D 14049.01
07.2007 35
TANDBERG VIDEO COMMUNICATION SERVER
ADMINISTRATOR GUIDE
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Introduction Getting
Started
System
Overview
System
Configuration
H.323 & SIP
Configuration
Registration
Control
Zones and
Neighbors
Call
Processing
Firewall
Traversal
Bandwidth
Control Maintenance Appe ndices
TANDBERG VIDEO COMMUNICATION SERVER
ADMINISTRATOR GUIDE
H.323 & SIP
Configuration
SIP protocols and ports
The VCS supports SIP over UD P, TCP and TLS transport protocols. You can c onfigure whether or
not incoming calls using each pro tocol are supported, and if s o, the ports on which the VCS wi ll
listen for such calls.
Using the VCS as a SIP Registrar
In order for a SIP endpoint to be con tactable via its register ed alias, it must register its loc ation
with a SIP Registrar. The VCS can act as a S IP Registrar for up to 20 domains.
SIP aliases always take the form use rname@domain. To enable the VCS to a ct as a SIP Registrar,
you must configure it with the SI P Domain(s) for which it will be author itative. It will then accept
registration requests for a ny endpoints attempting to re gister with an alias that includ es that
domain.
If no Domains are configured, th en the VCS will not act as a SIP Registr ar.
Proxying Registration Requests
If the VCS has no domains configure d, or it receives a registrati on request for a domain for which
it is not acting as a Registrar, then the VC S may proxy the registrati on request. This depends on
the SIP Registration Proxy M ode setting, as follows;
Off: the VCS will not proxy any re gistration requests. Th e request will be rejected wit h a “403
Forbidden” message.
Proxy to Known Only: the VCS will p roxy the registration req uest but only to its neighbor s.
Proxy to any: the VCS will proxy the r egistration requests in a ccordance with its call po licy (e.g.
administrator policy and tra nsforms). See Call Processing for m ore information.
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About SIP on the VCS
The VCS supports the SIP pr otocol: it is both a SIP Proxy and SI P Registrar, and will provide
interworking between S IP and H.323 calls. In order to suppo rt SIP, SIP mode must be enabled
and at least one of the SIP transpo rt protocols must be acti ve.
Using the VCS as a SIP Proxy Server
When in SIP mode, the VCS may act as a SI P Proxy Server. The role of a Prox y Server is to forward
requests (such as REGISTER and INVIT E) from endpoints or other Pr oxy Servers. These req uests
are forwarded on to other Prox y Servers or to the destin ation endpoint.
Whether or not the VCS acts as a SIP Pr oxy Server, and its exact beh avior when proxying requ ests,
is determined by the SIP Registr ation Proxy Mode settin g. This in turn depends on the pr esence
of Route Set information in the re quest header and whether or no t the Proxy Server from wh ich the
request was received is a Neigh bor of the VCS.
A Route Set can specify the pa th that must be taken when requ ests are being proxied betwe en
an endpoint and its Registrar. For exa mple, when a REGISTER request is pr oxied by a VCS, the
VCS adds a Path header compone nt to the request which signals t hat the VCS must be included
on any call to that endpoint. The info rmation is usually required in si tuations where firewalls exis t
and the media must follow a specif ied path in order to success fully traverse the firewall. F or more
information about the path h eader field, see RFC 3327 [10].
When the VCS proxies a request th at contains existing Route Set in formation, it will forward i t
directly to the URI specifie d in the path. Any call policy conf igured on the VCS will therefor e be
bypassed. This may present a sec urity risk if the informati on in the Route Set cannot be trus ted.
For this reason, you can configur e the VCS with three differe nt behaviors when proxyi ng requests,
as follows:
If the SIP Registration Prox y Mode setting is Off, the VCS w ill not proxy any requests tha t have
an existing Route Set. Requests t hat do not have an existing Route Set wi ll still be proxied in
accordance with existing c all policy (e.g. zone searches and tr ansforms). This setting provid es
the highest level of security.
If the setting is Proxy to Know n Only, the VCS will proxy requests w ith an existing Route Set
only if the request was receive d from a Neighbor zone (includi ng Traversal Client and Traversal
Server zones). Requests that do n ot have an existing Route Set will be pr oxied in accordance
with existing call policy.
If the setting is Proxy to any, the VCS will p roxy all requests. Those wit h existing Route Sets
will be proxied to the specifie d URI; those without will be proxi ed in accordance with exist ing
call policy.
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SIP Registration Expiry
SIP endpoints must periodi cally re-register wit h the SIP Registrar in order to p revent their
registration expiring. You can det ermine the interval with w hich SIP endpoints must regis ter with
the VCS.
SIP Overview
Working with SIP
This setting also impacts the VC S’s behavior when acting as a SIP Prox y Server.
This setting applies only whe n the VCS is acting as a SIP Registr ar, and to endpoints
registered with the VCS. It does n ot apply to endpoints whose reg istrations are being
proxied through the VCS.
At least one of these protocols must b e set to a Mode of On in order for SIP f unctionality to
be supported.