Is an internal ISDN "modem" better than external?

Is an internal ISDN "modem" better than external?

Post by Thomas Krehbi » Sat, 26 Oct 1996 04:00:00



I'm in the initial stages of getting a Bell Atlantic Residential ISDN
line here in VA.  When they asked me whether I wanted an internal or
external modem, I instinctively said "external" because I've always
gotten external modems in the past.  But now that I'm thinking about
it more, it seems like going through the serial port like that would
become a bottleneck at 128K.  So the question is, will I get better
performance from a card instead?

A related question:  Should I be getting one of these "modems" at all?
Or should I be looking at something like a router for best possible
performance?  (I'm not entirely sure what a router is/does so I may be
way off there.)

BTW, my goal is to do dial-up ISDN access to Internet at 128K.  My
computer is a P6-200.

Any information appreciated.

        - Tom

------------------------------------------------------------------------
Thomas Krehbiel                   "I got dozens of friends
Nova Design, Inc                   and the fun never ends
http://www.infi.net/~tek           that is as long as I'm buyin'"  -Styx

 
 
 

Is an internal ISDN "modem" better than external?

Post by Cronin B. Vini » Sat, 26 Oct 1996 04:00:00


I'm at about the same stage as you are, so I only know what I've been
reading.  cnet has a fairly recent review
   http://www.cnet.com/Content/Reviews/Compare/Isdn/
which shows the USR Sportster ISDN (an internal)  25% faster than
exterals like Bitsurfer. And for just the reason you said: at the high
end the serial port is a bottleneck.   The USR is also pretty cheap,
but it needs an add-on to actually ring the analog line  so that your
FAX machine works.

But there is a pretty new Bitsurfer Pro ISA internal model that wasn't
in the cnet review.  Does anybody out there really know how the
Bitsurfer speed compares to the externals or the USR?

Tnks in advance!

 
 
 

Is an internal ISDN "modem" better than external?

Post by Bob Larribea » Sat, 26 Oct 1996 04:00:00


I've done a limited amount of testing.  I compared the Adtran Express XRT
and 3Com Impact IQ external TAs against the Eicon Diva and NTT-IT
ThunderCard PC Cards (PCMCIA).

I went to the trouble of installing a 230.4 kb/s capabile I/O port.  The PC
Cards gave me 120 kb/s for both FTP GETs and PUTs in all cases.

At 230.4 kb/s both the external boxes gave between 100 to 115 kb/s on GETs
and 75 to 90 kb/s on PUTs.  The Adtran was a hair faster on the PUTs.
There was little difference on GETs.

I did not do much testing at 115.2 kb/s, but it looks to me like both the
external boxes would max at a little better than 80 kb/s.

ISA cards should give similar performance to the PC Cards I tested.  The
ISA and cards PC Cards can give significantly better performance than the
external TAs.

There is one caveat.  You need internal cards with Microsoft's ISDN v1.1
drivers to get this kind of performance.  The cards I have tested with AT
interfaces that emulate a modem without the miniport drivers have reduced
throughput.

Bob Larribeau
ISDN Consultant
San Francisco



Quote:> I'm in the initial stages of getting a Bell Atlantic Residential ISDN
> line here in VA.  When they asked me whether I wanted an internal or
> external modem, I instinctively said "external" because I've always
> gotten external modems in the past.  But now that I'm thinking about
> it more, it seems like going through the serial port like that would
> become a bottleneck at 128K.  So the question is, will I get better
> performance from a card instead?

> A related question:  Should I be getting one of these "modems" at all?
> Or should I be looking at something like a router for best possible
> performance?  (I'm not entirely sure what a router is/does so I may be
> way off there.)

> BTW, my goal is to do dial-up ISDN access to Internet at 128K.  My
> computer is a P6-200.

> Any information appreciated.

>         - Tom

> ------------------------------------------------------------------------
> Thomas Krehbiel                   "I got dozens of friends
> Nova Design, Inc                   and the fun never ends
> http://www.infi.net/~tek           that is as long as I'm buyin'"  -Styx

 
 
 

Is an internal ISDN "modem" better than external?

Post by David Riew » Sun, 27 Oct 1996 04:00:00


I was prompted to get an ISDN line for my Internet Quake Activities.  Since
quake clients transmit between 2-4kbytes a second I went with 1b
subscription.  Initially I used an external 3ComImpact with my 16550 uart.
In games with others that had Ascend Pipeline 50's (also using same ISP) I
noticed thier pings in quake were 75ms vs mine of 170ms.  It was then it
dawned on me that though ISDN modems have a separate d channel for control
information, it all gets combined in the Asynchronous UART.  Every byte
(8bits) that comes through the UART is going to include 1 1/2 start bits
and 1 stop bits.  Quite a bit of overhead there.  I put an USR Sportster
128k Internal ISDN modem in last night and now I am pinging the between
75-100ms in the Quake games.  The difference is like night and day.  

