Black Box LPB2910A User Manual page 146

Parameter d escription:
Fast s tart r epeat c ount
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 t hat are specifically relevant to particular endpoint types (for example only advertise the
voice network policy to permitted voice-­‐capable devices), both to conserve the limited LLDPU space
and t o r educe s ecurity a nd s ystem i ntegrity i ssues t hat c an c ome w ith i nappropriate k nowledge o f t he
network p olicy.
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, 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 s peed u p t he t ransmission o f t he L LDPDU t o s tart w ithin a s econd, w hen a n ew L LDP-­‐MED
neighbor i s d etected t o s hare L LDP-­‐MED i nformation a s f ast a s p ossible w ith n ew n eighbors.
Because there is a risk of an LLDP frame being lost during transmission between neighbors, we
recommend that you repeat the fast start transmission multiple times to increase the possibility of
the neighbors receiving the LLDP frame. With Fast start repeat count, you can specify the number of
times the fast start transmission will be repeated. The recommended value is 4 times, given that 4
LLDP frames with a 1 second interval will be transmitted, when an LLDP frame with new information
is r eceived.
Note that the 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 does not apply to links
between L AN i nfrastructure e lements, i ncluding N etwork C onnectivity D evices, o r o ther t ypes o f l inks.
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Publication date: Sept, 2015
Revision A1