GARP Timers
The GARP protocol defines four timers:
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Join timer
The Join timer controls sending of Join messages including JoinIn messages and JoinEmpty
messages.
After sending the first Join message, a participant starts the Join timer. If the participant
receives a JoinIn message before the Join timer expires, it does not send the second Join
message. If the participant does not receive any JoinIn message, it sends the second Join
message when the Join timer expires. This ensures that the Join message can be sent to
other participants. Each port maintains an independent Join timer.
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Hold timer
The Hold timer controls sending of Join messages (JoinIn messages and JoinEmpty
messages) and Leave messages (LeaveIn messages and LeaveEmpty messages).
After a participant is configured with an attribute or receives a message, it does not send
the message to other participants before the Hold timer expires. The participant
encapsulates messages received within the hold time into a minimum number of packets,
reducing the packets sent to other participants. If the participant does not use the Hold timer
but forwards a message immediately after receiving one, a large number of packets are
transmitted on the network. This makes the network unstable and wastes data fields of
packets.
Each port maintains an independent Hold timer. The Hold timer value must be equal to or
smaller than half of the Join timer value.
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Leave timer
The Leave timer controls attribute deregistration.
A participant starts the Leave timer after receiving a Leave or LeaveAll message. If the
participant does not receive any Join message of the corresponding attribute before the
Leave timer expires, the participant deregisters the attribute.
A participant sends a Leave message if one of its attributes is deleted, but this attribute may
still exist on other participants. Therefore, the participant receiving the Leave message
cannot deregister the attribute immediately and needs to wait for messages from other
participants.
For example, an attribute has two sources on the network: participant A and participant B.
Other participants register the attribute through GARP. If the attribute is deleted from
participant A, participant A sends a Leave message to other participants. After receiving
the Leave message, participant B sends a Join message to other participants because the
attribute still exists on participant B. After receiving the Join message from participant B,
other participants retain the attribute. Other participants deregister the attribute only if they
do not receive any Join message of the attribute within a period longer than two times the
Join timer value. Therefore, the Leave timer value must be greater than two times the Join
timer value.
Each port maintains an independent Leave timer.
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LeaveAll timer
When a GARP participant starts, it starts the LeaveAll timer. When the LeaveAll timer
expires, the participant sends a LeaveAll message and restarts the LeaveAll timer.
Huawei AR530&AR550 Series Industrial Switch Routers
Configuration Guide - Ethernet Switching
5 GVRP Configuration
Issue 01 (2014-11-30)
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