Networking: topic of discussion at nblug?

ME dugan at
Sun Jan 23 20:02:12 PST 2000

On Sun, 23 Jan 2000, Nancy Harrison wrote:

> ... I found that it would be good if you included a completely simple
> ... example ... based on a simple task that actually takes place on a
> network: 

This is a good idea.

> For example, I am at home, I connect
> via PPP to the Internet, I call up a browser and click on a URL in
> my bookmarks to view the page, I view the page and close the
> browser and the PPP connection.

I would like to go over the detail of some common PPP transactions in how
the handshaking takes place, and what information is exchanged in setting
up the connection and maintaining it. This *detailed* review would be
placed later in the full on-line networking document near the Data Link
Layer section of . A general
review of packetization using PPP and Ethernet may be possible in the
5-layer model section. 

> How would this simple task percolate through all the layers, and
> what would be involved at each layer? Assume I have an Intel or
> Mac box with an internal modem, connected to my home phone
> line.

This is a good idea. :-)

I have presently mapped an example of what processes take place when
performing a login to a shell over Telnet down to the Network layer, and
there is a URL for that within the main networking page. However, the web
and http are both used more commonly now-a-days than telnet, and a review
of an HTTP request and response through the layers, to the remote host,
and the responses is a good idea. Also, since the Telnet example stops at
the Networking Layer, this would give opportunity to explore a complete
transacted session for files transmitted as well as screen control
(layout) of text. 

The difficulty comes in making it detailed enough for it to keep the
technical people happy, verbose enough to have a greater population
understand it, yet not so long and boring that (*yawn*) people lose
interest. (The evil world of market analysis and demographics.)

The likely answer would be to use an outline format which allows the novice
to dig through the generalizations and go as deep as they have an
attention span to review, while allowing those that understand the lower
layers, focus on only the things they do not know.

I will eventually add a section showing a complete process for displaying
a sample web page as it passes through the different layers. However, I
will use the 5-layer model as the guiding reference and include side
comments on where a particular mechanism might normally be located
somewhere else in the 7-layer model. (The TCP/IP 5-layer model would be
better to use to describe an application that normally resides over the
TCP and IP layers for the reasons outline in the 5 -layer model page.)

(Know this: a complete (can anything ever be truly "complete" ?) review of
a transfer of HTML files will be long and tedious, so it may take a
while, but will be done.) 

>   Or, for a person on a LAN, at work, say - they log on, they ask for the
> grade record for last semester's Biology 666 class, they print this, they
> log off. They are using a dumb terminal on a HP-UX system networking
> all the departments and offices.  How would the layers work in this
> case?

This might be good so as to bring up the topic of serialized connections,
and I'll look for a way to include this somewhere else as well. Possible
including of networking devices like terminal servers on an Ethernet could
be good too.

> ... I need to visualize what is happening on a more personal level.  I
> just need a bit more help understanding the concepts of the layers.

OK, I will see how much can be added on this to offer a tangible reference
from the real world to anchor the ethereal concepts in more people's
brains. (As you pointed out, it is a lot easier to understand something
foreign when you can attach it to something about which you are familiar.) 

(Other additions will eventually include a review of theory for various
forms of NAT (including IP Masquerading), deeper review of firewall
theory, and then suggestions of how to set up a Linux box with these by
referencing the "How-To" that others have prepared.)

Thanks for the comments, and suggestions. When they additions are included
others would benefit from the improvements.

If anyone else has suggestions, feel free to e-mail me directly. If you
want credit for your suggestions, please let me know if I am permitted to
display your name, and/or e-mail address within the document or if you
prefer to remain anonymous! (I am willing to post aliases, and include
things like "NO-SPAM" in your addresses on the web pages if that is


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