[IP] more on response from Google to yet another twist
Begin forwarded message:
From: Karl Auerbach <karl@xxxxxxxxxxxx>
Date: January 10, 2006 3:52:31 PM EST
To: David Farber <dave@xxxxxxxxxx>
Subject: Re: [IP] response from Google to yet another twist
Reply-To: Karl Auerbach <karl@xxxxxxxxxxxx>
On Tue, 10 Jan 2006, David Farber wrote:
From: David Presotto via RT <support@xxxxxxxxxxxxxx>
The idea is to use some number of reference points (planet lab
nodes, google datacenters, etc) and measure latencies from google
customers to them. We then use those latencies to try to place the
nodes in the 6D space.
What do you think? Are we doing something bad?
Well, apart from the notion of doing experiments on unknowning
subjects...
Latency is only one of several factors that one wants to know when
determining "proximity" on the net when selecting a peer and path to
that peer.
For example, if one is proposing to do a large video transfer then
latency is not really important. More important is the bandwidth of
the path and its ability to handle that bandwidth without packet loss
during a TCP flow. So for big video you want a content source that
you can reach with a fat clean pipe even if it has somewhat longer
latency than a skinny or noisy pipe.
If one is proposing to do a VOIP call, then the desired path not only
has latency must also have low variation in that latency (i.e. low
jitter.) Thus for voip a low latency+jitter path that is skinny is
preferred over a fatter path that has worse latency+jitter.
A while back I created a draft of a protocol to find the numbers that
are needed - and yes, there are still gaps in the protocol. But it
would, I believe, blow the socks off path and peer selelection using
simple latency.
See my blog entry "What Is The Internet Distance From Hither To Yon?"
at http://www.cavebear.com/cbblog-archives/000151.html
At the end of that blog entry there's a pointer to the year 2000 note
that describes what I called the Fast Path Characterization protocol.
(FPCP).
(Shortcut - http://www.cavebear.com/fpcp/fpcp-sept-19-2000.html)
--karl--
-------------------------------------
You are subscribed as roessler@xxxxxxxxxxxxxxxxxx
To manage your subscription, go to
http://v2.listbox.com/member/?listname=ip
Archives at: http://www.interesting-people.org/archives/interesting-people/