What is the difference between LLDP and LLDP-MED? Is LLDP-MED an add-on to LLDP or something completely different?

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Media Endpoint Discovery is an enhancement of LLDP, known as LLDP-MED, that provides the following facilities:

  • Auto-discovery of LAN policies (such as VLAN, Layer 2 Priority and Differentiated services (Diffserv) settings) enabling plug and play networking.
  • Device location discovery to allow creation of location databases and, in the case of Voice over Internet Protocol (VoIP), Enhanced 911 services.
  • Extended and automated power management of Power over Ethernet (PoE) end points.
  • Inventory management, allowing network administrators to track their network devices, and determine their characteristics (manufacturer, software and hardware versions, serial or asset number).

The LLDP-MED protocol extension was formally approved and published as the standard ANSI/TIA-1057 by the Telecommunications Industry Association (TIA) in April 2006.


Link Layer Discovery (IEEE-802.1AB-2005) provides the base capabilities for discovery, but was seen as insufficent for IP Telephony and Real Time Video. So the LLDP-MED initiative was formed by HP, Mitel and Avaya in 2004. What does LLDP-MED provide?

  • Interoperability > provide vendor independent management capabilities, enabling different convergence endpoints to interoperate on one network.
  • Automatic deployment of convergence network policies > voice VLAN, Layer 2 and DSCP QoS policies.
  • Location Services, including Emergency Call Services > enablement of E-911, 999, 112for IP Telephony through physical location.
  • Detailed Inventory Management Capabilities > location information and accurate topology is made available. Switch acts as proxy to collect inventory, as few endpoints support SNMP.
  • Advanced PoE > Fine grain power management to support more phones per switch. Backup power conservation to extend UPS battery life during disasters.
  • IP Telephony network troubleshooting > detect incorrect voice VLAN, QoS and duplex mismatch.

Further, LLDP-MED provides a fast start behaviour which is very important for IP telephony, this means at Startup the endpoints will initially advertise at a faster rate for a limited time.

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