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

[Lachlan Andrew]

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.

Cheers,
Lachlan

-- 
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