As far as downloading I have only seen a slight, hardly noticeable
improvement.  On cost outlay I saved $87 going with the internal and
returning the 3com + extra serial card.

Since I don't have 2b service I cannot verify anything there.  I did read
in PC Magazine that they noticed much more difference at 2b than 1b for
whatever that is worth.

For myself and thousands of others out there that want to eliminate the
bottle necks present when playing online games, the internal ISDN modem
seems to be the ticket.
--
David Riewe



Quote:> I've done a limited amount of testing.  I compared the Adtran Express XRT
> and 3Com Impact IQ external TAs against the Eicon Diva and NTT-IT
> ThunderCard PC Cards (PCMCIA).

> I went to the trouble of installing a 230.4 kb/s capabile I/O port.  The
PC
> Cards gave me 120 kb/s for both FTP GETs and PUTs in all cases.

> At 230.4 kb/s both the external boxes gave between 100 to 115 kb/s on
GETs
> and 75 to 90 kb/s on PUTs.  The Adtran was a hair faster on the PUTs.
> There was little difference on GETs.

 
 
 

Is an internal ISDN "modem" better than external?

Post by David Riew » Sun, 27 Oct 1996 04:00:00


As far as getting low pings in online games that use small packets, it
almost cut my pings in half.  Originally, with external I would
consistantly ping at 70 ms.  Now with the Sportster internal I ping
consistently at 37msecs.  Plus my outlay was less.
--
David Riewe



Quote:> I'm at about the same stage as you are, so I only know what I've been
> reading.  cnet has a fairly recent review
>    http://www.cnet.com/Content/Reviews/Compare/Isdn/
> which shows the USR Sportster ISDN (an internal)  25% faster than
> exterals like Bitsurfer. And for just the reason you said: at the high
> end the serial port is a bottleneck.   The USR is also pretty cheap,
> but it needs an add-on to actually ring the analog line  so that your
> FAX machine works.

> But there is a pretty new Bitsurfer Pro ISA internal model that wasn't
> in the cnet review.  Does anybody out there really know how the
> Bitsurfer speed compares to the externals or the USR?

> Tnks in advance!

 
 
 

Is an internal ISDN "modem" better than external?

Post by Bill Lutt » Mon, 28 Oct 1996 03:00:00



>I put an USR Sportster
>128k Internal ISDN modem in last night and now I am pinging the between
>75-100ms in the Quake games.  The difference is like night and day.  

Just FYI, right answer, wrong reason.
The D channel is used for call control (placing & receiving calls).
It doesn't have anything to do with "clocking" or "syncing" the
data on the B channels (i.e. it is not related to the function that
start/stop bits do on a serial connected TA).
The serial interface of an external serial TAs does have to pass
2 extra bits per byte (start+stop).

The amount of delay an external TA adds to ping times depends
more, however, on the design of the TA's firmware than it does
on the 20% "overhead" of the async serial interface.
Just as an example, connecting to the same ISP with an Ascend
P75 and with a Zyxel 2864iu, I see ping times of 35 and 40 ms
repectively.

Hope this helps,
Bill

 
 
 

Is an internal ISDN "modem" better than external?

Post by r » Fri, 01 Nov 1996 04:00:00




>I was prompted to get an ISDN line for my Internet Quake Activities.  Since
>quake clients transmit between 2-4kbytes a second I went with 1b
>subscription.  Initially I used an external 3ComImpact with my 16550 uart.
>In games with others that had Ascend Pipeline 50's (also using same ISP) I
>noticed thier pings in quake were 75ms vs mine of 170ms.  It was then it
>dawned on me that though ISDN modems have a separate d channel for control
>information, it all gets combined in the Asynchronous UART.  Every byte
>(8bits) that comes through the UART is going to include 1 1/2 start bits
>and 1 stop bits.  Quite a bit of overhead there.  I put an USR Sportster
>128k Internal ISDN modem in last night and now I am pinging the between
>75-100ms in the Quake games.  The difference is like night and day.  

This is exactly the reason I changed my mine from going with an external
Bitsurfer Pro to a Pipeline 25PX.  I was going to get an internal
Sportster myself, but I need the POTS ability's of the Ascend unit.
Besides, I won't complain about having an ethernet card in my machine
hooking into the net. Very easy to configure for DOS or Win95.  Plus
the speed should be screaming. ;)

rj of the Quake clan IHoS
--
sig?  I don't need no stinkin sig

 
 
 

Is an internal ISDN "modem" better than external?

Post by James Moo » Thu, 07 Nov 1996 04:00:00




>This is exactly the reason I changed my mine from going with an external
>Bitsurfer Pro to a Pipeline 25PX.  I was going to get an internal
>Sportster myself, but I need the POTS ability's of the Ascend unit.

