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Local Zone and subzones
The Traversal Subzone is a conceptual subzone; no endpoints can be registered to it, but all
traversal calls (i.e. calls for which the VCS is taking the media in addition to the signaling) will pass
through it. The Traversal Subzone exists in order to allow you to control the amount of bandwidth
used by traversal calls, as these can be particularly resource-intensive. See the chapter on
Bandwidth control
and the section
Bandwidth consumption of traversal calls
on controlling the bandwidth of traversal calls.
What are traversal calls?
A traversal call is any call passing through the VCS that includes both the signaling (information
about the call) and media (voice and video). The only other type of call is a non-traversal call,
where the signaling passes through the VCS but the media goes directly between the endpoints (or
between one endpoint and another VCS in the call route, or between two VCSs in the call route).
The following types of calls require the VCS to take the media. They are classified as traversal calls
and will always pass through the Traversal Subzone:
•
firewall traversal calls, where the local VCS is either the traversal client or traversal server
•
calls that are gatewayed (interworked) between H.323 and SIP on the local VCS
•
calls that are gatewayed (interworked) between IPv4 and IPv6 on the local VCS
•
for VCSs with Dual Network Interfaces enabled, calls that are inbound from one LAN port and
outbound on the other
•
a SIP to SIP call when one of the participants is behind a NAT.
All such calls will require a traversal call licence each time they pass through the Traversal
Subzone.
Traversal calls use more resource than non-traversal calls, and the numbers of each type of call
are licensed separately. The VCS has one license for the maximum number of concurrent traversal
calls it can take, and another for the maximum number of concurrent non-traversal calls. You can
increase the number of each type of call available on your VCS by purchasing and installing the
appropriate
option
key.
A call is "traversal" or "non-traversal" from the point of view of the VCS through which it is
being routed at the time. A call between two endpoints may pass through two or more
VCSs. Some of these VCSs may just take the signaling, in which case the call will be a
non-traversal call for that VCS. Other VCSs in the route may need to take the media as well, and so
the call will count as a traversal call on that particular VCS.
STUN Relays also consume traversal call licences (three relays take one licence) but they
do not actually pass through the Traversal Subzone.
Overview and
Introduction
Getting started
status
D14049.05
February 2009
Traversal Subzone
for more information
System
VCS
Zones and
configuration
configuration
neighbors
Configuring the Traversal Subzone ports
The VCS allows you to configure the range of ports to be used for the media in traversal calls. A
single traversal call can consist of up to 5 types of media (audio, video, far end camera control,
dual streams and BFCP) and each type of media may require a pair of ports – for example, audio
and video each require one port for RTP, and one for RTCP. Separate pairs of ports are required
for the inbound and outbound portions of a call. A single traversal call can therefore take up to 20
ports.
The default range for the ports to be used for media is 50000 - 51119 UDP, but these can be
changed to anywhere between 1024 and 65533. Ports are allocated from this range in pairs, the
first of each being even. Therefore the range must start with an even number and end with an odd
number.
To configure the ports used for media in traversal calls:
•
VCS configuration > Local Zone > Traversal Subzone
•
xConfiguration Traversal Media Port Star
•
xConfiguration Traversal Media Port En
You must ensure that the port range is large enough to support the maximum number of
!
traversal calls available on your VCS. A single traversal call can take up to 20 ports (5
pairs in each direction). So for example, if your VCS is licensed for 5 traversal calls you
must ensure that the range of ports configured for traversal media is at least 100. If you add extra
traversal calls to your system, you must also ensure that the range of ports available is sufficient.
Call
Bandwidth
processing
control
75
TANDBERG
VIDEO COMMUNICATIONS SERVER
t
d
Firewall
Applications
Maintenance
traversal
ADMINISTRATOR GUIDE
Appendices
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