R0106-HP MSR Router Series Layer 2 - LAN Switching Configuration Guide(V7)

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Each time the LLDP operating mode of an LLDP agent changes, its LLDP protocol state machine
reinitializes. A configurable reinitialization delay prevents frequent initializations caused by frequent
changes to the operating mode. If you configure the reinitialization delay, an LLDP agent must wait the
specified amount of time to initialize LLDP after the LLDP operating mode changes.
Transmitting LLDP frames
An LLDP agent operating in TxRx mode or Tx mode sends LLDP frames to its directly connected devices
both periodically and when the local configuration changes. To prevent LLDP frames from overwhelming
the network during times of frequent changes to local device information, LLDP uses the token bucket
mechanism to rate limit LLDP frames. For more information about the token bucket mechanism, see ACL
and QoS Configuration Guide.
LLDP automatically enables the fast LLDP frame transmission mechanism in either of the following cases:
• A new LLDP frame is received and carries device information new to the local device.
• The LLDP operating mode of the LLDP agent changes from Disable or Rx to TxRx or Tx.
The fast LLDP frame transmission mechanism successively sends the specified number of LLDP frames at
a configurable fast LLDP frame transmission interval. The mechanism helps LLDP neighbors discover the
local device as soon as possible. Then, the normal LLDP frame transmission interval resumes.
Receiving LLDP frames
An LLDP agent operating in TxRx mode or Rx mode confirms the validity of TLVs carried in every received
LLDP frame. If the TLVs are valid, the LLDP agent saves the information and starts an aging timer. When
the TTL value in the Time To Live TLV carried in the LLDP frame becomes zero, the information ages out
immediately.
Protocols and standards
• IEEE 802.1AB-2005, Station and Media Access Control Connectivity Discovery
• IEEE 802.1AB-2009, Station and Media Access Control Connectivity Discovery
• ANSI/TIA-1057, Link Layer Discovery Protocol for Media Endpoint Devices
• IEEE Std 802.1Qaz™-2011, Media Access Control (MAC) Bridges and Virtual Bridged Local Area
Networks-Amendment 18: Enhanced Transmission Selection for Bandwidth Sharing Between Traffic
Classes
• IEEE 802.3AT-2009