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OSI Model

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April 12, 2005 7:46:40 AM

Archived from groups: comp.dcom.lans.ethernet,microsoft.public.certification.networking (More info?)

I studied the OSI model, but nobody could ever tell me why I need to know
it.
The answer I always got was "you definitely need to know the OSI model" but
when I ask why I always get "you just do".

Can anyone tell me why I need to know it and how I would apply the
knowledge? Perhaps a lab exercise or something??

Thanks,
CJ

More about : osi model

Anonymous
April 12, 2005 7:46:41 AM

Archived from groups: comp.dcom.lans.ethernet,microsoft.public.certification.networking (More info?)

"CJ" <chrisj@illicom.net> prattled ceaslessly in
news:AwH6e.689$Cz3.64167@monger.newsread.com:

> I studied the OSI model, but nobody could ever tell me why I need to
> know it.
> The answer I always got was "you definitely need to know the OSI
> model" but when I ask why I always get "you just do".
>
> Can anyone tell me why I need to know it and how I would apply the
> knowledge? Perhaps a lab exercise or something??
>
> Thanks,
> CJ
>
>
>

The OSI model is a theoretical model that specifies, in a very general
way, how data gets from the application on one machine across the network
to the application on another machine. There are no labs unless you are
developing a protocol to operate at a layer in the model. Understanding
the model helps you undestand how the protocols fit together to get data
onto the network and back off of it.

--
Catwalker
aka Pu$$y Feet
BS, MCP, MCSA
MCNGP #43
www.mcngp.com
faq.mcngp.com
"If man could be crossed with the cat, it would improve man, but it would
deteriorate the cat." Mark Twain
Anonymous
April 12, 2005 10:39:22 AM

Archived from groups: comp.dcom.lans.ethernet,microsoft.public.certification.networking (More info?)

"CJ" <chrisj@illicom.net> writes:

>I studied the OSI model, but nobody could ever tell me why I need to know
>it.
>The answer I always got was "you definitely need to know the OSI model" but
>when I ask why I always get "you just do".

You need to know it just like other kinds of terminology: to understand
people and publications which use it to illustrate something that they want
to teach you.

>Can anyone tell me why I need to know it and how I would apply the
>knowledge? Perhaps a lab exercise or something??

Definitely not. The OSI model has no relevance in _practise_.

best regards
Patrick
Related resources
Anonymous
April 12, 2005 10:44:02 AM

Archived from groups: comp.dcom.lans.ethernet,microsoft.public.certification.networking (More info?)

CJ wrote:

> I studied the OSI model, but nobody could ever tell me why I need to know
> it.
> The answer I always got was "you definitely need to know the OSI model"
> but when I ask why I always get "you just do".
>
> Can anyone tell me why I need to know it and how I would apply the
> knowledge? Perhaps a lab exercise or something??

It's just a method of learning the general layers of the protocol stack.
It's also a stack that was intended to be used, but was soon surpassed by
TCP/IP.
Anonymous
April 12, 2005 10:44:03 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

James Knott <james.knott@rogers.com> prattled ceaslessly in
news:o uqdnYFYXaDuO8bfRVn-pg@rogers.com:

> CJ wrote:
>
>> I studied the OSI model, but nobody could ever tell me why I need to
>> know it.
>> The answer I always got was "you definitely need to know the OSI
>> model" but when I ask why I always get "you just do".
>>
>> Can anyone tell me why I need to know it and how I would apply the
>> knowledge? Perhaps a lab exercise or something??
>
> It's just a method of learning the general layers of the protocol
> stack. It's also a stack that was intended to be used, but was soon
> surpassed by TCP/IP.
>

Once again, OSI is not a protocol stack. It is a general model that was
actually followed when developing TCP/IP as well as other protocol
stacks.

--
Catwalker
aka Pu$$y Feet
BS, MCP, MCSA
MCNGP #43
www.mcngp.com
faq.mcngp.com
"If man could be crossed with the cat, it would improve man, but it would
deteriorate the cat." Mark Twain
Anonymous
April 12, 2005 10:45:52 AM

Archived from groups: comp.dcom.lans.ethernet,microsoft.public.certification.networking (More info?)

> The answer I always got was "you definitely
> need to know the OSI model" but
> when I ask why I always get "you just do".

The issue is that the people who create all of
this networking stuff use this model to simplify
what would otherwise be a more difficult problem.

This has a couple of consequences:-

If you are designing or troubleshooting a network
then it helps to be able to think about the kit in the same
way as the designers and implementors do.

In a purer application of the model, the most critical
phase of troubleshooting for me is to determine
what layer the problem resides in.

e.g. 1. If the link light is not on it is an L1 problem and
we do not (yet) need to worry about possible IP
addressing issues (L3).

e.g. 2. If we are getting ARP entries in our arp cache for
the target then L2 must be working since we are exchanging frames.
There is no point in worrying about STP any further.

In many cases this is just _obvious_ however in more
subtle cases or when learning about networking
it can help a great deal to have a formal structure
to hang on to.

The KEY idea is that the respective layers at each end of
a communications link talk DIRECTLY to each other.

If L3 at end A can talk to L3 at end B then L1 and L2 and L3
must be working correctly at both ends and at all points
between.

Finally, it is a MODEL and for example, TCP/IP is quite a close fit
to the OSI model but it seems to be generally accepted that it
is a 4 layer system with layes 5, 6, 7 of the OSI model not being
applicable.

PS
The critical thing is not knowing the names of the 7 layers (which
I don't, unless you need to pass tests) but having the concept in
your head that TCP/IP has been constructed using a layered model.
Anonymous
April 12, 2005 10:47:21 AM

Archived from groups: comp.dcom.lans.ethernet,microsoft.public.certification.networking (More info?)

Patrick Schaaf wrote:

> Definitely not. The OSI model has no relevance in practice.
>

Actually, at one time, it was intended to be the "standard", but instead,
TCP/IP became the defacto standard.

http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_do...
Anonymous
April 12, 2005 10:47:22 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

James Knott <james.knott@rogers.com> prattled ceaslessly in
news:o uqdnYBYXaCkOsbfRVn-pg@rogers.com:

> Patrick Schaaf wrote:
>
>> Definitely not. The OSI model has no relevance in practice.
>>
>
> Actually, at one time, it was intended to be the "standard", but
> instead, TCP/IP became the defacto standard.
>
> http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_do...
>

TCP/IP is a protocol suite. The OSI model is a general model for
networking. TCP/IP follows the OSI and DOD model and the various
protocols in the suite fit into the model at different layers.

