The Cisco Unified Border Element (CUBE) facilitates the mapping of E.164 called numbers to Session Initiation Protocol (SIP) Uniform Resource Identifiers (URIs). The SIP ENUM technology allows the traditional telephony part of the network (using E.164 numbering to address destinations) to interwork with the SIP telephony part of the network, generally using SIP URIs. From the Public Switched Telephone Network (PSTN) network, if an end user dials an E.164 called party, the number can be translated by an ENUM gateway into the corresponding SIP URI. This SIP URI is then used to look up the Domain Name System (DNS) Naming Authority Pointer (NAPTR) Resource Records (RR). The NAPTR RR (as defined in RFC 2915) describes how the call should be forwarded or terminated and records information, such as email addresses, a fax number, a personal website, a VoIP number, mobile phone numbers, voicemail systems, IP-telephony addresses, and web pages. Alternately, when the calling party is a VoIP endpoint and dials an E.164 number, then the originator's SIP user agent (UA) converts it into a SIP URI to be used to look up at the ENUM gateway DNS and fetch the NAPTR RR.

The ENUM enhancement per Kaplan draft RFC provides source-based routing, that is, SIP-to-SIP calls can be routed based on the source SIP requests. To provide source-based routing and to interact with the Policy Server, an EDNS0 OPT pseudo resource record with source URI, incoming SIP call ID, outbound SIP call ID, and Call Session Identification are added to the ENUM DNS query, according to draft-kaplan-enum-sip-routing-04. The incoming SIP call ID, outbound SIP call ID, and Call Session Identification are automatically included with an EDNS0 OPT pseudo resource record in the ENUM DNS query only if “source-uri no-cache” is enabled and XCC service is registered. This feature also provides the flexibility to disable route caching.

SIP-to-SIP calls can be routed based on the source SIP requests, using the ENUM enhancement feature. To provide source-based routing and to interact with Policy Server, an EDNS0 OPT pseudo resource record with source URI, incoming SIP call ID, outbound SIP call ID, and Call session Identification are added to the ENUM DNS query. The DNS server filters its response based on the source URI and call ID information and returns the appropriate NAPTR entries. To enable this feature, you must use the source-uri option in the voice enum-match-table <table-number> command. In addition, you can use the no-cache option to disable caching.

Refer to RFC 3761 and draft-kaplan-enum-sip-routing-04 for more information about routing SIP requests with ENUM.

• Supported only for SIP-to-SIP calls.

• The full command of voice enum-match-table , including the options, needs to be specified whenever being referenced by its subcommand. If not, the defaults, no source-uri and no no-cached (or caching) will take effect.

• As the maximum number of characters of the host shown in the show host command is 25, the source URI may not be displayed completely.

• The source URI is displayed in a separate line below, starting with “source-uri=”. Refer to the show command outputs in this chapter.

• If no-cache is configured in the voice enum-match-table, no cache table look-up would be made and hence an ENUM query would be made regardless of what is in the cache table.

• Both the target and source, where the source can be null/undefined or defined, need to be matched when looking up the cache table.

• The OPT RR will be added to the query for a SIP-to-SIP call only if the source-uri is configured for the outbound enum-match-table.

• The route will not be cached if the server does not support the OPT RR (it is recommended to remove the source-uri for this scenario if caching is preferred).

• The source URL can be prefixed with a host/target in the host name field in a double quote in the show host host command to display routes for the host specific with this source.

• A wild card, “*”, can be used to denote “all” hosts in the show host command. It can be by itself or any host matched with its prefix. The prefix can be a host name, partial or complete, or a domain name with partial or complete source URL.

Refer to the document titled Cisco Unified Border Element ENUM Support Configuration Example for a detailed message format.

Use the following commands for debugging information:

• debug voip enum detail

• debug ip domain

• debug ccsip message

• debug voip ccapi inout

• clear voip fpi session correlator-id —This command is used to clear the hung FPI sessions. After the hung session is identified using the existing show commands and its correlator is obtained, the clear voip fpi session correlator-id command can be used to clear the session.

Use the following show command that is helpful for debugging:

• show host [all | * | host-name | partial -host -name*]

Below is an extract of a sample ENUM DNS query containing the EDNS0 OPT psedo resource record fields as per Kaplan Draft that is helpful in debugging. In the below query the values corresponding to ibcall-id, obcall-id, and sbc-id represent the incoming SIP call ID, outbound SIP call ID and Call Session Identification respectively.

7.7.7.7.1.1.1.e164.arpa sip:1116666@10.1.50.16enum_dns_query: name = 7.7.7.7.1.1.1.e164.arpa
sip:1116666@10.1.50.16 type = 35, ns_server = 0x0 no_cache 1 more_data ;ibcall-id=1-23735@10.1.50.16;
obcall-id=7190DF-39DD11E4-8008EDAD-F1AA3CF1@10.1.110.222;sbc-id=1