Cisco Cisco TelePresence Video Communication Server Expressway 관리 매뉴얼
Incoming calls
To enable endpoints registered to your VCS to receive calls from non-locally registered endpoints using URI dialing
via DNS, you must:
via DNS, you must:
■
ensure all endpoints are registered with an AOR (SIP) or H.323 ID in the form of a URI
■
configure appropriate DNS records, depending on the protocols and transport types you want to use
Firewall traversal calls
To configure your system so that you can place and receive calls using URI dialing through a firewall, see the
section.
URI Resolution Process Using DNS
When the VCS attempts to locate a destination URI address using the DNS system, the general process is as follows:
H.323
1.
The VCS sends a query to its DNS server for an SRV record for the domain in the URI. (If more than one DNS
server has been configured on the VCS, the query will be sent to all servers at the same time, and all
responses will be prioritized by the VCS with only the most relevant SRV record being used.) If available, this
SRV record returns information (such as the FQDN and listening port) about either the device itself or the
authoritative H.323 gatekeeper for that domain.
server has been configured on the VCS, the query will be sent to all servers at the same time, and all
responses will be prioritized by the VCS with only the most relevant SRV record being used.) If available, this
SRV record returns information (such as the FQDN and listening port) about either the device itself or the
authoritative H.323 gatekeeper for that domain.
—
If the domain part of the URI address was resolved successfully using an H.323 Location SRV record (that
is, for _ h323ls) then the VCS will send an A/AAAA record query for each name record returned. These will
resolve to one or more IP addresses, and the VCS then sends, in priority order, an LRQ for the full URI to
those IP addresses.
is, for _ h323ls) then the VCS will send an A/AAAA record query for each name record returned. These will
resolve to one or more IP addresses, and the VCS then sends, in priority order, an LRQ for the full URI to
those IP addresses.
—
If the domain part of the URI address was resolved using an H.323 Call Signaling SRV record (that is, for _
h323cs) then the VCS will send an A/AAAA record query for each name record returned. These will resolve
to one or more IP addresses, and the VCS then routes the call, in priority order to the IP addresses returned
in those records. (An exception to this is where the original dial string has a port specified - for example,
h323cs) then the VCS will send an A/AAAA record query for each name record returned. These will resolve
to one or more IP addresses, and the VCS then routes the call, in priority order to the IP addresses returned
in those records. (An exception to this is where the original dial string has a port specified - for example,
user@example.com:1719
- in which case the address returned is queried via an LRQ for the full URI address.)
2.
If a relevant SRV record cannot be located:
—
If the Include address record setting for the DNS zone being queried is set to On, the system will fall back
to looking for an A or AAAA record for the domain in the URI. If such a record is found, the call will be routed
to that IP address and the search will terminate. Note that if the A and AAAA records that are found at this
domain are for systems other than those that support SIP or H.323, the VCS will still forward the call to this
zone, and the call will therefore fail. For this reason, you are recommended to use the default setting of Off.
to looking for an A or AAAA record for the domain in the URI. If such a record is found, the call will be routed
to that IP address and the search will terminate. Note that if the A and AAAA records that are found at this
domain are for systems other than those that support SIP or H.323, the VCS will still forward the call to this
zone, and the call will therefore fail. For this reason, you are recommended to use the default setting of Off.
—
If the Include address record setting for the DNS zone being queried is set to Off, the VCS will not query
for A and AAAA records and instead will continue with the search, querying the remaining lower priority
zones.
for A and AAAA records and instead will continue with the search, querying the remaining lower priority
zones.
SIP
. An example of how the VCS implements this
process is as follows:
1.
The VCS sends a NAPTR query for the domain in the URI. If available, the result set of this query describes a
prioritized list of SRV records and transport protocols that should be used to contact that domain.
If no NAPTR records are present in DNS for this domain name then the VCS will use a default list of
prioritized list of SRV records and transport protocols that should be used to contact that domain.
If no NAPTR records are present in DNS for this domain name then the VCS will use a default list of
_sips._
tcp.<domain>
,
_sip._tcp.<domain>
and
_sip._udp.<domain>
for that domain as if they had been returned from
the NAPTR query.
—
The VCS sends SRV queries for each result returned from the NAPTR record lookup. A prioritized list of
A/AAAA records returned is built.
A/AAAA records returned is built.
—
The VCS sends an A/AAAA record query for each name record returned by the SRV record lookup.
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Cisco TelePresence Video Communication Server Administrator Guide
Dial Plan and Call Processing