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The Link Layer Discovery Protocol (LLDP) is a vendor-neutral link layer protocol in the Internet Protocol Suite used by network devices for advertising their identity, capabilities, and neighbors on an IEEE 802 local area network, principally wired Ethernet.〔(【引用サイトリンク】url=http://www.ieee802.org/1/pages/802.1AB-rev.html )〕 The protocol is formally referred to by the IEEE as ''Station and Media Access Control Connectivity Discovery'' specified in standards document IEEE 802.1AB. LLDP performs functions similar to several proprietary protocols, such as the Cisco Discovery Protocol (CDP), Extreme Discovery Protocol, Foundry Discovery Protocol (FDP), Nortel Discovery Protocol (also known as SONMP), and Microsoft's Link Layer Topology Discovery (LLTD). ==Frame structure== LLDP information is sent by devices from each of their interfaces at a fixed interval, in the form of an Ethernet frame. Each frame contains one LLDP Data Unit (LLDPDU). Each LLDPDU is a sequence of type-length-value (TLV) structures. The Ethernet frame used in LLDP has its destination MAC address typically set to a special multicast address that 802.1D-compliant bridges do not forward.〔IEEE 802.1AB-2009 suggests three such addresses, 01:80:c2:00:00:0e, 01:80:c2:00:00:03 and 01:80:c2:00:00:00.〕 Other multicast and unicast destination addresses are permitted. The EtherType field is set to 0x88cc. Each LLDP frame starts with the following mandatory TLVs: ''Chassis ID'', ''Port ID'', and ''Time-to-Live''. The mandatory TLVs are followed by any number of optional TLVs. The frame ends with a special TLV, named ''end of LLDPDU'' in which both the ''type'' and ''length'' fields are 0. Accordingly, an Ethernet frame containing an LLDPDU has the following structure: Each of the TLV components has the following basic structure: Custom TLVs〔Termed ''Organizationally Specific TLVs'' by IEEE 802.1AB〕 are supported via a TLV type 127. The value of a custom TLV starts with a 24-bit organizationally unique identifier and a 1 byte organizationally specific subtype followed by data. The basic format for an organizationally specific TLV is shown below: According to IEEE Std 802.1AB, §9.6.1.3, "The Organizationally Unique Identifier shall contain the organization's OUI as defined in IEEE Std 802-2001." Each organization is responsible for managing their subtypes. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Link Layer Discovery Protocol」の詳細全文を読む スポンサード リンク
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