IEEE 802.1AB-2016 pdf free download – IEEE Standard for Local and metropolitan area networks— Station and Media Access Control Connectivity Discovery.
6.1 Transmission and reception
l’he information fields in each LLDP frame are contained in a Link Layer Discovery Protocol Data Unit ILLDPDU) as a sequence of variable length information elements, that each include type, length, and value fields (known as TINs), where
at Type identifies what kind of information is being sent
b) Length indicates the length of the information string in ociets.
ci Value is the actual information that needs to be anti t for example, a binary bit map or an alphanumeric string that can contain one or more fields).
Each LLDPDU contains the following three mandatory TINs (see Table 8-I), and can contain optional TLVs as selected by network management:
di A Cbassis ID TLV.
ci APortIDTLV.
t’i A Time To Live TIN
g) Zero or more optional TLVs. as allowed by the maximum size of the LLDPDU.
h) An optional End Of LLDPDU TLV.
The chassis ID and the port ID values are concatenated to form a logical MSAP identifier that is used by the recipient to identify the sending I LOP agent.port. Both the chassis ID and port ID values can be defined in a number of convenient forms. Once selected, however, the chassis IDpott ID value combination remains the same as long as the particular port remains operable.
NOW t —the stateineni above is true for any LLDP agent; however, there can he rnuliipte LLDP agents sending and receiving Lt.DPOtJs wang different SAC addresses
A non-zero value in the time to live (‘I’l’L) field of the Time To Live TiN tells the receiving LLDP agent how long all information pertaining to this LLDPDIT’s MSAP identifier is valid so that all the associated information can later be autonatically discarded by the receiving ILOP agent if the sender fails to update it in a timely manner. A zero value indicates that any information pertaining to this LLDPOU’s MSAP identifier is to be discarded immediately.
NOW 2—A iTt value ol zero can be used. foe esançte. to signat that the sending port has initiated a poet shutdown prucedire.
Tlse End Of LLDPDU TIN marks the end of the LLDPDU.
Tlse format for the LLDPDU is defined in 8.2. The TIN categories and the basic TLV format are defined in
8.3 and 8.4. The specific formal and field contents for the Chassis ID TIN are defined in 8.5.2; for the
Port ID TIN. in 8.5.3; for the Time To Live TLV in 8.54; and for the End Of LLDPOLI TLV, in 8.5.1.
6.2 LLDP operational modes
LLDP is a one way protocol. An LLDP agent can transmit information about the capabilities and current status of the system associated with its MSAP identifier The LLDP agent can also receive information about the capabilities and current status of the system associated with a remote MSAP identifier. LLOP does not itself contain a mechanism for soliciting specific information from other LLDP agents. nor don it provide a specific means of confirnsing the receipt of information.IEEE 802.1AB pdf download.