Lldp; Overview Of Lldp; Lldp Operation - GE PACSystems RX3i User Manual

Chapter 7. Network Management
7.2

LLDP

The PROFINET Controller implements the Link Layer Discovery Protocol (LLDP). A PROFINET IO-Supervisor or
other network host may use LLDP to discover the PROFINET network.
7.2.1

Overview of LLDP

The Link Layer Discovery Protocol is an IEEE standardized protocol used by network devices to advertise their
identities and capabilities and receive that information from physically adjacent link layer peers.
LLDP data packets are sent by devices from each of their interfaces at fixed intervals. The LLDP packets are
multicast and are not forwarded by network switches.
Each LLDP packet consists of one LLDP Data Unit (LLDPDU). Each LLDPDU is a sequence of Type-Length-Value
(TLV) structures.
7.2.1.1 LLDP Data Unit Contents
Chassis ID TLV structure (mandatory, always first)
Port ID TLV structure (mandatory, always second)
Time to Live TLV structure (mandatory, always third)
Optional Structures (any number of these, in any order)
End of PDU TLV (mandatory, always last)
7.2.2

LLDP Operation

The LLDP agent in the PROFINET Controller multicasts LLDP messages to the network at 5 second intervals, or
when a change occurs in any of the local data that is delivered within the LLDP message. The LLDP messages
are transmitted from each external port that is connected to a network.
146 PACSystems* RX3i & RSTi-EP PROFINET IO-Controller User Manual
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