1. ACLI Configuration Guide
  2. Session Routing and Load Balancing
  3. About Local Policy

About Local Policy

This section explains the role of local policy. Local policy lets you indicate where session requests, such as SIP INVITES, should be routed and/or forwarded. You use a local policy to set a preference for selecting one route over another. The local policy contains the following information that affects the routing of the SIP and H.323 signaling messages:

  • information in the From header

    Information in the message’s From header is matched against the entries in the local policy’s from address parameter to determine if the local policy applies.

  • list of configured realms

    This list identifies from what realm traffic is coming and is used for routing by ingress realm. The source realms identified in the list must correspond to the valid realm IDs you have already configured

  • local policy attributes

    The attributes serve as an expression of preference, a means of selecting one route over another. They contain information such as the next signaling address to use (next hop) or whether you want to select the next hop by codec, the realm of the next hop, and the application protocol to use when sending a message to the next hop. You can also use the attributes to filter specific types of traffic.

Routing Calls by Matching Digits

Local policy routing of a call can be based on matching a sequence of digits against what is defined in the local policy. This sequence refers to the first digits in the (phone) number, matching left to right.

The following examples show how the Oracle® Enterprise Session Border Controller matches an area code or number code against configured local policies.

  • If the number or area code being matched is 1234567 (where 123 is an area code), and the from address value in one local policy is 123, and the from address value in another local policy is 12, the Oracle® Enterprise Session Border Controller forwards the call to the server that is defined as the next hop in the local policy with 123 as the from address value.
  • If the number or area code being matched is 21234, and the from address value in one local policy is 123, and the from address value in another local policy is 12, the Oracle® Enterprise Session Border Controller will not find a match to either local policy because the first character of the number or area code must match the first character in a from address or to address field.

The following examples show how the Oracle® Enterprise Session Border Controller matches an area or number code against different local policies: the first one has a From address value of 12 and the second has a From address value of 123. The Oracle® Enterprise Session Border Controller chooses the route of the local policy that is configured with the most digits matching the area or number code in its From address and To address fields.

  • When the two different local policies route to two different servers, and the area or number code being matched is 123, the Oracle® Enterprise Session Border Controller selects the second local policy based on the From address value of 123.
  • When the two different local policies route to two different servers, and the area or number code being matched is 124, the Oracle® Enterprise Session Border Controller selects the first local policy based on the From address value of 12.

SIP and H.323 Interworking

You need to configure local policies, including the requisite local policy attributes, to use the H.323<—>SIP interworking (IWF). Flow progression in H.323<—>SIP traffic depends heavily on the local policies configured for the Oracle® Enterprise Session Border Controller, which determine what protocol is used on the egress side of a session.

You set the application protocol (an local policy attribute option) to instruct the Oracle® Enterprise Session Border Controller to interwork the protocol of an ingress message into a different protocol (H.323<—>SIP or SIP—>H.323) upon its egress to the next hop.

For example, if the application protocol is set to SIP, an inbound H.323 message will be interworked to SIP as it is sent to the next hop. An inbound SIP message would pass to the next hop unaffected. If the application protocol is set to H323, an inbound SIP message will be interworked to H.323 before being sent to the next hop.

Route Preference

The Oracle® Enterprise Session Border Controller builds a list of possible routes based on the source realm and the From-address (From-URI) and To-address (Request-URI), which forms a subset from which preference then decides. Any local policy routes currently outside of the configured time/day are not used, if time/day are set. Also, any local policy routes not on the list of carriers (if carriers is set and the requests has a Carrier header) are not used.

Note:

Source realm is used in the local policy lookup process, but it is not used in route preference calculations.

The Oracle® Enterprise Session Border Controller applies preference to configured local policies in the following order:

  1. Cost (cost in local policy attributes) is always given preference.
  2. Matching media codec (media profiles option in local policy attributes).
  3. Longest matching To address (to address list in local policy).
  4. Shortest matching To address (to address list in local policy).
  5. Longest matching From address (from address list in local policy).
  6. Shortest matching From address (from address list in local policy).
  7. Narrowest/strictest day of week specification (days of week option in local policy attributes).
  8. Narrowest/strictest time of day specification (start time and end time options in local policy attributes).
  9. Wildcard matches (use of an asterisk as a wildcard value for the from address and to address lists in local policy).
  10. Wild card matches are given the least preference. A prefix value of 6 is given a higher preference than a prefix value of * even though both prefix values are, in theory, the same length.

DTMF-Style URI Routing

The Oracle® Enterprise Session Border Controller supports the alphanumeric characters a-d, A-D, the asterisk (*), and the ampersand (#) for local policy matching purposes. The Oracle® Enterprise Session Border Controller handles these characters as standards DN (POTS) or FQDN when found in the to-addr (req-uri username) or from-addr (from0uri username for SIP, SIPS, and TEL URIs.

In addition, before performing the lookup match, the Oracle® Enterprise Session Border Controller strips characters that provide ease-of-reading separation. For example, if the Oracle® Enterprise Session Border Controller were to receive a req-uri containing tel:a-#1-781-328-5555, it would treat it as tel:a#17813285555.