Multi-layer detection
BFD is gradually developed from basic transmission technology, so it can detect failures at all levels of the network. It can be used to detect various types of transmission correctness including Ethernet, multi-protocol mark switch (MPLS) paths, ordinary routing encapsulation, and IPSec tunnels.
Essentially, BFD is a high-speed independent HELLO protocol (similar to those used in routing protocols such as Open Shortest Path First Protocol (OSPF), or an intermediate system to intermediate system protocol that can establish contact with links, interfaces, tunnels, routing, or other network forwarding components).
BFDs are able to establish peer relationships with adjacent systems, and each system then monitors the BFD rate from other systems at a negotiated rate. The monitoring rate can be set in millisecond increments.
When the peer system does not receive a preset number of packets, it infers that the software or hardware infrastructure protected by the BFD has failed, regardless of whether the infrastructure is a tag switch path, other types of tunnels, or a switched Ethernet network.
BFD is deployed on the control plane of routers and other systems. Network failures detected by BFD can be restored by a forwarding plane (e.g. in MPLS fast restart routing) or by a control plane (e.g. when BFD is used to speed up routing protocols).
Simple solution
The simplicity of BFD enables it to be used in some forwarding fault detection solutions. For example, VoIP media gateways are connected to applications on IP cores over switched Ethernet.
This type of application presents two challenges: 1. Currently, media gateways do not maintain peer relationships on the IP layer, so there is a lack of a visible means to detect failures between media gateways and IP edge routers. 2. Ethernet cannot notify hosts or routers that a long-distance part of the switched network has failed. Rapid fault detection is very important for the high availability of VoIP networks, but it is not easy to quickly detect link failures when there is an intermediate router between the host and the router.
BFD is simple enough to be included in the media gateway platform. In the example of a media gateway, the BFD may be used to maintain connectivity between the gateway and the edge router.
The fault on the intermediate Ethernet segment will be detected by the BFD, which allows the gateway and router to switch to the prepared redundant path. Once the failure is detected and confirmed, BFD can trigger problem-solving mechanisms in all routing, transmission and tunneling systems.
Because BFD's mission is simple and abstract, it can focus on detecting forwarding failures as quickly as possible, thereby allowing voice, video and other demanding services to be successful. A protocol like BFD will enable service providers to provide VoIP and other real-time services on IP at the level of reliability and availability required by customers.
Article entry: csh Editor in charge: csh