112
D14049.05
February 2009
Grey Headline
(continued)
TANDBERG
VIDEO COMMUNICATIONS SERVER
ADMINISTRATOR GUIDE
Introduction
Getting started
Overview and
status
System
configuration
VCS
configuration
Zones and
neighbors
Call
processing
Bandwidth
control
Firewall
traversal
Appendices
Applications
Maintenance
ENUM dialing
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 whilst 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.
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 section
Configuring 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 section
Configuring ENUM dialing
for incoming calls
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.
Overview
When a VCS is attempting to locate a destination endpoint using
ENUM, the general process is as follows:
The user dials the E.164 number from their endpoint.
1.
The VCS converts the E.164 number into an ENUM domain as
2.
follows:
the digits are reversed and separated by a dot
a.
the name of the domain that is hosting the NAPTR records
b.
for that E.164 number is added as a suffix.
DNS is then queried for the resulting ENUM domain.
3.
If a NAPTR record exists for that ENUM domain, this will
4.
advise how the number should be converted into one (or
possibly more) H.323/SIP URIs.
The VCS begins the search again, this time for the converted
5.
URI as per the
URI dialing process
. Note that this is
considered to be a completely new search, and so pre-search
transforms and Call Policy will therefore apply.
Process
Enabling ENUM dialing