--
Catwalker
aka Pu$$y Feet
BS, MCP, MCSA
MCNGP #43
www.mcngp.com
faq.mcngp.com
"If man could be crossed with the cat, it would improve man, but it
would deteriorate the cat." Mark Twain
Anonymous
April 12, 2005 11:16:36 AM

Archived from groups: comp.dcom.lans.ethernet,microsoft.public.certification.networking (More info?)

> I studied the OSI model, but nobody could ever tell me why I need to know
> it.
> The answer I always got was "you definitely need to know the OSI model" but
> when I ask why I always get "you just do".
>
> Can anyone tell me why I need to know it and how I would apply the
> knowledge? Perhaps a lab exercise or something??

So you can read all those articles in Datamation and ComputerWorld in
the 80s that argued whether or not the OSI model should be a requirement
or not and whether or not IBM's SNA was OSI compliant and .....

It got rather tedious after a while.
Anonymous
April 12, 2005 12:15:57 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

catwalker63 wrote:

> James Knott <james.knott@rogers.com> prattled ceaslessly in
> news:o uqdnYFYXaDuO8bfRVn-pg@rogers.com:
>
>> CJ wrote:
>>
>>> I studied the OSI model, but nobody could ever tell me why I need to
>>> know it.
>>> The answer I always got was "you definitely need to know the OSI
>>> model" but when I ask why I always get "you just do".
>>>
>>> Can anyone tell me why I need to know it and how I would apply the
>>> knowledge? Perhaps a lab exercise or something??
>>
>> It's just a method of learning the general layers of the protocol
>> stack. It's also a stack that was intended to be used, but was soon
>> surpassed by TCP/IP.
>>
>
> Once again, OSI is not a protocol stack. It is a general model that was
> actually followed when developing TCP/IP as well as other protocol
> stacks.

??? The OSI model was first proposed in 1977 published in preliminary form
in March 1978, with a second preliminary release in June, 1979, and
adoption as a standard coming later. TCP/IP was first defined in 1973 as
TCP, and split out into TCP and IP as separate components in TCP/IP
Revision 4, released in January, 1978.

So it's difficult to attribute any part of the development of TCP/IP to the
influence of the OSI model. It could be that the 1979 or 1980 or later
specification revisions may reference the OSI model in some manner but that
is not the same as using the model when developing the protocol.
>

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
Anonymous
April 12, 2005 1:06:30 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

James Knott <james.knott@rogers.com> prattled ceaslessly in
news:o uqdnYBYXaCkOsbfRVn-pg@rogers.com:

> Patrick Schaaf wrote:
>
>> Definitely not. The OSI model has no relevance in practice.
>>
>
> Actually, at one time, it was intended to be the "standard", but
> instead, TCP/IP became the defacto standard.
>
> http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_do...

The OSI model is not a protocol suite. TCP/IP is a protocol stack based
on the OSI or DOD model. TCP/IP did not replace the OSI model, it
followed it. The OSI model is a very general specification for how to
build a protocol stack.

--
Catwalker
aka Pu$$y Feet
BS, MCP, MCSA
MCNGP #43
www.mcngp.com
faq.mcngp.com
"If man could be crossed with the cat, it would improve man, but it
would deteriorate the cat." Mark Twain
Anonymous
April 12, 2005 2:51:00 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

James Knott <james.knott@rogers.com> writes:

>Patrick Schaaf wrote:

>> Definitely not. The OSI model has no relevance in practice.

>Actually, at one time, it was intended to be the "standard", but instead,
>TCP/IP became the defacto standard.

No argument here. Some parts of those sets of standards even survive
today, for example the IS-IS routing protocol, which is used as an
interiour routing protocol in lots of contemporary IP networks.

best regards
Patrick
Anonymous
April 12, 2005 2:51:01 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <425ba814$0$17607$9b622d9e@news.freenet.de>,
Patrick Schaaf <mailer-daemon@bof.de> wrote:
>James Knott <james.knott@rogers.com> writes:
>
>>Patrick Schaaf wrote:
>
>>> Definitely not. The OSI model has no relevance in practice.
>
>>Actually, at one time, it was intended to be the "standard", but instead,
>>TCP/IP became the defacto standard.
>
>No argument here. Some parts of those sets of standards even survive
>today, for example the IS-IS routing protocol, which is used as an
>interiour routing protocol in lots of contemporary IP networks.
>
>best regards
> Patrick




ISTR that LDAP is a version of X.400, another standard from
the same period.


Remember to keep OSI (Open System Interconnect) and ISO
(International Standards Org). The fact that the ISO standards were
created by ISO can be confusing.)

The 7 layer model OSI is important and very useful when you are trying
to understand different protocols, ie IP and SS7, even in one or both
are not OSI-based, and figure out how to make them work together.
It's a common framework when you are trying to explain how some
component fits with other components. Try explaining how IP runs over
a broadcast medium (ethernet) and also a serial connection without
refering to layers.

For a few years the US gov't had a policy that said as of some date
all equipment purchased had to conform to relevant OSI standards and
there was lots of lip service but departments started to buy TCP-based
systems anyway. At some point they came out with GOSSIP (Government
Open Systems .something... Plan) to tray to make something of
themess. Google for it.

Padlipsky's _The Elements of Networking Style_ is a great book about
how IP and ISO competed in the 80's. Every communications book by
Tannenbaum I've seen has covered the 7 layer model well.

--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore.
Anonymous
April 12, 2005 5:02:47 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

catwalker63 wrote:

> James Knott <james.knott@rogers.com> prattled ceaslessly in
> news:o uqdnYBYXaCkOsbfRVn-pg@rogers.com:
>
>> Patrick Schaaf wrote:
>>
>>> Definitely not. The OSI model has no relevance in practice.
>>>
>>
>> Actually, at one time, it was intended to be the "standard", but
>> instead, TCP/IP became the defacto standard.
>>
>> http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_do...
>
> The OSI model is not a protocol suite. TCP/IP is a protocol stack based
> on the OSI or DOD model. TCP/IP did not replace the OSI model, it
> followed it. The OSI model is a very general specification for how to
> build a protocol stack.

