off and sent to the
upper layers. When a number of packets flow from a sender to a receiver, it can
observed that many fields in the packet headers at various layers posses the same value
in every packet header. In other words, there is redundancy observed in many fields of
the packet headers. For example, the source IP address and destination IP address
remains the same for every packet at the Internet layer. Similarly at the transport layer,
the source port and destination port remains the same. Header compression techniques
explore the possibilities and mechanisms of compressing header information by
removing redundancy of the packet header fields in packets that belong to the same
stream. Amongst various header compression schemes, Robust Header Compression has
proved to be the most efficient. Voice over IP (VoIP) plays a very important role in
carrying voice data over internet and relies on the Real Time Protocol (RTP) as its
transport layer protocol. The data generally carried in these packets are quite small when
compared to the information carried in the headers. R TP is also used in streaming of
media content like audio or video over internet. Hence the headers cause an overhead
due to redundant information in them. This objective of this thesis is to design a Robust
Header Compression mechanism for a RTP profile that compresses IP, UDP and RTP
header fields attached to the data. Further, the RTP timestamp field in the RTP header is
used in the compression framework to define parameters based on the timestamp. These
parameters namely TS_STRIDE and TS_OFFSET are dependent on the codec that is
used in the compression scheme. This thesis successfully proposes and implements a
statistical approach in the calculation of these parameters which removes the
dependency on the codec that is used. This thesis concentrates on the R TP header in the
RTP profile. The implementation is evaluated on an Ethernet based test-bed for potential
compression gains. The total header length for IPv4, UDP and RTP headers which is a
minimum of 40 bytes is compressed to achieve a header compression gain of nearly 50%
using the implemented Robust Header Compression mechanism.
Description
Keywords
Robust header compression , RTP