Polycom Version 2.0.3B manual Recommended Practices for Server Fallback Deployments, Before SIP

Technical Bulletin

SoundPoint ® IP, SIP 2.1

Changes From Previous Phone Behavior (Releases Before SIP 2.1)

Before SIP 2.1	In SIP 2.1
A Line is only capable of maintaining	A Line will maintain registrations with
one server registration.	all servers that are configured as
	registrar servers.
If two servers are configured (for	If two servers are configured (for
example, reg.1.server.1.address =	example, reg.1.server.1.address =
"server1" and	"server1" and
reg.1.server.2.address =	reg.1.server.2.address =
"server2", the phone will initially	"server2", the phone will register with
register with Server1 as the working	both Server1 as the working and
server. Phone calls will be placed and	Server2. Phone calls will be placed
received through Server1 only. If the	through Server1, but may be received
registration to Server1 fails or expires,	through either Server1 or Server2. If
then the phone will attempt to register	the registration to Server1 fails or
with Server2. If this registration	expires, then the Server2 will become
succeeds, then incoming calls will be	the working server.
received using this server. At this point,
Server2 takes over as the working
server.
The phone will continually attempt	The phone will continually attempt to
registration using SIP registration	register with Server1 and, when this is
protocols with Server1. At the point that	successful, will switch back to using
this succeeds, the registration with	Server1 as the working server. The
Server2 will expire and Server1 will	Server2 registration will be maintained.
resume as the working server.
The phone attempts to maintain full SIP	Only basic SIP registration for INVITE
functionality with each server, but it is	functions is maintained with servers
questionable how effective this is.	other than the primary server.

Recommended Practices for Server Fallback Deployments

The best method for ensuring optimum server redundancy is to deploy two identical call servers and use either DNS methods or “IP Address Moving” together with call server recommended practices for maintaining synchronization of records between the redundant servers. This is termed fail-over (refer to Terminology on page 2). Deployment varies dependent on the SIP call server being used. Consult your SIP call server supplier for recommended practices for fail-over configuration.

In situations where server redundancy for fall-back purpose is used, the following measures should be taken to optimize the effectiveness of the solution:

1.Deploy an on-site DNS server to avoid long call initiation delays that can result if the DNS server records expire.

6