Cisco Cisco TelePresence Video Communication Server Expressway 관리 매뉴얼
Dial plan and call processing
n
ensure all endpoints are registered with an AOR (SIP) or H.323 ID in the form of a URI
n
configure appropriate DNS records, depending on the protocols and transport types you want to use
This is described in the
section.
Firewall traversal calls
To configure your system so that you can place and receive calls using URI dialing through a firewall,
see the
see the
section.
URI resolution process using DNS
When a Cisco VCS is attempting to locate a destination URI address using the DNS system, the
general process is as follows:
general process is as follows:
H.323
1. The Cisco 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 Cisco VCS, the query will be sent to all
servers at the same time, and all responses will be prioritized by the Cisco 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.
servers at the same time, and all responses will be prioritized by the Cisco 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.
l
If the domain part of the URI address was resolved successfully using an H.323 Location SRV
record (that is, for _ h323ls) then the Cisco VCS will send an A/AAAA record query for each
name record returned. These will resolve to one or more IP addresses, and the Cisco VCS then
sends, in priority order, an LRQ for the full URI to those IP addresses.
record (that is, for _ h323ls) then the Cisco VCS will send an A/AAAA record query for each
name record returned. These will resolve to one or more IP addresses, and the Cisco VCS then
sends, in priority order, an LRQ for the full URI to those IP addresses.
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If the domain part of the URI address was resolved using an H.323 Call Signaling SRV record
(that is, for _ h323cs) then the Cisco VCS will send an A/AAAA record query for each name
record returned. These will resolve to one or more IP addresses, and the Cisco 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.)
(that is, for _ h323cs) then the Cisco VCS will send an A/AAAA record query for each name
record returned. These will resolve to one or more IP addresses, and the Cisco 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:
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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 Cisco 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.
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 Cisco 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.
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If the Include address record setting for the DNS zone being queried is set to Off, the Cisco
VCS will not query for A and AAAA records and instead will continue with the search, querying
the remaining lower priority zones.
VCS will not query for A and AAAA records and instead will continue with the search, querying
the remaining lower priority zones.
SIP
The Cisco VCS supports the SIP resolution process as outlined in RFC 3263 [
]. An example of how
the Cisco VCS implements this process is as follows:
1. The Cisco 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 Cisco 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.
contact that domain.
If no NAPTR records are present in DNS for this domain name then the Cisco 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.
Cisco VCS Administrator Guide (X6)
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