Attribution of congestion contributions

1. A method of attributing contributions to congestion of a shared resource to respective user registers, said resource being operable to serve requests for service received from users sharing said resource; the method comprising:

repeatedly updating each respective user register; and

updating a multi-user congestion measure in dependence on each of a plurality of requests for service received from users sharing said resource, the respective requests for service each having a user indication associated therewith indicating with which of said user registers the respective request for service is associated;

wherein the repeated updating of each respective user register is performed in dependence on a predetermined characteristic of said respective user register, the respective characteristics of said respective user registers being individually settable; and

wherein the method further comprises, in respect of one of the received requests for service:

identifying from the user indication associated therewith the user register with which said request for service is associated;

updating the state of said associated user register in dependence on said updated multi-user congestion measure;

determining the contribution to congestion of the shared resource attributable to said associated user register in dependence on the updated state of said associated user register;

making a service determination in dependence on the contribution to congestion so-determined in relation to the serving of requests for service associated with that user register and/or in relation to the service provided to a user associated with that user register; and

serving requests for service in accordance with said service determination or sending an indication of said service determination whereby to enable requests for service to be served in accordance with said service determination.

2. A method according to claim 1 wherein said resource is operable to serve requests for service within a data network.

3. A method according to claim 1 wherein said requests for service comprise data units.

4. A method according to claim 3 wherein the user indication in respect of a data unit is indicative of one or more of: a sender of said data unit; one or more intended receivers of said data unit; or an entity accountable for the sending and/or receiving of said data unit.

5. A method according to claim 3 wherein the service requested comprises the forwarding of said data units via one or more data networks.

6. A method according to claim 1 wherein said updated multi-user congestion measure is communicated separately from said received request for service whereby to allow the state of said associated user register to be updated.

7. A method according to claim 1 wherein the state of said associated user register is updated by an amount that depends on a measure of the amount of said resource required to serve said request for service and on the multi-user congestion measure.

8. A method according to claim 1 wherein the step of updating the multi-user congestion measure comprises updating the multi-user congestion measure in dependence on whether or not said resource serves said request for service.

9. A method according to claim 1 wherein a request for service that has been rejected is re-used as the means to communicate said updated multi-user congestion measure whereby to allow the state of said associated user register to be updated.

10. A method according to claim 1 wherein the multi-user congestion measure is updated in dependence on the state of a multi-user register itself updated in dependence on said received requests for service whereby to mimic how said received requests would be served by a resource less capable than said shared resource.

11. A method according to claim 1 wherein each respective user register is updated in one or both of the following manners:

periodically in dependence on the predetermined characteristic of that user register; and

in dependence on the predetermined characteristic of that user register in the event of a request for service being received having a user indication indicating an association with that user register.

12. A method according to claim 1 wherein each user register comprises one or more modules implementing token bucket or leaky bucket functionality.

13. Apparatus for performing a method of attributing contributions to congestion of a shared resource to respective user registers, said resource being operable to serve requests for service received from users sharing said resource; the apparatus being configured to at least:

repeatedly update each respective user register; and

update a multi-user congestion measure in dependence on each of a plurality of requests for service received from users sharing said resource, the respective requests for service each having a user indication associated therewith indicating with which of said user registers the respective request for service is associated;

wherein the repeated update of each respective user register is performed in dependence on a predetermined characteristic of said respective user register, the respective characteristics of said respective user registers being individually settable; and

wherein the apparatus is further configured to, in respect of one of the received requests for service:

identify from the user indication associated therewith the user register with which said request for service is associated;

update the state of said associated user register in dependence on said updated multi-user congestion measure;

determine the contribution to congestion of the shared resource attributable to said associated user register in dependence on the updated state of said associated user register;

make a service determination in dependence on the contribution to congestion so-determined in relation to the serving of requests for service associated with that user register and/or in relation to the service provided to a user associated with that user register; and

serve requests for service in accordance with said service determination or send an indication of said service determination whereby to enable requests for service to be served in accordance with said service determination.

14. The apparatus according to claim 13 wherein said resource is operable to serve requests for service within a data network.

15. The apparatus according to claim 13 wherein said requests for service comprise data units.