Handling traffic in a synchronous communication network

1. A method for dynamically adding a new channel to and/or dynamically removing a selected channel from a group of virtually concatenated channels carrying traffic to a network element (NE) of a synchronous network:

for dynamically adding said new channel:

if a network delay associated with said new channel is longer than a network delay associated with said group of virtually concatenated channels:

delaying traffic received along the group of virtually concatenated channels until the group of virtually concatenated channels and the new channel are time-aligned, and

adding said new channel to the group of virtually concatenated channels following said time-alignment of the group of virtually concatenated channels and the new channel; and

if the network delay associated with the new channel is shorter than the network delay associated with said group of virtually concatenated channels:

delaying traffic in the new channel until the new channel and the group of virtually concatenated channels are time-aligned, and

adding said new channel to the group following said time-alignment of the new channel and the group of virtually concatenated channels,

for dynamically removing said selected channel:

removing the selected channel from said group of virtually concatenated channels; and

applying, after said step of removing, at least one negative pointer justification action on the group of virtually concatenated channels excluding the removed channel if a network delay associated with the group of virtually concatenated channels excluding the removed channel is shorter than a network delay associated with the removed channel.

2. The method according to claim 1 for dynamically adding said new channel and wherein any of the delaying steps comprises a step of applying at least one positive pointer justification action.

3. The method according to claim 1 for dynamically adding said new channel and wherein if the network delay associated with the new channel is shorter by a period TD2 than the network delay associated with the group of virtually concatenated channels, said step of delaying traffic in the new channel comprises one of the following:

a step of applying at least one direct delay action on said new channel for a period TD2; and

a step of delaying traffic in the new channel for NC2 consecutive positive pointer justification actions, each having a duration TL2 j , where j is an index running from 1 to NC2, and

TD2

=

∑

j

=

1

NC2

⁢

TL2

j

.

4. The method according to claim 2 and wherein said step of applying at least one positive pointer justification action comprises applying a plurality of consecutive positive pointer justification actions until the new channel and the group of virtually concatenated channels are time-aligned.

5. The method according to claim 1 for dynamically adding said new channel and wherein if the network delay associated with the new channel is longer by a period TD1 than the network delay associated with the group of virtually concatenated channels, said step of delaying the traffic received along the group of virtually concatenated channels comprises a step of applying on the traffic received along the group of virtually concatenated channels NC1 consecutive positive pointer justification actions, each having a duration TL1 i , where i is an index running from 1 to NC1, and

TD1

=

∑

i

=

1

NC1

⁢

⁢

TL1

i

.

6. The method according claim 1 , and wherein said synchronous network comprises at least one of the following: a network based on the Synchronous Optical Network (SONET); and a network based on the Synchronous Digital Hierarchy (SDH).

7. The method according to claim 1 for dynamically removing said selected channel and wherein said step of applying at least one negative pointer justification action comprises applying a plurality of consecutive negative pointer justification actions until the network delay associated with the group of virtually concatenated channels excluding said removed channel is minimized.

8. The method according to claim 1 for dynamically removing said selected channel and wherein if the network delay associated with the removed channel is longer by a period TD than the network delay associated with the group of virtually concatenated channels excluding said removed channel, said applying step comprises applying at most NC consecutive negative pointer justification actions on the group of virtually concatenated channels excluding said removed channel, where each of said NC consecutive negative pointer justification action has a duration TL i , i is an index running from 1 to NC, and

TD

=

∑

i

=

1

NC1

⁢

⁢

TL

i

.

9. A method for dynamically adding a new channel to a group of virtually concatenated channels carrying traffic to network element (NE) of a synchronous network, the method comprising the steps of:

pausing traffic received from a client;

adding said new channel to the group of virtually concatenated channels;

time-aligning the group of virtually concatenated channels and the new channel; and

resuming reception of traffic from the client and transmission of traffic along said group of virtually concatenated channels including the new channel,

and wherein if the network delay associated with the new channel is shorter than the network delay associated with said group of virtually concatenated channels, the time-aligning step is carried out by delaying the group by a period of time which is substantially equal to the difference between the network delay associated with the group and the delay associated with the channel to be added.

10. Apparatus for dynamically adding a new channel to a group of virtually concatenated channels carrying traffic, the apparatus comprising:

a controller; and

a synchronous processor operatively associated with said group of virtually concatenated channels and said new channel, and operative, under control of the controller, to perform the following:

delay traffic received along the group of virtually concatenated channels until time-aligning the group of virtually concatenated channels and the new channel and add said new channel to the group of virtually concatenated channels following said time-alignment of the group of virtually concatenated channels and the new channel if a network delay associated with said new channel is longer than a network delay associated with said group of virtually concatenated channels, and

delay traffic in the new channel until time-aligning the new channel and the group of virtually concatenated channels and add said new channel to the group following said time-alignment of the new channel and the group of virtually concatenated channels if the network delay associated with the new channel is shorter than the network delay associated with said group of virtually concatenated channels.

11. A network element (NE) comprising the apparatus of claim 10 and operative in a synchronous network which comprises at least one of the following: a network based at least partially on the Synchronous Optical Network (SONET); and a network based at least partially on the Synchronous Digital Hierarchy (SDH).

12. The apparatus according to claim 10 and wherein said synchronous processor is operative to delay the traffic received along the group of virtually concatenated channels by applying, under control of the controller, at least one positive pointer justification action.

13. The apparatus according to claim 10 and wherein said synchronous processor is operative to delay the traffic received along the group of virtually concatenated channels or the traffic in the new channel by applying, under control of the controller, a plurality of consecutive positive pointer justification actions until time-alignment of the group of virtually concatenated channels and the new channel.

14. The apparatus according to claim 10 and wherein if the network delay associated with the new channel is shorter by a period TD2 than the network delay associated with the group of virtually concatenated channels, said synchronous processor is operative to delay the traffic in the new channel by applying, under control of the controller, one of the following:

at least one direct delay action on said new channel for a period TD2; and

NC2 consecutive positive pointer justification actions, each having a duration TL2 j , where j is an index running from 1 to NC2, and

TD2

=

∑

j

=

1

NC2

⁢

⁢

TL2

j

.

15. The apparatus according to claim 10 and wherein if the network delay associated with the new channel is longer by a period TD1 than the network delay associated with the group of virtually concatenated channels, said synchronous processor is operative to delay the traffic received along the group of virtually concatenated channels by applying on the traffic received along the group of virtually concatenated channels NC1 consecutive positive pointer justification actions, each having a duration TL1 i , where i is an index running from 1 to NC1, and

TD1

=

∑

i

=

1

NC1

⁢

⁢

TL1

i

.