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ENUM dialing
Overview
ENUM dialing allows an endpoint to be contacted by a caller
dialing an E.164 number - a telephone number - even if that
endpoint has registered using a different format of alias.
Using ENUM dialing, when an E.164 number is dialed it is
converted into a URI using information stored in DNS. The VCS
then attempts to find the endpoint based on the URI that has
been returned.
The ENUM dialing facility allows you to retain the flexibility of
URI dialing while having the simplicity of being called using
just a number - particularly important if any of your callers are
restricted to dialing using a numeric keypad.
The VCS supports outward ENUM dialing by allowing you
to configure ENUM zones on the VCS. When an ENUM
zone is queried, this triggers the VCS to transform the
E.164 number that was dialed into an ENUM domain which is
then queried for using DNS.
Note however that ENUM dialing relies on the presence of
relevant DNS NAPTR records for the ENUM domain being
queried. These are the responsibility of the administrator of that
domain.
Overview and
System
Introduction
status
configuration
D14049.07
March 2010
ENUM dialing process
When a VCS is attempting to locate a destination endpoint using
ENUM, the general process is as follows:
1. The user dials the E.164 number from their endpoint.
2. The VCS converts the E.164 number into an ENUM domain as
follows:
a. the digits are reversed and separated by a dot
b. the name of the domain that is hosting the NAPTR records
for that E.164 number is added as a suffix.
3. DNS is then queried for the resulting ENUM domain.
4. If a NAPTR record exists for that ENUM domain, this will
advise how the number should be converted into one (or
possibly more) H.323/SIP URIs.
5. The VCS begins the search again, this time for the converted
URI as per the
URI dialing
considered to be a completely new search, and so pre-search
transforms and Call Policy will therefore apply.
VCS
Zones and
Clustering and
configuration
neighbors
peers
process. Note that this is
Call
Bandwidth
processing
control
110
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VIDEO COMMUNICATION SERVER
Enabling ENUM dialing
ENUM dialing is enabled separately for incoming and outgoing
calls.
Outgoing Calls
To allow locally registered endpoints to dial out to other
endpoints using ENUM, you must
•
configure at least one ENUM zone, and
•
configure at least one DNS Server.
This is described in the
ENUM dialing for outgoing calls
Incoming Calls
To enable endpoints in your enterprise to receive incoming calls
from other endpoints via ENUM dialing, you must configure a
DNS NAPTR record mapping your endpoints' E.164 numbers to
their SIP/H.323 URIs. See the
ENUM dialing for incoming calls
section for instructions on how to do this.
If an ENUM zone and a DNS server have not been
configured on the local VCS, calls made using ENUM
dialing could still be placed if the local VCS is neighbored
with another VCS that has been appropriately configured for
ENUM dialing. Any ENUM dialed calls will go via the neighbor.
This configuration is useful if you want all ENUM dialing from
your enterprise to be configured on one particular system.
Firewall
Applications
Maintenance
traversal
ADMINISTRATOR GUIDE
section.
Appendices
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