ZyXEL GS1920 Series User Guide - Page 251
LLDP-MED Overview
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Chapter 32 Link Layer Discovery Protocol (LLDP) Figure 183 LLDP Overview 32.2 LLDP-MED Overview LLDP-MED (Link Layer Discovery Protocol for Media Endpoint Devices) is an extension to the standard LLDP developed by the Telecommunications Industry Association (TIA) TR-41.4 subcommittee which defines the enhanced discovery capabilities, such as VoIP applications, to enable network administrators manage their network topology application more efficiently. Unlike the traditional LLDP, which has some limitations when handling multiple application devices, the LLDP-MED offers display of accurate physical topology, interoperability of devices, and easy trouble shooting for misconfigured IP addresses. There are three classes of endpoint devices that the LLDPMED supports: Class I: IP Communications Controllers or other communication related servers Class II: Voice Gateways, Conference Bridges or Media Servers Class III: IP-Phones, PC-based Softphones, End user Communication Appliances supporting IP Media The following figure shows that with the LLDP-MED, network connectivity devices (NCD) like Switches and Routers will transmit LLDP TLV to endpoint device (ED) like IP Phone first (1), to get its device type and capabilities information, then it will receive that information in LLDP-MED TLV back from endpoint devices (2), after that the network connectivity devices will transmit LLDP-MED TLV (3) to provision the endpoint device to such that the endpoint device's network policy and location identification information is updated. Since LLDPDU updates status and configuration information periodically, network managers may check the result of provision via remote status. The remote status is updated by receiving LLDP-MED TLVs from endpoint devices. GS1920 Series User's Guide 251