9-2z Hold timer –– When a GARP application entity receives the first registration request, it starts aHold timer and collects succeeding requests. When the timer expires, the entity sends all theserequests in one Join message. This helps you save bandwidth.z Join timer –– A GARP participant sends a Join message at most twice for reliability sake and usesa Join timer to set the sending interval. If the first Join message has not been acknowledgedbefore the Join timer expires, the GARP participant sends the second Join message.z Leave timer –– Starts upon receipt of a Leave message sent for deregistering some attributeinformation. If no Join message is received before this timer expires, the GARP participantremoves the attribute information as requested.z LeaveAll timer –– Starts when a GARP participant starts. When this timer expires, the entity sendsa LeaveAll message so that other participants can re-register its attribute information. Then, aLeaveAll timer starts again.z The settings of GARP timers apply to all GARP applications, such as GVRP, on a LAN.z On a GARP-enabled network, a device may send LeaveAll messages at the interval set by itsLeaveAll timer or the LeaveAll timer on another device on the network, whichever is smaller. Thisis because each time a device on the network receives a LeaveAll message it resets its LeaveAlltimer.Operating mechanism of GARPThe GARP mechanism allows the configuration of a GARP application entity to propagate throughouta LAN quickly. In GARP, a GARP application entity registers or deregisters its attributes with otherentities by making or withdrawing declarations of attributes and at the same time, based on receiveddeclarations or withdrawals, handles attributes of other entities. When a port receives an attributedeclaration, it registers the attribute; when a port receives an attribute withdrawal, it deregisters theattribute.GARP application entities send protocol data units (PDUs) with a particular multicast MAC address asdestination. Based on this address, a device can identify to which GVRP application (GVRP forexample) a GARP PDU will be delivered.
