Load balancing network traffic on a label switched path using resource reservation protocol with traffic engineering

Abstract

Techniques are describe for establishing an overall label switched path (LSP) for load balancing network traffic being sent across a network using the a resource reservation protocol such as Resource Reservation Protocol with Traffic Engineering (RSVP-TE). The techniques include extensions to the RSVP-TE protocol that enable a router to send Path messages for establishing a tunnel that includes a plurality of sub-paths for the overall LSP. The tunnel may comprise a single RSVP-TE Label Switched Path (LSP) that is configured to load balance network traffic across different sub-paths of the RSVP-TE LSP over the network.

1 . A method comprising:
 with an ingress device, establishing an overall label switched path (LSP) from the ingress device to an egress device, wherein the overall LSP includes a plurality of different sub-paths to the egress device that satisfy one or more traffic-engineering constraints; and   forwarding received network traffic to the egress device over the overall LSP by load balancing the network traffic across the sub-paths of the overall LSP.   
     
     
         2 . The method of  claim 1 , further comprising:
 computing for the overall LSP a plurality of sub-paths to the egress device that satisfy a set of traffic-engineering constraints;   sending resource reservation requests to label-switching routers (LSRs) along two or more of the plurality of sub-paths of the overall LSP, wherein the resource reservation requests include an identifier associating the requests with the same overall LSP, and wherein the resource reservation requests each include an indicator specifying the requested overall LSP as a load-balancing LSP; and   receiving resource reservation messages in response to the resource reservation requests that specify reserved resources and labels allocated to the overall LSP to be used for forwarding network traffic to corresponding next hops along the sub-paths of the overall LSP, wherein the resource reservation messages include an identifier associating the messages with the same overall LSP, and wherein the resource reservation messages each include an indicator specifying the overall LSP as a load-balancing LSP.   
     
     
         3 . The method of  claim 1 , further comprising:
 configuring a forwarding plane of the ingress device to store allocated labels and corresponding next hops for the sub-paths of the overall LSP;   configuring the forwarding plane with load balancing requirements that specify how network traffic is to be load-balanced across the sub-paths of the overall LSP;   receiving network traffic at the ingress device of the overall LSP;   in the forwarding plane of the ingress device, load balancing the network traffic across the sub-paths by selecting from among the stored labels and corresponding next hops for forwarding the network traffic in accordance with load balancing requirements; and   forwarding the network traffic with the selected labels onto sub-paths of the overall LSP.   
     
     
         4 . The method of  claim 1 , wherein the network traffic comprises packets associated with a plurality of packet flowsdestined for the egress device of the overall LSP, wherein load balancing the network traffic across the sub-paths comprises applying flow-level load balancing to the received network traffic. 
     
     
         5 . The method of  claim 1 , wherein load balancing the network traffic comprises applying a hash function to a portion of a packet of the network traffic, and accessing a hash map based on the hash function to determine a Multiprotocol Label Switching (MPLS) label to apply to the packet and an output interface from which to output the packet. 
     
     
         6 . The method of  claim 1 , further comprising load balancing the network traffic across the sub-paths without re-ordering packets in packet flows of the network traffic. 
     
     
         7 . The method of  claim 1 , wherein the traffic engineering constraints comprise one or more of bandwidth, link color, and Shared Risk Link Group (SRLG). 
     
     
         8 . The method of  claim 1 , further comprising enforcing a maximum number of the sub-paths in the overall LSP. 
     
     
         9 . The method of  claim 1 , further comprising:
 evaluating traffic statistics to determine whether the sub-paths are being utilized consistent with configured traffic-engineering requirements of the overall LSP, and   dynamically updating a hash map to correct inconsistencies with respect to the configured traffic-engineering requirements.   
     
     
         10 . The method of  claim 1 , wherein the overall LSP comprises a unicast LSP. 
     
     
         11 . The method of  claim 1 , further comprising:
 detecting a network failure; and   upon detecting the network failure, dynamically updating a hash map to re-balance network traffic across the sub-paths.   
     
