Cisco Cisco TelePresence Video Communication Server Expressway
Appendix 5: Configuring endpoints to work with a
VCS cluster
VCS cluster
When configuring endpoints it is desirable for them to know about all the VCS peers in a cluster, so that at
initial registration or later, if they lose connection to their VCS peer, they have the ability to register with and
use another peer in the VCS cluster.
initial registration or later, if they lose connection to their VCS peer, they have the ability to register with and
use another peer in the VCS cluster.
SIP and H.323 endpoints behave differently – the following sections show the methods that can be used, and
list them in preferred order.
list them in preferred order.
For additional details about DNS SRV and round-robin DNS see the URI dialing section in VCS
Administrator Guide.
Administrator Guide.
H.323 endpoints
The options below are listed in preference order for providing resilience of connectivity of endpoints to a
cluster of VCSs where 1 or more VCS cluster peers become inaccessible. The choice of option will depend
on what functionality the endpoint you are using supports.
cluster of VCSs where 1 or more VCS cluster peers become inaccessible. The choice of option will depend
on what functionality the endpoint you are using supports.
Option 1 – DNS SRV (preferred)
To use this option, there must be a DNS SRV record available for the DNS name of the VCS cluster that
defines an equal weighting and priority for each cluster peer.
defines an equal weighting and priority for each cluster peer.
On each H.323 endpoint, configure the Gatekeeper Settings as:
n
Discovery = Manual
n
IP Address = DNS name of the VCS cluster
If the endpoint supports DNS SRV, on startup the endpoint issues a DNS SRV request and receives a DNS
SRV record back defining an equal weighting and priority for each cluster peer.
SRV record back defining an equal weighting and priority for each cluster peer.
The endpoint then tries to register with a relevant cluster peer (having taken into account the priority /
weightings). If that peer is not available, the endpoint will try and register to another listed peer at the same
priority, or if all peers at that priority have been tried, a peer at the next lower (higher numbered) priority.
weightings). If that peer is not available, the endpoint will try and register to another listed peer at the same
priority, or if all peers at that priority have been tried, a peer at the next lower (higher numbered) priority.
This will be repeated until the endpoint can register with a VCS. On registering with the VCS, the VCS will
respond with the H.323 “Alternate Gatekeepers” list containing the list of VCS cluster peer members.
respond with the H.323 “Alternate Gatekeepers” list containing the list of VCS cluster peer members.
The endpoint will continue to use the first VCS that it registered to for re-registrations and for calls. If it ever
loses connection to its VCS then it will select an “Alternate Gatekeeper” from the list it was supplied with.
loses connection to its VCS then it will select an “Alternate Gatekeeper” from the list it was supplied with.
DNS SRV cache timeout should be set to a fairly long time (e.g. 24 hours) to minimize DNS traffic.
Option 2 – DNS Round-Robin (2nd choice)
To use this option, there must be a DNS A-record available for the DNS name of the VCS cluster that
supplies a round-robin list of IP addresses.
supplies a round-robin list of IP addresses.
On each H.323 endpoint configure the Gatekeeper Settings as:
n
Discovery = Manual
n
IP Address = DNS name of the VCS cluster
Cisco TelePresence VCS Cluster Creation and Maintenance Deployment Guide (X8.5)
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Appendix 5: Configuring endpoints to work with a VCS cluster