Re: MTU of the Internet?

[Phil Howard <phil () charon milepost com>]

Paul A Vixie writes:

> explorer and navigator have both done this since their respective 3.0's.
> however, they both still open N (where N defaults to 4) connections to the
> same server rather than depending on persistence and limiting themselves
> to 1 connection per server.  so they will reuse their N connections for more
> than one fetch if there are more than N objects to be fetched from some 
> server to fill out one "page".  phil howard says this is a feature, but now
> that the size of a graphic can be given in its enclosing page it is no longer
> nec'y to get the graphic objects' headers before laying out the page, and
> i think that for the good of the network and the origin servers it would be
> nicer if these browsers could learn to serialize their fetching a LOT more.

Merely laying out the page isn't enough.  It helps, and unfortunately some
browsers (e.g. explorer) don't seem to even use this feature correctly.
Having a bunch of blank positions where buttons are supposed to be doesn't
give one any idea a button is supposed to be there, or even where "there"
is, until some stuff, either the first pixels of that button, or the buttons
around it, are getting loaded.  Seeing only the top button of a table of
buttons doesn't help to find where the active space is for the green one
you know you always click on, or the one with the person's head.

One approach that can be used to get around this is to make all the images
be very small low res only files, and include some Javascript that will
detect when those are loaded and then start the medium res loading, and
after that, the high res loading.  But I would not want to depend on people
who have degrees in graphical arts to be in a position to manage network
bandwidth controls, so other fundamental solutions are still needed.

My multiplexing protocol would need a persistent TCP connection.  There
would be 254 different subchannels.  A byte code of 255 is a flag to the
multiplex control.  255,255 means a real 255 in the current subchannel.
255,0 means EOF in the current subchannel.  255,N means a switch to
subchannel N (1-254).  The sender can determine how many bytes can be
sent in one subchannel before switching to another.  If more features
might be required, such as per subchannel flow control, then more codes
could be reserved (it might be good to reserve all of 200-254 for now).
AFAIK, no valid HTTP would begin with a 255,1 so this multiplexing would
likely be detectable dynamically against HTTP.

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