RSI/RSA Address Resolution

When dialing a number from a telephone attached to the local Passport 4400 unit, the destination address is resolved in one of the following three ways:

• Local number, locally resolved. If the number appears in the local Egress Table, it is a local number. No network address resolution is required, and the address is resolved within the voice application of the local Passport 4400 unit. If that number is not busy, a connection will be established when the local number answers.
• Remote number, locally resolved. If the number does not appear in the local Egress Table, it is referred to the local RSI for further resolution. The RSI consults its cache, a table that stores network addresses that have been previously resolved. This network address is then used by the voice application of the Passport 4400 unit to contact the remote Passport 4400 unit where the called number is located. If that number is not busy, a connection will be established when the called number answers.
• Remote number, resolved by the Remote Server Agent (RSA). If the number does not appear in either the Egress Table or the cache, the RSI contacts the RSA in its associated Passport 6400 for address resolution. In turn, the RSA accesses its Voice Network Call Server (VNCS) where all valid network addresses are stored. If the called number appears within the VNCS, its network address is returned through the RSA to the RSI, and then to the voice application of the local Passport 4400 unit. Ultimately, the voice application contacts the remote Passport 4400 unit where the called number is located. If that number is not busy a connection will be established when the called number answers.

Simultaneously, this number is entered in cache. All future calls to this number will then be resolved locally without accessing the server. The illustration below highlights the sequence of events involved in resolving network addresses.

Special Cases

• Link is down
• VNCS server is down
• Number not valid