3Com 2928 - Baseline Plus Switch PWR, User Manual

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1-2
Field Description
Source MAC address
The MAC address of the sending port. If the port does not have a MAC
address, the MAC address of the sending bridge is used.
Type The Ethernet type for the upper layer protocol. It is 0x88CC for LLDP.
Data LLDP data.
FCS
Frame check sequence, a 32-bit CRC value used to determine the
validity of the received Ethernet frame.
2) LLDPDUs encapsulated in SNAP
Figure 1-2
LLDPDU encapsulated in SNAP
Data = LLDPU
(n bytes)
0
Destination MAC address
Source MAC address
Type
15 31
FCS
The fields in the frame are described in
Table 1-2 :
Table 1-2
Description of the fields in a SNAP encapsulated LLDPDU
Field Description
Destination MAC address The MAC address to which the LLDPDU is advertised. It is fixed to
0x0180-C200-000E, a multicast MAC address.
Source MAC address
The MAC address of the sending port. If the port does not have a MAC
address, the MAC address of the sending bridge is used.
Type
The SNAP-encoded LLDP Ethernet type for the upper layer protocol. It
is 0xAAAA-0300-0000-88CC for LLDP.
Data LLDP data unit.
FCS
Frame check sequence, a 32-bit CRC value used to determine the
validity of the received Ethernet frame.
LLDPDUs
LLDP uses LLDPDUs to exchange information. An LLDPDU comprises multiple type, length, and value
(TLV) sequences, each carrying a type of device information, as shown in
Figure 1-3 .
Figure 1-3
An LLDPDU