Since TCP/IP preceded the OSI model it's difficult to see how it could be
based on that model.

As for the DOD model, since TCP/IP was developed as part of a DOD advanced
research project, one would expect the DOD model to be based on TCP/IP.

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
Anonymous
April 12, 2005 10:22:52 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <Xns9636484FCB54Ecatwalker63athotmail@216.196.97.136>,
catwalker63 <_catwalker63_@hotmamamail.com> wrote:
>James Knott <james.knott@rogers.com> prattled ceaslessly in
>news:o uqdnYBYXaCkOsbfRVn-pg@rogers.com:
>
>> Patrick Schaaf wrote:
>>
>>> Definitely not. The OSI model has no relevance in practice.
>>>
>>
>> Actually, at one time, it was intended to be the "standard", but
>> instead, TCP/IP became the defacto standard.
>>
>> http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_do...
>
>The OSI model is not a protocol suite. TCP/IP is a protocol stack based
>on the OSI or DOD model. TCP/IP did not replace the OSI model, it
>followed it. The OSI model is a very general specification for how to
>build a protocol stack.
>
>--
>Catwalker
>aka Pu$$y Feet
>BS, MCP, MCSA
>MCNGP #43
>www.mcngp.com
>faq.mcngp.com
>"If man could be crossed with the cat, it would improve man, but it
>would deteriorate the cat." Mark Twain

IP and parts of the ISO _standard_ were co-developed. The problem is
that RFC standards process emphesised practical working functionality
designed by the programers that wrote the code as they went and the
OSI standard was written by teco engineers who included every function
they could think of without any thought of was it was possibe to code.
It took years for products based on OSI mode to be useful.
--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore.
April 13, 2005 12:18:05 AM

Archived from groups: comp.dcom.lans.ethernet,microsoft.public.certification.networking (More info?)

I understand how OSI works in general. But I can know alot of information
about alot of things....doesn't mean its of any use to me.

From what I am reading knowing the OSI is a "nice to know" thing, but
knowing it, unless I am a protocol developer or something, is useless to me.

Sound about right?


"catwalker63" <_catwalker63_@hotmamamail.com> wrote in message
news:Xns9635D5BA2DD3Bcatwalker63athotmail@216.196.97.136...
> "CJ" <chrisj@illicom.net> prattled ceaslessly in
> news:AwH6e.689$Cz3.64167@monger.newsread.com:
>
>> I studied the OSI model, but nobody could ever tell me why I need to
>> know it.
>> The answer I always got was "you definitely need to know the OSI
>> model" but when I ask why I always get "you just do".
>>
>> Can anyone tell me why I need to know it and how I would apply the
>> knowledge? Perhaps a lab exercise or something??
>>
>> Thanks,
>> CJ
>>
>>
>>
>
> The OSI model is a theoretical model that specifies, in a very general
> way, how data gets from the application on one machine across the network
> to the application on another machine. There are no labs unless you are
> developing a protocol to operate at a layer in the model. Understanding
> the model helps you undestand how the protocols fit together to get data
> onto the network and back off of it.
>
> --
> Catwalker
> aka Pu$$y Feet
> BS, MCP, MCSA
> MCNGP #43
> www.mcngp.com
> faq.mcngp.com
> "If man could be crossed with the cat, it would improve man, but it would
> deteriorate the cat." Mark Twain
Anonymous
April 13, 2005 12:18:06 AM

Archived from groups: comp.dcom.lans.ethernet,microsoft.public.certification.networking (More info?)

"CJ" <chrisj@illicom.net> prattled ceaslessly in
news:12W6e.726$Cz3.75041@monger.newsread.com:

> I understand how OSI works in general. But I can know alot of
> information about alot of things....doesn't mean its of any use to me.
>
> From what I am reading knowing the OSI is a "nice to know" thing, but
> knowing it, unless I am a protocol developer or something, is useless
> to me.
>
> Sound about right?


No, it is useful to know if you want to understand how networks work. It
is also necessary if you are contemplating any type of certification in
networking. Those layers will come up over and over again.

--
Catwalker
aka Pu$$y Feet
BS, MCP, MCSA
MCNGP #43
www.mcngp.com
faq.mcngp.com
"If man could be crossed with the cat, it would improve man, but it would
deteriorate the cat." Mark Twain
Anonymous
April 13, 2005 12:18:06 AM

Archived from groups: comp.dcom.lans.ethernet,microsoft.public.certification.networking (More info?)

CJ wrote:

> I understand how OSI works in general. But I can know alot of information
> about alot of things....doesn't mean its of any use to me.
>
> From what I am reading knowing the OSI is a "nice to know" thing, but
> knowing it, unless I am a protocol developer or something, is useless to
> me.
>
> Sound about right?

Until some guy in a job interview asks you to explain your understanding of
the OSI model.

> "catwalker63" <_catwalker63_@hotmamamail.com> wrote in message
> news:Xns9635D5BA2DD3Bcatwalker63athotmail@216.196.97.136...
>> "CJ" <chrisj@illicom.net> prattled ceaslessly in
>> news:AwH6e.689$Cz3.64167@monger.newsread.com:
>>
>>> I studied the OSI model, but nobody could ever tell me why I need to
>>> know it.
>>> The answer I always got was "you definitely need to know the OSI
>>> model" but when I ask why I always get "you just do".
>>>
>>> Can anyone tell me why I need to know it and how I would apply the
>>> knowledge? Perhaps a lab exercise or something??
>>>
>>> Thanks,
>>> CJ
>>>
>>>
>>>
>>
>> The OSI model is a theoretical model that specifies, in a very general
>> way, how data gets from the application on one machine across the network
>> to the application on another machine. There are no labs unless you are
>> developing a protocol to operate at a layer in the model. Understanding
>> the model helps you undestand how the protocols fit together to get data
>> onto the network and back off of it.
>>
>> --
>> Catwalker
>> aka Pu$$y Feet
>> BS, MCP, MCSA
>> MCNGP #43
>> www.mcngp.com
>> faq.mcngp.com
>> "If man could be crossed with the cat, it would improve man, but it would
>> deteriorate the cat." Mark Twain

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
Anonymous
April 13, 2005 11:07:47 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

catwalker63 wrote:

>> Actually, at one time, it was intended to be the "standard", but
>> instead, TCP/IP became the defacto standard.
>>
>> http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_do...
>>
>
> TCP/IP is a protocol suite.  The OSI model is a general model for
> networking.  TCP/IP follows the OSI and DOD model and the various
> protocols in the suite fit into the model at different layers.
>

At one time, OSI was intended to be the common networking method, but didn't
make it. It was at that point that it was declared a "model".
Anonymous
April 13, 2005 11:11:16 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

catwalker63 wrote:

>> It's just a method of learning the general layers of the protocol
>> stack. It's also a stack that was intended to be used, but was soon
>> surpassed by TCP/IP.
>>
>
> Once again, OSI is not a protocol stack.  It is a general model that was
> actually followed when developing TCP/IP as well as other protocol
> stacks.

