Mitel 6867i Administrator's Manual page 216

Mitel 6800 Series SIP Phone Release 4.2.0 Administrator Guide
BACKUP PROXY/REGISTRAR SUPPORT
The IP phones support a backup SIP proxy and backup SIP registrar feature. If the primary
server is unavailable, the phone automatically switches to the backup server allowing the user's
phone to remain in service.
How it Works
All SIP registration messages are sent to the primary registrar first. If the server is unavailable,
then a new registration request is sent to the backup registrar. This also applies to registration
renewal messages, which try the primary server before the backup.
Similarly, any outgoing calls attempt to use the primary proxy first, then the backup if necessary.
In addition, subscriptions for BLF, BLA, and explicit MWI can also use the backup proxy when
the primary fails. Outgoing calls and the previously mentioned subscriptions behave the same
as registrations, where the primary proxy is tried before the backup.
You can configure the backup SIP proxy on a global or per-line basis via the configuration files
or the Mitel Web UI.
SIP OUTBOUND SUPPORT
The IP Phones support draft-ietf-sip-outbound-15. That specification describes how a SIP User
Agent (UA) behind a firewall, reuses an existing connection (usually the REGISTER outbound
connection) for the inbound request if the proxy supports it. The UA uses keep-alive packets
to monitor the connection status.
An Administrator can enable or disable this feature using the following parameter in the
configuration files:
• sip outbound support
Note: If the Global SIP parameter "Persistent TLS" is set on the phone, then only one
TLS persistent connection can be established since the phone uses the local port 5061
for connection. If the Global SIP parameter "TLS" is set on the phone, more than one
connection can be setup since the phone uses a random local port for connection.
ENABLING/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,
"SIP Outbound Support"
BACKUP OUTBOUND PROXY AND FAILOVER SUPPORT
The IP phones support a backup outbound proxy and failover. This feature provides the
following:
• The ability to specify a backup outbound proxy.
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