Link Layer Discovery Protocol And Lldp-Med - Enterasys N Standalone (NSA) Series Configuration Manual

3.2.4

Link Layer Discovery Protocol and LLDP-MED

The IEEE 802.1AB standard, commonly referred to as the Link Layer Discovery Protocol (LLDP),
is described in "IEEE 802.1AB-2005 Edition, IEEE Standard for Local and Metropolitan Networks:
Station and Media Access Control Connectivity Discovery, May 2005."
LLDP-MED is described in the ANSI TIA Standards document "TIA-1057-2006, Link Layer
Discovery Protocol for Media Endpoint Devices."
LLDP is similar to the Enterasys Discovery Protocol and the Cisco Discovery Protocol in that it
provides an industry standard, vendor-neutral way to allow network devices to advertise their
identities and capabilities on a local area network, and to discover that information about their
neighbors.
LLDP-MED is an enhancement to LLDP that provides the following benefits:
•
Auto-discovery of LAN policies, such as VLAN id, 802.1p priority, and DiffServ codepoint
settings, leading to "plug-and-play" networking
•
Device location and topology discovery, allowing creation of location databases and, in the case
of VoIP, provision of E911 services
•
Extended and automated power management of Power over Ethernet endpoints
•
Inventory management, allowing network administrators to track their network devices and to
determine their characteristics, such as manufacturer, software and hardware versions, and serial
or asset numbers
The information sent by an LLDP-enabled device is extracted and tabulated by its peers. The
communication can be done when information changes or on a periodic basis. The information
tabulated is aged to ensure that it is kept up to date. Ports can be configured to send this information,
receive this information, or both send and receive.
Either LLDP or LLDP-MED, but not both, can be used on an interface between two devices. A
switch port uses LLDP-MED when it detects that an LLDP-MED-capable device is connected to it.
LLDP Frames
LLDP information is contained within a Link Layer Discovery Protocol Data Unit (LLDPDU) sent
in a single 802.3 Ethernet frame. The information fields in LLDPDU are a sequence of short,
variable-length, information elements known as TLVs — type, length, and value fields where:
•
Type identifies what kind of information is being sent
•
Length indicates the length of the information string in octets
•
Value is the actual information that needs to be sent
Discovery Protocols Command Set
Link Layer Discovery Protocol and LLDP-MED
Matrix NSA Series Configuration Guide 3-25