Cisco SPA2102-SF Administration Guide - Page 28

Introducing Cisco Small Business Analog Telephone Adapters ATA Software Features 1 SIP Proxy Redundancy In typical commercial IP Telephony deployments, all calls are established through a SIP proxy server. An average SIP proxy server may handle thousands of subscribers. It is important that a backup server be available so that an active server can be temporarily switched out for maintenance. The ATA device supports the use of backup SIP proxy servers (via DNS SRV) so that service disruption should be nearly eliminated. A relatively simple way to support proxy redundancy is to configure your DNS server with a list of SIP proxy addresses. The ATA device can be instructed to contact a SIP proxy server in a domain named in the SIP message. The ATA device consults the DNS server to get a list of hosts in the given domain that provides SIP services. If an entry exists, the DNS server returns an SRV record that contains a list of SIP proxy servers for the domain, with their host names, priority, listening ports, and so on. The ATA device tries to contact the list of hosts in the order of their stated priority. If the ATA device is currently using a lower priority proxy server, it periodically probes the higher priority proxy to see whether it is back on line, and switches back to the higher priority proxy when possible. SIP Proxy Redundancy is configured in the Line and PSTN Line tabs in the Administration Web Server. See "ATA Routing Field Reference," on page 105. Other ATA Software Features The following table summarizes other features provided by ATA devices. Feature Streaming Audio Server T.38 Fax Relay Silence Suppression Description See "Configuring a Streaming Audio Server," on page 88. See "Using a FAX Machine," on page 55. See "Silence Suppression and Comfort Noise Generation," on page 60. Cisco Small Business ATA Administration Guide 28