Aastra 9143i Series Administrator's Manual page 259

Enablling/Disabling SIP Outbound Draft 15 Support.
Use the following procedure to enable/disable SIP outbound Draft 15 support.
Configuration Files
For the specific parameter you can set in the configuration files, see Appendix A, the section,
Support" on page A-75.
Limitations
The following are limitations to this feature:
• SIP outbound on the phones is only supported for TLS and TCP based
messages. UDP is not supported.
• The "keep-alive" only works with REGISTER connections.
SIP Server (SRV) Lookup
The SIP SRV Lookup feature allows you to configure the IP phone to perform a
DNS server lookup on a SIP proxy, a SIP registrar, or a SIP outbound proxy.
The IP phone performs an SRV lookup when the IP address of the server is FQDN
and the corresponding port is 0.
For example, if the phone is configured with sip proxy ip of "ana.aastra.com",
and sip proxy port of "0", the SRV lookup may return multiple servers, based on
the priorities if one is selected as primary and others are selected as secondary.
However, if the IP address is an FQDN and the corresponding server port is
non-zero, then the phone performs a DNS "A" Name Query to resolve the FQDN
into dot notation form.
If the IP address is a valid dot notation and the port is zero, then a default port
5060 is used.
You can configure SRV lookup using the configuration files (aastra.cfg and
<mac>.cfg) only. The parameters to use are:
• sip proxy ip
• sip proxy port
41-001160-03 Rev 00, Release 2.5
Configuring Network and Session Initiation Protocol (SIP) Features
Global SIP Settings
"SIP Outbound
4-75