3com WX3000 User Manual
1-3
Figure 1-1 Format of GARP packets
Ethernet Frame
PDU
DA
DA
length
DSAP
Ctrl
SSAP
Protocol ID
Message 1
Message N
...
End Mark
1
3
N
Attribute Type
Attribute List
1
2
N
Attribute 1
Attribute N
...
End Mark
1
N
Attribute Length
Attribute Event
Attribute Vlaue
1
2
3
N
GARP PDU structure
Message structure
Attribute List structure
Attribute structure
The following table describes the fields of a GARP packet.
Table 1-1 Description of GARP packet fields
Field
Description
Value
Protocol ID
Protocol ID
1
Message
Each message consists of two parts:
Attribute Type and Attribute List.
Attribute Type and Attribute List.
—
Attribute Type
Defined by the specific GARP
application
application
The attribute type of GVRP is 0x01.
Attribute List
It contains multiple attributes.
—
Attribute
Each general attribute consists of
three parts: Attribute Length,
Attribute Event, and Attribute Value.
three parts: Attribute Length,
Attribute Event, and Attribute Value.
Each LeaveAll attribute consists of
two parts: Attribute Length and
LeaveAll Event.
two parts: Attribute Length and
LeaveAll Event.
—
Attribute Length
The length of the attribute
2 to 255 (in bytes)
Attribute Event
The event described by the attribute
0: LeaveAll Event
1: JoinEmpty
2: JoinIn
3: LeaveEmpty
4: LeaveIn
5: Empty
Attribute Value
The value of the attribute
For GVRP packets, the value of this
field is the VLAN ID; however, for
LeaveAll messages, this field is invalid.
field is the VLAN ID; however, for
LeaveAll messages, this field is invalid.
End Mark
End mark of an GARP PDU
The value of this field is fixed to 0x00.