Demand mode
If one system requests Demand mode, the other system stops sending periodic control packets; it only sends a
response to status inquiries from the Demand mode initiator. Either system (but not both) can request Demand
mode at any time.
NOTE:
Dell Networking OS supports Asynchronous mode only.
A session can have four states: Administratively Down, Down, Init, and Up.
State
Description
Administratively
Down
The local system does not participate in a particular session.
Down
The remote system is not sending control packets or at least not within the detection time for a particular session.
Init
The local system is communicating.
Up
Both systems are exchanging control packets.
The session is declared down if:
•
A control packet is not received within the detection time.
•
Sufficient echo packets are lost.
•
Demand mode is active and a control packet is not received in response to a poll packet.
BFD Three-Way Handshake
A three-way handshake must take place between the systems that participate in the BFD session.
The handshake shown in the following illustration assumes that there is one active and one passive system, and that this session is the first
session established on this link. The default session state on both ports is Down.
1
The active system sends a steady stream of control packets that indicates that its session state is Down, until the passive system
responds. These packets are sent at the desired transmit interval of the Active system. The Your Discriminator field is set to zero.
2
When the passive system receives any of these control packets, it changes its session state to Init and sends a response that
indicates its state change. The response includes its session ID in the My Discriminator field and the session ID of the remote system
in the Your Discriminator field.
3
The active system receives the response from the passive system and changes its session state to Up. It then sends a control packet
indicating this state change. This is the third and final part of the handshake. Now the discriminator values have been exchanged and
the transmit intervals have been negotiated.
4
The passive system receives the control packet and changes its state to Up. Both systems agree that a session has been established.
However, because both members must send a control packet — that requires a response — anytime there is a state change or
change in a session parameter, the passive system sends a final response indicating the state change. After this, periodic control
packets are exchanged.
Bidirectional Forwarding Detection (BFD)
147
Содержание S4048T-ON
Страница 1: ...Dell Configuration Guide for the S4048 ON System 9 11 2 1 ...
Страница 148: ...Figure 10 BFD Three Way Handshake State Changes 148 Bidirectional Forwarding Detection BFD ...
Страница 251: ...Dell Control Plane Policing CoPP 251 ...
Страница 363: ... RPM Synchronization GARP VLAN Registration Protocol GVRP 363 ...
Страница 511: ...Figure 64 Inspecting the LAG Configuration Link Aggregation Control Protocol LACP 511 ...
Страница 512: ...Figure 65 Inspecting Configuration of LAG 10 on ALPHA 512 Link Aggregation Control Protocol LACP ...
Страница 515: ...Figure 67 Inspecting a LAG Port on BRAVO Using the show interface Command Link Aggregation Control Protocol LACP 515 ...
Страница 516: ...Figure 68 Inspecting LAG 10 Using the show interfaces port channel Command 516 Link Aggregation Control Protocol LACP ...
Страница 558: ...Figure 84 Configuring Interfaces for MSDP 558 Multicast Source Discovery Protocol MSDP ...
Страница 559: ...Figure 85 Configuring OSPF and BGP for MSDP Multicast Source Discovery Protocol MSDP 559 ...
Страница 560: ...Figure 86 Configuring PIM in Multiple Routing Domains 560 Multicast Source Discovery Protocol MSDP ...
Страница 564: ...Figure 88 MSDP Default Peer Scenario 2 564 Multicast Source Discovery Protocol MSDP ...
Страница 565: ...Figure 89 MSDP Default Peer Scenario 3 Multicast Source Discovery Protocol MSDP 565 ...
Страница 729: ...protocol spanning tree pvst no disable vlan 300 bridge priority 4096 Per VLAN Spanning Tree Plus PVST 729 ...
Страница 841: ...Figure 115 Single and Double Tag TPID Match Service Provider Bridging 841 ...
Страница 842: ...Figure 116 Single and Double Tag First byte TPID Match 842 Service Provider Bridging ...