The Oracle Communications Session Border Controller can intelligently distribute ENUM queries among all configured ENUM servers. By setting the enum config’s query method parameter to round robin, the Oracle Communications Session Border Controller will cycle ENUM queries, sequentially, among all configured ENUM servers. For example, query 1 will be directed to server 1, query 2 will be directed to server 2, query 3 will be directed to server 3, and so on.

The default query method, hunt, directs all ENUM queries toward the first configured ENUM server. If the first server is unreachable, the Oracle Communications Session Border Controller directs all ENUM queries toward the next configured ENUM server, and so on.

When an enum-config’s configured servers are unreachable via the network, i.e., no response is received on a query, the Oracle Communications Session Border Controller can failover to a defined ENUM config that contains different enum servers to query. This failover behavior works when all servers in an enum config are unreachable, rather than when the Oracle Communications Session Border Controller receives not-found type responses.

The Oracle Communications Session Border Controller queries each ENUM server once before trying the next configured server, and then ultimately trying the servers listed in the failover-to enum config. If the failover-to servers also are unreachable, the Oracle Communications Session Border Controller fails the call; the failover-to behavior does not recurse among enum-configs, it only checks the first, linked enum-config.

After 5 consecutive failed attempts, an ENUM server is considered Out of Service (OOS). All subsequent queries which would be directed to the OOS servers are immediately directed to the first non-OOS server. ENUM servers return to in-service after 600 seconds. If all configured ENUM servers are OOS, the Oracle Communications Session Border Controller fails the call.

After the first failed attempt to reach an ENUM server, it is placed in a Time Out state, which it stays in for 30 seconds. Within this 30 seconds it will not be contacted when an ENUM query is made. After the 30 seconds pass, the ENUM server goes back to an in-service state.

The Oracle Communications Session Border Controller can probe an ENUM server’s health by sending it a standard ENUM NAPTR query and receiving a valid answer. The query is for the phone number defined in the health query number parameter, which should be one that the ENUM servers can positively resolve. As long as the query succeeds, that ENUM server maintains its in-service state and is available for ENUM queries. Any lack of response, whether network based (time-outs), or application based (DNS error or not found response) is considered a query failure and the server is set to OOS and unavailable for ENUM queries.

The Oracle Communications Session Border Controller continuously checks the health of all configured ENUM servers to determine their current state and monitor for failed servers’ return to service. All servers are checked for availability at the health query interval parameter, as defined in seconds.

You can configure an IP address and port for each enum server listed in the enum-servers parameter. IP address and port are specified in XXX.XXX.XXX.XXX:YYYY format with a port value range of 1024-65535. If the port number is not specified, 53 is assumed.

The Oracle Communications Session Border Controller supports IPv6 ENUM configurations in IPv6 realms. The enumservers parameter in the enum-config configuration parameter can be configured IPv6 addresses in addition to IPv4 addresses. When IPv6 Addresses are used, the realm configured in the realm-id parameter must be an IPv6 realm.

When only IPv4 ENUM servers are configured, all legacy SNMP object and trap functionality remains the same. When IPv6 addressing is used for ENUM servers, these existing SNMP objects are obsoleted.

apSysMgmtENUMStatusChangeTrap           NOTIFICATION-TYPE
apENUMServerStatusTable OBJECT-TYPE

New SNMP trap notifies operators of ENUM Server Status change.

apAppsENUMServerStatusChangeTrap           NOTIFICATION-TYPE
        OBJECTS         { apAppsENUMConfigName,
                          apAppsENUMServerInetAddressType,
                          apAppsENUMServerInetAddress,
                          apAppsENUMServerStatus }
        STATUS          current
        DESCRIPTION
        " The trap will be generated if the reachability status of an ENUM
        server changes." 
        ::= { apAppsNotifications 1 }

The following objects support this trap.

