Basic concepts

An LLDP agent is a mapping of an entity where LLDP runs. Multiple LLDP agents can run on the same interface.

LLDP agents are divided into the following types:

• Nearest bridge agent.

• Nearest customer bridge agent.

• Nearest non-TPMR bridge agent.

A Two-port MAC Relay (TPMR) is a type of bridge that has only two externally-accessible bridge ports. It supports a subset of the features of a MAC bridge. A TPMR is transparent to all frame-based media-independent protocols except for the following protocols:

• Protocols destined to it.

• Protocols destined to reserved MAC addresses that the relay feature of the TPMR is configured not to forward.

LLDP exchanges packets between neighbor agents and creates and maintains neighbor information for them. Figure 47 shows the neighbor relationships for these LLDP agents. LLDP has two bridge modes: customer bridge (CB) and service bridge (SB).

LLDP sends device information in LLDP frames. LLDP frames are encapsulated in Ethernet II or Subnetwork Access Protocol (SNAP) frames.

• LLDP frame encapsulated in Ethernet II

  Figure 48: Ethernet II-encapsulated LLDP frame

• LLDP frame encapsulated in SNAP

  Figure 49: SNAP-encapsulated LLDP frame

LLDP uses LLDPDUs to exchange information. An LLDPDU comprises multiple TLVs. Each TLV carries a type of device information, as shown in Figure 50.

An LLDPDU can carry up to 32 types of TLVs. Mandatory TLVs include Chassis ID TLV, Port ID TLV, and Time to Live TLV. Other TLVs are optional.

A TLV is an information element that contains the type, length, and value fields.

LLDPDU TLVs include the following categories:

• Basic management TLVs

• Organizationally (IEEE 802.1 and IEEE 802.3) specific TLVs

• LLDP-MED (media endpoint discovery) TLVs

Basic management TLVs are essential to device management.

Organizationally specific TLVs and LLDP-MED TLVs are used for enhanced device management. They are defined by standardization or other organizations and are optional for LLDPDUs.

• Basic management TLVs

  Table 15 lists the basic management TLV types. Some of them are mandatory for LLDPDUs.

  Table 15: Basic management TLVs

  Type	Description	Remarks
  Chassis ID	Specifies the bridge MAC address of the sending device.	Mandatory.
  Port ID	Specifies the ID of the sending port: If the LLDPDU carries LLDP-MED TLVs, the port ID TLV carries the MAC address of the sending port. Otherwise, the port ID TLV carries the port name.
  Time to Live	Specifies the life of the transmitted information on the receiving device.
  End of LLDPDU	Marks the end of the TLV sequence in the LLDPDU.	Optional.
  Port Description	Specifies the description for the sending port.
  System Name	Specifies the assigned name of the sending device.
  System Description	Specifies the description for the sending device.
  System Capabilities	Identifies the primary features of the sending device and the enabled primary features.
  Management Address	Specifies the following elements: The management address of the local device. The interface number and object identifier (OID) associated with the address.

• IEEE 802.1 organizationally specific TLVs

  Table 16: IEEE 802.1 organizationally specific TLVs

  Type	Description
  Port VLAN ID (PVID)	Specifies the port VLAN identifier.
  Port And Protocol VLAN ID (PPVID)	Indicates whether the device supports protocol VLANs and, if so, what VLAN IDs these protocols will be associated with.
  VLAN Name	Specifies the textual name of any VLAN to which the port belongs.
  Protocol Identity	Indicates protocols supported on the port.
  Link Aggregation	Indicates whether the port supports link aggregation, and if yes, whether link aggregation is enabled.
  Management VID	Management VLAN ID.
  VID Usage Digest	VLAN ID usage digest.
  ETS Configuration	Enhanced Transmission Selection configuration.
  ETS Recommendation	ETS recommendation.
  PFC	Priority-based Flow Control.
  APP	Application protocol.

	NOTE: HPE devices support only receiving protocol identity TLVs and VID usage digest TLVs. Layer 3 Ethernet ports support only link aggregation TLVs.

• IEEE 802.3 organizationally specific TLVs

  Table 17: IEEE 802.3 organizationally specific TLVs

  Type	Description
  MAC/PHY Configuration/Status	Contains the bit-rate and duplex capabilities of the port, support for autonegotiation, enabling status of autonegotiation, and the current rate and duplex mode.
  Power Via MDI	Contains the power supply capabilities of the port: Port class (PSE or PD). Power supply mode. Whether PSE power supply is supported. Whether PSE power supply is enabled. Whether pair selection can be controlled. Power supply type. Power source. Power priority. PD requested power. PSE allocated power.
  Maximum Frame Size	Indicates the supported maximum frame size.
  Power Stateful Control	Indicates the power state control configured on the sending port, including the following: Power supply mode of the PSE/PD. PSE/PD priority. PSE/PD power.
  Energy-Efficient Ethernet	Indicates Energy Efficient Ethernet (EEE).

	NOTE: The Power Stateful Control TLV is defined in IEEE P802.3at D1.0 and is not supported in later versions. HPE devices send this type of TLVs only after receiving them.

• LLDP-MED TLVs

  LLDP-MED TLVs provide multiple advanced applications for voice over IP (VoIP), such as basic configuration, network policy configuration, and address and directory management. LLDP-MED TLVs provide a cost-effective and easy-to-use solution for deploying voice devices in Ethernet. LLDP-MED TLVs are shown in Table 18.

  Table 18: LLDP-MED TLVs

  Type	Description
  LLDP-MED Capabilities	Allows a network device to advertise the LLDP-MED TLVs that it supports.
  Network Policy	Allows a network device or terminal device to advertise the VLAN ID of a port, the VLAN type, and the Layer 2 and Layer 3 priorities for specific applications.
  Extended Power-via-MDI	Allows a network device or terminal device to advertise power supply capability. This TLV is an extension of the Power Via MDI TLV.
  Hardware Revision	Allows a terminal device to advertise its hardware version.
  Firmware Revision	Allows a terminal device to advertise its firmware version.
  Software Revision	Allows a terminal device to advertise its software version.
  Serial Number	Allows a terminal device to advertise its serial number.
  Manufacturer Name	Allows a terminal device to advertise its vendor name.
  Model Name	Allows a terminal device to advertise its model name.
  Asset ID	Allows a terminal device to advertise its asset ID. The typical case is that the user specifies the asset ID for the endpoint to facilitate directory management and asset tracking.
  Location Identification	Allows a network device to advertise the appropriate location identifier information for a terminal device to use in the context of location-based applications.

	NOTE: If the MAC/PHY configuration/status TLV is not advertisable, none of the LLDP-MED TLVs will be advertised even if they are advertisable. If the LLDP-MED capabilities TLV is not advertisable, the other LLDP-MED TLVs will not be advertised even if they are advertisable.

The network management system uses the management address of a device to identify and manage the device for topology maintenance and network management. The management address is encapsulated in the management address TLV.