Cell Relay Archive

[Mike Conner <mconner@sntc.com>]

We have did a great deal of analysis on the performance characteristics
of ATM adapters in PC based systems under various types of applications.

I think it is bit incorrect to say that an OC-12 card cannot be used on
a PC server.  To a great degree this is dependent on the type of
application you are running as well as the CPU power of the server.  If
you are doing database or general file serving, web serving, etc. this
may be true in most cases.  You will likely run out of CPU resource long
before you have saturated your OC3 NIC due to CPU overhead in the
applications, protocol stacks and device drivers.  However, if you have
a video serving application which is using native ATM or UDP with large
MTU sizes you will have plenty of CPU bandwidth left for more than one
OC3.  I have personally witnessed CPU utilizations of less than 10%
running video serving applications at OC3 rates on Pentium II platforms
with our adapters.  This type of performance is greatly dependent on the
actual server card and device driver implementations.  Some server cards
are orders of magnitude better than others.  Additionally, some server
cards use more PCI bus bandwidth than others.  The PCI bus bandwidth can
and may ultimately limit the total system throughput.  Some server
vendors offer servers with multiple primary PCI bus architectures.   A
good OC3 card will use 20% or less of the PCI bus when transmitting at
line rate in a video application.  A bad one can use up to 65% of the
PCI bus at line rate.

In most applications I would say OC12 is overkill.  However, we have
been seeing improvements in applications, operating systems, protocol
stacks, and drivers which allow you to use more than OC3 server card
effectively.  The experienced buyer should make sure that the ATM OC3
card is a real server adapter, not a client type architecture made out
to be a server adapter.  Power users should consider buying server ATM
adapters which support dual homing or load balancing techniques such as
SNT's Entraserv product.  This would allow the user increased bandwidth
through multiple OC3s with the advantage of fault tolerance.  See
www.sntc.com.

Regards,

Mike Conner

> -----Original Message-----
> From:	crystal [SMTP:crystal@postme.net]
> Sent:	Wednesday, July 22, 1998 7:47 PM
> To:	cell-relay@cell.ucs.indiana.edu
> Subject:	CR: Re: What PC 155/622 Mb ATM Card to buy ???
> 
> If a OC-12 connector cannot be used on a PC-based server than what
> server can it be used on? Are we simply using terminology, in that: 
> PCs and servers don't have the same PCI bus, Pentium II, 133Mhz FSB,
> 256
> RAM? 
> 
> How does an OC-12 connector on the ATM switch/module connect to a
> server? Isn't it still one-to-one, and not like some multi-i/o serial
> port?  Do you mean that OC-12 connectors only connect from a ATM
> switch/module to a router/bridge unit only?
> 
> Is the Fore PMC-Sierra PM5355 practically worthless then?
> 
> Best Regards,
> Crystal.
> 
> "Tom Lawrence" <tom@argustech.com> wrote:
> > I know of almost no switches that don't support a mixture of OC-3 
> > and OC-12.  PC-based servers connecting at OC-3 make sense...  
> > PC-based servers connecting at OC-12 translates into about 470Mb 
> > of wasted bandwidth.
>