WebSphere brand IBM WebSphere IP Multimedia Subsystem Connector, Version 6.2

Connections, routes, channels, and call flows

The Diameter Enabler base utilizes connections as links between a Diameter Enabler base and a peer, as routes to determine the connection on which a Diameter packet should be sent, as channels to convert byte streams to and from Diameter packets, and as call flows to transmit and receive these packets.

A connection is the link between a Diameter Enabler base and a peer. The peer may be a Diameter server or a Diameter agent that is a hop in the path to the Diameter server. For each configured connection, there is exactly one TCP connection between the Diameter Enabler base and the peer that it communicates with.

Connections remain as long as both the Diameter Enabler base and the peer are operating. If neither party sends a packet over the connection for a specified period of time, a watchdog message is sent to ensure that both sides are still operating.

The Diameter layer uses routes to determine which connection it should send a packet on. To send Diameter application packets to a specific realm, you must configure at least one connection and one route that uses that connection.
Note: If the specified connection's destination is a Diameter agent, rather than a Diameter server, the Diameter packet passes through this connection as a single hop on its way to the Diameter server.

Each connection represents a chain of channels. These channel chains operate within the Channel Framework Architecture (CFA) and are comprised of Diameter Channels, SSL/TLS channels (optional), and TCP channels.

At the top of the channel chains, there are three applications: Rf accounting Web service, Ro online charging Web service, and Sh subscriber profile Web service. All three of these applications export APIs to external applications through Web services interfaces.
  • The Diameter Enabler base manages connections, routes, and state machines to insure compliance with the Diameter protocol.
  • Diameter Web services use the Diameter Enabler base to handle packets as they pass through the CFA.
  • The Diameter channel is a serialization and de-serialization layer that converts inbound byte streams into Diameter packets and outbound Diameter packets into byte streams. No state is kept within the Diameter channel.
Diameter applications use call flows to transmit and receive packets for accounting, online charging, subscriber profile retrieval and updates, or subscribe and notify messages for subscriber profiles.
  • For accounting messages, the Diameter Enabler base passes information through the Rf accounting Web service when sending messages to the CCF. The CCF receives the messages and sends its response back to the Rf accounting Web service, which responds to the client that initiated the Web service request.
  • For online service requests, the Ro online charging Web service interface receives the Web service request from the client. The request is then processed and forwarded through the Diameter Enabler base to the appropriate OCS. The OCS receives the message and sends its response to the Ro online charging Web service, which responds to the client that initiated the Web service request.
  • For subscribe/notify messages:
    • The Sh subscriber profile Web service interface receives subscription requests from the IMS™ Application Server. The requests are then forwarded as subscriptions to the HSS using the Diameter protocol. When an update occurs at the HSS, the HSS sends a notification to the Diameter Enabler informing it of the update. The Sh subscriber profile Web service then forwards the update to all IMS Application Servers that have subscribed to the update.
    • The Ro online charging Web service interface provides subscription and notification messages to the IMS Application Server. Notifications are sent when the CTF must reauthenticate with the OCS or when a reauthorization subscription expires.



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