Enum Dialing For Outgoing Calls; Prerequisites; Process - Cisco TelePresence Administrator's Manual

Grey Headline (continued)
ENUM dialing

Prerequisites

For a local endpoint to be able to dial another endpoint using
ENUM via your VCS, the following conditions must be met:
•
There must be a NAPTR record available in DNS that maps
the called endpoint's E.164 number to its URI. It is the
responsibility of the administrator of the enterprise to which
the called endpoint belongs to provide this record, and they
will only make it available if they wish the endpoints in their
enterprise to be contactable via ENUM dialing.
•
You must configure an ENUM zone on your local VCS. This
ENUM zone must have a DNS Suffix that is the same as the
domain where the NAPTR record for the called endpoint is
held.
•
You must configure your local VCS with the address of at least
one DNS server that it can query for the NAPTR record (and if
necessary any resulting URI).
After the ENUM process has returned one or more URIs, a new
search will begin for each of these URIs in accordance with
the URI dialing process. If the URIs belong to locally registered
endpoints, no further configuration is required. However, if one
or more of the URIs are not locally registered, you may also need
to configure a DNS zone if they are to be located using a DNS
lookup.
Overview and System
Introduction
status configuration
D14049.08
November 2010

ENUM dialing for outgoing calls

Process

The process below is followed when an ENUM (E.164) number is
dialed from an endpoint registered with your VCS:
1. The user dials the E.164 number from their endpoint.
2. The VCS initiates a search for the E.164 number as dialed. It
follows the usual search
3. After applying any pre-search transforms, the VCS checks its
to see if any of them are configured with a Mode
search rules
of either:
•
Any Alias, or
•
Alias Pattern Match with a pattern that matches the E.164
number
4. The target zones associated with any matching search rules
are queried in rule priority order.
•
If a target zone is a neighbor zone, the neighbor is queried
for the E.164 number. If the neighbor supports ENUM
dialing, it may route the call itself.
•
If a target zone is an ENUM zone, the VCS attempts to
locate the endpoint through ENUM. As and when each
ENUM zone configured on the VCS is queried, the E.164
number is transformed into an ENUM domain as follows:
a. The digits are reversed and separated by a dot
b. The DNS Suffix configured for that ENUM zone is
appended.
5. DNS is then queried for the resulting ENUM domain.
6. If the DNS server finds at that ENUM domain a NAPTR record
that matches the transformed E.164 number (i.e. after it
has been reversed and separated by a dot), it returns the
associated URI to the VCS.
7. The VCS then initiates a new search for that URI (maintaining
the existing hop count). The VCS starts at the beginning of
the search process (i.e. applying any pre-search transforms,
then searching local and external zones in priority order).
From this point, as it is now searching for a SIP/H.323 URI,
the process for URI dialing
Cisco VCS Zones and Clustering and
configuration neighbors peers
process.
is followed.
Call Bandwidth
processing control
111
CISCO TELEPRESENCE VIDEO COMMUNICATION SERVER
Example
In this example, we want to call Fred at Example Corp. Fred's
endpoint is actually registered with the URI fred@example.com,
but to make it easier to contact him his system administrator
has configured a DNS NAPTR record mapping this alias to his
E.164 number: +44123456789.
We know that the NAPTR record for example.com uses the DNS
domain of e164.arpa.
1. We create an ENUM zone on our local VCS with a DNS suffix
of e164.arpa.
2. We configure a search rule with a pattern match mode of Any
Alias, and set the Target zone to the ENUM zone. This means
that ENUM will always be queried regardless of the format of
the alias being searched for.
3. We dial 44123456789 from our endpoint.
4. The VCS initiates a search for a registration of 44 118 123
456 and the search rule of Any Alias means the ENUM zone
is queried. (Note that other higher priority searches could
potentially match the number first.)
5. Because the zone being queried is an ENUM zone, the VCS is
automatically triggered to transform the number into an ENUM
domain as follows:
a. the digits are reversed and separated by a dot:
9.8.7.6.5.4.3.2.1.4.4
b. the DNS Suffix configured for this ENUM zone, e164.arpa,
is appended.
This results in a transformed domain of
9.8.7.6.5.4.3.2.1.4.4.e164.arpa.
6. DNS is then queried for that ENUM domain.
7. The DNS server finds the domain and returns the information
in the associated NAPTR record. This tells the VCS that the
E.164 number we have dialed is mapped to the SIP URI of
fred@example.com.
8. The VCS then starts another search, this time for
fred@example.com. From this point the process for
URI dialing is followed, and results in the call being forwarded
to Fred's endpoint.
Firewall
Applications Maintenance
traversal
ADMINISTRATOR GUIDE
Appendices