The special feature and advantage of the SI session initiation protocol is the ability to access a user terminal or information resource without specifying its technological address. Proxy and regional SI servers store technological addresses of connected user terminals. Thanks to this fact, local area networks may carry out a communication session initiation and protocol message transmission on any transport level using any network addressing rules.
During a communication session, proxy and regional servers use the communication session identifier to manage data transmission between users or between the user and an information resource. Meanwhile, in opposition to NAT server, SI server exchanges both source and destination addresses at once.
Fig. 35 illustrates the scheme of interaction between SI client running at a user terminal and a proxy SI server explaining independence of transport stratum protocols and respective addressing systems of local and outer infocommunication networks.
Thus, the SI technology provides independence of a local network addressing from the addressing of united infocommunication network. Meanwhile, SI proxy server may be combined with NAT server or completely carry out its functions.
Fig. 35. Scheme of interaction between a SI client and a proxy SI server.
SDA – source address plus destination address, while S1 - technological address of the terminal, D1 - technological address of the proxy server , S2 – source address (proxy server address) for interation with the regional server, D2 – technological address of the regional server, "ñ" – communication session ID.
Independence of a fixed location and wireless local area network addressing from the outer transport network is an effective way to shrink IP address space required by the united infocommunication transport network.
The potential advantage of the SI technology is the ability to provide communication session initiation via a united transport network that does not use IP addressing of its technological components (for example, SI servers and routers). (High-priority invention application #2007131316RU … #2007131322RU, #2007131337RU … #2007131343RU). |