From http://www.tcpipguide.com/free/t_HistoryoftheOSIReferen...

"One interesting aspect of the history of the OSI Reference Model is that
the original objective was not to create a model primarily for educational
purposes-even though many people today think that this was the case. The
OSI Reference Model was intended to serve as the foundation for the
establishment of a widely-adopted suite of protocols that would be used by
international internetworks-basically, what the Internet became. This was
called, unsurprisingly, the OSI Protocol Suite.



However, things didn't quite work out as planned. The rise in popularity of
the Internet and its TCP/IP protocols met the OSI suite head on, and in a
nutshell, TCP/IP won. Some of the OSI protocols were implemented, but as a
whole, the OSI protocols lost out to TCP/IP when the Internet started to
grow."
Anonymous
April 13, 2005 1:08:00 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <8P2dndeaErgeYMHfRVn-sA@rogers.com>,
James Knott <james.knott@rogers.com> wrote:
>catwalker63 wrote:
>
>>> Actually, at one time, it was intended to be the "standard", but
>>> instead, TCP/IP became the defacto standard.
>>>
>>> http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_do...
>>>
>>
>> TCP/IP is a protocol suite.  The OSI model is a general model for
>> networking.  TCP/IP follows the OSI and DOD model and the various
>> protocols in the suite fit into the model at different layers.
>>
>
>At one time, OSI was intended to be the common networking method, but didn't
>make it. It was at that point that it was declared a "model".
>


You need a smiley after that. The ISO folks were very serious about a
model.

--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore.
Anonymous
April 13, 2005 1:11:49 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <8P2dndaaErjJY8HfRVn-sA@rogers.com>,
James Knott <james.knott@rogers.com> wrote:
>catwalker63 wrote:
>
>>> It's just a method of learning the general layers of the protocol
>>> stack. It's also a stack that was intended to be used, but was soon
>>> surpassed by TCP/IP.
>>>
>>
>> Once again, OSI is not a protocol stack.  It is a general model that was
>> actually followed when developing TCP/IP as well as other protocol
>> stacks.
>
>From http://www.tcpipguide.com/free/t_HistoryoftheOSIReferen...
>
>"One interesting aspect of the history of the OSI Reference Model is that
>the original objective was not to create a model primarily for educational
>purposes-even though many people today think that this was the case. The
>OSI Reference Model was intended to serve as the foundation for the
>establishment of a widely-adopted suite of protocols that would be used by
>international internetworks-basically, what the Internet became. This was
>called, unsurprisingly, the OSI Protocol Suite.
>


Instead of "model" a better word would be to call it an architecture
for communications between objects. It was open ended. So was the RFC
process developed IP, for that matter.


--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore.
Anonymous
April 13, 2005 8:07:50 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

> IP and parts of the ISO _standard_ were co-developed. The problem is
> that RFC standards process emphesised practical working functionality
> designed by the programers that wrote the code as they went and the
> OSI standard was written by teco engineers who included every function
> they could think of without any thought of was it was possibe to code.
> It took years for products based on OSI mode to be useful.

Yep. In the 80s when this was being done it was very apparent that the
folks running the ISO process were from the mainframe sized side of the
camp. Of course this was when minicomputers and PCs were exploding and a
single meg of ram was a big deal. For many systems at the time to give
up all their ram to a protocol stack that no one was really using doomed
it from the start. And to be honest TCP/IP didn't even work very well
until the ram situation improved. These protocols need buffers to work
well. :) 
Anonymous
April 13, 2005 8:25:40 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <ScGdnR6NDr-K4cDfRVn-og@portbridge.com>,
David Ross <news02@raleighthings.com> wrote:
>> IP and parts of the ISO _standard_ were co-developed. The problem is
>> that RFC standards process emphesised practical working functionality
>> designed by the programers that wrote the code as they went and the
>> OSI standard was written by teco engineers who included every function
>> they could think of without any thought of was it was possibe to code.
>> It took years for products based on OSI mode to be useful.
>
>Yep. In the 80s when this was being done it was very apparent that the
>folks running the ISO process were from the mainframe sized side of the
>camp.


Worse. ISO was the international side of Ma Bell and the rest of the
telecom industry which for many countries was part of it's national
postal service.

The mainframe vendors were busy building their own proprietary
networks; SNA (IBM) and DECNET (DEC) were the big ones. IP was in the
universities and research labs. At least these products worked, within
the family. It's a stretch to say that overall the X. standards ever
came up to expectations.

Of course this was when minicomputers and PCs were exploding and a
>single meg of ram was a big deal. For many systems at the time to give
>up all their ram to a protocol stack that no one was really using doomed
>it from the start. And to be honest TCP/IP didn't even work very well
>until the ram situation improved. These protocols need buffers to work
>well. :) 


--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore.
Anonymous
April 13, 2005 10:58:37 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Al Dykes wrote:

>>At one time, OSI was intended to be the common networking method, but
>>didn't make it.  It was at that point that it was declared a "model".
>>
>
>
> You need a smiley after that.  The ISO folks were very serious about a
> model.

Please check the info and link I posted in another message.
Anonymous
April 14, 2005 12:44:01 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

David Ross <news02@raleighthings.com> wrote:
> Yep. In the 80s when this was being done it was very
> apparent that the folks running the ISO process were from
> the mainframe sized side of the camp. Of course this was
> when minicomputers and PCs were exploding and a single
> meg of ram was a big deal. For many systems at the time to
> give up all their ram to a protocol stack that no one was
> really using doomed it from the start. And to be honest
> TCP/IP didn't even work very well until the ram situation
> improved. These protocols need buffers to work well. :) 

I think TinyTCP will run nicely in 50 kB. The bigger problem was there
usually was no-one to talk to. When there was, no-one minded 50 kB of
lock-down after around 1980 or so when at least 16 kb chips existed.
Prior to that, UUCP ruled because it needed much less (2 kB?).

