Abstract
Session Initiation Protocol (SIP) has been proposed for multimedia services and wide-area connectivity in smart home environments (SHEs). An important issue for SIP deployment in SHEs is network address translator (NAT) traversing. SIP and Real-time Transport Protocol (RTP) packets are delivered between an SHE (i.e., private IP network) and Internet (i.e., a public IP network) through an NAT function of a home gateway, and the NAT translates the IP/transport layer address and port number but leaves the application layer content unchanged. This results in inconsistency between the IP addresses/port numbers in the IP/transport layers and those in the SIP layer. To resolve this issue, we describe six solutions including static route, UPnP, STUN, ICE, ALG, and SBC. Then we compare these solutions in terms of smart home appliance (SHA) modification, scope of NATs supported, multilayer NAT traversal, ease of configuration, security issue, and time complexities.
Highlights
Smart home appliances (SHAs) including information appliances and multimedia appliances have rapidly deployed in smart home environments (SHEs)
The smart home appliance (SHA) connect to Internet devices through a home gateway (HG), which is equipped with firewall to provide security and network address translator (NAT) to solve IP shortage problem
When an SHA resides in a private network within another private network, all solutions but Universal Plug and Play (UPnP) still support NAT traversing for Session Initiation Protocol (SIP)/Real-time Transport Protocol (RTP)
Summary
Smart home appliances (SHAs) including information appliances and multimedia appliances have rapidly deployed in smart home environments (SHEs). The SHAs connect to Internet devices through a home gateway (HG), which is equipped with firewall to provide security and network address translator (NAT) to solve IP shortage problem. SIP utilizes IP addresses/port numbers as location information in the SIP messages It cannot work correctly when a UA resides in a private network (i.e., SHE) behind a network address translator [8]. This issue referred to as SIP/RTP NAT traversing problem is described as follows. EURASIP Journal on Wireless Communications and Networking (a) Mapping table (a simplified version)
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