Monitoring carrier ethernet networks

1. A method of monitoring a Carrier Ethernet network comprising nodes connected by links, the network supporting connectionless traffic flows between edge nodes of the network, the method comprising, at a network management system:

the network management system determining when an event that has a potential to change bandwidth usage on a link of the network has occurred in the network;

the network management system, in response to a determination that the event that has the potential to change bandwidth usage on the link of the network has occurred in the network, performing:

determining traffic flows which use the link;

determining a total bandwidth demand of the traffic flows using the link;

comparing the total bandwidth demand with a bandwidth capacity of the link; and

reporting a link degradation if an outcome of the step of comparing the total bandwidth demand with a bandwidth capacity of the link indicates that the total bandwidth demand exceeds the bandwidth capacity of the link,

wherein the step of determining when an event has occurred in the network that has the potential to change bandwidth usage on a link of the network comprises:

receiving an alarm indicating a network fault; and

waiting for a time period for nodes of the network to converge on an active topology.

2. A method according to claim 1 wherein the step of determining traffic flows which use the link comprises querying a node of the network to retrieve active topology information.

3. A method according to claim 1 wherein the step of determining traffic flows which use the link comprises using a store of information which indicates a spanning tree instance and a traffic flow using that spanning tree.

4. A method according to claim 1 wherein the step of determining a total bandwidth demand of the traffic flows using the link comprises using a store of information which indicates traffic flows and parameters of each of the traffic flows.

5. A method according to claim 1 wherein the step of determining a total bandwidth demand of the traffic flows using the link comprises:

determining a Committed Information Rate for each of the traffic flows using the link; and

determining a sum of the Committed Information Rates of the traffic flows using the link.

6. A method according to claim 1 wherein the step of determining when an event that has a potential to change bandwidth usage on a link of the network has occurred in the network comprises at least one of:

receiving a topology change indication from a node of the network; and

receiving a new root indication from a node of the network.

7. A method according to claim 1 , comprising repeating for a plurality of different links of the network the steps of:

determining traffic flows which use the link,

determining the total bandwidth demand of the traffic flows using the link, and

comparing the total bandwidth demand with the bandwidth capacity of the link.

8. An apparatus for use at a network management system of a network comprising nodes connected by links, the network supporting connectionless traffic flows between edge nodes of the network, the apparatus comprising:

an event monitor which is arranged to determine when an event that has a potential to change bandwidth usage on a link of the network has occurred in the network;

a traffic monitor which is arranged to determine traffic flows which use the link;

a bandwidth monitor which is arranged to determine a total bandwidth demand of the traffic flows using the link; and

a comparator which is arranged to compare the total bandwidth demand with a bandwidth capacity of the link,

wherein the comparator is further arranged to report a link degradation if the total bandwidth demand exceeds the bandwidth capacity of the link,

wherein the traffic monitor, the bandwidth monitor, and the comparator are arranged to operate in response to a determination that the event that has the potential to change bandwidth usage on the link of the network has occurred in the network, and

wherein the event monitor is arranged to perform the determining by performing:

receiving an alarm indicating a network fault; and

waiting for a time period for nodes of the network to converge on an active topology.

9. The apparatus according to claim 8 wherein the traffic monitor is arranged to query nodes of the network to retrieve active topology information.

10. The apparatus according to claim 8 further comprising a store which is arranged to store information which indicates traffic flows and parameters of each of the traffic flows and the bandwidth monitor is arranged to use the store.

11. The apparatus of claim 8 , wherein the apparatus is an element in a Carrier Ethernet communication network comprising a plurality of nodes connected by links, the network supporting connectionless traffic flows between nodes.

12. A non-transitory machine-readable medium carrying instructions which, when executed by a processor, cause the processor to perform a method of monitoring a Carrier Ethernet network comprising nodes connected by links, the network supporting connectionless traffic flows between edge nodes of the network, the method comprising, at a network management system:

determining when an event that has a potential to change bandwidth usage on a link of the network has occurred in the network;

in response to a determination that the event that has the potential to change bandwidth usage on the link of the network has occurred in the network, performing:

determining traffic flows which use the link;

determining a total bandwidth demand of the traffic flows using the link;

comparing the total bandwidth demand with a bandwidth capacity of the link; and

reporting a link degradation if an outcome of the step of comparing the total bandwidth demand with a bandwidth capacity of the link indicates that the total bandwidth demand exceeds the bandwidth capacity of the link,

wherein the step of determining when an event has occurred in the network that has the potential to change bandwidth usage on a link of the network comprises:

receiving an alarm indicating a network fault; and

waiting for a time period for nodes of the network to converge on an active topology.