apAppsENUMServerStatusTable OBJECT-TYPE
        SYNTAX          SEQUENCE OF ApAppsENUMServerStatusEntry
        MAX-ACCESS      not-accessible
        STATUS          current
        DESCRIPTION
            "A read-only table to hold the status of configured ENUM servers, indexed by the name of the enum server, server address type and server IP.
            Please note this table is the replacement of apENUMServerStatusTable defined in ap-smgmt.mib, where the table was obsoleted."
        ::= { apAppsMIBTabularObjects 1 }
apAppsENUMServerStatusEntry OBJECT-TYPE
        SYNTAX          ApAppsENUMServerStatusEntry
        MAX-ACCESS      not-accessible
        STATUS          current
        DESCRIPTION
            "An entry designed to hold the status of a single ENUM server"
        INDEX { apAppsENUMConfigName,
                apAppsENUMServerInetAddressType,
                apAppsENUMServerInetAddress }
        ::= { apAppsENUMServerStatusTable 1 }
ApAppsENUMServerStatusEntry ::= SEQUENCE {
        apAppsENUMConfigName                DisplayString,
        apAppsENUMServerInetAddressType     InetAddressType,
        apAppsENUMServerInetAddress         InetAddress,
        apAppsENUMServerStatus              INTEGER
        }
apAppsENUMConfigName    OBJECT-TYPE
        SYNTAX          DisplayString
        MAX-ACCESS      read-only
        STATUS          current
        DESCRIPTION
            "The name of the enum-config element that contains this
            ENUM server."
        ::= { apAppsENUMServerStatusEntry 1 }
apAppsENUMServerInetAddressType   OBJECT-TYPE
        SYNTAX          InetAddressType
        MAX-ACCESS      read-only
        STATUS          current
        DESCRIPTION
            "The IP address of this ENUM server."
        ::= { apAppsENUMServerStatusEntry 2 }
apAppsENUMServerInetAddress   OBJECT-TYPE
        SYNTAX          InetAddress
        MAX-ACCESS      read-only
        STATUS          current
        DESCRIPTION
            "The IP address of this ENUM server."
        ::= { apAppsENUMServerStatusEntry 3 }
apAppsENUMServerStatus  OBJECT-TYPE
        SYNTAX          INTEGER {
                                inservice(0),
                                lowerpriority(1),
                                oosunreachable(2)
                                }
        MAX-ACCESS      read-only
        STATUS          current
        DESCRIPTION
            "The status of this ENUM server."
        ::= { apAppsENUMServerStatusEntry 4 }
apAppsENUMServerStatusGroup  OBJECT-GROUP
        OBJECTS {
                apAppsENUMConfigName,
                apAppsENUMServerInetAddressType,
                apAppsENUMServerInetAddress,
                apAppsENUMServerStatus
                }
        STATUS          current
        DESCRIPTION
                "Report the status of configured ENUM servers."
        ::= { apAppsObjectGroups 1  }
apAppsEnumServerNotificationsGroup NOTIFICATION-GROUP
      NOTIFICATIONS {
                        apAppsENUMServerStatusChangeTrap
                    }
                STATUS          current
                DESCRIPTION
                "A collection of traps to extend reporting capabilities."
      ::= {  apAppsNotificationGroups 1 }

As DNS responses often lead to further DNS queries, a DNS server can send additional multiple records in a response to attempt to anticipate the need for additional queries. The Oracle Communications Session Border Controller can locally cache additional NAPRT, SRV, and A records returned from an ENUM query to eliminate the need for unnecessary external DNS requests by enabling the cache addl records parameter. These cached records can then be accessed by internal ENUM and DNS agents.

The unprompted NAPTR, SRV, or A record returned to the Oracle Communications Session Border Controller must include complete information to resolve a call to be added to the local DNS/ENUM cache, otherwise the Oracle Communications Session Border Controller will preform an external query to fine the address it is looking to resolve.

Cached entries are per ENUM config. That means if one ENUM config has a number of cached entries, and an ENUM request is directed through a different ENUM config, the second configuration is not privy to what the first configuration has cached.

The Oracle Communications Session Border Controller uses the shorter lifetime of the DNS response’s TTL or the server dns attribute’s transaction-timeout to determine when to purge a DNS record from the local cache.

ENUM queries can be configured to include the source URI which caused the ENUM request by enabling the include source info parameter. The Oracle Communications Session Border Controller can add the P-Asserted-ID URI (only if not in an INVITE) or the From URI into an OPT-RR Additional Record to be sent to the ENUM server. It can be useful to specify the originating SIP or TEL URI from a SIP request which triggered the ENUM query, so the ENUM server can provide a customized response based on the caller.

This feature implements the functionality described in the Internet Draft, DNS Extension for ENUM Source-URI, draft-kaplan-enum-source-uri-00.

When a P-Asserted-ID is blocked or removed before the ENUM query is made, the Oracle Communications Session Border Controller only sends the URI in the From header.

Note that to support this feature, according to the Internet draft, ENUM clients must support 1220 bytes in UDP responses. Therefore, if this feature is enabled, and the max response size parameter is not set i.e., with a 512 byte default, the Oracle Communications Session Border Controller will set the size to 1200 on the OPT-RR records sent.

There are four modes of ENUM operation that are selected on a global basis:

• stateless proxy
• transaction stateful proxy
• session stateful proxy
• B2BUA with or without media

1. In Superuser mode, type configure terminal and press Enter.

   ORACLE# configure terminal

2. Type session-router and press Enter to access the signaling-level configuration elements.

   ORACLE(configure)# session-router
   ORACLE(session-router)#

3. Type enum-config and press Enter. The system prompt changes to let you know that you can begin configuring individual parameters.

   ORACLE(session-router)# enum-config
   ORACLE(enum-config)#

4. name—Enter a string that uniquely identifies this ENUM configuration. You use this name in other areas of the Oracle Communications Session Border Controller configuration to refer to this ENUM configuration. For example, in the local policy attributes.
5. top-level-domain—Enter the domain extension to be used when querying the ENUM servers for this configuration. For example, e164.arpa. The query name is a concatenation of the number and the domain.

   For example the number is +17813334444 and the domain is e164.arpa, the query name would be 4.4.4.4.3.3.3.1.8.7.1.e164.arpa.com.

