Chapter 33 Link Layer Discovery Protocol (LLDP)
GS2210 Series User’s Guide
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Figure 199
LLDP Overview
33.2 LLDP-MED Overview
LLDP- MED ( Link Layer Discover y Pr ot ocol for Media Endpoint Devices) is an ext ension t o t he
st andar d LLDP developed by t he Telecom m unicat ions I ndust r y Associat ion ( TI A) TR- 41.4
subcom m it t ee w hich defines t he enhanced discover y capabilit ies, such as VoI P applicat ions, t o
enable net w or k adm inist rat or s m anage t heir net w ork t opology applicat ion m or e efficient ly. Unlike
t he t radit ional LLDP, w hich has som e lim it at ions w hen handling m ult iple applicat ion devices, t he
LLDP- MED offers display of accurat e physical t opology, int er operabilit y of devices, and easy t r ouble
shoot ing for m isconfigur ed I P addr esses. Ther e ar e t hr ee classes of endpoint devices t hat t he LLDP-
MED support s:
Class I : I P Com m unicat ions Cont r oller s or ot her com m unicat ion r elat ed ser vers
Class I I : Voice Gat eways, Confer ence Br idges or Media Ser ver s
Class I I I : I P- Phones, PC- based Soft phones, End user Com m unicat ion Appliances suppor t ing I P
Media
The following figur e shows t hat wit h t he LLDP- MED, net w or k connect ivit y devices ( NCD) like
Swit ches and Rout er s w ill t ransm it LLDP TLV t o endpoint device ( ED) like I P Phone fir st ( 1) , t o get
it s device t y pe and capabilit ies infor m at ion, t hen it w ill r eceive t hat infor m at ion in LLDP- MED TLV
back fr om endpoint devices ( 2) , aft er t hat t he net w or k connect ivit y devices w ill t ransm it LLDP- MED
TLV ( 3) t o pr ov ision t he endpoint device t o such t hat t he endpoint device’s net w or k policy and
locat ion ident ificat ion infor m at ion is updat ed. Since LLDPDU updat es st at us and configurat ion
infor m at ion per iodically, net w or k m anager s m ay check t he r esult of pr ov ision via r em ot e st at us.
The r em ot e st at us is updat ed by r eceiving LLDP- MED TLVs fr om endpoint devices.
