HP 4800G Series Configuration Manual page 169

Hold timer –– When a GARP application entity receives the first registration request, it starts a Hold
timer and collects succeeding requests. When the timer expires, the entity sends all these requests
in one Join message. This helps you save bandwidth.
Join timer –– A GARP participant sends a Join message at most twice for reliability sake and uses
a Join timer to set the sending interval. If the first Join message has not been acknowledged before
the Join timer expires, the GARP participant sends the second Join message.
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 participant
removes the attribute information as requested.
LeaveAll timer –– Starts when a GARP participant starts. When this timer expires, the entity sends
a LeaveAll message so that other participants can re-register its attribute information. Then, a
LeaveAll timer starts again.
The settings of GARP timers apply to all GARP applications, such as GVRP, on a LAN.
On a GARP-enabled network, a device may send LeaveAll messages at the interval set by its
LeaveAll timer or the LeaveAll timer on another device on the network, whichever is smaller. This is
because each time a device on the network receives a LeaveAll message it resets its LeaveAll
timer.
Operating mechanism of GARP
The GARP mechanism allows the configuration of a GARP application entity to propagate throughout a
LAN quickly. In GARP, a GARP application entity registers or deregisters its attributes with other entities
by making or withdrawing declarations of attributes and at the same time, based on received
declarations or withdrawals, handles attributes of other entities. When a port receives an attribute
declaration, it registers the attribute; when a port receives an attribute withdrawal, it deregisters the
attribute.
GARP application entities send protocol data units (PDUs) with a particular multicast MAC address as
destination. Based on this address, a device can identify to which GVRP application (GVRP for example)
a GARP PDU will be delivered.
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