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ME60 V800R010C10SPC500 Feature Description - MPLS 01

This is ME60 V800R010C10SPC500 Feature Description - MPLS
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BFD for BGP Tunnel

BFD for BGP Tunnel

Background

The IP/MPLS network shown in Figure 5-19 transmits VPN services. PEs, such as a CSG, AGG, ASBR, and MASG, establish multi-segment MPLS tunnels between directly connected devices. In this case, VPN service provision on PEs is complex, and the VPN service scalability decreases. As PEs establish BGP peer relationships, a routing policy can be used to assign MPLS labels for BGP routes so that an E2E BGP tunnel can be established. The BGP tunnel consists of a primary BGP LSP and a backup BGP LSP. VPN services can travel along the E2E BGP tunnel, which simplifies service provision and improves VPN service scalability.

Figure 5-19 E2E BGP tunnel application

To rapidly detect faults in an E2E BGP tunnel, BFD for BGP tunnel is used. BFD for BGP tunnel establish a dynamic BFD session, also called a BGP BFD session, which is bound to both the primary and backup BGP LSPs. If both BGP LSPs fail, the BGP BFD session detects the faults and triggers VPN FRR switching.

Usage Scenarios

BFD for BGP tunnel is used in the following scenarios:

  • Inter-AS VPN Option C scenario

  • Intra- or inter-AS seamless MPLS scenario

Principles

Dynamic BGP BFD sessions are established using either of the following policies:

  • Host address-based policy: used when all host addresses are available to trigger the creation of BGP BFD sessions.

  • IP address prefix list-based policy: used when only some host addresses can be used to establish BFD sessions.

A BGP BFD session working in asynchronous mode monitors BGP LSPs over BGP tunnels. In Figure 5-20, the ingress (CSG) and egress (MASG) of E2E BGP LSPs exchange BFD packets periodically. The forward path is a BGP LSP, and the reverse path is an IP route. If either node receives no BFD packet after a specified detection period elapses, the node considers the BGP LSP faulty. If both the primary and backup BGP LSPs fail, the BGP BFD session triggers VPN FRR switching.

Figure 5-20 BFD for BGP tunnel
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Updated: 2019-01-04

Document ID: EDOC1100059460

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