Allied Telesis AT-S62 - Manual (Page 589)

AT-S62 Management Software Menus Interface User’s Guide
Section V: VLANs 589
Applicant and Registrar. This is shown in Figure 199.
Figure 199. GID Architecture
GARP registers and de-registers attribute values through GARP
messages sent at the GID level. A GARP Participant that wishes to make
a declaration (an Applicant registering an attribute value) sends a JoinIn or
JoinEmpty message. An Applicant that wishes to withdraw a declaration
(de-registering an attribute value) sends a LeaveEmpty or LeaveIn
message. Following the de-registration of an attribute value, the Applicant
sends a number of Empty messages. The purpose of the Empty message
is to prompt other Applicants to send JoinIn/JoinEmpty messages. For the
GARP protocol to be resilient against multiple lost messages, a LeaveAll
message is available. Timers are used in the state machines to generate
events and control state transitions.
The job of the Applicant is twofold:
ˆ To ensure that this Participant’s declarations are registered by other
Participants’ Registrars
ˆ To ensure that other Participants have a chance to re-declare (rejoin)
after anyone withdraws a declaration (leaves).
The Applicant is therefore looking after the interests of all would-be
Participants. This allows the Registrar to be very simple.
The job of the Registrar is to record whether an attribute is registered, in
the process of being de-registered, or is not registered for an instance of
GID.
Attribute ... state:
Attribute C state:
Attribute A state:
Applicant
State Registrar
State
Attribute B state:
GID