-- Robert
Anonymous
April 14, 2005 1:58:43 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <trSdnQnG-NCAOcDfRVn-sg@rogers.com>,
James Knott <james.knott@rogers.com> wrote:
>Al Dykes wrote:
>
>>>At one time, OSI was intended to be the common networking method, but
>>>didn't make it.  It was at that point that it was declared a "model".
>>>
>>
>>
>> You need a smiley after that.  The ISO folks were very serious about a
>> model.
>
>Please check the info and link I posted in another message.
>


I did, and didn't agree with it. Maybe we were quibbling over words.
G*d knows enough words were spilled in this topic in the late
70s/early 80s. The goal was, of course, to create specifications for
interoperable protocols that many companies could implement. But
those protocols are not the model. I'll agree that the use of the
model to describe protocols unrelated to X.dot was probably
unintended.

People forget that the full phrase was "ISO Reference Model". Google
for that and you'll find article after article saying that the purpose
was (and still is) to be a framework for interoperability.

For instance:

www.scit.wlv.ac.uk/~jphb/comms/std.7layer.html

ISO in association with CCITT have produced a model for Open
Systems Interconnection. This is a very loose standard which
promotes the development of protocols designed to permit open
systems interconnection. It also functions as a framework into
which existing standards may be slotted. It should act as an
aid in designing future protocol standards.

See this URL for an example of how the model is used to describe SS7,
which is NOT compatible with the X.dot standards.

http://www.pt.com/tutorials/ss7/stack.html
--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore.
April 14, 2005 2:03:50 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

"J. Clarke" <jclarke.usenet@snet.net.invalid> wrote in message
news:D 3heph0dnm@news3.newsguy.com...
> CJ wrote:
>
>> I understand how OSI works in general. But I can know alot of
>> information
>> about alot of things....doesn't mean its of any use to me.
>>
>> From what I am reading knowing the OSI is a "nice to know" thing, but
>> knowing it, unless I am a protocol developer or something, is useless to
>> me.
>>
>> Sound about right?
>
> Until some guy in a job interview asks you to explain your understanding
> of
> the OSI model.

Which is fine...but it still is useless to me otherwise. Ok...so I know how
a packet is created on one end and deconstructed on the other....phffft.


>
>> "catwalker63" <_catwalker63_@hotmamamail.com> wrote in message
>> news:Xns9635D5BA2DD3Bcatwalker63athotmail@216.196.97.136...
>>> "CJ" <chrisj@illicom.net> prattled ceaslessly in
>>> news:AwH6e.689$Cz3.64167@monger.newsread.com:
>>>
>>>> I studied the OSI model, but nobody could ever tell me why I need to
>>>> know it.
>>>> The answer I always got was "you definitely need to know the OSI
>>>> model" but when I ask why I always get "you just do".
>>>>
>>>> Can anyone tell me why I need to know it and how I would apply the
>>>> knowledge? Perhaps a lab exercise or something??
>>>>
>>>> Thanks,
>>>> CJ
>>>>
>>>>
>>>>
>>>
>>> The OSI model is a theoretical model that specifies, in a very general
>>> way, how data gets from the application on one machine across the
>>> network
>>> to the application on another machine. There are no labs unless you are
>>> developing a protocol to operate at a layer in the model. Understanding
>>> the model helps you undestand how the protocols fit together to get data
>>> onto the network and back off of it.
>>>
>>> --
>>> Catwalker
>>> aka Pu$$y Feet
>>> BS, MCP, MCSA
>>> MCNGP #43
>>> www.mcngp.com
>>> faq.mcngp.com
>>> "If man could be crossed with the cat, it would improve man, but it
>>> would
>>> deteriorate the cat." Mark Twain
>
> --
> --John
> to email, dial "usenet" and validate
> (was jclarke at eye bee em dot net)
Anonymous
April 14, 2005 2:03:51 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <aHg7e.780$Cz3.87456@monger.newsread.com>,
CJ <chrisj@illicom.net> wrote:
>"J. Clarke" <jclarke.usenet@snet.net.invalid> wrote in message
>news:D 3heph0dnm@news3.newsguy.com...
>> CJ wrote:
>>
>>> I understand how OSI works in general. But I can know alot of
>>> information
>>> about alot of things....doesn't mean its of any use to me.
>>>
>>> From what I am reading knowing the OSI is a "nice to know" thing, but
>>> knowing it, unless I am a protocol developer or something, is useless to
>>> me.
>>>
>>> Sound about right?
>>
>> Until some guy in a job interview asks you to explain your understanding
>> of
>> the OSI model.
>
>Which is fine...but it still is useless to me otherwise. Ok...so I know how
>a packet is created on one end and deconstructed on the other....phffft.
>
>

You'll use it to understand some new service you haven't heard of yet
or to explain something to someone else. For instance:

http://www.pt.com/tutorials/ss7/stack.html

--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore.
Anonymous
April 14, 2005 10:51:33 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Al Dykes wrote:

> I did, and didn't agree with it. Maybe we were quibbling over words.
> G*d knows enough words were spilled in this topic in the late
> 70s/early 80s.  The goal was, of course, to create specifications for
> interoperable protocols that many companies could implement.  But
> those protocols are not the model.  I'll agree that the use of the
> model to describe protocols unrelated to X.dot was probably
> unintended.
>
> People forget that the full phrase was "ISO Reference Model". Google
> for that and you'll find article after article saying that the purpose
> was (and still is) to be a framework for interoperability.

