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D14049.05
February 2009
Grey Headline
(continued)
TANDBERG
VIDEO COMMUNICATIONS SERVER
ADMINISTRATOR GUIDE
Introduction
Getting started
Overview and
status
System
configuration
VCS
configuration
Zones and
neighbors
Call
processing
Bandwidth
control
Firewall
traversal
Appendices
Applications
Maintenance
Firewall traversal protocols and ports
The VCS supports two different firewall traversal protocols for
H.323: Assent and H.460.18/H.460.19.
Assent is TANDBERG’s proprietary protocol.
•
H.460.18 and H.460.19 are ITU standards which define
•
protocols for the firewall traversal of signaling and media
respectively. These standards are based on the original
TANDBERG Assent protocol.
In order for a traversal server and traversal client to
communicate, they must be using the same protocol.
The two protocols each use a slightly different range of ports.
Overview
Ports play a vital part in firewall traversal configuration. The
correct ports must be set on the VCS Expressway, traversal
client and firewall in order for connections to be permitted.
Ports are initially configured on the VCS Expressway by the
VCS Expressway Administrator. The firewall administrator and
the traversal client administrator should then be notified of
the ports, and they then must then configure their systems to
connect to these specific ports on the server. The only port
configuration that is done on the client is the range of ports it
uses for outgoing connections; the firewall administrator may
need to know this information so that if necessary they can
configure the firewall to allow outgoing connections from those
ports.
The pages under the
Maintenance > Tools > Port usage
menu show, in table format, all the IP ports that are
being used on the VCS, both inbound and outbound.
This information can be provided to your Firewall Administrator in
order to allow them to configure the firewall appropriately. See
the
Port usage
section for further information.
The Expressway™ solution works as follows:
Each traversal client connects via the firewall to a unique port
1.
on the VCS Expressway.
The server identifies each client by the port on which it
2.
receives the connection, and the Authentication credentials
provided by the client.
Once established, the client constantly sends a probe to
3.
the VCS Expressway via this connection in order to keep the
connection alive.
When the VCS Expressway receives an incoming call for the
4.
client, it uses this initial connection to send an incoming call
request to the client.
The client then initiates one or more outbound connections.
5.
The destination ports used for these connections will differ
for signaling and/or media, and will depend on the protocol
being used (see the following sections for more details).
Expressway process
H.323 firewall traversal protocols
The VCS supports the Assent protocol for SIP firewall traversal
of media.
The signaling is traversed through TCP/TLS connection
established from the client to the server.
SIP firewall traversal protocols
