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Technical Bulletin
SoundPoint
®
IP, SIP 2.1
2
Terminology
Before you read this document, it is important to understand certain
terminology and become familiar with the server/registration configuration
as described in the references listed in the References on page 8. The behavior
described in this document supersedes that described in section 3.6.5 of the
SIP 2.0 Administrator's Guide.
SIP Registrations: SoundPoint IP phones support the ability to have multiple
SIP Registrations per phone. This is often used to support multiple “Lines” on
a single phone and normally the SIP server(s) used for each Registration are
the same. However, they could be different.
Primary and Fallback Servers: Each of these SIP Registrations may be
configured for concurrent registration with multiple servers for fallback
purposes. For example, a phone may be configured to have two SIP
Registrations and each SIP Registration may be configured with two separate
servers (a primary server and a fallback server). DNS mechanisms (as
described in RFC3263) may be used such that the servers are capable of
resolving to multiple physical SIP servers for fail-over purposes.
Working Server: The phone maintains a list of all possible servers gained from
both DNS and configuration. The highest priority server which has an active
registration is treated as the working server and will be the first server tried for
call initiation purposes. At any time, there is only one working server
recognized by the phone.
Registrar Server: Servers (both primary and fallback) may be configured with
registration enabled or disabled using the
reg.x.server.y.register
configuration parameter. Servers that have this parameter enabled will
attempt registrations and are termed a registrar server. If a server is not a
registrar server, calls will be attempted on that server if appropriate, but
registration will not be attempted. Only a registrar server can become the
working server.
For the purposes of this document, we will use examples where the phone has
only one SIP Registration.
The sections Server <server/> on page 95 and Registration <reg/> on page 149
of the SIP 2.0 Administrator's Guide describe the parameters that are relevant to
the configuration of the phones for server redundancy and fallback behavior.
Configuration file changes for SIP 2.1 are described in Configuration File
Changes on page 7.
Note
The primary server is the only one that will be used for advanced SIP features such
as shared lines, message waiting indicators, and presence. This is a change in
behavior from software releases before SIP 2.1 All other configured servers are
referred to as fallback servers.