LIR/LIA Lookup to Home Subscriber Server from I-BCF

LIR LIA Lookup to Home Subscriber Server from I-BCF

The Oracle Communications Session Border Controller, acting as an I-BCF, can perform a Location Information Lookup (LIR) to a Home Subscriber Server (HSS) to find the S-CSCF where to forward a request message. LIR/LIA messages are part of the Diameter Cx interface, which is used to communicate with HSS.

In an IMS environment, a user registers with S-CSCF and that S-CSCF assigns itself with an HSS as the serving registrar for that user. When a call needs to be routed to the user, an I-BCF performs a location information lookup to the HSS to determine the S-CSCF for that user and route the request toward that S-CSCF.

Home Subscriber Server

The Oracle Communications Session Border Controlleris configured with an HSS configuration element called home subscriber server. When the Oracle Communications Session Border Controlleri receives an INVITE from a user, a local policy routing lookup is performed.

The home subscriber server configuration element is configured with a name, which is referenced in a local policy next-hop parameter. It also includes, a state, IP address, port, and realm.

P-Acme-Serving Parameter Creation

The Oracle Communications Session Border Controlleri can insert a P-Acme-Serving parameter into the Route header of a message. This parameter is inserted when the add-lookup-parameter parameter is enabled in the home subscriber server configuration element and the Oracle Communications Session Border Controlleri queried that HSS to find the message’s destination.

The P-Acme-Serving parameter can be helpful for informing other Oracle Communications Session Border Controllers that this system is acting as the UA’s I-BCF and that the HSS lookup has been done.

HSS Watchdog Keepalives

The home subscriber server configuration element contains a watchdog-ka-timer parameter that sets a time to send DWR messages to the HSS. This is similar to external policy server Diameter Heartbeat functionality. When 3/4 of this timer elapses, the Oracle Communications Session Border Controlleri begins disconnection processes. DWR message creation is suspended when any other activity with the HSS occurs within watchdog-ka-timer seconds. DWR creation resumes watchdog-ka-timer seconds if all other traffic stops.

Local Policy

The Oracle Communications Session Border Controlleri performs all expected processing on an incoming message and begins a local policy lookup. When it encounters a policy attribute with a next hop in the form of cx:element-name, it will perform an LIR/LIA transaction over the Cx Diameter interface to the home subscriber server referenced as element-name.

The Oracle Communications Session Border Controlleri forwards the initial INVITE to the address in the Server-Name AVP returned by the HSS in the LIA message.

LIR LIA Transaction

The LIR includes the Public-User-Identity AVP containing the request URI from the SIP request. The HSS responds with the assigned S-CSCF server (a Oracle Communications Session Border Controlleri) for this PUID. The answer is the form of a Location Info Answer (LIA) and is in the Server Name AVP. If the S-CSCF specified in this AVP is not the current Oracle Communications Session Border Controlleri, then the INVITE is forwarded to the address specified in the LIR.

If the S-CSCF returned in the LIR is this Oracle Communications Session Border Controlleri, then the AoR from the request URI is found in the registration cache and the message is forwarded to that endpoint. When the registration cache entry does not exist or is invalid, local policy processing continues with the next policy-attribute following "stop-recurse" rules. If there are no other routes, then a 404 is sent to the UA who sent the INVITE.

The LIR LIA Transaction call flow is described above.

LIR Format

The LIR contains the following information:

Vendor-Id: 9148
Supported-Vendor-Id: 10415
Supported-Vendor-Id: 13019
Vendor-Specific-Application-Id (grouped):
	Vendor-ID: 10415
	Vendor-ID: 13019
	Auth-Application-ID: 16777216
Origin-Host: IP Address:port of the system’s source interface.
Origin-Realm: Realm-name where the system talks to this HSS.
Destination-Host: IP address of the HSS.
Public-Identity: Request URI of SIP Request

LIA Format

The LIA is expected to contain:

Server-Name: S-CSCF address to forward this message

Home Subscriber Server Configuration

To configure a home subscriber server (HSS):

In Superuser mode, type configure terminal and press Enter.
```
ORACLE# configure terminal
```
Type session-router and press Enter to access the session router path.
```
ORACLE(configure)# session-router
```
Type home-subscriber-server and press Enter. The system prompt changes to let you know that you can begin configuring individual parameters.
```
ORACLE(session-router)# home-subscriber-server
ORACLE(home-subscriber-server)#
```
name—Enter the name for this home subscriber server configuration element to reference from other configuration elements.
state—Set this to enabled to use this configuration element.
address—Enter the IP address of this HSS.
port—Enter the port number on the HSS where to connect. The default value is 80.
realm—Enter the realm name where this HSS exists.
watchdog-ka-timer—Enter the period of time to send DWRs to the HSS.
add-lookup-parameter—Set this to enabled for the Oracle Communications Session Border Controlleri to add a P-Acme-Serving parameter to the Route header.
Type done when finished.

Local Policy Configuration

To direct a policy attribute to retrieve a next hop from an HSS via an LIR lookup:

In Superuser mode, type configure terminal and press Enter.
```
ORACLE# configure terminal
```
Type session-router and press Enter to access the session router path.
```
ORACLE(configure)# session-router
```
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
```

Choose an existing local-local object with the select command.

ORACLE(local-policy)# select
<source-realm>:
1: realms 'realm01'; from *; to *
selection: 1

Type policy-attributes and press Enter. If you are adding this feature to a pre-existing local policy configuration, you will need to select and edit your local policy.
```
ORACLE(local-policy))# policy-attributes
ORACLE(policy-attributes)#
```
next-hop—Set this parameter to cx:name-of-HSS-configuration for this policy attribute to lookup routes by querrying the named HSS via an LIR.
Type done and save and activate your configuration.

Statistics

The show home-subscriber command displays detailed information about HSS transactions. For example:

ORACLE## show home-subscriber-server
17:54:58-186
HSS Status                 -- Period -- -------- Lifetime --------
                 Active    High   Total      Total  PerMax    High
Client Trans          0       0       0         12       4       1
Server Trans          0       0       0          1       1       1
Sockets               1       1       0          1       1       1
Connections           1       1       0          1       1       1
                           ---- Lifetime ----
                    Recent      Total  PerMax
LIR                      0          0       0
Sent Req Accepted        0         11       3
Sent Req Rejected        0          0       0
Sent Req Expired         0          0       0
Sent Req Error           0          0       0
Internal Errors          0          0       0

Note the following statistics provided for Recent and Lifetime periods:

LIR—Number of LIR requests sent
Sent Req Accepted—Number of requests for which we got success response (2xxx)
Sent Req Rejected—Number of permanent failures (5xxx)
Sent Req Expired—Number of requests for which there was no response
Sent Req Error—Number of protocol errors/bad requests (1xxx, 3xxx, 4xxx)