Cisco Cisco TelePresence Video Communication Server Expressway 관리 매뉴얼
Field
Description
H.323
preference
preference
Determines which protocol the VCS Expressway uses if an endpoint supports both Assent and
H.460.18.
H.460.18.
UDP probe
retry interval
retry interval
The frequency (in seconds) with which locally registered endpoints send a UDP probe to the VCS
Expressway.
Expressway.
UDP probe
retry count
retry count
The number of times locally registered endpoints attempt to send a UDP probe to the VCS
Expressway.
Expressway.
UDP probe
keep alive
interval
keep alive
interval
The interval (in seconds) with which locally registered endpoints send a UDP probe to the VCS
Expressway after a call is established, in order to keep the firewall’s NAT bindings open.
Expressway after a call is established, in order to keep the firewall’s NAT bindings open.
TCP probe
retry interval
retry interval
The frequency (in seconds) with which locally registered endpoints send a TCP probe to the VCS
Expressway.
Expressway.
TCP probe
retry count
retry count
The number of times locally registered endpoints attempt to send a TCP probe to the VCS
Expressway.
Expressway.
TCP probe
keep alive
interval
keep alive
interval
The interval (in seconds) with which locally registered endpoints send a TCP probe to the VCS
Expressway after a call is established, in order to keep the firewall’s NAT bindings open.
Expressway after a call is established, in order to keep the firewall’s NAT bindings open.
About ICE and TURN Services
About ICE
ICE (Interactive Connectivity Establishment) provides a mechanism for SIP client NAT traversal. ICE is not a protocol,
but a framework which pulls together a number of different techniques such as TURN and STUN.
but a framework which pulls together a number of different techniques such as TURN and STUN.
It allows endpoints (clients) residing behind NAT devices to discover paths through which they can pass media, verify
peer-to-peer connectivity via each of these paths and then select the optimum media connection path. The available
paths typically depend on any inbound and outbound connection restrictions that have been configured on the NAT
device. Such behavior is described in
peer-to-peer connectivity via each of these paths and then select the optimum media connection path. The available
paths typically depend on any inbound and outbound connection restrictions that have been configured on the NAT
device. Such behavior is described in
.
An example usage of ICE is two home workers communicating via the internet. If the two endpoints can communicate
via ICE the VCS Expressway may (depending on how the NAT devices are configured) only need to take the signaling
and not take the media (and is therefore a non-traversal call). If the initiating ICE client attempts to call a non-ICE
client, the call set-up process reverts to a conventional SIP call requiring NAT traversal via media latching where the
VCS also takes the media and thus requires a traversal license.
via ICE the VCS Expressway may (depending on how the NAT devices are configured) only need to take the signaling
and not take the media (and is therefore a non-traversal call). If the initiating ICE client attempts to call a non-ICE
client, the call set-up process reverts to a conventional SIP call requiring NAT traversal via media latching where the
VCS also takes the media and thus requires a traversal license.
About TURN
TURN (Traversal Using Relays around NAT) services are relay extensions to the STUN network protocol that enable a
SIP or H.323 client to communicate via UDP or TCP from behind a NAT device.
SIP or H.323 client to communicate via UDP or TCP from behind a NAT device.
, and for detailed information about the base STUN protocol, see
.
Each ICE client requests the TURN server to allocate relays for the media components of the call. A relay is required
for each component in the media stream between each client.
for each component in the media stream between each client.
After the relays are allocated, each ICE client has 3 potential connection paths (addresses) through which it can send
and receive media:
and receive media:
■
its host address which is behind the NAT device (and thus not reachable from endpoints on the other side of
the NAT)
the NAT)
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Cisco TelePresence Video Communication Server Administrator Guide