Allied Telesis AlliedWare Plus Operating System Version 5.4.4C (x310-26FT,x310-26FP,x310-50FT,x310-50FP) - Manual (Page 1908)

LLDP, LLDP-MED and Voice VLAN Introduction and Configuration
Software Reference for x310 Series Switches
70.4 AlliedWare Plus TM Operating System - Version 5.4.4C C613-50046-01 REV A
LLDP Advertisements
LLDP transmits advertisements as packets called LLDP Data Units (LLDPDUs). An LLDPDU
consists of a set of Type-Length-Value elements (TLV), each of which contains a particular
type of information about the device or port transmitting it.
Type-Length-Value (TLV)
A single LLDPDU contains multiple TLVs. TLVs are short information elements that
communicate complex data, such as variable length strings, in a standardized format.
Each TLV advertises a single type of information, such as its device ID, type, or
management addresses. The following table describes fields in a TLV.
LLDP sends mandatory TLVs in each advertisement; it can also be configured to send one
or more optional TLVs, from the following groups:
■ Mandatory Base TLVs, included in all LLDP advertisements. See IEEE 802.1AB-2005.
■ Optional Base TLVs, which may be included in any LLDP advertisements. See
IEEE 802.1AB-2005.
■ IEEE 802.1 Organizationally Specific TLVs (802.1 TLVs). See IEEE 802.1AB-2005 Annex F.
■ IEEE 802.3 Organizationally Specific TLVs (802.3 TLVs). See IEEE 802.1AB-2005 Annex G.
■ LLDP-MED Organizationally Specific TLVs (LLDP-MED TLVs), included in LLDP-MED
advertisements. See ANSI/TIA-1057- 2006.
Mandatory and optional TLVs for LLDP and LLDP-MED advertisements are shown in
Table 70-2 .
Table 70-1: Fields in a Type Length Value element
Field Description
Type Identifies the kind of information. It consists of a 7-bit Type code.
Length Identifies the length of the information. It consists of a 9-bit value
that specifies the number of bytes of data in the Value field.
Value Contains the actual value of the advertised information. This is a
variable length data field.
Table 70-2: TLVs in LLDP advertisements
TLV Description
Mandatory Base TLVs—IEEE 802.1AB-2005
Chassis ID Identifies the device's chassis. On this switch, this is the MAC
address of the switch or stack.
Port ID Identifies the port that transmitted the LLDPDU.
Time To Live (TTL) Indicates the length of time in seconds for which the information
received in the LLDPDU remains valid. If the value is greater than
zero, the information is stored in the LLDP remote system MIB. If
the value is zero, the information previously received is no longer
valid, and is removed from the MIB.
End of LLDPDU Signals that there are no more TLVs in the LLDPDU.
Optional Base TLVs—IEEE 802.1AB-2005
Port description A description of the device’s port in alpha-numeric format.