It currently is a "model", but as someone else mentioned, it wasn't a model
for TCP/IP, which was in service before there was an ISO stack. You'll
also find TCP/IP doesn't quite line up with ISO. Also, you can find a lot
of stuff on the net, that isn't entirely accurate.
April 14, 2005 4:50:38 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

"Al Dykes" <adykes@panix.com> wrote in message
news:D 3kgvq$ha5$1@panix5.panix.com...
> In article <aHg7e.780$Cz3.87456@monger.newsread.com>,
> CJ <chrisj@illicom.net> wrote:
>>"J. Clarke" <jclarke.usenet@snet.net.invalid> wrote in message
>>news:D 3heph0dnm@news3.newsguy.com...
>>> CJ wrote:
>>>
>>>> I understand how OSI works in general. But I can know alot of
>>>> information
>>>> about alot of things....doesn't mean its of any use to me.
>>>>
>>>> From what I am reading knowing the OSI is a "nice to know" thing, but
>>>> knowing it, unless I am a protocol developer or something, is useless
>>>> to
>>>> me.
>>>>
>>>> Sound about right?
>>>
>>> Until some guy in a job interview asks you to explain your understanding
>>> of
>>> the OSI model.
>>
>>Which is fine...but it still is useless to me otherwise. Ok...so I know
>>how
>>a packet is created on one end and deconstructed on the other....phffft.
>>
>>
>
> You'll use it to understand some new service you haven't heard of yet
> or to explain something to someone else. For instance:
>
> http://www.pt.com/tutorials/ss7/stack.html

Thats all nice to know info. But yet still NOBODY has any real example of
how to apply this knowledge. Why is that?
Anonymous
April 14, 2005 4:50:39 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <yGt7e.1537$5I5.73913@newshog.newsread.com>,
CJ <chrisj@illicom.net> wrote:
>"Al Dykes" <adykes@panix.com> wrote in message
>news:D 3kgvq$ha5$1@panix5.panix.com...
>> In article <aHg7e.780$Cz3.87456@monger.newsread.com>,
>> CJ <chrisj@illicom.net> wrote:
>>>"J. Clarke" <jclarke.usenet@snet.net.invalid> wrote in message
>>>news:D 3heph0dnm@news3.newsguy.com...
>>>> CJ wrote:
>>>>
>>>>> I understand how OSI works in general. But I can know alot of
>>>>> information
>>>>> about alot of things....doesn't mean its of any use to me.
>>>>>
>>>>> From what I am reading knowing the OSI is a "nice to know" thing, but
>>>>> knowing it, unless I am a protocol developer or something, is useless
>>>>> to
>>>>> me.
>>>>>
>>>>> Sound about right?
>>>>
>>>> Until some guy in a job interview asks you to explain your understanding
>>>> of
>>>> the OSI model.
>>>
>>>Which is fine...but it still is useless to me otherwise. Ok...so I know
>>>how
>>>a packet is created on one end and deconstructed on the other....phffft.
>>>
>>>
>>
>> You'll use it to understand some new service you haven't heard of yet
>> or to explain something to someone else. For instance:
>>
>> http://www.pt.com/tutorials/ss7/stack.html
>
>Thats all nice to know info. But yet still NOBODY has any real example of
>how to apply this knowledge. Why is that?
>
>


How simple can we make this; In your career, if you have one, in
computers and telecom you will routinely be presented with information
structured with in a conceptual model described by ISORM. It ain't
rocket science or magic. it encourages apples-apples comparisions
which make learning faster and less error prone.

As for real products and systems, Any product that says it implements
an X.something standard is something out of the ISO and to some degree
is part of OSI. There are lots of X roducts in major use. Go to any
tech library and look in _Newton's Telecom Dictionary_ under X....
and you'll find several pages of X.nnn standards.
--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore.
Anonymous
April 14, 2005 4:50:39 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

CJ wrote:

> "Al Dykes" <adykes@panix.com> wrote in message
> news:D 3kgvq$ha5$1@panix5.panix.com...
>> In article <aHg7e.780$Cz3.87456@monger.newsread.com>,
>> CJ <chrisj@illicom.net> wrote:
>>>"J. Clarke" <jclarke.usenet@snet.net.invalid> wrote in message
>>>news:D 3heph0dnm@news3.newsguy.com...
>>>> CJ wrote:
>>>>
>>>>> I understand how OSI works in general. But I can know alot of
>>>>> information
>>>>> about alot of things....doesn't mean its of any use to me.
>>>>>
>>>>> From what I am reading knowing the OSI is a "nice to know" thing, but
>>>>> knowing it, unless I am a protocol developer or something, is useless
>>>>> to
>>>>> me.
>>>>>
>>>>> Sound about right?
>>>>
>>>> Until some guy in a job interview asks you to explain your
>>>> understanding of
>>>> the OSI model.
>>>
>>>Which is fine...but it still is useless to me otherwise. Ok...so I know
>>>how
>>>a packet is created on one end and deconstructed on the other....phffft.
>>>
>>>
>>
>> You'll use it to understand some new service you haven't heard of yet
>> or to explain something to someone else. For instance:
>>
>> http://www.pt.com/tutorials/ss7/stack.html
>
> Thats all nice to know info. But yet still NOBODY has any real example of
> how to apply this knowledge. Why is that?

What do you mean by a "real example"? Its utility is that it provides a
framework, not that you will be digging into the depths of it every day.
If you don't know the OSI model and someone says "This is a Layer 3 switch"
you won't have a clue what they're talking about. If you do know the model
then you will know immediately that it has routing capability. To take one
example.

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
Anonymous
April 14, 2005 4:50:40 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <d3lprv$8il$1@panix5.panix.com>, Al Dykes <adykes@panix.com> wrote:
>In article <yGt7e.1537$5I5.73913@newshog.newsread.com>,
>CJ <chrisj@illicom.net> wrote:
>>"Al Dykes" <adykes@panix.com> wrote in message
>>news:D 3kgvq$ha5$1@panix5.panix.com...
>>> In article <aHg7e.780$Cz3.87456@monger.newsread.com>,
>>> CJ <chrisj@illicom.net> wrote:
>>>>"J. Clarke" <jclarke.usenet@snet.net.invalid> wrote in message
>>>>news:D 3heph0dnm@news3.newsguy.com...
>>>>> CJ wrote:
>>>>>
>>>>>> I understand how OSI works in general. But I can know alot of
>>>>>> information
>>>>>> about alot of things....doesn't mean its of any use to me.
>>>>>>
>>>>>> From what I am reading knowing the OSI is a "nice to know" thing, but
>>>>>> knowing it, unless I am a protocol developer or something, is useless
>>>>>> to
>>>>>> me.
>>>>>>
>>>>>> Sound about right?
>>>>>
>>>>> Until some guy in a job interview asks you to explain your understanding
>>>>> of
>>>>> the OSI model.
>>>>
>>>>Which is fine...but it still is useless to me otherwise. Ok...so I know
>>>>how
>>>>a packet is created on one end and deconstructed on the other....phffft.
>>>>
>>>>
>>>
>>> You'll use it to understand some new service you haven't heard of yet
>>> or to explain something to someone else. For instance:
>>>
>>> http://www.pt.com/tutorials/ss7/stack.html
>>
>>Thats all nice to know info. But yet still NOBODY has any real example of
>>how to apply this knowledge. Why is that?
>>
>>
>
>
>How simple can we make this; In your career, if you have one, in
>computers and telecom you will routinely be presented with information
>structured with in a conceptual model described by ISORM. It ain't
>rocket science or magic. it encourages apples-apples comparisions
>which make learning faster and less error prone.
>
>As for real products and systems, Any product that says it implements
>an X.something standard is something out of the ISO and to some degree
>is part of OSI. There are lots of X roducts in major use. Go to any
>tech library and look in _Newton's Telecom Dictionary_ under X....
>and you'll find several pages of X.nnn standards.
>--
>a d y k e s @ p a n i x . c o m