     
         12 . The method of  claim 1 ,
 wherein the overall LSP extends across a network from the ingress device to a plurality of egress devices, and   further comprising computing for the overall LSP a plurality of sub-paths to each of the plurality of egress devices.   
     
     
         13 . The method of  claim 12 , wherein the overall LSP comprises a unicast LSP. 
     
     
         14 . The method of  claim 12 , wherein the overall LSP comprises a load-balancing point-to-multipoint LSP for load-balancing multicast traffic, and wherein one or more of the plurality of sub-paths comprises a point-to-multipoint sub-path. 
     
     
         15 . A router comprising:
 a control unit configured to establish an overall label switched path (LSP) from an ingress device to an egress device, wherein the overall LSP includes a plurality of different sub-paths to the egress device that satisfy one or more traffic-engineering constraints, wherein the control unit is configured to load balance received network traffic across the sub-paths of the overall LSP; and   a physical interface configured to send the received network traffic across the sub-paths of the overall LSP.   
     
     
         16 . The router of  claim 15 , wherein the control unit is configured to execute a resource reservation protocol to compute for the overall LSP a plurality of alternate sub-paths to the egress device that satisfy a set of traffic-engineering constraints;
 wherein the physical interface is configured to send resource reservation requests generated by the resource reservation protocol to label-switching routers (LSRs) along two or more of the plurality of sub-paths of the overall LSP, wherein the resource reservation requests include an identifier associating the requests with the same overall LSP, and wherein the resource reservation requests each include an indicator specifying the requested overall LSP as a load-balancing LSP, and receive resource reservation messages in response to the resource reservation requests that specify reserved resources and labels allocated to the overall LSP to be used for forwarding network traffic to corresponding next hops along the sub-paths of the overall LSP, wherein the resource reservation messages include an identifier associating the messages with the same overall LSP, and wherein the resource reservation messages each include an indicator specifying the overall LSP as a load-balancing LSP.   
     
     
         17 . The router of  claim 15 , further comprising:
 a forwarding plane configured to store allocated labels and corresponding next hops for the sub-paths of the overall LSP; and   a load balancing module executing on the forwarding plane, wherein the load balancing module is configured to load balance the network traffic across the sub-paths by selecting from among the stored labels and corresponding next hops for forwarding the network traffic in accordance with load balancing requirements, and   wherein the physical interface is configured to forward the network traffic with the selected labels onto sub-paths of the overall LSP.   
     
     
         18 . The router of  claim 17 , wherein the load balancing module is configured to apply flow-level load balancing to packets associated with a plurality of packet flows received by the physical interface to load balance the packet flows across the sub-paths, wherein the load balancing module is configured to load balance the packets of the packet flows across the sub-paths without re-ordering packets in the packet flows. 
     
     
         19 . The router of  claim 15 , wherein the traffic engineering constraints comprise one or more of bandwidth, link color, and Shared Risk Link Group (SRLG). 
     
     
         20 . The router of  claim 15 , wherein the resource reservation protocol is configured to enforce a maximum number of the computed sub-paths for which resource reservation requests are sent. 
     
     
         21 . The router of  claim 15 , further comprising a link monitoring module that evaluates traffic statistics associated with each of a plurality of links of the router to determine whether the sub-paths associated with the links are being utilized consistent with configured traffic-engineering requirements of the overall LSP,
 wherein the load balancing module dynamically updates a hash map to correct inconsistencies with respect to the configured traffic-engineering requirements based on the evaluation by the link monitoring module.   
     
     
         22 . A computer-readable storage medium comprising instructions for causing a programmable processor to:
 establish an overall label switched path (LSP) from an ingress device to an egress device, wherein the overall LSP includes a plurality of different sub-paths to the egress device that satisfy one or more traffic-engineering constraints; and   forward received network traffic to the egress device over the overall LSP by load balancing the network traffic across the sub-paths of the overall LSP.