FreeBSD and filePro weirdness

[Fairlight]

The honourable and venerable John Esak spoke thus:
> I think this hits it on the head exactly... there is not much else it can
> be... and my latency at times is of mythic proportion. The *worst* thing I
> *ever* did was dump my T1 for a snazzier sounding "faster" calbe connection.
> 5meg down, 1.5 up.  *Bullsh*t* to the nth degree.

Ewwww.  Not only less robust technology, but asymmetrical as well.  Not so
hot for heavy use on uplinks.  It's going to be like ADSL that has 1.5/256.
Normally you'd get about 148KB/sec, let's say...down, of course.  If you
push the envelope uploading and use the full 25KB/sec, you have no ACK
space left (well, very sparse ACK space).  So when you fill it, your normal
148KB/sec suddenly drops like a stone to about 3.5-4.5KB/sec, which is all
it can do because there's no room on the smaller uplink side for the ACKs
to be slid in fast enough to accomodate the downlink speed.

Your speeds are going to be 6* faster, give or take.  There's a sliding
discrepancy between 1.5 vs 5mbit and 256kbit vs 1.5mbit...the ratio is off.
But it wouldn't surprise me if you could normally get REALLY bad speeds
on your downlink if you upload a single file at full-bore of your 1.5 to
someone's lowly 1.5/256 DSL, even.  It's your uplink that matters.  So
extrapolating using best case numbers, let's look at this for everyone else
as to what you can expect if you make this kind of move:

5 / 1.5 = 3.33

That's the factor of how much faster 5mbit is than 1.5mbit, 3.33 times
faster.

3.33 * 151 = 522.81

That's about the best you're going to see on download speeds is 523KB/sec,
based on 1.5mbit DSL's maximum I've ever seen of 157KB/sec, translated by
that 3.33 speed increase factor.  Sounds great, right?

1500 / 256 = 5.85

There's your factor of how much faster 1.5mbit is than 256kbit.  Just under
6 times faster.

5.85 * 25 = 146.25

There's approximately your maximum throughput, extrapolating the highest
DSL uplink speed I've seen (25KB/sec) by that 5.85 factor.

5.85 * 4.5 =  26.32

And this...  This is what you will roughly get when your ACK space is eaten
up on the uplink side.  It's the factor difference on the uplink times the
highest I've seen in downloads (4.5KB/sec out of 157KB/sec potential) when
the uplink is full and ACK space is in high contention.

So in the end, assuming some -slight- fudge factors for the way it scales
and potential difference in overhead (DSL uses ATM, I don't know what Cable
is using), you're looking at the following:

502.83 - 26.32 =  476.51
476.51 / 502.83 = .94

When you upload a single file to somewhere, you're losing roughly 94% of
your "fantastic" downlink speed.  A reverse calculation of 6% of the max
502.83 came out to 30.16KB/sec, which is pretty close to what I'd guessed
based on my estimate and gotten on my first calculation.  So I'd expect
to see downloads hover in the 26-31KB/sec range when the uplink is fully
saturated.

-THIS- is why asymmetrical connections suck for business and even heavy
personal use when you know you'll be doing a lot on the uplink side.  And
it's NOT hard to max your async uplink even at 1.5mbit, since that's the
minimum broadband downlink these days for anything except DSL Lite from
some places.  1.5mbit is probably the lowest common denomenator since
they introduced the higher speeds (3mbit and 5mbit).  So if you upload
a large .zip of something, a backup archive of your data to a remote
storage facility, anything, and your downlink speeds are negligible for the
duration.  For personal use, asymmetrical connections are usually okay.  I
tolerate it for the little bits I upload (although uploading 30MB+ really
ticks me off at times--one of my wife's products is that large, and I've
taken the hit for the duration it takes to upload it).  For business, I
would never recommend it.

We won't get into the "best effort" speed guarantees most places have.
Reference my other posts on the subject.  In short, if it goes haywire, you
lump it or leave it--and they don't really care if you leave it.  -Try-
getting proper service.  And your only recourse is the FCC in Washington,
since the deregulation a few years back when they stripped all state
control from DSL.  I don't know how/if Cable was affected by that.  To get
any relief, you have to go federal.

Neither Cable nor DSL are nearly as robust as a full, dedicated T1 circuit.
I'd take 1.5/1.5 over 5/1.5 any day of the week, honestly, if it was a
real T1.  The stability is there, as is the symmetry.  And honestly,
most places throttle downloads these days with QoS software, so even
downloading patches from file distribution sites (FilePlanet, FileShack,
etc., not to mention most adult sites I've tried) will often limit you to
significantly less than even 1.5mbit worth and sometimes even disallow
segmented multi-connection downloading (a la GetRight).  So many times the
5mbit would simply be going to waste.

I know John knows this (now).  I'm hoping to spare others the same pain.
The raw numbers don't lie.  I've made the argument before, but this is the
first time I've done the analysis on a larger pipe than I have.  I have to
say, 30KB/sec downloads do not sound attractive to me, and it's not at all
hard to push yourself into that area.  Granted, my own 3.5-4.5KB/sec
downloads when I hit that condition are even less endearing.  But to dump a
full T1 for either has to really hurt.

Truthfully, I wouldn't switch even for SDSL 1.5/1.5 or even a 3/3.  The
technology is far too fragile compared to a real T1.  Any disturbance in
the Force--er, the EM fields around the lines renders it squirrelly (that's
the technical term!) to unusable.  It's subject to a host of issues to
which T1's are not.  Cable has its own issues as well, from what I've
heard, although I'm nowhere near as intimately familiar with them.

mark->
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