14169000-IG, Edition 11.0
January 2018, Original document
31
Multicast
The PTPv2 multicast packets cannot traverse routers and consequently the IP-DECT base stations
that needs to be synchronized must be on the same switched network segment.
Regardless of the transport selected, IPv4, IPv6 or Ethernet, the network switches must allow mul-
ticast traffic to and from all the LAN base stations. The multicast addresses used are listed below:
If IPv4 or IPv6 is used as transport and IGMP snooping
(http://en.wikipedia.org/wiki/IGMP_snooping) is supported by the switch, the switch can utilize this to
automatically configure on which ports the multicast packets should be sent. Note that this requires
an IGMP querier to be present on the network segment (many IGMP snooping switches offers this
functionality).
If multicast is not working properly on the network, the IP-DECT base stations will not be able to
achieve LAN synchronization.
Timing and Jitter
For PTPv2 to be accurate enough to synchronize the DECT radios the network jitter must be low,
that is the network packet delay must be close to constant.
The PTPv2 algorithms in the base stations have built-in filtering, which make them able to cope with
some level of jitter. However, prolonged periods of large jitter can cause unstable or even loss of syn-
chronization.
The corporate LAN must support the following specifications:
l Maximum of 500 nanoseconds jitter of multicast Ethernet packets between all IP-DECT base
stations being synchronized.
l Any single switch in the network cannot exceed 100nsec of jitter.
l PTPv2 event traffic must be given strict priority over all other network traffic.
l Multicast and the IGMP protocol (if used) must be configured per Spectralink requirements.
l Network topology
l The traffic patterns on the network
l The quality and configuration of the switches
Spectralink IP-DECT Server 400/6500 and DECT Server 2500/8000 Synchronization and Deployment Guide
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