[e2e] Skype and congestion collapse.

[Marc Herbert]

On Fri, 4 Mar 2005, David P. Reed wrote:

> I was going to give a technical response, but it might be better to
> think whether the question is at all meaningful.
>
> Why would Skype be worse than RealVideo, which continuously sends at
> hundreds of kb/sec, or internet radio, which does no silence
> suppression, and listeners listen to continuously longer than I
> typically converse on the phone?   These are in heavy use today.
>
> Or bittorrent, which when I use it generates bits at me at about 500 KB/sec?

I am a basic consumer and I subscribed to this cheap DSL line. I use
Bittorrent and emule, as well as Skype and some real-time video games.
I don't really understand your discussion because it seems to me that
Skype and gaming are the victims and not the issue. I tell you why: I
can't play or phone and download at the same time. Actually I can, but
then the phoning or gaming experience is randomly (but then severly!)
disturbed: the phone communication seems to suddenly go through some
satellite, and the games become totally unresponsive, unplayable. At
first I did not understand why but then some gamers told me "you're
lagging, don't download while you play, stop downloading!". This
seemed so evident to them, they instantly knew I was a newbie.

Well recently some network wizard friend of mine tried to explain to
me that I actually can do everything simultaneously thanks to very
tricky computations and the use of some weird tweaks like
"--max_upload_rate" in bittorrent or bizarre settings in emule ("max
bandwith", "max connections", "max connections per 5s", etc.)

After a lot of hair-pulling (and a lot of crappy calls and games) I
was pleased we finally figured out a more or less stable "network
configuration" (that's how my friend calls it). But the other day I
was using Skype with my brother and he told me "check the movie
I sent to you", so I opened my mailbox and it went wrong again! I
could not talk to him until the movie was downloaded. When I told that
to my friend, he laughed at me and said : "Great! You learned about
parallelism through time-sharing". This did not help me much.

I am a bit disappointed, especially since I learned that my ISP will
soon "upgrade my line capacity": I guess I will have to go through all
these difficult computations again.

Another thing worries me: my wife wants to buy an iBook and share the
DSL line with me. I think we will go back to the point where we use
the network only one application at a time. This is surely some kind
of waste but at least this is simple and we are sure it works fine.
Glad our house is not so big, so we can shout to the other when the
internet line is free.


> What about H.323 video conferencing, also very common in networks that
> have moderate capacity?
>
> Congestion collapse is a well-defined term.   It's not the plural of
> "heavy user".

Sorry if my terms are not well-defined. I hope you nevertheless
understand my issue.

Cheers,

Marc.

-- 
So einfach wie möglich. Aber nicht einfacher -- Albert Einstein