Network address translator (NAT) mapping keep-alive method and system based on session initiation protocol (SIP)

Abstract

The invention provides a network address translator (NAT) mapping keep-alive method and a system for realizing the method, and in the method, the mapping relationship can be timely reconstructed after being eliminated and can be mapped on NAT with less network consumption. The NAT mapping keep-alive method based on SIP comprises the following steps: a. an SIP terminal launches registration to an SIP server via an NAT device, and when the SIP terminal launches registration, the NAT device stores the mapping relationship between the SIP terminal and the NAT device; b. after the SIP server receives the registration of SIP terminal, the SIP server sends a keep-alive message of the user datagram protocol (UDP) style to the SIP terminal via the NAT device periodically; c. the SIP terminal starts a timer after receiving the keep-alive message; and d. the SIP terminal judges whether the keep-alive message is received or not in overtime of the timer, if so, resetting the timer and returning to the step; and if not, triggering the SIP terminal for registration again, eliminating the timer and returning to step a.

Description

Technical field [0001] The technical solution involves SIP (Session Initiation Protocol, Session Initiation Protocol) technology and NAT (Network Address Translator, Network Address Translator) mapping keep-alive technology. Background technique [0002] Although IPv6 is an inevitable trend to replace IPv4, IPv4 will still exist for a long time, and the existence of IPv4 will inevitably be accompanied by a large number of NATs. With the increasing popularity of VOIP (Voice over IP) services, NAT has an increasing impact on P2P media services. Significantly. [0003] In a network environment with NAT devices, if the SIP terminal is on the private network and the SIP server is on the public network, then when the SIP terminal initiates registration with the server, a mapping relationship between the private network address and the public network address will be generated on the NAT. This mapping The relationship can ensure that the SIP server can deliver the SIP call request to the ...

AI Technical Summary

Problems solved by technology

However, under normal circumstances, the mapping relationship generated on the NAT device is temporary, and the time of this mapping may be very short, only a few seconds

If this address mapping is not used for a period of time, the mapping will be deleted over time, causing the server to no longer be able to call the end user

So in order to ensure that the SIP server can call the SIP terminal at any time, the SIP server needs to keep this mapping alive. The existing implementation method is usually that the SIP server regularly sends SIP messages such as notify and option to the public network port of the NAT device to keep the mapping. Keep alive this mapping, but the SIP message is relatively large, and the terminal needs complex decoding. If the mapping is short-lived, then it is necessary to send keep-alive messages frequently. At this time, the pressure on the terminal, network, and server is all is big

[0004] In addition, when the NAT device is restarted and the NAT address mapping is manually cleared or abnormally deleted, the server can no longer call the SIP terminal. For the existing implementation, see Chinese patent application "200610119375.5 A method for maintaining NAT address binding in a SIP network system and its device", usually the terminal also sends a keep-alive message, such as an option message, but the option message can only keep alive the existing NAT mapping, and cannot make the server update its saved terminal mapping relationship, unless the terminal re-initiates registration, but the terminal does not It cannot perceive the abnormality of the NAT device, so the registration will only be initiated when the registration times out, and this time may be very long (RFC3261 recommends one hour), then the terminal user may not receive the call request from the server within an hour, yes VOIP business has a big impact

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