I considered doing this, but when I bought my Bitsurfr Pro two months ago
(that's about 4 ISDN years) the Ascend units were around $600 and the BSPs
were around $250.  I decided there wasn't really a several-hundred-dollar
difference in functionality between the two approaches.  I would have gone the
other way if the cost diff was ~= $100.

I've been perfectly happy with the BSP, although getting everything configured
was a pain in the neck.

James Moore    
  Stupid elephant tricks!  http://www.wa-democrats.org/stupid/index.html

 
 
 

Is an internal ISDN "modem" better than external?

Post by Carl Rebeir » Mon, 11 Nov 1996 04:00:00



> I'm in the initial stages of getting a Bell Atlantic Residential ISDN
> line here in VA.  When they asked me whether I wanted an internal or
> external modem, I instinctively said "external" because I've always
> gotten external modems in the past.  But now that I'm thinking about
> it more, it seems like going through the serial port like that would
> become a bottleneck at 128K.  So the question is, will I get better
> performance from a card instead?

> A related question:  Should I be getting one of these "modems" at all?
> Or should I be looking at something like a router for best possible
> performance?  (I'm not entirely sure what a router is/does so I may be
> way off there.)

> BTW, my goal is to do dial-up ISDN access to Internet at 128K.  My
> computer is a P6-200.

> Any information appreciated.

>         - Tom

> ------------------------------------------------------------------------
> Thomas Krehbiel                   "I got dozens of friends
> Nova Design, Inc                   and the fun never ends
> http://www.infi.net/~tek           that is as long as I'm buyin'"  -Styx

Tom:

        This is a VERY complicated subject. It can vary from manufacturer to
manufacturer. The best semi-technical discusion I have seen on the
subject is at the Ascend website listed below. From the 2 Tecnical
Overviews I read at the website (they are in Adobe Acrobat .pdf format -
free reader available at http://www.adobe.com), it seems that some
internal TA's  don't take advantage of the full bandwidth of the ISA bus
and still have bandwidth bottlenecks. Although I don't personally have a
router, I have spent lots of "quality time" with an Ascend Pipeline
25-PX router (2 POTS ports, dynamic IP addressing, and NEW Java based
GUI setup software for a MUCH easier installation than in the past), and
I must say that the performance difference over a TA is not small. If
you shop around you can find a P25-PX for under $600.00 (check out some
of the subject headers in this newsgroup for links). If you are
primarily using ISDN for suffing the 'net you can skip the $300.00
Stacker compression option, as just about everything on the 'net is
already compressed to death. If you are willing to give up the POTS
ports, Ascend has a new internal card that appears to your computer as a
Ethernet NIC (network interface card), and lacks any bottlenecks. The
Ascend NetWarp 128 is a passive device, i.e. the brains of the card are
in software and is partially executed by the CPU (and you certainly have
the CPU horesepower, although the demands on the CPU are not that
heavy). The big advantage here is that for upgrades all you have to do
is install a new driver and away you go! The process for upgrading a
router's internal software are much more complex. You should be able to
find a NetWarp 128 ISA card for $300.00 - $400.00. I highly recomend the
2 Technical Overviews listed on the NetWarp 128 page. No I don't work
for Ascend, I just appreciate good, high performance products.

        I told you it was complicated :-) Good luck! if I can be of any further
assistance just ring...Carl.

http://www.ascend.com/products/p25px/p25pxindex.html

http://www.ascend.com/products/netwarp128/nw128index.html

--
Carl Rebeiro
P.O. Box 575
Campbell, CA 95009

 
 
 

Is an internal ISDN "modem" better than external?

Post by Helge Hielsch » Sun, 17 Nov 1996 04:00:00


Quote:>Ascend NetWarp 128 is a passive device, i.e. the brains of the card are
>in software and is partially executed by the CPU (and you certainly have
>the CPU horesepower, although the demands on the CPU are not that
>heavy). The big advantage here is that for upgrades all you have to do
>is install a new driver and away you go!

And that's the main problem of internal passive devices. What's when I
have to change my operating system. No one really supports more than
Windows 95!
A external adapter  communicates with the PC like a Modem, that means
you can use it in DOS, Win95, WinNT, OS/2,Linux,Mac.........

You should consider that!!!

Helge Hielscher

 
 
 

Is an internal ISDN "modem" better than external?

Post by Kevin Kad » Mon, 18 Nov 1996 04:00:00


Rules of thumb:

1. If you plan to connect more than one machine, use an ISDN router.
2. If you need 128K throughput, use an ISDN router, or if you must go the
   cheap route, an internal card.
3. If you need POTS functionality, use an external TA or router, and choose
   carefully- POTS quality varies widely between vendors.
4. If you're paying per channel-minute and need to add/drop the second B
   channel based on bandwidth used, go with an ISDN router.
5. If you want to use the two B channels in two different locations or
   dedicate them to two different purposes, you need an external NT-1 and
   S-interface devices.