6. realm-id—Enter the realm where the ENUM servers can be reached. The realm ID is used to determine on which network interface to issue the ENUM query.
7. enum-servers—Enter the list of ENUM servers (an ENUM server and corresponding redundant servers) to be queried. Separate each server address with a space and enclose list within parentheses.

   The first server on this list is the first one to be queried. If the query times out (including retransmissions) without getting a response, the next server on the list is queried and so on.

8. service-type—Enter the ENUM service types you want supported in this ENUM configuration. Possible entries are E2U+sip and sip+E2U (the default), and the types outlines in RFCs 2916 and 3721.

   This parameter defaults to the following service types: E2U+sip and sip+E2U.

   You can enter multiple services types in the same entry, as in this example:

   ORACLE(enum-config)# service-type E2U+sip,sip+E2U,E2U+voicemsg

9. query-method—Set the strategy the Oracle Communications Session Border Controller uses to contact ENUM servers. Valid values are:

   • hunt—Directs all ENUM queries toward the first configured ENUM server. If the first server is unreachable, the Oracle Communications Session Border Controller directs all ENUM queries toward the next configured ENUM server, and so on.

   • round-robin—Cycles all ENUM queries, sequentially, among all configured in-service ENUM servers. Query 1 will be directed to server 1, query 2 will be directed to server 2, query 3 will be directed to server 3.

10. timeout—Enter the total time in seconds that should elapse before a query sent to a server (and its retransmissions) will timeout. If the first query times out, the next server is queried and the same timeout is applied. This process continues until all the servers in the list have timed out or until one of the servers responds.

    The retransmission of ENUM queries is controlled by three timers. These timers are derived from this timeout value and from underlying logic that the minimum allowed retransmission interval should be 250 milliseconds; and that the Oracle Communications Session Border Controller should retransmit 3 times before timing out to give the server a chance to respond. The valid values are:

    • Init-timer—Is the initial retransmission interval. If a response to a query is not received within this interval, the query is retransmitted. To safeguard from performance degradation, the minimum value allowed for this timer is 250 milliseconds.

    • Max-timer—Is the maximum retransmission interval. The interval is doubled after every retransmission. If the resulting retransmission interval is greater than the value of max-timer, it is set to the max-timer value.

    • Expire-timer—Is the query expiration timer. If a response is not received for a query and its retransmissions within this interval, the server will be considered non-responsive and the next server in the list will be tried.

      The following examples show different timeout values and the corresponding timers derived from them.

      timeout >= 3 seconds

      Init-timer = Timeout/11
      Max-Timer = 4 * Init-timer
      Expire-Timer = Timeout

      timeout = 1 second

      Init-Timer = 250 ms
      Max-Timer = 250 ms
      Expire-Timer = 1 sec

      timeout = 2 seconds

      Init-Timer = 250 ms
      Max-Timer = 650 ms
      Expire-Timer = 2sec

11. cache-inactivity-timer—Enter the time interval in seconds after which you want cache entries created by ENUM requests deleted, if inactive for this interval. If the cache entry gets a hit, the timer restarts and the algorithm is continued until the cache entry reaches its actual time to live.

    Setting this value to zero disables caching. For optimal performance, set this to one hour. Rarely used cache entries are purged and frequently used entries are retained. The default value is 3600. The valid range is:

    • Minimum—0

    • Maximum—999999999

12. lookup-length—Specify the length of the ENUM query, starting from the most significant digit. The default is 0. The valid range is:

    • Minimum—1

    • Maximum—255

13. max-response-size—Enter the maximum size in bytes for UDP datagrams in DNS NAPTR responses. This parameter takes values from 512 (default) to 65535. Although the maximum value you can set is 65535, Oracle recommends configuring values that do not exceed 4096 bytes.
14. health-query-number—Set this parameter to a standard ENUM NAPTR query that will consistently return a positive response from the ENUM server.
15. health-query-interval—Set this parameter to the number of seconds to perpetually probe ENUM servers for health.
16. failover-to—Set this parameter to the name of another ENUM-config which to failover to under appropriate conditions.
17. cache-addl-records—Set this parameter to enabled for the Oracle Communications Session Border Controller to add additional records received in an ENUM query to the local DNS cache.
18. include-source-info—Set this parameter to enabled for the Oracle Communications Session Border Controller to send source URI information to the ENUM server with any ENUM queries.
19. Save your work.

1. In Superuser mode, type configure terminal and press Enter.

   ORACLE# configure terminal

2. Type session-router and press Enter.

   ORACLE(configure)# session-router

3. Type local-policy and press Enter. The system prompt changes to let you know that you can begin configuring individual parameters.

   ORACLE(session-router)# local-policy
   ORACLE(local-policy)#

4. next-hop—Enter the name of the ENUM configuration with the prefix enum:. For example, enum:test.
5. action—Set to redirect if you want to send a REDIRECT message back to the calling party with the information returned by ENUM in the Contact. The calling party then needs to send a REDIRECT using that information. The default value is none. Valid values are:

   • none—No specific actions requested.

   • replace-uri—To replace the next Request-URI with the next hop.

   • redirect—To send a redirect response with this next hop as contact.

6. Save and activate your configuration.