Multi-constraint routing system and method

1. A method of performing multi-constraint routing comprising:

determining a link composite cost for each of a plurality of links under consideration in a network topology, wherein

description="In-line Formulae" end="lead"link composite cost=f(metric1, . . . , metricN);description="In-line Formulae" end="tail"

the link composite cost being a function f of a plurality of metrics metric1, . . . metricN for each link, where N>=2; and

performing routing through the network topology from a source to a destination based on the link composite costs, wherein the link composite cost is determined according to:

composite ⁢ ⁢ cost ⁢ ⁢ ( link ) = ∑ i = 1 N ⁢ c i ⁡ ( metric i ) n ⁡ ( i )

where ci is a constant for the ith metric, and n(i) is an exponent for the ith metric.

2. A method according to claim 1, wherein the link composite cost is determined according to:

description="In-line Formulae" end="lead"link composite cost=a*(1/abw)+b*Admin cost+c*Delaydescription="In-line Formulae" end="tail"

where metric1=abw(available bandwidth), metric2=Admin cost and metric3=Delay, and wherein c1=“a”, which is the available bandwidth coefficient, C2=“b”, which is the Administrative cost coefficient, and c3=“c”, which is the delay coefficient, n(1)=−1, n(2)=1 and n(3)=1.

3. A method according to claim 1, further comprising, for each link, at least one network node advertising the link's metrics across the network such that any node in the network may implement the multi-constraint routing.

4. A method according to claim 2, wherein the link composite cost increases with decreasing available bandwidth and routing is performed in a manner which promotes load balancing.

5. A method according to claim 4, further comprising performing the routing in a manner which promotes load balancing with demand reservation on at least one link.

6. A method according to claim 5, further comprising defining a respective demand threshold for at least one link representing demand reservation for the at least one link.

7. A method according to claim 6, further comprising:

computing a cost for each said at least one link as follows:

if (available bandwidth

description="In-line Formulae" end="lead"cost for a link=link composite cost+MAX COSTdescription="In-line Formulae" end="tail"

description="In-line Formulae" end="lead"else cost_for a link=link composite costdescription="In-line Formulae" end="tail"

where demand_threshold is a respective demand reservation for the link and MAX COST is a very large value.

8. A method according to claim 7, wherein the demand_threshold is set to a first value for at least one of the links, and is set to a second larger value for at least one of the links whereby bandwidth on the at least one of the links having the first value is reserved for larger bandwidth requests.

9. A method according to claim 1, comprising computation of a link cost based on the link composite cost for switching between a load balancing mode and a bin-packing mode based on available bandwidth of each of a plurality of links under consideration in the network topology.

10. A method according to claim 9, wherein the switching between the load balancing and the bin-packing modes is performed based on a predetermined demand_threshold value.

11. A method according to claim 9, further comprising:

determining the cost for each said at least one link as follows:

If (abw<=demand_threshold)

description="In-line Formulae" end="lead"cost of linkt=a*Admin cost+b*(abwK /PIR)+c*Delay+MAX COSTdescription="In-line Formulae" end="tail"

description="In-line Formulae" end="lead"elsedescription="In-line Formulae" end="tail"

description="In-line Formulae" end="lead"cost of link=a*Admin cost+b*(PIR/abwK)+c*Delay;description="In-line Formulae" end="tail"

wherein PIR=Peak Information Rate, MAX COST is a large number, abw is the available bandwidth and K is a constant.

12. A method according to claim 11, wherein the constant K can be used to control a rate at which the cost changes with a variation in the available bandwidth.

13. A method according to claim 11, wherein a different demand_threshold value is used for at least one link for achieving a different switch over point between load balancing and bin-packing.

14. A method according to claim 11, comprising, performing the load balancing, when the available bandwidth is higher than the demand_threshold.

15. A method according to claim 11, comprising performing the bin-packing, when the available bandwidth is less than or equal to the demand_threshold.

