Introductory Article on Embedded Systems-Routers

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Hello everyone,

The following article is a basic overview of embedded systems as they
apply to routers. It was written as part of a college project for an
introductory PC hardware course. We encourage you to read our article
at the address listed below and we welcome your comments. Please let us
know if there is anything that you think we should have included but
didn't, or if there is anything that you think is inaccurate or
inappropriate. Please keep in mind that this is not a highly technical
review of the subject, but rather a brief summary. The article
concentrates on the hardware used in routers rather than the software
and includes a brief discussion on RISC architecture. We also discuss
how an ordinary PC can be tranformed into a router.

http://www.mochima.com/net/routers /

Outline:
-Embedded Systems
-Hardware
    -CPUs
         -RISC
            -MIPS
            -ARM
    -Memory
-Cisco IOS
-PC-Based Routers


Thank you,

Scott Drummond
Devin Patel


Re: Introductory Article on Embedded Systems-Routers

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As a brief intoduction it is fine as far as it goes but I feel you may need
to consider improving the depth of the material. Perhaps there is more to
come?

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Re: Introductory Article on Embedded Systems-Routers
Thanks for your comments Paul.

It is just supposed to be an overview of the subject. Since we are
certainly not experts in the subject, we wanted to get some feedback
from more knowledgeable people.

Was there any particular area that you thought needed more attention?

Scott Drummond


Re: Introductory Article on Embedded Systems-Routers

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To answer a question in your other response, there are also other players
in the router market like Netgear, Interpoch, Welltech etc. I am sure that
spending some time with Google will turn up a number of others. It may
require some digging to find out what they run as an OS (if any).

Even though your article is an overview, I felt that the treatment was
still very light and seemed to cover probably a page and a little. It is
the sort of level that I would expect Secondary/High School pupils to be
able to churn out with ease (even my son, who is 13, could do so). Perhaps
applying yourselves a little more would get you a slightly more detailed
analysis which, as an overview, would have been more illuminating. I was
just left feeling that you hadn't really revealed anything new to me.

Now, I am not an expert in routers. However, even I am aware that various
router products exist that support things like IEEE1588 with some leanings
towards also supporting the requirements of LXI. You may not have come
across those in your searches yet because they appear to be quite new
facilities of the routers and Ethernet networking in general.

You could also have mentioned a bit about the general structure of routers
and introduced routing tables and the fact that routers deal with security
issues in a number of ways.

In short. Try harder and I will look forward to reading the improved
version.

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Re: Introductory Article on Embedded Systems-Routers
Not that bad, but WAY to Cisco centric. IMHO only Cisco routers use
CIOS - many others are also using their own or some flavour of Linux.

Just my 2

Markus


Re: Introductory Article on Embedded Systems-Routers
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Thanks for your comments Markus.

I agree that Linux can be used, but I thought that it was only used
with PCs and  not dedicated routers (ie, embedded systems). Is this not
true? Our topic was supposed to be mainly on embedded systems, so we
didn't devote much attention to using PCs as routers.

Yes, our article was quite Cisco centric but aren't they the leading
brand? Are there any other brands that you think we should have
discussed?

Scott Drummond


Re: Introductory Article on Embedded Systems-Routers
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I agree that Linux can be used, but I thought that it was only used
with PCs and  not dedicated routers (ie, embedded systems). Is this not
true? Our topic was supposed to be mainly on embedded systems, so we
didn't devote much attention to using PCs as routers.
<<

Beware of terminology. "Embedded systems" includes "embedded PCs". I know of
a fair few routers that are i386 architecture running e.g. FreeBSD (there
are other Unices than Linux).

Steve
http://www.fivetrees.com



Re: Introductory Article on Embedded Systems-Routers
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There are dozens of "Wireless routers" using MIPS cpu's and
wireless chipsets from Broadcom, all running Linux.  The Linksys
variations are the most popular (e.g., the WRT54G routers), but
there are many different brands all based on Broadcom designs.

Their popularity is to some degree the result of using
GNU/Linux, and releasing not just the specific GPL's software
packages they are required to distribute, but also the entire
software toolchain required to cross compile and generate a new
system.  They are inexpensive and fun, so people are buying them
just to play with!

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That borders on being an arbitrary division, and probably would
be better stated as a line that you have chosen rather than
trying to argue that it is some natural line in the sand.

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I didn't have a problem with that as such.  I guess there were
limits on just how big you wanted your article to be, and of
course everyone else would like to see "more", each of use with
a different idea of exactly what "more" ought to be... :-)

I won't complain if you devote time to more research and expand
it to twice, or even larger, its current size.

--
Floyd L. Davidson           <http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)                         snipped-for-privacy@barrow.com

Re: Introductory Article on Embedded Systems-Routers
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Scott,

Yes, Cisco is the leader by far in the enterprise space (corporations);
a little less so in the consumer space (they own LinkSys now); in the
ISP space there are many strong players.

While there's more to routers than Cisco, I think you'll find far more
writen on Cisco's inner workings than any of the other vendors, so using
them as an example is appropriate.  For example, this book is excellent:
(Amazon.com product link shortened)
It gives a really interesting look inside the architecture, queuing
mechanisms, processes, etc. inside IOS.  I can't say I've seen similar
internal details for any other vendor.

Regarding Unix/Linux... it's more widely used in embedded systems that
you realize.

For example, many of the popular Linksys router / firewalls are
Linux-based, and their source is freely available under GPL:
http://www.linksys.com/support/gpl.asp
So, for under $60 you can get a pretty nice embedded system with
wireless, and then customize it.

On the article... it's a good scratch on the surface.

Embedded is a pandora's box, and spans something like 95% of the CPUs
sold each year, dwarfing the PCs that people perceive to be the
computing market - it's a huge topic, as are many of the sub-topics you
touched on.  So, you could expand that article into an entire book and
it'd still be missing aspects for some readers.

E.g., hard drive controllers, modems, microwave ovens, VCRs, TVs, remote
controls, cellphones, wristwatches - look around, and virtually anything
with some degree of intelligence is "embedded" with a microcontroller,
and the range of features/capability/complexity is very wide.  Your
article will need to draw the line somewhere, and this will probably be
dictated by the requirements of the assignment.

My two cents,
Richard

Re: Introductory Article on Embedded Systems-Routers

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I thought that, with the subject title chosen by the OP, he had set himself
a sensible boundary to work to. Of course, for the article to get more
interesting than a mere "scratch at the surface" he does need to look a bit
more into it than his initial posting. I am sure that there is a lot of
interesting stuff on routers that, had we all got sufficient time, we would
all research quite deeply. Instead, we hope to find a useful paper or book
on the topic that gives us a reasonable view. Embedded systems in routers
is quite an interesting topic given the breadth of just that little portion.

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Re: Introductory Article on Embedded Systems-Routers
Thanks Richard for your comments and thanks to everyone else who
commented. I really appreciate your advice. This topic is huge and
trying to give a brief overview is not easy when you are learning it as
you are writing it. The problem that I found when researching the topic
was that, while there is a ton of information out there, it is usually
very specific and detailed. This makes it easy to overlook a topic. You
(Richard and the others) have openned my eyes to some of the areas that
I missed.

Thanks everyone,

Scott Drummond

Richard H. wrote:
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