User manual

C HAPTER 4 | Configuring the Switch
Link Layer Discovery Protocol
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CONFIGURING
LLDP-MED TLVS
Use the LLDP-MED Configuration page to set the device information which
is advertised for end-point devices.
LLDP-MED (Link Layer Discovery Protocol - Media Endpoint Discovery) is an
extension of LLDP intended for managing endpoint devices such as Voice
over IP phones and network switches. The LLDP-MED TLVs advertise
information such as network policy, power, inventory, and device location
details. Both LLDP and LLDP-MED information can be used by SNMP
applications to simplify troubleshooting, enhance network management,
and maintain an accurate network topology.
PATH
Advanced Configuration, LLDP-MED
PARAMETERS
These parameters are displayed:
◆ Fast Start Repeat Count – Rapid startup and Emergency Call Service
Location Identification Discovery of endpoints is a critically important
aspect of VoIP systems in general.In addition, it is best to advertise
only those pieces of information which are specifically relevant to
particular endpoint types (for example only advertise the voice network
policy to permitted voice-capable devices), both in order to conserve
the limited LLDPU space and to reduce security and system integrity
issues that can come with inappropriate knowledge of the network
policy.
With this in mind LLDP-MED defines an LLDP-MED Fast Start interaction
between the protocol and the application layers on top of the protocol,
in order to achieve these related properties. Initially, a Network
Connectivity Device will only transmit LLDP TLVs in an LLDPDU. Only
after an LLDP-MED Endpoint Device is detected, will an LLDP-MED
capable Network Connectivity Device start to advertise LLDP-MED TLVs
in outgoing LLDPDUs on the associated port. The LLDP-MED application
will temporarily speed up the transmission of the LLDPDU to start
within a second, when a new LLDP-MED neighbor has been detected in
order share LLDP-MED information as fast as possible to new
neighbors.
Because there is a risk that a LLDP frame being lost during transmission
between neighbors, it is recommended to repeat the fast start
transmission multiple times to increase the possibility for that the
neighbors has received the LLDP frame. With Fast start repeat count it
is possible to specify the number of times the fast start transmission is
repeated. The recommended value is 4 times, giving that 4 LLDP
frames with a 1 second interval will be transmitted, when a LLDP frame
with new information is received.
It should be noted that LLDP-MED and the LLDP-MED Fast Start
mechanism is only intended to run on links between LLDP-MED
Network Connectivity Devices and Endpoint Devices, and as such does
not apply to links between LAN infrastructure elements, including
between Network Connectivity Devices, or to other types of links.