Paper Info
Title
Measurements of SIP signaling over 802.11b links
Abstract
The Session Initiation Protocol (SIP) is a popular application-level signaling protocol that is used for a wide variety of applications such as session control and mobility handling. In some of these applications, the exchange of SIP messages is time-critical, for instance when SIP is used to handle mobility for voice over IP sessions. SIP may however introduce significant delays when it runs on top of UDP over lossy (wireless) links. These delays are the result of the exponential back-off retransmission scheme that SIP uses to recover from packet loss, which has a default back-off time of half a second.In this paper, we empirically investigate the delay introduced by SIP when it runs on top of UDP over IEEE 802.11b links. We focus on the operation of SIP at the edge of an 802.11b cell (e.g., to update a mobile host's IP address after a handoff) as this is where SIP's retransmissions scheme is most likely to come into play. We experiment with a few 802.11 parameters that influence packet loss on the wireless link, specifically with different link-level retransmission thresholds, signal-to-noise-ratios (SNRs), and amounts of background traffic. We conduct these experiments in a controlled environment that is free from interfering 802.11 sources.Our results indicate that (1) SIP usually introduces little delay except for an SNR range of a few dBs at the very edge of an 802.11 cell in which the delay increases sharply, and (2) that a maximum of four 802.11 retransmissions suffices to limit the delay introduced by SIP retransmissions. The first result is of interest to developers of SIP applications who have to decide at which SNR to initiate a handoff to another network. The second result allows network providers to optimize their 802.11b networks for delay sensitive SIP applications.
Year
DOI
Venue
2005
10.1145/1080730.1080743
WMASH
Keywords
Field
DocType
snr range,sip message,ip session,sip retransmissions,ip address,retransmissions scheme,delay sensitive sip application,significant delay,sip application,retransmissions suffices,sip,packet loss,signal to noise ratio,measurements,voice over ip,session initiation protocol,signaling
Wireless,Lossy compression,Computer science,Retransmission,Packet loss,Computer network,Session Initiation Protocol,Signaling protocol,Handover,Voice over IP
Conference
ISBN
Citations 
PageRank 
1-59593-143-0
3
0.45
References 
Authors
18
4
Name
Order
Citations
PageRank
Cristian Hesselman115021.01
Henk Eertink214625.83
Ing Widya39018.52
Erik Huizer4163.97