Registration Method Of The Failover/Fallback Mode; Fallback Server Redundancy Configuration - Yealink T54S Administrator's Manual

Administrator's Guide for SIP-T2 Series/T4 Series/T5 Series IP Phones
When you initiate a call, the IP phone will go through the following steps to connect the call:
Sends the INVITE request to the primary server.
1.
If the primary server does not respond correctly to the INVITE (that is, the primary server responds to
2.
the INVITE with 503 message or the request for responding with 100 Trying message times out
(64*T1 seconds, defined in
If the secondary server is also unavailable, the IP phone will try the fallback server until it either
3.
succeeds in making a call or exhausts all servers at which point the call will fail.
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
maximum number of retries depends on the configured retry counts (configured by the
account.X.sip_server.Y.retry_counts
parameter "

Registration Method of the Failover/Fallback Mode

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 be 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. If it fails, 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.

Fallback Server Redundancy Configuration

The following table lists the parameters you can use to configure fallback server redundancy.
account.X.fallback.redundancy_type
Parameter
RFC 3261)), then tries to make the call using the secondary server.
RFC 3261. If it is not the last server in the list, the
[1][2]
").
<MAC>.cfg
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