PS - note that this *still* takes a penalty of up to two packet times,
worst case. Even if you have different ports for messages to arrive
on, they still come over the same wire. Unless (as in Ethernet) you
can preempt a packet in transit, there's always the possibility that:
a cache update packet is in transit to the server before
your direct request
transmitting your cache update packet would have
to be preempted by your transmitting a cache update.
transmitted speculation packets would have to be
preempted at the server as well.
and few protocol implementations provide for preemption
Joe