Cisco Cisco TelePresence Video Communication Server Expressway
Appendix 1 – Troubleshooting
Cisco VCS Deployment Guide: Microsoft OCS 2007 R2, Lync 2010 and Cisco VCS X7.1
Page 77 of 104
Video endpoints only support UDP media. ICE usually offers 3 candidates:
Host (private IP)
Server Reflexive (outside IP address of firewall local to the media supplying agent – B2BUA or
MOC/Lync Client)
MOC/Lync Client)
TURN server (typically the Edge Server/VCS Expressway)
For ICE to work where an endpoint is behind a firewall, the endpoint must offer at least one publicly
accessible address (the Server Reflexive address or the TURN server address). This is used both for
the B2BUA to try and send media to, but also to validate bind requests sent to the VCS Expressway’s
TURN server – bind requests are only accepted by the TURN server if they come from an IP address
that is ‘known’.
accessible address (the Server Reflexive address or the TURN server address). This is used both for
the B2BUA to try and send media to, but also to validate bind requests sent to the VCS Expressway’s
TURN server – bind requests are only accepted by the TURN server if they come from an IP address
that is ‘known’.
If an OCS/Lync INVITE offers only host candidates for UDP, e.g.:
a=candidate:1 1 UDP 2130706431 192.168.1.7 30580 typ host
a=candidate:1 2 UDP 2130705918 192.168.1.7 30581 typ host
a=candidate:2 1 TCP-ACT 1684798975 192.168.1.7 30580 typ srflx raddr 192.168.1.7 rport 30580
a=candidate:2 2 TCP-ACT 1684798462 192.168.1.7 30580 typ srflx raddr 192.168.1.7 rport 30580
•
Only one UDP candidate (two lines, one for RTP and one for RTCP) and they are for the host
(private, presumably non-routable by VCS address)
(private, presumably non-routable by VCS address)
and the B2BUA responds e.g.:
a=candidate:1 1 UDP 2130706431 84.233.149.125 56056 typ host
a=candidate:1 2 UDP 2130706430 84.233.149.125 56057 typ host
a=candidate:4 1 UDP 16777215 194.100.47.5 60000 typ relay raddr 84.233.149.125 rport 56056
a=candidate:4 2 UDP 16777214 194.100.47.5 60001 typ relay raddr 84.233.149.125 rport 56057
•
Host and Relay candidates both offered
neither device will be able to reach the other’s private (host) address, and if the MOC/Lync client tries
to bind to the VCS Expressway TURN server it will get rejected because the request will come from
the server reflexive address rather than private address and MOC/Lync client has not told the B2BUA
what that IP address is.
to bind to the VCS Expressway TURN server it will get rejected because the request will come from
the server reflexive address rather than private address and MOC/Lync client has not told the B2BUA
what that IP address is.
Thus, OCS/Lync server and the Microsoft Edge Server must be configured such that a MOC/Lync
client offers at least one public address with UDP media for this scenario to work.
client offers at least one public address with UDP media for this scenario to work.
Note that in the above scenario the B2BUA may not offer the Server Reflexive address if the Server
Reflexive address is seen to be the same as the host address.
Reflexive address is seen to be the same as the host address.
One way media: MOC/Lync client
endpoint
registered to VCS
When using Microsoft Edge Server
When MOC/Lync clients register to OCS/Lync through a Microsoft Edge Server, the local IP address
and port that the MOC/Lync client declares is usually private and un-routable (assuming that the
MOC/Lync client is behind a firewall and not registered on a public IP address). In order to identify
alternate addresses to route media to, the MOC/Lync client uses SDP candidate lines.
and port that the MOC/Lync client declares is usually private and un-routable (assuming that the
MOC/Lync client is behind a firewall and not registered on a public IP address). In order to identify
alternate addresses to route media to, the MOC/Lync client uses SDP candidate lines.
X7.0 and later using B2BUA
Calls traveling through the Microsoft Edge server are supported when using the B2BUA with the
Enhanced Collaboration option key applied to the “OCS/Lync gateway” VCS, and where the video
Enhanced Collaboration option key applied to the “OCS/Lync gateway” VCS, and where the video