No relevant resource is found in the selected language.

This site uses cookies. By continuing to browse the site you are agreeing to our use of cookies. Read our privacy policy>Search


To have a better experience, please upgrade your IE browser.


Feature Description - MPLS 01

NE05E and NE08E V300R003C10SPC500

This is NE05E and NE08E V300R003C10SPC500 Feature Description - MPLS

Rate and give feedback:
Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).


BFD for TE is an end-to-end rapid detection mechanism supported by MPLS TE. BFD for TE rapidly detects faults in links on an MPLS TE tunnel. BFD for TE supports BFD for TE tunnel and BFD for TE CR-LSP. This section describes BFD for TE CR-LSP only.

Traditional detection mechanisms, such as RSVP Hello and Srefresh, detect faults slowly. BFD rapidly sends and receives packets to detect faults in a tunnel. If a fault occurs, BFD triggers a traffic switchover to protect traffic.

Figure 4-32 BFD

On the network shown in Figure 4-32, BFD is disabled. If LSRE fails, LSRA or LSRF cannot promptly detect the fault because a Layer 2 switch exists between them. Although the Hello mechanism detects the fault, detection lasts for a long time.

If LSRE fails, LSRA and LSRF detect the fault rapidly, and traffic switches to the path LSRA -> LSRB -> LSRD -> LSRF.

BFD for TE detects faults in a CR-LSP. After detecting a fault in a CR-LSP, BFD for TE immediately notifies the forwarding plane of the fault to rapidly trigger a traffic switchover. BFD for TE is usually used together with a hot-standby CR-LSP.

The concepts associated with BFD are as follows:

  • Static BFD session: established by manually setting the local and remote discriminators. The local discriminator on a local node must match the remote discriminator on a remote node. The minimum intervals at which BFD packets are sent and received are changeable after a static BFD session is established.

  • Detection period: an interval at which the system checks the BFD session status. If no packet is received from the remote end within a detection period, the BFD session is considered Down.

A BFD session is bound to a CR-LSP. A BFD session is set up between the ingress and egress. A BFD packet is sent by the ingress to the egress along a CR-LSP. Upon receipt, the egress responds to the BFD packet. The ingress can rapidly monitor the status of links through which the CR-LSP passes based on whether a reply packet is received.

If a link fault is detected, BFD notifies the forwarding module of the fault. The forwarding module searches for a backup CR-LSP and switches traffic to the backup CR-LSP. In addition, the forwarding module reports the fault to the control plane. If static BFD for TE CR-LSP is used, a BFD session is created manually to detect faults in the backup CR-LSP if necessary.

Figure 4-33 BFD sessions before and after a switchover

On the network shown in Figure 4-33, a BFD session is set up to detect faults in the link through which the primary CR-LSP passes. If a link fault occurs, the BFD session on the ingress immediately notifies the forwarding plane of the fault. The ingress switches traffic to the bypass CR-LSP and sets up a new BFD session to detect faults in the bypass CR-LSP.

BFD for TE Deployment

The networking shown in Figure 4-34 applies to BFD for TE CR-LSP and BFD for hot-standby CR-LSP.

Figure 4-34 BFD for TE

Switchover between the primary and hot-standby CR-LSPs

On the network shown in Figure 4-34, a primary CR-LSP is established along the path LSRA -> LSRB, and a hot-standby CR-LSP is configured. A BFD session is set up between LSRA and LSRB to detect faults in the primary CR-LSP. If a fault occurs on the primary CR-LSP, the BFD session rapidly notifies LSRA of the fault. After receiving the fault information, LSRA rapidly switches traffic to the hot-standby CR-LSP to ensure traffic continuity.

Updated: 2019-01-14

Document ID: EDOC1100058933

Views: 11258

Downloads: 12

Average rating:
This Document Applies to these Products

Related Version

Related Documents

Previous Next