This article relates to Cisco TelePresence Video Communication Server Expressway.
Q. When do calls on a VCS Expressway use a local (non-traversal) call license?
A. A traversal call is any call where the VCS takes the media as well as the signaling. Usually a VCS Expressway needs a traversal call license to route calls, even for calls between devices directly registered to it. This is because endpoints behind firewalls need the VCS Expressway to receive and forward media in order to guarantee that the media is routable between the endpoints in the call.
The only situation where a call passing through a VCS Expressway is classified as a local (non-traversal) call is when:
there is no SIP to H.323 interworking required, and
there is no IPv4 to IPv6 interworking required, and
the call is not being routed from the VCS Expressway through a Traversal Zone, and
neither endpoint is traversal enabled (in other words, neither endpoint has registered with Assent or H.460.18/19 and neither endpoint has made the call requesting Assent or H.460.18/19), and
the call is received from and sent to:
an endpoint or a Neighbor Zone directly connected to the Wide Area Network, or
an endpoint or a Neighbor Zone behind a firewall that has a SIP or H.323 application-level gateway (ALG) that supports video calling (which makes the signaling appear as though the endpoint is directly connected to the Wide Area Network), or
locally registered ICE-enabled endpoints (if using VCS version X5 or later)
Note: to aid firewall traversal, all TANDBERG endpoints are traversal enabled and so a traversal license will always be needed when at least one of the endpoints involved in the call is a TANDBERG endpoint.
Note: a non-traversal call on a VCS Expressway will consume a traversal license if there are no non-traversal call licenses available (if using VCS version X5 or later).