3Com 2928 User Guide - Page 256

Type Manufacturer Name Model Name Asset ID Location Identification Description Allows a MED endpoint to advertise its vendor name. Allows a MED endpoint to advertise its model name. Allows a MED endpoint 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. Allows a network device to advertise the appropriate location identifier information for an endpoint to use in the context of location-based applications. See the IEEE standard (LLDP) 802.1AB-2005 and the LLDP-MED standard (ANSI/TIA-1057) for more information about LLDPDU TLVs. Management address The management address of a device is used by the network management system to identify and manage the device for topology maintenance and network management. The management address is encapsulated in the management address TLV. Operating Modes of LLDP LLDP can operate in one of the following modes: z TxRx mode. A port in this mode sends and receives LLDPDUs. z Tx mode. A port in this mode only sends LLDPDUs. z Rx mode. A port in this mode only receives LLDPDUs. z Disable mode. A port in this mode does not send or receive LLDPDUs. Each time the LLDP operating mode of a port changes, its LLDP protocol state machine re-initializes. To prevent LLDP from being initialized too frequently at times of frequent operating mode change, an initialization delay, which is user configurable, is introduced. With this delay mechanism, a port must wait for the specified interval before it can initialize LLDP after the LLDP operating mode changes. How LLDP Works Transmitting LLDPDUs An LLDP-enabled port operating in TxRx mode or Tx mode sends LLDPDUs to its directly connected devices both periodically and when the local configuration changes. To prevent the network from being overwhelmed by LLDPDUs at times of frequent local device information change, an interval is introduced between two successive LLDPDUs. This interval is shortened to 1 second in either of the following two cases: z A new neighbor is discovered, that is, a new LLDPDU is received carrying device information new to the local device. z The LLDP operating mode of the port changes from Disable/Rx to TxRx or Tx. 1-5