Subject: TPF Prioritisation (on a different note)

From: Dave Finnie <[email-masked]>
Date: Fri, 15 Sep 1995 22:33:21 +1000

All,

One of our customers has an environment where multiple PUs (aka LSs)
share the same line (aka port). It is multi-dropped SDLC in the
example, but the problem we have would apply equally to LANs, etc.

We have implemented the suggested 4 queues per instance of PC, and we
weight the transmissions progressively in favour of the higher TPF
values, with an aging mechanism.

However, the customer has the situation whereby low priority traffic
(batch file transfer) flows over one of the PUs sharing the line, and
high priority interactive traffic over one of the other PUs sharing
the line.

While our algorithm works beautifully for servicing differing TPF
value traffic on a PU basis, in this example the low priority traffic
is getting as much service as the high priority traffic because the
prioritisation does not extend to the line level.

*An* obvious solution is to internally extend the queues down to the
line level, but I wanted to see if other implementers had addressed
this issue, and what their preferred solutions were.

Also, does the architecture team have a preferred solution to this for
APPN implementers so that a consistent mechanism is presented to the
customer ?

Also... does the AIW forum feel that a consistent weighting and aging
mechanism be employed by all APPN implementations (which choose to
implement it) ? ie should we discuss *a* solution so that we have some
point in which to start ? My reasoning is that an APPN network of
heterogeneous implementations could become difficult to tune if all
implementions do different things in this area. I'm prepared to throw
our algorithm in as a starting point if this is seen to be a useful
thing to pursue.

Thanks in advance to all who can give some help...

Dave