Deployment Guide

Figure 20. Type, Length, Value (TLV) Segment
TLVs are encapsulated in a frame called an LLDP data unit (LLDPDU), which is transmitted from one LLDP-enabled device to its LLDP-
enabled neighbors. LLDP is a one-way protocol. LLDP-enabled devices (LLDP agents) can transmit and/or receive advertisements, but
they cannot solicit and do not respond to advertisements.
There are ve types of TLVs (as shown in the below table). All types are mandatory in the construction of an LLDPDU except Optional
TLVs. You can congure the inclusion of individual Optional TLVs.
Table 14. Type, Length, Value (TLV) Types
Type TLV Description
0
End of LLDPDU Marks the end of an LLDPDU.
1
Chassis ID The Chassis ID TLV is a mandatory TLV that identies the chassis containing the IEEE
802 LAN station associated with the transmitting LLDP agent.
2
Port ID The Port ID TLV is a mandatory TLV that identies the port component of the MSAP
identier associated with the transmitting LLDP agent.
3
Time to Live The Time To Live TLV indicates the number of seconds that the recipient LLDP agent
considers the information associated with this MSAP identier to be valid.
—
Optional Includes sub-types of TLVs that advertise specic conguration information. These sub-
types are Management TLVs, IEEE 802.1, IEEE 802.3, and TIA-1057 Organizationally
Specic TLVs.
Figure 21. LLDPDU Frame
156
Link Layer Discovery Protocol (LLDP)