North American Network Operators Group

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Re: MTU of the Internet?

  • From: Perry E. Metzger
  • Date: Sun Feb 08 12:56:40 1998

Phil Howard writes:
> By loading the images in parallel, with the initial part of the image files
> being a fuzzy approximation, you get to see about where every button is
> located, and in many cases you know exactly what it is, and you can click
> on them as soon as you know where to go.

By loading the images in parallel over multiple TCP connections, you
also totally screw the TCP congestion avoidance mechanisms, and hurt
the net as a whole, especially given how prevalent HTTP is these days.
Unfortunately, as has been seen here, very few people working with the
net these days actually understand the details of things the net
depends on, and TCP congestion avoidance is one of them.

HTTP 1.1 allows multiplexing in a single stream, and even (amazingly
enough) ends up working faster in practice than multiple TCP

As I've noted, few people seem to understand this.

> There is also a psychological perception of speed when images load in
> parallel.  When someone complains about the slowness, and is given the
> low MTU solution, they often end up being happier.

I note that ignorance about what MTU means persists.

> I still say the solution is a way to transmit multiple images in parallel
> over a single connection.

You mean, like HTTP 1.1?