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SIP
TANDBERG VIDEO COMMUNICATIONS SERVER ADMINISTRATOR GUIDE
SIP Overview
Using the VCS as a SIP Proxy Server
When SIP mode has been enabled the VCS may act as a SIP Proxy Server. The role of a Proxy Server is to forward requests (such as REGISTER and INVITE) from endpoints or other Proxy Servers. These requests are forwarded on to other Proxy Servers or to the destination endpoint.
Whether or not the VCS acts as a SIP Proxy Server, and its exact behavior when proxying requests, is determined by the SIP Registration Proxy Mode setting. In addition, this also depends on the presence of Route Set information in the request header and whether or not the Proxy Server from which the request was received is a Neighbor of the VCS.
A Route Set can specify the path that must be taken when requests are being proxied between an endpoint and its Registrar. For example, when a REGISTER request is proxied by a VCS, the VCS adds a Path header component to the request which signals that the VCS must be included on any call to that endpoint. The information is usually required in situations where firewalls exist and the media must follow a specified path in order to successfully traverse the firewall. For more information about the path header field, see RFC 3327 [10].
When the VCS proxies a request that contains existing Route Set information, it will forward it directly to the URI specified in the path. Any call policy configured on the VCS will therefore be bypassed. This may present a security risk if the information in the Route Set cannot be trusted. For this reason, you can configure the VCS with three different behaviors when proxying requests, as follows:
•If the SIP Registration Proxy Mode setting is Off, the VCS will not proxy any requests that have an existing Route Set. Requests that do not have an existing Route Set will still be proxied in accordance with existing call policy (e.g. zone searches and transforms). This setting provides the highest level of security.
•If the setting is Proxy to Known Only, the VCS will proxy requests with an existing Route Set only if the request was received from a Neighbor zone (including Traversal Client and Traversal Server zones). Requests that do not have an existing Route Set will be proxied in accordance with existing call policy.
•If the setting is Proxy to any, the VCS will proxy all requests. Those with existing Route Sets will be proxied to the specified URI; those without will be proxied in accordance with existing call policy.
SIP protocols and ports
The VCS supports SIP over UDP, TCP and TLS transport protocols. You can configure whether or not incoming calls using each protocol are supported, and if so, the ports on which the VCS will listen for such calls. You can also specify the range of ports the VCS will use once calls are established. This range must be sufficient to support all required concurrent calls.
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Introduction | Getting Started |
| Overview and |
| System | VCS | Zones and |
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| Call |
| Bandwidth |
| Firewall |
| Maintenance |
| Appendices |
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| Status |
| Configuration | Configuration | Neighbors |
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| Processing |
| Control |
| Traversal |
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D14049.03 |
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MAY 2008 |
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