Uri Dialing Via Dns For Incoming Calls - Cisco TelePresence Video Communication Server Administrator's Manual

a Pattern string of .*@.* and a Pattern type of Regex will query DNS for all aliases in the form of
n
typical URI addresses
a Pattern string of (?!.*@example.com$).* and a Pattern type of Regex will query DNS for all
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aliases in the form of typical URI addresses except those for the domain example.com
To set up further filters, configure extra search rules that target the same DNS zone. You do not need
to create new DNS zones for each rule unless you want to filter based on the protocol (SIP or H.323)
or use different hop counts.
Note: you are not recommended to configure search rules with a Mode of Any alias for DNS zones.
This will result in DNS always being queried for all aliases, including those that may be locally
registered and those that are not in the form of URI addresses.

URI dialing via DNS for incoming calls

DNS record types
The ability of the VCS to receive incoming calls made using URI dialing via DNS relies on the
presence of DNS records for each domain the VCS is hosting.
These records can be of various types including:
A records, which provide the IPv4 address of the VCS
n
AAAA records, which provide the IPv6 address of the VCS
n
Service (SRV) records, which specify the FQDN of the VCS and the port on it to be queried for a
n
particular protocol and transport type.
NAPTR records, which specify SRV record and transport preferences for a SIP domain.
n
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
applying any pre-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 RFC 2782 [3] as:
_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
n
transport type being used
Name is the domain in the URI that the VCS is hosting (such as example.com)
n
Port is the IP port on the VCS that has been configured to listen for that particular service and
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protocol combination
Target is the FQDN of the VCS.
n
Configuring H.323 SRV records
Annex O of H.323 specification [15] defines the procedures for using DNS to locate gatekeepers and
endpoints and for resolving H.323 URL aliases. It also defines parameters for use with the H.323
URL.
Cisco VCS Administrator Guide (X6.1)
Dial plan and call processing
call routing process,
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