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From: tedm@agora.rdrop.com
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: Batch FTP and Web Pages
Date: 4 Jul 1996 10:40:43 GMT
Organization: Symantec Corporation
Lines: 66
Message-ID: <4rg73b$539@symiserver2.symantec.com>
References: <31D4AA3A.BC0@www.play-hookey.com> <836073421snz@dsl.co.uk> <31D87436.7C7F@www.play-hookey.com> <836295557snz@dsl.co.uk> <4rcr6v$dh@anorak.coverform.lan>
Reply-To: tedm%toybox@agora.rdrop.com
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In <4rcr6v$dh@anorak.coverform.lan>, brian@awfulhak.demon.co.uk (Brian Somers) writes:
>Brian {Hamilton Kelly} (bhk@dsl.co.uk) wrote:
>
[discussion about Netscape's design decisions deleted]
>I find that difficult to believe. What do you mean by TCP/IP packages?
>Do you mean the machines on which netscape is running (such as maybe
>Windows & OS/2)? If this is the case, then the OS is broken. RTTs
>should be variable and should adjust according to connection throughput.
No, what the problem really is is a lack of resources on the server. Netscape
actually gets about 60% of it's revenue these days from Intranets, not from
Internet sales. Naturally, they are really optimizing Netscape Navigator for the
market bringing them the cash!
Running a browser on a LAN is a lot different than running it over a dialup. With
a 28.8k modem connection, it doesen't matter how many simultaneous connections
that the client starts up, you are still limited at the maximum throughput of 3.3k
per second for compressed data. (keep in mind graphic images these days are
pretty much uncompressible as their already jpeged)
Even the most anemic web server can easily send out packets at a faster rate
than that. What it boils down to is do you want to get 4 images at .8k per second
simultaneously, or 4 images at 3.3k per second serially. Either way, your going to
totally saturate the dialup 28.8k link, and you won't notice a difference on the
client.
Now, on a LAN things are a lot different. With a client hitting a web server
at 10Mbts you actually can run up against bottlenecks in the client and server
unrelated to the data transfer speed that will make the observed speed that a
web page is drawn much faster if all the images are fetched simmultaneously,
instead of serially. (mainly related to if the web server spins off a separate
thread per data object, the client spins off a separate thread per received item,
etc) Needless to say, this is the real reason Netscape is pushing the
"simultaneous received data objects" model on their browser, because it makes
the page look snappier on an internal corporate 10Mbt network.
The problem with this on the Internet is your hitting an Internet server with
hundreds of simultaneous connections, each one that takes a small amount of
resources. Eventually you hit a ceiling where the server starts swapping, and
that is when all hell breaks loose.
In this model, the browser sends out a request packet for a data item that is
currently being fetched, however the thread that is fetching the item happens
to be swapped out. Perhaps the web server is also processing some mail, and
CGI, and has many, many simultaneous processes swapped out. So, it's going to
take a lot longer for that swapped out process to come back into core, and
process the request packet. By that time maybe the client has gotten tired
waiting and decided the initial packet is lost, and so retransmits.
This is the core reason why Unix is used for Internet servers, and NT and other
server operating systems are never going to hold much share in the Internet
server market, while in contrast NT and other server OS/es will dominate in the
Intranet market. NT and other server OS/es are simply not designed to
handle many hundreds and hundreds of simultaneous processes, their swapping
algorithims are crude, their overhead for context switching is tremendous,
and it is well known among the database crowd that the only way to speed
up an NT server that has more than 4 processors is to toss it off a cliff.
I'm quite sure that Microsoft, Apple, Novell and friends aren't going to shed many
tears over this however. They have already decided that the Intranet market is
where the money is at, and would just as soon see the Internet people go away.
Seriously, do you really think a model like Java is designed for the 28.8k dialup
market?!?!