Subject: a few issues

From: [email-masked] (John Krawczyk)
Date: Wed, 19 Jul 95 04:49:45 EDT

I thought I'd pop out a message to the list regarding a few things in
order to (hopefully) not use up time in the WG session (unless they
are deemed worth discussing further).  A couple of these are not new,
but have not been answered either.

1) The ST2 flowspec gives the router a PDU size.  This allows the
router to figure out how much additional bandwidth will be necessary
to transmit the link-level headers.  This bandwidth can be
significant, especially for the very small PDUs.  The service
documents do not mention PDU size at all.  How do I figure out how
much bw I need for the headers?

2) The service documents do not deal with the need for policing at
reservation merge points.  For example, at a particular router, there
may not be a merging of data streams from senders, but one outgoing
interface may have a reservation for X while another has 2X.  If the
senders are sending 2X, I need to police on one of these interfaces.

3) It seems that the current model allows me to deny best-effort
service for a flow by doing a reservation.  Suppose a number of hosts
are receiving a session via best-effort and getting very good quality
(whatever that is).  If I make a reservation requesting only half the
bitrate that is necessary to achieve this quality, the sender (or the
router closest to the sender) is required to police the flow according
to my resource reservation, thus degrading the service to the
best-effort users.  Is this an intended side-effect?  It doesn't sit
very well with me.

-jj