Load Balancing in an MPLS Network > Using Bandwidth to Unevenly Load-Balance RSVP LSPs

Purpose

With RSVP LSPs, load-balancing LSP traffic using bandwidth allows uneven load balancing across multiple external links that have varying amounts of available bandwidth. When you use bandwidth to load-balance an RSVP LSP, the distribution of traffic is proportional to the bandwidth configuration of each LSP. You configure load balancing at the [edit protocols rsvp] hierarchy level on the ingress router.

For uneven load balancing using bandwidth to work, you must have at least two equal-cost LSPs toward the same egress router and at least one of the LSPs must have a bandwidth value configured at the [edit protocols mpls label-switched-path lsp-path-name] hierarchy level. If no LSPs have bandwidth configured, equal distribution load balancing is performed. If only some LSPs have bandwidth configured, the LSPs without any bandwidth configured do not receive any traffic.

Keep the following information in mind when you use the load-balance statement at the [edit protocols rsvp] hierarchy level:

• The behavior of currently running LSPs is not altered. To force the currently running LSPs to use the new behavior, issue the clear mpls lsp command.
• The load-balance statement at the [edit protocols rsvp] hierarchy level only applies to ingress LSPs that have a policy with the load-balancing per-packet statement configured.
• For Differentiated Services-aware traffic-engineered LSPs, the bandwidth of an LSP is calculated by summing the bandwidth of all of the class types.

Before you can use bandwidth to unevenly load-balance LSP traffic, you must have the following configured on the ingress router:

• A policy with the load-balance per-packet statement at the [edit policy-options] hierarchy level and that policy applied as an export policy at the [edit forwarding-options] hierarchy level. For more information about configuring load balancing, see Configuring and Verifying Load Balancing.
• Bandwidth configured for each LSP at the [edit protocols mpls label-switched-path lsp-path-name] hierarchy level. For more information on configuring LSP bandwidth, see the JUNOS MPLS Applications Configuration Guide.

Figure 13 illustrates a network configured with RSVP bandwidth.

Figure 13: RSVP Bandwidth Network

The network topology in Figure 13 illustrates a router-only network with SONET and Ethernet interfaces that consists of the following components:

• A full-mesh IBGP topology, using AS 65432
• MPLS and RSVP enabled on all routers
• A send-statics policy on routers R1 and R0 that allows a new route to be advertised into the network
• Four unidirectional LSPs configured with uneven bandwidth between R1 and R0
• One reverse direction LSP between R0 and R1, which allows for bidirectional traffic
• Load balancing configured on the ingress router R1
• RSVP bandwidth configured on the ingress router R1

In addition, the example network uses OSPF as the IGP with OSPF area 0.0.0.0. An IGP is required for the CSPF LSP, which is the default for the JUNOS software. Also, the example network uses a policy to create BGP traffic.

The following information is included in this example:

1. Configure Bandwidth to Unevenly Load-Balance Traffic
2. Verify the Operation of Uneven Bandwidth Load Balancing
3. Router Configurations for Bandwidth Load Balancing