16. A method according to claim 11, comprising selection of a less congested link with higher available bandwidth over a link with a lesser available bandwidth; wherein the link composite cost increases with decrease in the available bandwidth.

17. A method according to claim 16, comprising selection of a link with a lower available bandwidth over a less congested link, wherein the link composite cost increases with an increase in available bandwidth.

18. A method according to claim 11, comprising adding a large number (MAX COST) to the link composite cost for preventing the link from being selected, when there is at least one link with available bandwidth higher than the demand_threshold.

19. A method according to claim 11, comprising setting the demand_threshold to zero, for always operating in the load balancing node.

20. A method according to claim 11, comprising setting the demand_threshold to any value higher than PIR, for always operating in the bin-packing mode.

21. A method according to claim 9, comprising:

determining the cost for each said at least one link as follows:

If (abw<=demand_threshold)

description="In-line Formulae" end="lead"cost of link=a*Admin cost+b*(PIR/abwK)+c*Delay+MAX COSTdescription="In-line Formulae" end="tail"

description="In-line Formulae" end="lead"elsedescription="In-line Formulae" end="tail"

description="In-line Formulae" end="lead"cost of link=a*Admin cost+b*(abwK /PIR)+c*Delay;description="In-line Formulae" end="tail"

wherein PIR=Peak Information Rate, MAX COST is a large number, abw is the available bandwidth and K is a constant.

22. A method according to claim 21, wherein the constant K can be used to control a rate at which the cost changes with a variation of the available bandwidth.

23. A method according to claim 21, wherein a different demand_threshold value is used for at least one link for achieving a different switch over point between load balancing and bin-packing.

24. A method according to claim 21, comprising performing the bin-packing, wherein the available bandwidth is higher than the demand_threshold.

25. A method according to claim 21, comprising performing the load balancing, wherein the available bandwidth is less than or equal to the demand_threshold.

26. A method according to claim 21, comprising selection of a less congested link with higher available bandwidth over a link with a lesser available bandwidth, wherein the link composite cost increases with a decrease in the available bandwidth.

27. A method according to claim 26, comprising selection of a link with a lower available bandwidth over a less congested link, wherein the link composite cost increases with an increase in available bandwidth.

28. A method according to claim 21, comprising adding a large number (MAX COST) to the link composite cost for preventing the link front being selected, when there is at least one link with available bandwidth higher than the demand_threshold.

29. A method according to claim 21, comprising setting the demand_threshold to zero, for always operating in the bin-packing mode.

30. A method according to claim 21, comprising setting the demand_threshold to any value higher than PIR, for operating always in the load balancing mode.

31. A method according to claim 1, comprising for each of a plurality of different traffic types, using a respective different composite cost equation for calculating the composite costs.

32. A method according to claim 31, wherein the different traffic types include video, voice and data.

33. A method according to claim 31, wherein the different traffic type s include different classes of service/qualities of service.

34. A routing system adapted to perform multi-constraint routing, the system comprising:

a topology repository adapted to store information identifying links, nodes and connections of a network; and

a multi-constraint router adapted to determine a link composite cost:

description="In-line Formulae" end="lead"link composite cost=f (metric1, . . . , metricN);description="In-line Formulae" end="tail"

for each of a plurality of the links in a network topology, the composite cost being a function f of a plurality of metrics metric1, . . . , metricN for each link, where N>=2, and to perform routing through the network topology from a source to a destination based on the composite costs, wherein the multi-constraint router is adapted to determine the composite cost is determined according to:

link ⁢ ⁢ composite ⁢ ⁢ cost = ∑ i = 1 N ⁢ c i ⁡ ( metric i ) n ⁡ ( i )

where ci is a constant for the ith metric, and n(i) is an exponent for the ith metric.

