Load control in a communication network

1. A gateway apparatus for interfacing an access network to a service network, the apparatus comprising:

an input for receiving access requests from the access network at a first flow rate;

an output for forwarding access requests to a gateway controller at a second flow rate; and

a flow controller for controlling the flow of access requests from said input to said output, the flow controller comprising

a receiver for receiving a restriction value from gateway controller,

first processing means for determining whether the received restriction value is more restrictive than any currently in use restriction value and, if so, determining a leak rate on the basis of the ratio between the received restriction value divided by the currently in use restriction value, multiplied by the second flow rate,

second processing means for allowing access requests to pass to said output at a rate up to the determined leak rate at least until a further restriction value is received.

2. The apparatus according to claim 1 , the apparatus interfacing at access network and an IP network.

3. The apparatus according to claim 1 , wherein said first processing means is arranged, in the event that the restriction value is less restrictive than the currently in use restriction value, to determine a new leak rate on the basis of the received restriction value and the current first flow rate.

4. The apparatus according to claim 2 , wherein said access network is a PSTN network, and said gateway controller is a call control server and said access requests received at said input are off-hook notifications.

5. The apparatus according to claim 2 , wherein said output comprises an H.248 interface for communicating with a gateway controller.

6. The apparatus according to claim 3 , wherein said new flow rate is a target leak rate, and the first means is arranged to increase the current leak rate incrementally to said target leak rate.

7. The apparatus according to claim 6 , wherein first means is arranged to increase the leak rate after fixed time intervals, or after time intervals determined randomly between upper and lower limits.

8. A method of operating a gateway interfacing an access network to a service network, the method comprising;

receiving access requests from the access network at a first flow rate;

forwarding access requests to a gateway controller at a second flow rate; receiving a restriction value from the gateway controller;

determining whether the received restriction value is more restrictive than any currently in use restriction value and, if so, determining a leak rate on the basis of the ratio between the received restriction value divided by the currently in use restriction value, multiplied by the second flow rate, and

restricting said second flow rate to the determined leak rate at least until a further restriction value is received.

9. A method of controlling an overload condition at a gateway controller of a communications network, the controller being responsible for a plurality of access gateways in the network, the method comprising:

at the gateway controller, monitoring the load level on the controller to detect the occurrence of an overload condition and, when an overload condition is detected, determining a restriction value and sending this to the access gateways; and

at each said gateway, determining whether the received restriction value is more restrictive than any currently in use restriction value and, if so, determining a leak rate on the basis of the ratio between the received restriction value divided by the currently in use restriction value, multiplied by the second flow rate, and restricting said second flow rate to the determined leak rate at least until a further restriction value is received.