Quick technical correction -- X. series standards (note the "dot")
are from ITU-T (previously known as CCITT). The International
Organization for Standardization (ISO) is a different beast,
although today many of the ISO standards are also published as
ITU-T standards. ISO standards can be recognized by the title
"ISO/IEC-xxxxx" where xxxx is the standard number and ISO/IEC stands
for "International Organization for Standardization/International
Electrotechnical Commission". You may also see older ISO standards
with an IS, DIS or DP prefix (for International Standard, Draft IS
or Draft Proposal, respectively).

Note also that the IEEE and ANSI LAN and MAN standards are also
under the ISO umbrella, and may get published as IS standards as
they mature. For example, the stable IEEE 802.3 is also available
as ISO/IEC-8802-3. Virtually every physical layer standard currently
in use in the TCP/IP protocol architecture is an ISO/OSI product.

Technical trivia: ISO is not an acronym, it is the Greek prefix "iso"
meaining "same," a pun on the goal of international standards. Note
that ISO does far more than just networking standards. Long before
computers were invented they were standardizing everything from
fire hose couplings to screw threads. CCITT (which mutated to ITU-T
circa 1990) was created by the League of Nations to standardize
international telecommunications, they are the reason you have
been able take for granted the ability to talk by phone or send a
FAX worldwide.

The IETF and IAB are still learning how to deal with the impact of
politics on technical standards as the monetary stakes involved rise
in significance. Funny how as they do, they start to look more and
more like the standards organizations they despised back in the 80's.

Getting back to the topic at hand... why learn the ISO OSIRM? There
is no reason to "learn" it if your only goal is to get a job
in networking. The world is full of network techs with a faulty
understanding of OSI and network layering who are making a good
living. Many of them even do a good job maintaining and even
designing networks. Indeed, a thorough understanding of the OSIRM
can be dangerous, as it can make it difficult to avoid disrupting
meetings with fits of laughter as other's massacre the concepts
and use flawed logic to make their points.

However, if your goal is to understand how networks work
(and sometimes more important, how they can fail), a thorough
understanding of the OSIRM is indispensible. As I tell students,
networking is fundamentally simple, the confusion comes from the
profusion of simple concepts which must be combined to create a
functional system (and from bogus explanations of simple concepts
by those who don't really understand them, and from the need for
backwards compatibility with concepts and technologies which died
out long before most practitioners were even born...we are still
living with the remains of teletype support and the like).

If you want to be able to communicate clearly and concisely with
other knowledgeable networkers, you need to be able to correctly
use OSIRM terminology. And correct usage requires you to understand
how layered protocols work and the standard terms used to describe
those workings. Just as biology uses latin names to formally describe
flora and fauna, so that confusion over local and colloquial names
can be avoided (whether the same name is used for different species
or different names used for the same species), network professionals
need to be able to communicate fundamental networking concepts, and
for better or for worse, the vendor & architecture neutral OSIRM
is the language that has been selected for use. Your opinion of
the relevance of the OSIRM to TCP/IP is irrelevant, even the most
academic biologist will agree that Latin is a very dead language,
but that does not make it any less useful for the purpose.

Unfortunately, the real world will measure your understanding
not only by your ability to correctly use OSIRM terminology when
communicating with others, but also your ability to recognize the
misuse of OSIRM terminology by others and apply the breadth and
depth of your networking knowledge to determine what concept they
are actually trying to express.

Good luck and have fun.
--
Vincent C Jones, Consultant Expert advice and a helping hand
Networking Unlimited, Inc. for those who want to manage and
Tenafly, NJ Phone: 201 568-7810 control their networking destiny
http://www.networkingunlimited.com
Anonymous
April 14, 2005 9:40:20 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <d3lrdr0hml@news3.newsguy.com>,
J. Clarke <jclarke.usenet@snet.net.invalid> wrote:
>CJ wrote:
>
>> "Al Dykes" <adykes@panix.com> wrote in message
>> news:D 3kgvq$ha5$1@panix5.panix.com...
>>> In article <aHg7e.780$Cz3.87456@monger.newsread.com>,
>>> CJ <chrisj@illicom.net> wrote:
>>>>"J. Clarke" <jclarke.usenet@snet.net.invalid> wrote in message
>>>>news:D 3heph0dnm@news3.newsguy.com...
>>>>> CJ wrote:
>>>>>
>>>>>> I understand how OSI works in general. But I can know alot of
>>>>>> information
>>>>>> about alot of things....doesn't mean its of any use to me.
>>>>>>
>>>>>> From what I am reading knowing the OSI is a "nice to know" thing, but
>>>>>> knowing it, unless I am a protocol developer or something, is useless
>>>>>> to
>>>>>> me.
>>>>>>
>>>>>> Sound about right?
>>>>>
>>>>> Until some guy in a job interview asks you to explain your
>>>>> understanding of
>>>>> the OSI model.
>>>>
>>>>Which is fine...but it still is useless to me otherwise. Ok...so I know
>>>>how
>>>>a packet is created on one end and deconstructed on the other....phffft.
>>>>
>>>>
>>>
>>> You'll use it to understand some new service you haven't heard of yet
>>> or to explain something to someone else. For instance:
>>>
>>> http://www.pt.com/tutorials/ss7/stack.html
>>
>> Thats all nice to know info. But yet still NOBODY has any real example of
>> how to apply this knowledge. Why is that?
>
>What do you mean by a "real example"? Its utility is that it provides a
>framework, not that you will be digging into the depths of it every day.
>If you don't know the OSI model and someone says "This is a Layer 3 switch"
>you won't have a clue what they're talking about. If you do know the model
>then you will know immediately that it has routing capability. To take one
>example.
>
>--
>--John
>to email, dial "usenet" and validate
>(was jclarke at eye bee em dot net)


Whenever someone refers to the PHY interface on a mobo or other hardware
the're refering to layer 1.