>>Ascend NetWarp 128 is a passive device, i.e. the brains of the card are
>>in software and is partially executed by the CPU (and you certainly have
>>the CPU horesepower, although the demands on the CPU are not that
>>heavy). The big advantage here is that for upgrades all you have to do
>>is install a new driver and away you go!

>And that's the main problem of internal passive devices. What's when I
>have to change my operating system. No one really supports more than
>Windows 95!

The Linux and *BSD guys are doing good work. And there are 'active'
internal devices that appear to the OS as a (slow) ethernet card.

Quote:>A external adapter  communicates with the PC like a Modem, that means
>you can use it in DOS, Win95, WinNT, OS/2,Linux,Mac.........

If you plan to only use PPP and perhaps analog ports, the "best" solution
is the most expensive one- an external ISDN router instead of a "modem",
connected to one (or many) computer with an ethernet card.

An ISDN router provides the throughput of an internal card, but with
lower CPU load, the ability to use POTS jacks without booting your PC,
and for upgrades you just load new flash code (firmware). Plus it makes
it very easy to connect multiple machines without having to dedicate one
as a router.

The downside is that while a TA may run $280-$400, a router runs $800-$1200.

ISDN Router and TA reviews:             http://www.veryComputer.com/

--
David Richards                             Ripco, since Nine*-Eighty-Three
My opinions are my own,                    Public Access in Chicago
But they are available for rental          Shell/SLIP/PPP/UUCP/ISDN/Leased

 
 
 

Is an internal ISDN "modem" better than external?

Post by Ted Mille » Fri, 22 Nov 1996 04:00:00


Strange statement, since Windows NT 4.0 comes with drivers for several
non-UART ISDN boards, including USR Sportster, Eicon, and Digi.

Communicating with the PC like a modem is exactly the problem. UARTs are
not a very efficient way of passing data around at high speeds.



Quote:> >Ascend NetWarp 128 is a passive device, i.e. the brains of the card are
> >in software and is partially executed by the CPU (and you certainly have
> >the CPU horesepower, although the demands on the CPU are not that
> >heavy). The big advantage here is that for upgrades all you have to do
> >is install a new driver and away you go!

> And that's the main problem of internal passive devices. What's when I
> have to change my operating system. No one really supports more than
> Windows 95!
> A external adapter  communicates with the PC like a Modem, that means
> you can use it in DOS, Win95, WinNT, OS/2,Linux,Mac.........

> You should consider that!!!

> Helge Hielscher

 
 
 

Is an internal ISDN "modem" better than external?

Post by Helge Hielsch » Sun, 24 Nov 1996 04:00:00



Quote:>Strange statement, since Windows NT 4.0 comes with drivers for several
>non-UART ISDN boards, including USR Sportster, Eicon, and Digi.

>Communicating with the PC like a modem is exactly the problem. UARTs are
>not a very efficient way of passing data around at high speeds.

First modern UARTs are somewhat cached, don't they? That should be
enough even for a real multitasking system. Also there are high speed
serial ports, e.g.  Zyxel's Omni can transmit datas at 460 kbit/s
using a serial port.
Also what needs more power a driver for a passive card including modem
emulation by software for the old programms or the need to get the
data using the serial port?

Second, NT 4.0 is not the only OS out there.

And third are you speaking about passive or active ISDN cards? I also
run NT (3.51) and considered buying an external adapter b/c I only
heard of problems with the public ISDN cards here (Teles and AVM
Fritz). I would love to use an active internal ISDN card, but who can
afford it?

If you know a solution which works (also with X.75, cFos...) AND is
cheap enough, please let me know!

 
 
 

Is an internal ISDN "modem" better than external?

Post by Stan Siel » Mon, 25 Nov 1996 04:00:00


: First modern UARTs are somewhat cached, don't they? That should be
: enough even for a real multitasking system. Also there are high speed
: serial ports, e.g.  Zyxel's Omni can transmit datas at 460 kbit/s
: using a serial port.

Still, most serial ports seem to top out at 115200, a little slower than
the max uncompressed data rate of 2 B channels.

I used to always recommend external modems over internal modems, due to
the inheritly better flexibility, observability, and repairabilty.

Now, however, I realize that if my external ISDN "modem" is communicating
with 2 B channels *and* using compression, and the other end of the
connection is being fed off a LAN, there's a real possibility of having
the data flow being throttled back to about 11520 with the external modem,
whereas an internal "modem" might not have the same restriction (assuming
the decompression is being done by the card, not by the CPU/driver).

Still, I just bought the Courier I-Modem external, because I wanted to be
able to share it with another PC.

--
Stan Sieler

 
 
 

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