I'm one of the system architects for cisco's eLearning web-portal if
that's worth anything.
i'm not sure what you mean by "cpu requests".
Post by Jim D.Post by henriPost by Jim D.Post by henriPost by Jim D.I haven't found any automated snipe service or software to be
dependable. What happens if esnipe needs to place 1000 bids all at 3
seconds to some specific time. Unless it has 1000 different
connections to the Intenet, they can't be placed simultaneously.
i'm saying that a single computer can make more than 1000 simultaneous**
http (ie web) requests to ebay's servers given one internet connection
** where simultaneous means within milliseconds of each
other. the requests themselves are sent one after the other unless the
machine has more than one cpu and/or network card.
again, from the point of view of esnipe the placing of the request is much
more important than when the response from ebay comes back.
lets break it down:
step 1: esnipe sends out request
step 2: ebay receives request
step 3: ebay processes request
step 4: ebay responds to request
step 5: esnipe receives response
so, assuming #1 can happen simultaneously (for all intents and purposes),
step #2 depends on network traffic and the servers accepting the requests,
assuming no Denial of Service attack is going on both should be fine
step #3 by process i mean: lets assume that ebay is smart (a stretch i
know, but let me not confuse the software guys with the business guys)
they accept the connection and then process it. if the processing is
backed up or slow due to load they still have the time stamp of when they
accepted the request and will use that time stamp instead of when they get
around to actually processing the request
step #4: this is where we see a slow down on sunday nights, just because
the rendering of the page takes some time (get the auction text, get the
current high bid, get the number of bids, update the time left, put it
all together, etc) does not impact when the bid was placed. This could
take 30 seconds from esnipes point of view and they wouldn't care, all
they care about is that the bid got posted when they sent it
step 5 again depends on network traffic between ebay and esnipe
i'm sticking to: esnipe can handle placing thousands of bids on the exact
same auction at exactly the same time and ebay will handle it as
long as there are not network and/or server glitches. (well, also as long
as both sides don't have total idiots writing the code)
henri
Post by Jim D.I get the feeling you're talking about CPU requests and I'm talking about
application requests. Different animals. No question a CPU can process
millions of instructions per second. Even billions nowadays. And, high
speed Intenet connections pass The bottleneck isn't processor speed. It's
the size of the pipe, the efficiency of the communications protocol, and the
ability of the receiving party to process the request once it receives it. I
guarantee you that come Sunday evening eBay's ability to process is
diminished by the sheer volume of messages. Not as bad as it used to be as
when they were growing faster than they could install hardware but
noticeable nonetheless.
Where are the communications engineers when you need one? I'm no computer
scientist, but somebody please explain to me what happens when a message is
sent via an application protocol like HTTP over TCP/IP over a T-1 or cable
modem and how fast such messages can be successfully exchanged.
Jim D.
Post by henrii'm sorry, but all the REQUESTS _do_ occur simultaneously (for all
intents and purpose, i'm sure they don't happen within the same cpu
instruction, but at XXXmhz it happens so quickly that it basically is
simultaneous).
your example shows that with a slow connection the RESPONSES do not
complete simultaneously. not the same thing.
esnipe doesn't really care about the response (well, they do, but it is
not time critical)
so from the point of view of esnipe and ebay there is no real limit to
how many people they can have bid on the same auction with only 3 seconds
to go (like i said earlier, the limit _might_ be around 32K per computer
esnipe is using to send bids to ebay)
henri
Post by Jim D.Although I have been working with computers for 40 years, there's
definitely
Post by henriPost by Jim D.a lot I don't know. When people start talking about pipelining,
persistent
Post by henriPost by Jim D.connections and transport compression, my eyes glaze over. However, one
thing has not changed in 40 years. You can't put 10 lbs of manure in a
5
Post by henriPost by Jim D.pound bag. Yes, you can initiate a single request that causes many
links to
Post by henriPost by Jim D.be loaded but the subsequent events do not occur simultaneously. Events
can
Post by henriPost by Jim D.occur in very quick succession, of course. When you load a page, the
viewer
Post by henriPost by Jim D.is making a single request but a series of requests usually go off after
the
Post by henriPost by Jim D.initial request to gather, execute, and/or display all the components.
You
Post by henriPost by Jim D.can see this when you load a page with a lot of images on a slow
connection.
Post by henriPost by Jim D.Neither the links nor the displays are executed simultaneously but
sequentially as the process is ultimately limited by the communications
protocol.
Unfortunately, if you want to get into a discussion of the relationship
of
Post by henriPost by Jim D.HTTP and PPP & HDLC over TCP/IP, I'm not your man. I long ago reached
my
Post by henriPost by Jim D.level of incompetency and now I just have to sound sagacious and throw
out a
Post by henriPost by Jim D.few acronyms & buzz words.
Post by henrithink about when you load the front page of ebay
And think about when you try to load the front page of eBay into two
different browser windows simultaneously.
Jim D..
Post by henriPost by Jim D.Not necessarily true. The trick is to have one window monitoring the
bidding
Post by henriPost by Jim D.and another with a bid ready to confirm. You can do this easily in
the
Post by henriPost by Jim D.last
Post by henriPost by Jim D.6 seconds IF network response time & eBay response time is good.
Don't
Post by henriPost by Jim D.try
Post by henriPost by Jim D.it at 9PM EST on a Sunday but then automated sniping tools may fail
also,
Post by henriPost by Jim D.Some good ones have adaptive bid times. They moitor bid response
times
Post by henriPost by Jim D.Post by henriPost by Jim D.frequently and adapt the bid lead times accordingly.
I haven't found any automated snipe service or software to be totally
dependable. What happens if esnipe needs to place 1000 bids all at 3
seconds to some specific time. Unless it has 1000 different
connections
Post by henriPost by Jim D.to
Post by henriPost by Jim D.the Intenet, they can't be placed simultaneously.
while no software will be totally dependable (i've never used esnipe or
others), i'm not sure you get how internet "connections" work....
there is no limit to how many concurrent requests your computer can
make
Post by henriPost by Jim D.Post by henriwell, there is, and it is set by the operating system and how much
memory/cpu/resources you have available at that moment in time - and
it's
Post by henriPost by Jim D.Post by henrimore than 1000, closer to 32,000 on a standard unix machine)
think about when you load the front page of ebay: you are in fact
making a
Post by henriPost by Jim D.Post by henrirequest for each image on the page and you are making all those
requests
Post by henriPost by Jim D.Post by henriat the same time, yet you only have "one internet connection".
henri