(Optional) Configuring Flow Label-based Load Balancing

Context

Flow label-based load balancing enables Layer 2 virtual private network (L2VPN) data flows to be forwarded along different paths based on flow labels.

In an L2VPN scenario shown in Figure 1, the interfaces connecting the P device and PE2 as well as connecting PE2 and the CE are added to Eth-Trunks. Service flows from the same L2VPN use the same inner private label and outer public label. If label-based load balancing is used, the service flows cannot be load balanced along links in an Eth-Trunk because the service flows have the same hash factor. Flow labels can solve this problem. Ingress PE1 distributes a flow label to each service flow to uniquely identify this service flow. This flow label is stored in the innermost layer in the label stack on Ingress PE1. Egress PE2 can pop out flow labels. After flow labels are assigned, the P device and Egress PE2 can load balance flows in an Eth-Trunk based on the flow labels.

Figure 1 Eth-Trunk load balancing based on flow labels in an L2VPN scenario

Currently, only the following techniques support flow label-based load balancing in an L2VPN scenario: static virtual circuit (SVC) and Martini virtual leased line (VLL), dynamic pseudo wire emulation edge-to-edge (PWE3), and Martini virtual private LAN service (VPLS)

Procedure

Perform the following operations to enable flow label-based load balancing on all PWs in a VSI:
1. Run system-view
  The system view is displayed.
2. Run vsi vsi-name
  The VSI view is displayed.
3. Run pwsignal ldp
  The VSI-LDP view is displayed.
4. Run flow-label { both | send | receive } [ static ]
  Flow label-based load balancing is enabled.
  - Flow label-based load balancing can be enabled only when any of the following conditions is true:
    The receive parameter is configured on the local PE, and the send parameter is configured on the remote PE.
    The send parameter is configured on the local PE, and the receive parameter is configured on the remote PE.
    Both the send and receive parameters are configured on the local and remote PEs.
  - If static is configured, the flow label-based load balancing capability is statically configured. For dynamic PWs, if static is not configured, the flow label-based load balancing capability of the local end is negotiated by the remote end. For static PWs, the flow label-based load balancing capability is statically configured, irrespective of whether static is configured.
    
    If the static flow label-based load balancing configuration does not match on both ends, the device discards packets carrying a flow label, causing packet loss.
Perform the following operations to enable flow label-based load balancing on a specified PW in a VSI:
1. Run system-view
  The system view is displayed.
2. Run vsi vsi-name
  The VSI view is displayed.
3. Run pwsignal ldp
  The VSI-LDP view is displayed.
4. Run peer peer-address [ negotiation-vc-id vc-id ] pw pw-name
  The PW view is displayed.
5. (Optional) Run flow-label disable
  The flow label function is disabled for the PW.
  
  The flow label function has been enabled for a VSI by using the flow-label command. If the PW does not require the flow label function, you can run this command to disable the flow label function for the PW.
6. Run flow-label { both | send | receive } [ static ]
  Flow label-based load balancing is enabled.
  - Flow label-based load balancing can be enabled only when any of the following conditions is true:
    The receive parameter is configured on the local PE, and the send parameter is configured on the remote PE.
    The send parameter is configured on the local PE, and the receive parameter is configured on the remote PE.
    Both the send and receive parameters are configured on the local and remote PEs.
  - If static is configured, the flow label-based load balancing capability is statically configured. For dynamic PWs, if static is not configured, the flow label-based load balancing capability of the local end is negotiated by the remote end. For static PWs, the flow label-based load balancing capability is statically configured, irrespective of whether static is configured.
    
    If the static flow label-based load balancing configuration does not match on both ends, the device discards packets carrying a flow label, causing packet loss.