[e2e] Some thoughts on WLAN etc., was: Re: RES: Why Buffering?

Lachlan Andrew lachlan.andrew at gmail.com
Sat Jul 4 11:31:22 PDT 2009

2009/7/5 Detlef Bosau <detlef.bosau at web.de>:
> Hence, some of my questions are:
> - What is a wireless "channel"? What is a wireless "connection"?
> I once was asked about the behaviour of some protocol in the presence of
> "short time disconnections". What is a "short time disconnection"? Or, the
> other way round, what is a connection all about in a wireless network?

There are many concepts of "connection" at different layers of the
protocol stack which runs on top of a wireless physical layer, and
many protocols/layers are not connection oriented.  However, some are.

In the e2e context, a "disconnection" of a lower layer roughly means
"a period of time over which all packets are lost, which extends for
more than a few average RTTs plus a few hundred milliseconds".  That
is what it means in a phrase like "transport protocols need to handle
short time disconnections".

> From an end to end point of view, I would like to abandon terms like
> "channel" and "connection" in a wireless environment.

We shouldn't throw the baby out with the bathwater.  The concept of "a
period in which most packets are delivered within a (vague) short
period of time" is useful.  If we don't call it a "connection", we'd
come up with another word for it.

Rather than pointing out weaknesses in current terminology, it may be
better to propose a concept which better models (dis)connectivity, and
then do a useful design/calculation which is possible using the new
concept but was impossible with the old concepts.  Without that
validation, the new concept won't replace the old.


Lachlan Andrew  Centre for Advanced Internet Architectures (CAIA)
Swinburne University of Technology, Melbourne, Australia
<http://caia.swin.edu.au/cv/landrew> <http://netlab.caltech.edu/lachlan>
Ph +61 3 9214 4837

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