
Operation Manual – BFD-GR
H3C S3610&S5510 Series Ethernet Switches
Chapter 1 BFD Configuration
1-3
During session initialization, at least one end of the two in communication must operate
in the active mode for a session to be established.
After a BFD session is established, there are two BFD operation modes: asynchronous
and query. Both ends in communication must operate in the same mode.
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Asynchronous mode: A device operating in the asynchronous mode periodically
sends BFD control packets. It tears down the BFD session if it receives no BFD
control packet from the peer within the BFD interval.
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Query mode: This mode assumes that every protocol acknowledges its
connection to another protocol by using its unique method. In this way, the
protocol stops sending BFD control packets as long as a BFD session is
established, unless a protocol needs to explicitly verify the connectivity.
Note:
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At present, only the asynchronous mode is supported.
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At present, BFD can be implemented in the Echo mode for static routes only and in
a way different from that defined in the BFD draft.
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When a BFD session operates in the Echo mode, the session is independent of the
operation mode.
V. Dynamic BFD parameter changes
After a BFD session is established, both ends can negotiate the related BFD
parameters, such as the minimum transmit interval, minimum receive interval,
initialization mode, and packet authentication. After that, both ends use the negotiated
parameter settings, without affecting the current session state.
VI. Authentication modes
BFD provides the following authentication methods:
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Simple: Plain text authentication
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MD5: MD5 (Message Digest 5) authentication
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SHA1: SHA1 (Secure Hash Algorithm 1) authentication
1.1.2 BFD Packet Format
illustrates the BFD control packet format.