Cisco TelePresence Video Communication Server Administrator's Manual page 145

The VCS supports two types of SRV record as defined by this Annex. These are Location and Call,
with _Service set to _h323ls and _h323cs respectively.
If you want the VCS to be contactable using H.323 URI dialing, you should provide at least a Location
SRV record, as it provides the most flexibility and the simplest configuration.
Location SRV records
For each domain hosted by the VCS, you should configure a Location SRV record as follows:
_Service is _h323ls
n
_Proto is _udp
n
Port is the port number that has been configured from
n
the Registration UDP port
Call SRV records
Call SRV records (and A/AAAA records) are intended primarily for use by endpoints which cannot
participate in a location transaction, exchanging LRQ and LCF. The configuration of a Call SRV record
should be as follows:
_Service is _h323cs
n
_Proto is _tcp
n
Port is the port number that has been configured from
n
the Call signaling TCP port.
Configuring SIP SRV records
RFC 3263 [16] describes the DNS procedures used to resolve a SIP URI into the IP address, port,
and transport protocol of the next hop to contact.
If you want the VCS to be contactable using SIP URI dialing, you should configure an SRV record for
each SIP transport protocol enabled on the VCS (that is, UDP, TCP or TLS) as follows:
Valid combinations of _Service and _Proto are:
n
_sips._tcp
l
_sip._tcp
l
_sip._udp
l
Port is the IP port number that has been configured from
n
the port for that particular transport protocol.
Example DNS record configuration
A company with the domain name example.com wants to enable incoming H.323 and SIP calls
using URI addresses in the format user@example.com. The VCS hosting the domain has the
FQDN vcs.example.com.
Their DNS records would typically be as follows:
SRV record for _ h323ls. _ udp.example.com returns vcs.example.com
n
SRV record for _ h323cs. _ tcp.example.com returns vcs.example.com
n
NAPTR record for example.com returns
n
_sip._tcp.example.com and
l
_sip._udp.example.com and
l
_sips._tcp.example.com
l
SRV record for _sip._udp.example.com returns vcs.example.com
n
SRV record for _sip._tcp.example.com returns vcs.example.com
n
SRV record for _sips._tcp.example.com returns vcs.example.com
n
A record for vcs.example.com returns the IPv4 address of the VCS
n
AAAA record for vcs.example.com returns the IPv6 address of the VCS
n
Cisco VCS Administrator Guide (X6.1)
Dial plan and call processing
VCS configuration > Protocols > H.323
VCS configuration > Protocols > H.323
VCS configuration > Protocols > SIP
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as
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