Grey Headline (continued)
ENUM Dialing
TANDBERG VIDEO COMMUNICATIONS SERVER ADMINISTRATOR GUIDE
ENUM Dialing for Outgoing Calls
Prerequisites
In order for a local endpoint to be able to dial another endpoint using ENUM via your VCS, the following three conditions must be met:
1.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.
2.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.
3.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).
Once 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 via a DNS lookup.
Process
Below is the process that 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 alias search process, first applying any local zone transforms, then searching local and Alternate registrations and FindMe names for the E.164 number.
3.If the E.164 number is not found locally, the VCS will check all its zones to see if any of them are configured with either:
•an AlwaysMatch, or
•a PatternMatch with pattern that matches the E.164 number.
These zones will then be queried in priority order.
4.If one or more of the zones that contain a match is a neighbor zone, the neighbor will be queried for the E.164 number. If the neighbor supports ENUM dialing, it may route the call itself.
5.If one or more of the zones that contain a match is an
ENUM zone, this will trigger the VCS to attempt 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.
6.DNS is then queried for the resulting ENUM domain.
7.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.
8.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 local zone transforms, then searching locally, then searching zones). From this point, as it is now searching for a SIP/H.323 URI, the process for
URI Dialing is followed.
Example
In this example, we wish 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 this zone with a pattern match mode of AlwaysMatch, so 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. Because the ENUM zone we have configured has a match mode of AlwaysMatch, it is queried at the same time as any other zones with a matching priority.
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.
Introduction | Getting Started |
| Overview and |
| System |
| VCS |
| Zones and | Call | Bandwidth |
| Firewall |
| Maintenance |
| Appendices |
| Status |
| Configuration |
| Configuration |
| Neighbors | Processing | Control |
| Traversal |
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D14049.03 |
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