35. A routing system according to claim 34 wherein the multi-constraint router is adapted to determine the composite cost according to:

description="In-line Formulae" end="lead"link composite cost=a*(1/abw)+b*Admin cost+c*Delaydescription="In-line Formulae" end="tail"

where metric1=abw is availabie bandwidth, metric2=Admin cost and metric3=Delay, and c1=“a”, which is the available bandwidth coefficient, c2=“b”, whish is the administrative cost coefficient, and c3=“c”, which is the delay coefficient, n(1)=−1, n(2)=1 and n(3)=1.

36. A routing system according to claim 34, further comprising an input for receiving on an ongoing basis for each link, updated values for the metrics for the link.

37. A routing system according to claim 34, wherein the multi-constraint router is adapted to perform the routing in a manner which promotes load balancing.

38. A routing system according to claim 37, wherein the multi-constraint router is adapted to perform the routing in a manner which promotes load balancing with demand reservation for at least one link.

39. A routing system according to claim 38, wherein the multi-constraint router is adapted to allocate at least one link to contain bandwidth reserved for higher bandwidth requests.

40. A routing system according to claim 35, wherein the multi-constraint router is adapted to compute the cost for each said at least one link as follows:

if (available bandwidth

description="In-line Formulae" end="lead"cost of link=link composite cost+MAX COSTdescription="In-line Formulae" end="tail"

description="In-line Formulae" end="lead"else cost of link=link composite costdescription="In-line Formulae" end="tail"

where demand_threshold is respective demand reservation for the link and MAX COST is a very large value.

41. A routing system according to claim 34, adapted to compute the cost for each said at least one link based on the composite cost, comprising a switching means, for switching between a load balancing mode and a bin-packing mode based on available bandwidth of each of a plurality of links under consideration in the network topology.

42. A routing system according to claim 41, wherein the switching between the load balancing and the bin-packing modes is performed based on a predetermined demand_threshold value.

43. A routing system according to claim 41, wherein the multi-constraint router is adapted to compute the cost for each link as follows:

If (abw<=demand_threshold)

description="In-line Formulae" end="lead"cost of link=a*Admin cost+b*(abwK/PIR)+c*Delay+MAX COSTdescription="In-line Formulae" end="tail"

description="In-line Formulae" end="lead"elsedescription="In-line Formulae" end="tail"

description="In-line Formulae" end="lead"cost of link=a*Admin cost+b*(PIR/abwK)+c*Delay;description="In-line Formulae" end="tail"

wherein PIR=Peak Information Rate, MAX COST is a large number, abw is the available bandwidth and K is a constant.

44. A routing system according to claim 43, wherein the constant K is used to control a rate at which the cost changes with a variation in the available bandwidth.

45. A routing system according to claim 43, wherein a different demand_threshold value is used for at least one link for achieving a different switch over point between load balancing and bin-packing.

46. A routing system according to claim 41, wherein the multi-constraint router is adapted to compute the cost for each link as follows:

If (abw<=demand_threshold)

description="In-line Formulae" end="lead"cost of link=a*Admin cost+b*(PIR/abwK)+c*Delay+MAX COSTdescription="In-line Formulae" end="tail"

description="In-line Formulae" end="lead"elsedescription="In-line Formulae" end="tail"

description="In-line Formulae" end="lead"cost of link=a*Admin cost+b*(abwK/PIR)+c*Delay;description="In-line Formulae" end="tail"

wherein PIR=Peak Information Rate, MAX COST is a large number, abw is the available bandwidth and K is a constant.

47. A routing system according to claim 45, wherein the constant K can be used to control a rate at which the cost changes with a variation in the available bandwidth.

48. A routing system according to claim 46, wherein a different demand_threshold value is used for at least one link or achieving a different switch over point between load balancing and bin-packing.

49. A routing system according to claim 34, wherein the multi-constraint router is adapted to, for each of a plurality of different traffic types, use a respective different composite cost equation for calculating the link composite costs.

50. A routing system according to claim 49, adapted to prune and compute costs only for links belonging to routes in a candidate list.