Cisco Cisco TelePresence Video Communication Server Expressway 관리 매뉴얼
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)
■
its publicly-accessible address on the NAT device
■
a relay address on the TURN server
The endpoints then decide, by performing connectivity checks through ICE, how they are going to communicate.
Depending upon how the NAT devices are configured, the endpoints may be able to communicate between their
public-facing addresses on the NAT devices or they may have to relay the media via the TURN server. If both
endpoints are behind the same NAT device they can send media directly between themselves using their internal host
addresses.
Depending upon how the NAT devices are configured, the endpoints may be able to communicate between their
public-facing addresses on the NAT devices or they may have to relay the media via the TURN server. If both
endpoints are behind the same NAT device they can send media directly between themselves using their internal host
addresses.
After the media route has been selected, the TURN relay allocations are released if the chosen connection paths do
not involve routing via the TURN server. Note that the signaling always goes via the VCS, regardless of the final media
communication path chosen by the endpoints.
not involve routing via the TURN server. Note that the signaling always goes via the VCS, regardless of the final media
communication path chosen by the endpoints.
Capabilities and limitations
■
systems support up to 1800 relay allocations. This is typically enough to support 100 calls but
does depend on the network topology and the number of media stream components used for the call (for
example, some calls may use Duo Video, or other calls might be audio only).
example, some calls may use Duo Video, or other calls might be audio only).
■
system supports up to 6000 relays, spread evenly across 6 ports where each port is limited to handling
1000 relays. This limit is not strictly enforced, so we recommend adding an SRV record for each port to enable
round robin.
round robin.
■
Clustered VCSs: if the requested TURN server's relays are fully allocated the server will respond to the
requesting client with the details of an alternative server in the cluster (the TURN server currently with the
most available resources).
requesting client with the details of an alternative server in the cluster (the TURN server currently with the
most available resources).
■
The VCS's TURN services are supported over single and dual network interfaces (via the Advanced
Networking option). For dual network interfaces, the TURN server listens on both interfaces but relays are
allocated only on the VCS's externally facing LAN interface.
Networking option). For dual network interfaces, the TURN server listens on both interfaces but relays are
allocated only on the VCS's externally facing LAN interface.
■
Media negotiation may fail when VCS Control version X7.2 (or newer) TURN client negotiates with VCS
Expressway version X7.1 TURN server. Because the more recent client version can support IPv6 TURN, it adds
a new attribute in the request to the server (irrespective of whether the request is for IPv4 or IPv6 TURN). The
X7.1 TURN server does not understand the new attribute.
Expressway version X7.1 TURN server. Because the more recent client version can support IPv6 TURN, it adds
a new attribute in the request to the server (irrespective of whether the request is for IPv4 or IPv6 TURN). The
X7.1 TURN server does not understand the new attribute.
You can work around this issue by upgrading the VCS Expressway to version X7.2 or newer, preferably the
same version as on the VCS Control. We recommend that you maintain the same software versions on the
VCS Control and VCS Expressway.
same version as on the VCS Control. We recommend that you maintain the same software versions on the
VCS Control and VCS Expressway.
■
Microsoft ICE (which is not standards-based) is not supported by the VCS Expressway's TURN server; to
enable communications between the VCS and Microsoft clients that are registered through a Microsoft Edge
Server you need to use the
enable communications between the VCS and Microsoft clients that are registered through a Microsoft Edge
Server you need to use the
.
■
The TURN server does not support bandwidth requests. Traversal zone bandwidth limits do not apply.
■
The VCS Expressway TURN server supports TURN media over TCP and UDP. Configuration of the supported
protocols is available only through the CLI command
protocols is available only through the CLI command
xConfiguration Traversal Server TURN ProtocolMode
.
■
The VCS Expressway TURN server supports UDP relays over TCP; it does not currently support TCP relays.
Configuring TURN Services
you need the TURN Relay
option key (this controls the number of TURN relays that can be simultaneously allocated by the TURN server).
62
Cisco TelePresence Video Communication Server Administrator Guide
Firewall Traversal