Bidirectional Forwarding Detection
(BFD)
BFD is a protocol that is used to rapidly detect communication failures between two adjacent systems. It is a
simple and lightweight replacement for existing routing protocol link state detection mechanisms. It also
provides a failure detection solution for links on which no routing protocol is used.
BFD is a simple hello mechanism. Two neighboring systems running BFD establish a session using a three-
way handshake. After the session has been established, the systems exchange periodic control packets at
sub-second intervals. If a system does not receive a hello packet within a specified amount of time, routing
protocols are notified that the forwarding path is down.
BFD provides forwarding path failure detection times on the order of milliseconds rather than seconds as with
conventional routing protocol hellos. It is independent of routing protocols, and as such, provides a
consistent method of failure detection when used across a network. Networks converge faster because BFD
triggers link state changes in the routing protocol sooner and more consistently because BFD eliminates the
use of multiple protocol-dependent timers and methods.
BFD also carries less overhead than routing protocol hello mechanisms. Control packets can be encapsulated
in any form that is convenient, and, on Dell Networking routers, BFD agents maintain sessions that reside on
the line card, which frees resources on the route processor. Only session state changes are reported to the
BFD Manager (on the route processor), which in turn notifies the routing protocols that are registered with it.
BFD is an independent and generic protocol, which all media, topologies, and routing protocols can support
using any encapsulation. Dell Networking has implemented BFD at Layer 3 and with user datagram protocol
(UDP) encapsulation. BFD is supported on static routing protocols and dynamic routing protocols such as
VRRP, OSPF, OSPFv3, IS-IS, and BGP.
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How BFD Works
Two neighboring systems running BFD establish a session using a three-way handshake.
After the session has been established, the systems exchange control packets at agreed upon intervals. In
addition, systems send a control packet anytime there is a state change or change in a session parameter.
These control packets are sent without regard to transmit and receive intervals.
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Bidirectional Forwarding Detection (BFD)
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Содержание S4048T
Страница 1: ...Dell Configuration Guide for the S4048T ON System 9 10 0 1 ...
Страница 98: ... saveenv 7 Reload the system uBoot mode reset Management 98 ...
Страница 113: ...Total CFM Pkts 10303 CCM Pkts 0 LBM Pkts 0 LTM Pkts 3 LBR Pkts 0 LTR Pkts 0 802 1ag 113 ...
Страница 411: ...mode transit no disable Force10 Resilient Ring Protocol FRRP 411 ...
Страница 590: ...Figure 67 Inspecting the LAG Configuration Link Aggregation Control Protocol LACP 590 ...
Страница 591: ...Figure 68 Inspecting Configuration of LAG 10 on ALPHA Link Aggregation Control Protocol LACP 591 ...
Страница 594: ...Figure 70 Inspecting a LAG Port on BRAVO Using the show interface Command Link Aggregation Control Protocol LACP 594 ...
Страница 595: ...Figure 71 Inspecting LAG 10 Using the show interfaces port channel Command Link Aggregation Control Protocol LACP 595 ...
Страница 646: ...Figure 87 Configuring Interfaces for MSDP Multicast Source Discovery Protocol MSDP 646 ...
Страница 647: ...Figure 88 Configuring OSPF and BGP for MSDP Multicast Source Discovery Protocol MSDP 647 ...
Страница 648: ...Figure 89 Configuring PIM in Multiple Routing Domains Multicast Source Discovery Protocol MSDP 648 ...
Страница 653: ...Figure 91 MSDP Default Peer Scenario 2 Multicast Source Discovery Protocol MSDP 653 ...
Страница 654: ...Figure 92 MSDP Default Peer Scenario 3 Multicast Source Discovery Protocol MSDP 654 ...
Страница 955: ...Figure 119 Single and Double Tag First byte TPID Match Service Provider Bridging 955 ...
Страница 1179: ...Figure 147 Create Hypervisor Figure 148 Edit Hypervisor Figure 149 Create Transport Connector Virtual Extensible LAN VXLAN 1179 ...