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BFD does not have a discovery mechanism; sessions must be explicitly configured between endpoints. BFD may be used on many different underlying transport mechanisms and layers, and operates independently of all of these. Therefore, it needs to be encapsulated by whatever transport it uses. For
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In June 2011 the BFD protocol standardization process entered the
Proposed Standard stage. RFC 5880 defines the BFD protocol, detecting MPLS LSP failure, using BFD to monitor connectivity across multiple network hops, and using BFD for
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BFD establishes a session between two endpoints over a particular link. If more than one link exists between two systems, multiple BFD sessions may be established to monitor each one of them. The session is established with a
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function. When this function is active, a stream of Echo packets is sent, and the other endpoint then sends these back to the sender via its forwarding plane. This is used to test the forwarding path on the remote system.
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packets are exchanged after the session is established; it is assumed that the endpoints have another way to verify connectivity to each other, perhaps on the underlying physical layer. However, either host may still send
82:, BGP or RIP may also be used to bootstrap a BFD session. These protocols may then use BFD to receive faster notification of failing links than would normally be possible using the protocol's own
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66:, and is torn down the same way. Authentication may be enabled on the session. A choice of simple password, MD5 or SHA1 authentication is available.
42:. It provides low-overhead detection of faults even on physical media that doesn't support failure detection of any kind, such as
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packets to each other. If a number of those packets are not received, the session is considered down.
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example, monitoring MPLS LSPs involves piggybacking session establishment on
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Regardless of which mode is in use, either endpoint may also initiate an
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Bidirectional
Forwarding Detection (BFD) for IPv4 and IPv6 (Single Hop)
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packets. Protocols that support some form of adjacency setup, such as
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97:. In asynchronous mode, both endpoints periodically send
146:protocols has also been outlined in RFC 5881..
311:Reducing Link Failure Detection Time with BFD
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89:A session may operate in one of two modes:
30:that is used to detect faults between two
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166:Bidirectional Forwarding Detection (BFD)
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284:"BFD presentation by Juniper Networks"
138:. BFD's operation in conjunction with
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20:Bidirectional Forwarding Detection
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233:Internet Engineering Task Force
171:Internet Engineering Task Force
225:D. Katz; D. Ward (June 2010).
163:D. Katz; D. Ward (June 2010).
1:
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215:.
56:MPLS label-switched paths
140:Open Shortest Path First
16:Fault detection protocol
309:NetworkWorld article:
278:IETF BFD Working Group
203:Updated by RFC
113:packets if needed.
104:In demand mode, no
64:three-way handshake
336:Network management
331:Internet Standards
326:Internet protocols
263:Proposed Standard.
201:Proposed Standard.
91:asynchronous mode
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289:. Archived from
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242:10.17487/RFC5881
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180:10.17487/RFC5880
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48:virtual circuits
28:network protocol
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125:Standardization
38:connected by a
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296:on 2005-11-04.
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272:External links
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291:the original
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142:(OSPF) and
95:demand mode
86:mechanism.
320:Categories
150:References
251:2070-1721
189:2070-1721
84:keepalive
235:(IETF).
173:(IETF).
72:LSP-Ping
44:Ethernet
36:switches
52:tunnels
32:routers
26:) is a
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294:(PDF)
287:(PDF)
144:IS-IS
111:Hello
106:Hello
99:Hello
80:IS-IS
305:5880
258:5881
247:ISSN
213:8562
211:and
209:7880
205:7419
196:5880
185:ISSN
136:IPv6
134:and
132:IPv4
118:Echo
93:and
76:OSPF
54:and
40:link
301:RFC
255:RFC
237:doi
193:RFC
175:doi
34:or
24:BFD
322::
253:.
245:.
231:.
207:,
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183:.
169:.
78:,
58:.
50:,
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260:.
239::
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177::
22:(
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