R3303-HP HSR6800 Routers Layer 2 - LAN Switching Configuration Guide

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• Join messages
A GARP participant sends Join messages when it wishes to declare its attribute values or receives
Join messages from other GARP participants.
Join messages include the following categories:
{ JoinEmpty—A GARP participant sends JoinEmpty messages to declare attribute values that it
has not registered.
{ JoinIn—A GARP participant sends JoinIn messages to declare attribute values that it has
registered.
• Leave messages
A GARP participant sends Leave messages when it wishes to withdraw declarations of its attribute
values (because, for example, it has deregistered its attribute values), or receives Leave messages
from other participants.
Leave messages include the following categories:
{ LeaveEmpty—A GARP participant sends LeaveEmpty messages to withdraw declarations of the
attribute values that it has not registered.
{ LeaveIn—A GARP participant sends LeaveIn messages to withdraw declarations of the attribute
values that it has registered.
• LeaveAll messages
A GARP participant sends a LeaveAll message when it declares that it is deregistering all attribute
values or receives LeaveAll messages from other participants. If any participants want to maintain
the registration for a particular attribute value, they must send a Join message.
GARP timers
GARP uses the following timers to control GARP message transmission:
• Hold timer—The Hold timer sets the delay that a GARP participant waits before sending a Join or
Leave message.
When an attribute value changes or a Join or Leave message arrives, the GARP participant does
not send the message immediately. Rather, it assembles Join and Leave messages in the least
number of GARP PDUs, and sends them out when the Hold timer expires. This timer reduces the
number of GARP PDUs that are sent to save bandwidth.
• Join timer—A GARP participant can declare an attribute twice to ensure reliable transmission. The
Join timer sets the interval to wait between the two declarations.
A GARP participant starts a Join timer when it declares an attribute value or receives a JoinIn
message for the attribute value. If the GARP participant does not receive any declaration for the
attribute value when the Join timer expires, it re-declares the attribute value.
Because all attributes of a GARP participant share the same Join timer, you must set the Join timer
long enough so that all attributes can be sent in one declaration.
• Leave timer—A GARP participant starts a Leave timer when it receives a Leave message for an
attribute value. If the GARP participant has not received a Join message for the attribute value
before the Leave timer expires, it deregisters the attribute value.
• LeaveAll timer—When a GARP application is enabled, it starts a LeaveAll timer. The GARP
participant sends a LeaveAll message when the timer expires. Then, the LeaveAll timer restarts to
begin a new cycle. The LeaveAll timer and all other GARP timers also restart when the GARP
participant receives a LeaveAll message.