1. Range Based Address Resolution User Guide
  2. Range Based Address Resolution
  3. Range Based Address Resolution overview

2.1 Range Based Address Resolution overview

Range Based Address Resolution (RBAR) is an enhanced routing application that allows routing of Diameter end-to-end transactions based on Diameter Application ID, Command Code, Routing Entity Type, and Routing Entity Addresses (range and individual) as a Diameter Proxy Agent.

A Routing Entity can be any of the following:
  • A User Identity:
    • International Mobile Subscriber Identity (IMSI)
    • Mobile Subscriber Integrated Services Digital Network (Number) (MSISDN)
    • IP Multimedia Private Identity (IMPI)
    • IP Multimedia Public Identity (IMPU)
  • An IP Address associated with the User Equipment
    • IPv4 (based upon the full 32-bit value in the range of 0x00000000 to 0xFFFFFFFF)
    • IPv6-prefix (1 to 128 bits)
  • A general purpose data type: UNSIGNED16 (16-bit unsigned value)
Routing resolves to a Destination that can be configured with any combination of a Realm and Fully Qualified Domain Name (FQDN); Realm-only, FQDN-only, or Realm and FQDN.

When a message successfully resolves to a destination, RBAR replaces the destination information (Destination-Host and/or Destination-Realm) in the ingress message with the corresponding values assigned to the resolved destination, and forwards the message to the (integrated) Diameter Relay Agent for egress routing into the network.

RBAR Functions

RBAR provides the following functions:

Reserved MCC Ranges

Mobile Country Code (MCC) ranges that are reserved for future use are defined in a system-wide MCC Ranges table. If the MCC digits portion of the decoded IMSI digits fall within one of the ranges designated in the MCC Ranges table, the IMSI digits are NOT used for further Address Resolution. RBAR continues decoding the digits using other AVP instances, or next Priority AVP (if provisioned), or next Routing Entity (if provisioned).

Identifying IMSIs and MSISDNs

Address resolution applications like Full Address Based Resolution (FABR) and (RBAR) need to categorize User Identities (digit strings) decoded from the Diameter Request AVPs as either MSISDN or IMSI, to allow looking up the User Identity in the appropriate lookup table.

If there is no plus sign before the digits, the Routing Entity Type is IMPU, and decoded digits falls within MSISDN and IMSI overlap range, configured MCC+MNC combinations can be compared to the first 5 or 6 digits of the User Identity. If a match occurs, the User Identity is considered as an IMSI and used for IMSI lookup. If a match does not occur, the User Identity is considered as an MSISDN and used for MSISDN lookup.

Identifying IMSIs and MSISDNs provides more information about identifying IMSIs and MSISDNs using digit string lengths and MCC+MNC combinations.

Application Chaining

Application Routing Rules can be configured so that RBAR and the PCA applications can be run independently on a same DSR DA-MP without interfering with each other’s functionality.

Assumption and Limitation

In Diameter, all IMSIs are in the form of an ITU-T E.212 number. It is assumed that customers provision all IMSIs within the RBAR database as E.212 values. E.212 to E.214 conversion is not supported.