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I don't know if the cable modem has a buffer or not - the modem may depend
upon the ethernet card being as fast as or faster than the modem.
Keep in mind that there are three main components here: the hardware (modem
& ethernet card), the TCP/IP software, and the application (TradeStation).
The TCP/IP process obviously has some degree of buffering because it must be
able to collect all the packets, which may arrive out of order, which
constitute a "message" and rearrange them into proper order before passing
the assembled message (not the constituent packets) on to its application.
TCP/IP does detect missing packets and request resending, but I doubt if the
application is aware of this.
Also, it is possible that none of the above is applicable in the case of the
so-called "push" technique in which the server initiates the transmission
rather than responding to a request from a client. Perhaps someone on the
list who is knowledgeable about Internet Protocol could enlighten us.
Carroll Slemaker
-----Original Message-----
From: Gerrit Jacobsen <jrt@xxxxxxxxxx>
To: Carroll Slemaker <cslemaker1@xxxxxxxx>; omega-list@xxxxxxxxxx
<omega-list@xxxxxxxxxx>
Date: Sunday, May 23, 1999 7:47 AM
Subject: Re: PS2k SP2 Update, Tick Counts and Rant
> Cable modems connect directly to an ethernet card and do not need a
> serial port. No serial port that I know of could handle the 10MbPS
> or better speed of a cable modem!
Brilliant. This brings up another crucial question with IP delivery.
I would be interested to learn whether these cable modems buffer
data and how data is buffered by the internal drivers since TS cannot
work the data at 10Mbps.
Furthermore if the data gets through it is hanging in some internal
IP queue on the IP socket. It seems to happen often that IP queues
overflow and simply do not accept more packets when they are full and
the packets are dropped. This could be even more crucial with TS
since the data has to be stored in the database and to be dispatched
to the charting application which takes time.
Is there some mechanism that re-requests packets from the tick data
server if they are lost or is this happening undetected and the data
ticks are just lost ?
Gerrit
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