TTL-Based UDP Hole Punching Scheme in SIP Network
In this paper, we propose the low Time-To-Live (TTL)-based UDP hole punching scheme to reduce the load on the SIP registrar for Network Address Translator (NAT) traversal. For this purpose, the low TTL value is determined by executing ‘traceroute’ for the
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LG Uplus, Daejeon 305-350, Korea [email protected] 2 Dept. of Multimedia, Namseoul University, Chungnam 331-707, Korea [email protected] 3 Dept. of Computer Science, Korea National Open University, Seoul 110-791, Korea [email protected] 4 Dept. of Computer Software Eng., Soonchunhyang University, Chungnam 336-745, Korea [email protected] 5 School of IT Eng., Catholic University of Daegu, Gyeongbuk 712-702, Korea [email protected]
Abstract. In this paper, we propose the low Time-To-Live (TTL)-based UDP hole punching scheme to reduce the load on the SIP registrar for Network Address Translator (NAT) traversal. For this purpose, the low TTL value is determined by executing ‘traceroute’ for the server reflexive IP address obtained through the SIP registration. In the proposed scheme, since the UDP hole punching request with low TTL value will never reach the registrar, the load on the registrar can be significantly alleviated. We analyze the proposed scheme using the Markov chain model. Numerical results indicate that the proposed scheme can significantly alleviate the load on the registrar, compared to the existing SIP scheme. Keywords: NAT traversal, TTL, UDP hole punching, SIP.
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Introduction
Session Initiation Protocol (SIP) is popular for establishing media sessions [1]. There are many devices and servers which are interoperable to SIP. Since a Network Address Translator (NAT) has been widely deployed in the home network, the SIP User Agents (UAs) like SIP phones are very often located behind NATs even if the Internet service provider gives a global IP address. In real network, LG Uplus, one of the major carriers in Korea, uses the access point (AP) working as a NAT for VoIP services [2]. It means that most Wi-Fi phones should frequently send REGISTER message to the registrar for NAT traversal (e.g., within 60 sec) [3]. Therefore, for such frequent registrations, the SIP registrar tends to suffer from the heavy load. To overcome this problem, we propose the low Time-To-Live (TTL)-based UDP hole punching *
Corresponding author.
James J. (Jong Hyuk) Park et al. (eds.), Multimedia and Ubiquitous Engineering, Lecture Notes in Electrical Engineering 308, DOI: 10.1007/978-3-642-54900-7_21, © Springer-Verlag Berlin Heidelberg 2014
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scheme. In the proposed scheme, since the UDP hole punching request with low TTL value will never reach the registrar, the load on the registrar can be significantly alleviated. A recent work assumes that most NATs will not forward ‘Internet Control Message Protocol (ICMP) TTL Exceeded’ message back to an internal host [4]. But the assumption is not reasonable since the default setting of NAT device must allow ‘ICMP TTL Exceeded’ message to be originated [5]. In this paper, the assumption is not applicable. We determine the low TTL by executing ‘traceroute’ for the server reflexive IP address, currently an IP address owned by the NAT, obtained through the SIP registration procedure. To the best of our knowledge, this is the first work which supports the low
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