An example SMUX session

Let's examine a typical scenario by walking through an example SMUX session. There are three major participants in this SMUX session: a network management station, an SNMP agent, and an SMUX peer used to manage the multi-port serial board (see ``Example SMUX session'')

• The management station runs SNMP client software to send requests to, and receive responses from, the SNMP agent.

• The SNMP agent is a daemon running on the host. The agent responds to SNMP requests from the network management station. The agent acts as ``middleman'' between the management station and the SMUX peer: translating SNMP messages from the management station into SMUX messages for the peer; it also translates SMUX messages from the SMUX peer into SNMP messages for the management station.

• The SMUX peer is a daemon running on the host; it is responsible for that part of the MIB containing information about the multi-port serial board. The SMUX peer uses the SNMP Multiplexing protocol (SMUX) to communicate with the SNMP agent and a proprietary protocol to access data stored on the serial board.

The next four subsections, ``Initialization'' through ``Termination,'' describe the sequence of events in this interaction. In this example, the SMUX peer is used to manage the multi-port serial board installed in a host running the SCO OpenServer system. The system administrator wants to use the network management station to get the baud rate for serial line 2 of the multi-port serial board installed in the host.

Example SMUX session

Initialization

1. The host computer boots, which starts the SNMP agent.

2. The SMUX peer starts running.

3. The peer establishes a TCP connection to the agent. The subsequent interaction between the SMUX peer and the SNMP agent is called an ``SMUX association.''

4. The peer registers itself with the agent. During registration, the peer specifies which part of the MIB it wishes to maintain (this specified part of the MIB is called a ``MIB module''). In this example, the peer wishes to manage the MIB module that contains the variables pertaining to the multi-port serial board.

Exchange of MIB information

1. The process of information exchange between the management station and the SMUX peer begins when the system administrator uses the network management station to ask for the baud rate for serial line 2 on the multi-port serial board.

2. The SNMP client, running on the management station, sends a GetRequest message over the network to the agent.

3. The agent sees that the MIB module containing the baud rate of serial line 2 has been registered by the peer, so the agent sends an SMUX GetRequest message to the peer, requesting the baud rate for serial line 2.

4. Upon receiving the SMUX GetRequest message, the peer decodes it and finds a request for the baud rate of serial line 2 of the serial board.

5. The peer gets the baud rate from the serial board device driver.

6. The peer encodes the baud rate in an SMUX response message and sends the message to the SNMP agent.

7. The agent receives the SMUX message from the peer, translates it into an SNMP GetResponse message, and sends it on to the management station.

8. The management station receives the response message from the agent and displays the baud rate for serial line 2.

Asynchronous events

Not all messages in this system originate with the management station. If the peer detects a noteworthy condition from the serial board, the peer sends an unsolicited message called an ``SMUX trap'' to the agent. The agent translates it into an SNMP trap, which is then sent to the network management station.

Termination

1. Ultimately, the peer will receive a signal to terminate itself.

2. The peer removes its registration with the agent and closes the SMUX association.

3. Any subsequent requests by the SNMP client for information contained in the unregistered module will be handled by the SNMP agent (see the section ``Terminating an SMUX association'' for further information).