Measurement and analysis of the error characteristics of an in-building wireless network
Conference proceedings on Applications, technologies, architectures, and protocols for computer communications
Mobile IP: the Internet unplugged
Mobile IP: the Internet unplugged
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MediaPlayer™ versus RealPlayer™: a comparison of network turbulence
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Policy-Enabled Handoffs Across Heterogeneous Wireless Networks
WMCSA '99 Proceedings of the Second IEEE Workshop on Mobile Computer Systems and Applications
Hand-Off Delay Analysis in SIP-Based Mobility Management in Wireless Networks
IPDPS '03 Proceedings of the 17th International Symposium on Parallel and Distributed Processing
SIP Call Setup Delay in 3G Networks
ISCC '02 Proceedings of the Seventh International Symposium on Computers and Communications (ISCC'02)
Measuring the Impact of Slow User Motion on Packet Loss and Delay over IEEE 802.11b Wireless Links
LCN '03 Proceedings of the 28th Annual IEEE International Conference on Local Computer Networks
Link-level measurements from an 802.11b mesh network
Proceedings of the 2004 conference on Applications, technologies, architectures, and protocols for computer communications
Mobile Networks and Applications - Special issue: Wireless mobile wireless applications and services on WLAN hotspots
Analysis of SIP-based mobility management in 4G wireless networks
Computer Communications
Hotspot wireless LANs to enhance the performance of 3G and beyond cellular networks
IEEE Communications Magazine
Security aspects of 3G-WLAN interworking
IEEE Communications Magazine
Computer Standards & Interfaces
Benchmark of middleware protocols for application and service interaction
Proceedings of the 7th International Conference on Mobile and Ubiquitous Multimedia
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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.