Specifications

Understanding Neighbor Discovery
October 15, 2008 Page 6 of 14
LLDPDU Frames
AsshowninFig ure 3,eachLLDPDUframecontainsthefollowingmandatory TLVs:
•ChassisID—ThechassisidentificationforthedevicethattransmittedtheLLDPpacket.
•PortID—TheidentificationofthespecificportthattransmittedtheLLDPpacket.The
receivingLLDPagentjoinsthechassisIDandtheport
IDtocorrespondtotheentity
connectedtotheportwherethepacketwasreceived.
•TimetoLive—ThelengthoftimethatinformationcontainedinthereceiveLLDPpacketwill
bevalid.
•EndofLLDPDU—IndicatesthefinalTLVoftheLLDPDUframe.
Figure 3 Frame Format
EachLLDPDUframecanalso
containthefollowingoptionalTLVs:
•PortDescription—TheportfromwhichtheLLDPagenttransmittedtheframe.
•SystemName—Thesystem’sadministrativelyassignedname.
•SystemDescription—Includesthesystem’sname,hardwareversion,OSlevel,and
networkingsoftwareversion.
•SystemCapabilities—Abitmapthatdefinestheprimaryfunctionsofthe
system.The
currentlydefinedcapabilitiesinclude,amongotherthings,WLANaccesspoint,router,and
telephone.
• ManagementAddress—TheIPorMACaddressassociatedwiththelocalLLDPagentthat
maybeusedtoreachhigherlayerentities.
AnLLDPDUframecanalsocontainthefollowingextensionTLVs:
• 802.1VLANextension
TLVsdescribeattributesassociatedwithVLANs:
–PortVLANID—Allowsabridgeporttoadvertisetheport’sVLANidentifier(PVID)that
willbeassociatedwithuntaggedorprioritytaggedframesitreceives.
–Port&ProtocolVLANID—Allowsabridgetoadvertisewhetheritsupportsprotocol
VLANsand,if
so,whatVLANIDstheseprotocolswillbeassociatedwith.
LLDP_Multicast
address
Chassis ID TLV
(M)
Time to Live
TLV (M)
End of LLDPDU
TLV (M)
Port ID TLV (M) Optional TLV ... Optional TLV
MAC
address
88-CC LLDPDU FCS
6 octets
M = Mandatory TLV (required for all LLDPDUs)
DA SA
LLDP
Ethertype
6 octets 2 octets 1500 octets 4 octets
Data + pad
IEEE 802.3 LLDP frame format
LLDPDU format