Lldp-Med Overview - ZyXEL Communications GS3700 Series User Manual

Chapter 35 Link Layer Discovery Protocol (LLDP)
Figure 248 LLDP Overview

35.2 LLDP-MED Overview

LLDP- MED ( Link Layer Discovery Prot ocol for Media Endpoint Devices) is an ext ension t o t he
st andard LLDP developed by t he Telecom m unicat ions I ndust ry Associat ion ( TI A) TR- 41.4
subcom m it t ee which defines t he enhanced discovery capabilit ies, such as VoI P applicat ions, t o
enable net work adm inist rat ors m anage t heir net work t opology applicat ion m ore efficient ly. Unlike
t he t radit ional LLDP , which has som e lim it at ions when handling m ult iple applicat ion devices, t he
LLDP- MED offers display of accurat e physical t opology, int eroperabilit y of devices, and easy t rouble
shoot ing for m isconfigured I P addresses. There are t hree classes of endpoint devices t hat t he LLDP-
MED support s:
Class I : I P Com m unicat ions Cont rollers or ot her com m unicat ion relat ed servers
Class I I : Voice Gat eways, Conference Bridges or Media Servers
Class I I I : I P- Phones, PC- based Soft phones, End user Com m unicat ion Appliances support ing I P
Media
The following figure shows t hat wit h t he LLDP- MED, net work connect ivit y devices ( NCD) like
Swit ches and Rout ers will t ransm it LLDP TLV t o endpoint device ( ED) like I P Phone first ( 1) , t o get
it s device t ype and capabilit ies inform at ion, t hen it will receive t hat inform at ion in LLDP- MED TLV
back from endpoint devices ( 2) , aft er t hat t he net work connect ivit y devices will t ransm it LLDP- MED
TLV ( 3) t o provision t he endpoint device t o such t hat t he endpoint device's net work policy and
locat ion ident ificat ion inform at ion is updat ed. Since LLDPDU updat es st at us and configurat ion
inform at ion periodically, net work m anagers m ay check t he result of provision via rem ot e st at us.
The rem ot e st at us is updat ed by receiving LLDP- MED TLVs from endpoint devices.
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