P31003C1020M1000276A9, 01/2018
OpenScape Cordless IP V2, Administrator Documentation 33
Base stations
Base station synchronisation
Requirements for LAN synchronisation
Minimum packet delay jitter is crucial for successful synchronisation over LAN. As multiple LAN traffic parameters
could have an impact on packet delay and its jitter, specific switches and maximum number of switch hops are
required, to guarantee sufficient maximum packet delay jitter.
Consider the following:
• The less switch hops, the lower the transmission delay and its jitter will be.
• The higher the bandwidth or quality of used switches is regarding packet delay and its jitter, the lower the packet
delay and the lower the packet delay jitter will be.
• Enhanced packet processing logics (like L3 switching or packet inspection) could have significant negative
impact on the resulting packet delay jitter. If possible, they should be deactivated for UNIFY BSIP2 base stations
connected switch ports.
• Significantly increased traffic load on a switch, in the range of the maximum throughput, could have significant
negative impact on the packet delay jitter.
• VLAN based prioritisation of LAN packets could be a fruitful measure to minimize packet delay and its jitter for
UNIFY BSIP2 base stations.
Hints regarding PTP deviation
LAN synchronisation is base on a two layer design:
• Native PTPv2 is used to synchronise a common reference timer along all base stations involved.
Target quality benchmark to provide sufficient PTP synchronisation along the base stations, is to have a PTP
deviation lower than 500 ns (rms). For this PTP synchronisation a few single deviations > 500 ns are
accepted and might just generate first warnings. If the PTP sync packet deviation does continuously exceed this
limit of 500 ns, the PTP synchronisation is considered broken and will lead to new start synchronisation
procedure.
• Based on the PTP synchronisation LAN master and LAN slave adjust their DECT reference timer to one
common offset to the common PTP reference timer. This common offset will be permanently monitored by an
proprietary communication.
The target quality benchmark for this synchronisation level is to see reference timer deviation by this DECT
reference timer sync packets: DECT-LAN-Sync deviation lower than 1000 ns. A good mean value would be
500 ns (rms).
To meet this criteria the switches themselves do not necessarily need to be PTP aware. But the network should
consider the above mentioned guidelines to meet this criteria.
To Next Page
Loading...
Need help?
General