Cisco Cisco Expressway 维护手册
Capabilities and limitations
n
An Expressway running on Small/Medium VM servers supports 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). A Large VM supports up to 6000 relays, spread evenly across 6 ports where each port is limited
to handling 1000 relays.
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). A Large VM supports up to 6000 relays, spread evenly across 6 ports where each port is limited
to handling 1000 relays.
n
Clustered Expressways: 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).
to the requesting client with the details of an alternative server in the cluster (the TURN server currently
with the most available resources).
n
The Expressway'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 Expressway's externally facing LAN interface.
Advanced Networking option). For dual network interfaces, the TURN server listens on both interfaces but
relays are allocated only on the Expressway's externally facing LAN interface.
n
If static NAT is enabled on the Expressway-E, the TURN relay candidate address that is offered will be
the internal/private IP address of the Expressway-E, not its static NAT address. Thus ICE clients in the
public internet may not be able to route media via the TURN server.
the internal/private IP address of the Expressway-E, not its static NAT address. Thus ICE clients in the
public internet may not be able to route media via the TURN server.
n
Microsoft ICE (which is not standards-based) is not supported by the Expressway-E's TURN server; to
enable communications between the Expressway and Microsoft Lync clients that are registered through a
Microsoft Edge Server you need to use the
enable communications between the Expressway and Microsoft Lync clients that are registered through a
Microsoft Edge Server you need to use the
.
n
The TURN server does not support bandwidth requests. Traversal zone bandwidth limits do not apply.
Configuring TURN services
Relay option key (this controls the number of TURN relays that can be simultaneously allocated by the
TURN server).
TURN server).
The
TURN
page (
Configuration > Traversal > TURN
) is used to configure the Expressway-E's TURN
settings.
The configurable options are:
Field
Description
Usage tips
TURN
services
services
Determines whether the Expressway
offers TURN services to traversal
clients.
offers TURN services to traversal
clients.
TURN
requests port
requests port
The listening port for TURN requests.
The default is 3478.
The default is 3478.
On Large VM server deployments you
can configure a range of TURN
request listening ports. The default
range is 3478 – 3483.
can configure a range of TURN
request listening ports. The default
range is 3478 – 3483.
To allow endpoints such as Jabber Video to discover
TURN services, you need to set up a DNS SRV record
for _turn._udp. (either for the single port, or range of
ports as appropriate).
TURN services, you need to set up a DNS SRV record
for _turn._udp. (either for the single port, or range of
ports as appropriate).
If TURN services are already enabled, any changes to
the port numbers do not come into effect until the
TURN services are restarted.
the port numbers do not come into effect until the
TURN services are restarted.
Authentication
realm
realm
This is the realm sent by the server in
its authentication challenges.
its authentication challenges.
Ensure that the client's credentials are stored in the
local authentication database.
local authentication database.
Media port
range start /
end
range start /
end
The lower and upper port in the range
used for the allocation of TURN
relays.
used for the allocation of TURN
relays.
The default TURN relay media port
range is 24000 – 29999.
range is 24000 – 29999.
Cisco Expressway Administrator Guide (X8.1.1)
Page 51 of 343
Firewall traversal
About ICE and TURN services