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Control Association States

A control association is a relationship where the PGC is controlling the VPG. Each VPG has only one control association at any time.

Table 10 describes the control association states.

Table 10: Control Association States

Control Association State	Description
Disconnected	The control association is in the Disconnected state. No PGC is controlling the VPG, and incoming H.248 messages are ignored. The control association remains disconnected as long as the VPG is Out-of-Service. Depending on what caused the VPG to become Out-of-Service, the VPG either drops H.248 commands or answers them with a port-unreachable ICMP error.
Connecting	The control association is in Connecting state between the time the VPG sends a registration request to the PGC and the time the PGC accepts, rejects, or aborts the request. The VPG rejects incoming H.248 commands while the control association is in the Connecting state with error # 505: “Transaction Request Received before a ServiceChange Reply has been received”.
Draining	The control association enters the Draining state when an administrator instructs the VPG to gracefully transition from In-Service to Out-of-Service. The PGC transitions to Out-of-Service when the controlling PGC subtracts all of the VPG’s H.248 terminations. The VPG accepts only Subtract and AuditValue commands from the controlling PGC. It rejects all other commands with error # 502: “Not Ready”.

Control Association State

Description

Disconnected

The control association is in the Disconnected state. No PGC is controlling the VPG, and incoming H.248 messages are ignored. The control association remains disconnected as long as the VPG is Out-of-Service.

Depending on what caused the VPG to become Out-of-Service, the VPG either drops H.248 commands or answers them with a port-unreachable ICMP error.

Connecting

The control association is in Connecting state between the time the VPG sends a registration request to the PGC and the time the PGC accepts, rejects, or aborts the request.

The VPG rejects incoming H.248 commands while the control association is in the Connecting state with error # 505: “Transaction Request Received before a ServiceChange Reply has been received”.

Draining

The control association enters the Draining state when an administrator instructs the VPG to gracefully transition from In-Service to Out-of-Service. The PGC transitions to Out-of-Service when the controlling PGC subtracts all of the VPG’s H.248 terminations.

The VPG accepts only Subtract and AuditValue commands from the controlling PGC. It rejects all other commands with error # 502: “Not Ready”.

When the state of a control association changes, the VPG can send the following types of ServiceChange commands to the PGC:

Registration Requests—The VPG sends a Registration Request ServiceChange command to request that a PGC become its controlling PGC. The VPG sends these requests when a control association enters the Connecting state.
Unregistration Messages—The VPG sends an Unregistration ServiceChange command to its controlling PGC when it transitions to the Out-of-Service (Disconnected) service state because of an administration operation or a failure. The failure can be the result of a MultiServices PIC or Flexible PIC Concentrator (FPC) failure or because the MultiServices PIC was powered off or removed.
Notification Messages—The VPG sends a notification ServiceChange command to its controlling PGC when the control association transitions between the Connected and Draining states and vice versa.

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