Transmitting residence time information in a network

1. A method of operation of a Multiprotocol Label Switching network, the method comprising, in an active node of the network:

receiving a first data packet from a source node;

forwarding the first data packet to a destination node, the first data packet comprising a flag indicating if a two-step mode is being used; and

when the flag indicates that the two-step mode is being used:

measuring a residence time of the first data packet in the active node; and

sending a further data packet containing residence time information of the first data packet.

2. The method as claimed in claim 1 , wherein the first data packet is sent as part of a method for synchronization by two-way exchange of packets carrying timing information.

3. The method as claimed in claim 1 , comprising including in the further data packet information identifying the first data packet.

4. The method as claimed in claim 1 , wherein sending the further data packet containing residence time information comprises:

receiving a second data packet from the source node;

including the residence time information in the second data packet; and

forwarding the second data packet to the destination node.

5. The method as claimed in claim 1 , wherein:

the source node is a clock operating in a two-step mode; and

wherein the first data packet is sent as part of a method for synchronization, and the synchronization is based on at least one of a timestamp of transmission and receipt of the first data packet.

6. The method as claimed in claim 1 , wherein sending the further data packet containing residence time information comprises:

receiving a second data packet from the destination node;

including the residence time information in the second data packet, and

forwarding the second data packet to the source node.

7. The method as claimed in claim 1 , wherein sending the further data packet containing residence time information comprises:

creating a new data packet;

including the residence time information in the new data packet; and

sending the new data packet to the destination node.

8. The method as claimed in claim 1 , wherein:

the source node is a clock operating in a one-step mode; and

wherein the first data packet is sent as part of a method for synchronization, and the synchronization is based on at least one of a timestamp of transmission and receipt of the first data packet.

9. The method as claimed in claim 1 , further comprising setting a flag in the forwarded first data packet to indicate if a two-step mode is being used.

10. The method as claimed in claim 1 , wherein sending the further data packet containing residence time information comprises:

creating a new data packet;

including the residence time information in the new data packet; and

sending the new data packet to the source node.

11. The method as claimed in claim 1 , wherein the source node comprises one of a boundary clock and a clock connected to a boundary clock.

12. The method as claimed in claim 1 , comprising updating a correction field in the further data packet to include the residence time information.

13. The method as claimed in claim 1 , wherein the further data packet is encapsulated into a Generic Associated Channel packet.

14. A Multiprotocol Label Switching, MPLS, network node, being configured for:

receiving a first data packet from a source node;

forwarding the first data packet to a destination node, the first data packet comprising a flag indicating if a two-step mode is being used; and

when the flag indicates that the two-step mode is being used:

measuring a residence time of the first data packet in the active node; and

sending a further data packet containing residence time information of the first data packet.

15. The MPLS network node as claimed in claim 14 further configured for including in the further data packet information identifying the first data packet.

16. The MPLS network node as claimed in claim 14 , further configured for sending the further data packet containing residence time information by:

receiving a second data packet from the source node;

forwarding the second data packet to the destination node; and

including the residence time information in the second data packet forwarded to the destination node.

17. The MPLS network node as claimed in claim 14 , further configured for sending the further data packet containing residence time information by:

receiving a second data packet from the destination node;

forwarding the second data packet to the source node; and

including the residence time information in the second data packet forwarded to the source node.

18. The MPLS network node as claimed in claim 14 , being further configured for sending the further data packet containing residence time information by:

creating a new data packet;

including the residence time information in the new data packet; and

sending the new data packet to the destination node.

19. The MPLS network node as claimed in claim 14 , further configured for setting a flag in the forwarded first data packet to indicate that two-step mode is being used.

20. The MPLS network node as claimed in claim 14 , further configured for updating a correction field in the further data packet to include the residence time information.

21. The MPLS network node as claimed in claim 14 , wherein the further data packet is encapsulated into a Generic Associated Channel packet.

22. A Multiprotocol Label Switching, MPLS, network node, comprising:

a processor; and

a memory, said memory containing instructions executable by said processor to configure the node to:

receive a first data packet from a source node;

forward the first data packet to a destination node, the first data packet comprises a flag indicating if a two-step mode is being used; and

when the flag indicates that the two-step mode is being used:

measure a residence time of the first data packet in the active node; and

send a further data packet containing residence time information of the first data packet.