Yealink CP860 SERIES, Administrator'S Manual

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Configuring Advanced Features
751
At the start of a call, server availability is determined by SIP signaling failure. SIP signaling
failure depends on the SIP protocol being used as described below:

If TCP is used, then the signaling fails if the connection or the send fails.

If UDP is used, then the signaling fails if ICMP is detected or if the signal times out. If the
signaling has been attempted through all servers in the list (this list contains all the server
addresses resolved by the DNS server) and this is the last server, then the signaling fails
after the complete UDP timeout defined in
RFC 3261 . If it is not the last server in the list,
the maximum number of retries depends on the configured retry counts (configured by
the parameter “account.X.sip_server.Y.retry_counts”).
Phone Registration
Registration method of the failover mode:
The IP phone must always register to the primary server first except in failover conditions. If this
is unsuccessful, the phone will re-register as many times as configured until the registration is
successful. When the primary server registration is unavailable, the secondary server will serve
as the working server. As soon as the primary server registration succeeds, it returns to being
the working server.
Registration methods of the fallback mode include (not applicable to outbound proxy servers):

Concurrent registration (default)
: The IP phone registers to SIP server 1 and SIP server 2
(working server and fallback server) at the same time. Note that although the IP phone
registers to two SIP servers, only one server works at the same time. In a failure situation, a
fallback server can take over the basic calling capability, but without some advanced
features (for example, shared lines and MWI) offered by the working server.

Successive registration
: The IP phone only registers to one server at a time. The IP phone
first registers to the working server. In a failure situation, the IP phone registers to the
fallback server, and the fallback server can take over all calling capabilities.
For more information on server redundancy, refer to
Server Redundancy on Yealink IP Phones .
Procedure
Server redundancy can be configured using the following methods.
Central
Provisioning
(Configuration
File)
<MAC>.cfg
Configure the SIP server redundancy.
Parameters:
account.X.sip_server.Y.address
account.X.sip_server.Y.port
account.X.sip_server.Y.expires
account.X.sip_server.Y.retry_counts