3.8.3.3.1. Overview 
When using IPv6 for internal connectivity, the IP traffic between
the OpenScape 4000 central switch and the OpenScape 4000 SoftGates (TCP
signaling), as well as between individual OpenScape 4000 SoftGates (RTP
payload), will use IPv6.
IPv6 for OpenScape 4000 SoftGate (internal connectivity)
IPv6 is used for signaling (HSR connection) and payload (IPDA master
connection). In order to avoid bypassing the internal IPv6 connections
by IPv4 direct media connections (DMC), DMC must not be enabled at the
endpoints (IP phone).
When a call between two phones located at the same OpenScape 4000
SoftGate is made, only the signaling data (HSR connection) uses an IPv6
connection. The voice payload between the phones uses IPv4.
When a call between two phones located at two different OpenScape
4000 SoftGates is made, both the signaling data (HSR connection) as well
as the voice payload use IPv6 connections.