3Com MSR 50 Series Configuration Manual page 272

272 C 12: GVRP C
HAPTER ONFIGURATION
A GARP participant uses Join messages to have its attributes registered on
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other devices. A GARP participant also sends Join messages to register
attributes on other GARP participants when it receives Join messages from
other GARP participants or static attributes are configured on it.
A GARP participant uses Leave messages to have its attributes deregistered on
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other devices. A GARP participant also sends Leave messages when it receives
Leave messages from other GARP participants or static attributes are
deregistered on it.
LeaveAll messages are used to deregister all the attributes, through which all
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the other GARP participants begin to have all their attributes registered. A
GARP participant sends LeaveAll messages upon the expiration of the LeaveAll
timer, which is triggered when the GARP participant is created.
Join messages, Leave messages, and LeaveAll message make sure the
reregistration and deregistration of GARP attributes are performed in an orderly
way.
Through message exchange, all attribute information that needs registration
propagates to all GARP participants throughout a bridged LAN.
2 GARP timers
The interval of sending of GARP messages is controlled by the following four
timers.
Hold timer
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A GARP participant usually does not forwards a received registration request
immediately after it receives a registration request, instead, it waits for the
expiration of the hold timer. That is, a GARP participant sends Join messages when
the hold timer expires. The Join message contains all the registration information
received during the latest Hold timer cycle. Such a mechanism saves the
bandwidth.
Join timer
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Each GARP participant sends a Join message twice for reliability sake and uses a
join timer to set the sending interval. If the first Join message is not acknowledged
after the interval defined by the Join timer, the GARP participant sends the second
Join message.
Leave timer
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A Leave timer starts upon receipt of a Leave message sent for deregistering some
attribute information. If no Join message is received before this timer expires, the
GARP application entity removes the attribute information as requested.
LeaveAll timer
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A LeaveAll timer starts when a GARP application entity starts. When this timer
expires, the entity sends a LeaveAll message so that other entities can re-register
its attribute information. Then, a LeaveAll timer starts again.