Incoming Call Process; Srv Record Format; Location Srv Records - Cisco TelePresence Administrator's Manual

A records, which provide the IPv4 address of the VCS
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AAAA records, which provide the IPv6 address of the VCS
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Service (SRV) records, which specify the FQDN of the VCS and the port on it to be queried for a particular
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protocol and transport type.
NAPTR records, which specify SRV record and transport preferences for a SIP domain.
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You must provide an SRV or NAPTR record for each combination of domain hosted and protocol and
transport type enabled on the VCS.

Incoming call process

When an incoming call has been placed using URI dialing via DNS, the VCS will have been located by the
calling system using one of the DNS record lookups described above. The VCS will receive the request
containing the dialed URI in the form user@example.com. This will appear as coming from the Default Zone.
The VCS will then search for the URI in accordance with its normal
search transforms, Call Policy and FindMe policy, then searching its Local Zone and other configured zones,
in order of search rule priority.

SRV record format

The format of SRV records is defined by
_Service._Proto.Name TTL Class SRV Priority Weight Port Target
For the VCS, these are as follows:
_Service and _Proto will be different for H.323 and SIP, and will depend on the protocol and transport
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type being used
Name is the domain in the URI that the VCS is hosting (such as example.com)
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Port is the IP port on the VCS that has been configured to listen for that particular service and protocol
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combination
Target is the FQDN of the VCS.
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Configuring H.323 SRV records
Annex O of ITU Specification: H.323
endpoints and for resolving H.323 URL aliases. It also defines parameters for use with the H.323 URL.
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
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_Proto is _udp
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Cisco VCS Administrator Guide (X7.1)
RFC 2782 as:
defines the procedures for using DNS to locate gatekeepers and
Dial plan and call processing
call routing process, applying any pre-
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