Alcatel-Lucent 6850-48 ネットワークガイド

802.1AB Overview

Configuring 802.1AB

page 19-4

OmniSwitch AOS Release 6 Network Configuration Guide

LLDP is a Layer 2 protocol for detecting adjacent devices in a network. Each device in a network sends 
and receives LLDPDUs through all its ports, when the protocol is enabled. If the protocol is disabled on a 
port or on a device, then LLDPDUs received on that port or device are dropped. 

The LLDPDUs are transmitted at a certain interval that can be configured. When an LLDPDU is received 
from a neighboring device, the LLDPDU software validates the frame and stores the information in its 
remote device Management Information Base (MIB). This information is aged periodically, if an 
LLDPDU is not received from the same device within the time mentioned in the TTL TLV of the 
LLDPDU. By exchanging information with all the neighbors, each device will know its neighbor on each 
port. The information within the LLDPDU is transmitted in TLV (Type, Length, Value) format and falls 
under two categories:

• Mandatory

• Optional

Each LLDPDU contains all the four mandatory TLVs and optional TLVs.

The mandatory TLV's information contains the LAN device's MAC service access point (MSAP) identi-
fier and the time period for the validity of the LAN device's associated information.The mandatory TLVs 
contained in a LLDPDU are listed below:

• Chassis ID TLV

• Port ID TLV

• Time to live TLV

• End of LLDPDU TLV

The optional TLVs defined as part of LLDP are grouped into the following sets listed below:

• Port Description TLV

• System Name TLV

• System Description TLV

• System capabilities TLV

• Management address TLV

Note. This optional TLV set is required for all LLDP implementation.