IPv6 Throughput results

["Dixon, Alvin" <Alvin.G.Dixon --at-- msfc.nasa.gov>]

Has anyone had problems with getting lower TCP throughput results for IPv6
compared to IPv4 using IPERF between Windows machines connected to separate
routers?

Currently, I am testing within the lab.  The configuration is as follows:

Win XP<--->Router1<--->Router2<--->Router3<--->Win 2k3

Each machine is directly connected to a Fast Ethernet interface on separate
routers.  Each router connects to a common router via Fast Ethernet.  So we
are talking about a 100 M path and 3 router hops between hosts.  Everything
is local so we are looking at < 1 msec delay.  Each host network interface,
as well as router interface is configured with both IPv4 and IPv6 addresses.
We are currently doing native IPv6 only. I am running IPERF v1.7.0 on both
machines. 

I get about 50 Mb/s using IPv6 compared to about 95 Mb/s using IPv4.  If I
put the two machines in the same subnet and connect them to a common switch
(as shown below) I get about 94 Mb/s for both IPv4 and IPv6.
  
Win XP<--->Fast Ethernet Switch<--->Win 2k3



thanks, 

alvin