--
a d y k e s @ p a n i x . c o m

Don't blame me. I voted for Gore.
Anonymous
April 14, 2005 9:48:45 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Al Dykes wrote:

> In article <d3lrdr0hml@news3.newsguy.com>,
> J. Clarke <jclarke.usenet@snet.net.invalid> wrote:
>>CJ wrote:
>>
>>> "Al Dykes" <adykes@panix.com> wrote in message
>>> news:D 3kgvq$ha5$1@panix5.panix.com...
>>>> In article <aHg7e.780$Cz3.87456@monger.newsread.com>,
>>>> CJ <chrisj@illicom.net> wrote:
>>>>>"J. Clarke" <jclarke.usenet@snet.net.invalid> wrote in message
>>>>>news:D 3heph0dnm@news3.newsguy.com...
>>>>>> CJ wrote:
>>>>>>
>>>>>>> I understand how OSI works in general. But I can know alot of
>>>>>>> information
>>>>>>> about alot of things....doesn't mean its of any use to me.
>>>>>>>
>>>>>>> From what I am reading knowing the OSI is a "nice to know" thing,
>>>>>>> but knowing it, unless I am a protocol developer or something, is
>>>>>>> useless to
>>>>>>> me.
>>>>>>>
>>>>>>> Sound about right?
>>>>>>
>>>>>> Until some guy in a job interview asks you to explain your
>>>>>> understanding of
>>>>>> the OSI model.
>>>>>
>>>>>Which is fine...but it still is useless to me otherwise. Ok...so I
>>>>>know how
>>>>>a packet is created on one end and deconstructed on the
>>>>>other....phffft.
>>>>>
>>>>>
>>>>
>>>> You'll use it to understand some new service you haven't heard of yet
>>>> or to explain something to someone else. For instance:
>>>>
>>>> http://www.pt.com/tutorials/ss7/stack.html
>>>
>>> Thats all nice to know info. But yet still NOBODY has any real example
>>> of
>>> how to apply this knowledge. Why is that?
>>
>>What do you mean by a "real example"? Its utility is that it provides a
>>framework, not that you will be digging into the depths of it every day.
>>If you don't know the OSI model and someone says "This is a Layer 3
>>switch"
>>you won't have a clue what they're talking about. If you do know the
>>model
>>then you will know immediately that it has routing capability. To take
>>one example.
>>
>>--
>>--John
>>to email, dial "usenet" and validate
>>(was jclarke at eye bee em dot net)
>
>
> Whenever someone refers to the PHY interface on a mobo or other hardware
> the're refering to layer 1.

While that's true, you seldom see a PHY advertised as a "layer 1 interface".
You do however see routers advertised as "layer 3 switches" and bridges
advertised as "layer 2 switches", hence my use of that example.

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)
Anonymous
April 14, 2005 9:48:46 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <d3msqk22n3s@news4.newsguy.com>,
"J. Clarke" <jclarke.usenet@snet.net.invalid> wrote:

> While that's true, you seldom see a PHY advertised as a "layer 1 interface".
> You do however see routers advertised as "layer 3 switches" and bridges
> advertised as "layer 2 switches", hence my use of that example.

There used to be a company called "Level One Communications," in Folsom,
CA. They were so named because they made PHY devices. Level One was
acquired by Intel a few years back.

A former member of the senior management of Level One left that company
to form a new startup, primarily to make bridge/switch chips.
Recognizing that the name of the company tended to restrict the
business-thinking of company management (e.g., managers in a company
called Level One might reject new, non-PHY product lines as out of the
scope of the business model), he named his new company "Allayer
Communications." That left him a lot of leeway. (Allayer was acquired by
Broadcom.)


--
Rich Seifert Networks and Communications Consulting
21885 Bear Creek Way
(408) 395-5700 Los Gatos, CA 95033
(408) 228-0803 FAX

Send replies to: usenet at richseifert dot com
April 15, 2005 7:14:05 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

"Al Dykes" <adykes@panix.com> wrote in message
news:D 3lprv$8il$1@panix5.panix.com...
> In article <yGt7e.1537$5I5.73913@newshog.newsread.com>,
> CJ <chrisj@illicom.net> wrote:
>>"Al Dykes" <adykes@panix.com> wrote in message
>>news:D 3kgvq$ha5$1@panix5.panix.com...
>>> In article <aHg7e.780$Cz3.87456@monger.newsread.com>,
>>> CJ <chrisj@illicom.net> wrote:
>>>>"J. Clarke" <jclarke.usenet@snet.net.invalid> wrote in message
>>>>news:D 3heph0dnm@news3.newsguy.com...
>>>>> CJ wrote:
>>>>>
>>>>>> I understand how OSI works in general. But I can know alot of
>>>>>> information
>>>>>> about alot of things....doesn't mean its of any use to me.
>>>>>>
>>>>>> From what I am reading knowing the OSI is a "nice to know" thing, but
>>>>>> knowing it, unless I am a protocol developer or something, is useless
>>>>>> to
>>>>>> me.
>>>>>>
>>>>>> Sound about right?
>>>>>
>>>>> Until some guy in a job interview asks you to explain your
>>>>> understanding
>>>>> of
>>>>> the OSI model.
>>>>
>>>>Which is fine...but it still is useless to me otherwise. Ok...so I know
>>>>how
>>>>a packet is created on one end and deconstructed on the other....phffft.
>>>>
>>>>
>>>
>>> You'll use it to understand some new service you haven't heard of yet
>>> or to explain something to someone else. For instance:
>>>
>>> http://www.pt.com/tutorials/ss7/stack.html
>>
>>Thats all nice to know info. But yet still NOBODY has any real example of
>>how to apply this knowledge. Why is that?
>>
>>
>
>
> How simple can we make this; In your career, if you have one

Uh..yes, I've been working in IT for more than 6 years. And I know the OSI
model, although the TCP/IP model seem more relevant, I have NEVER needed to
count on that info for anything practical or NEVER has anyone provided
anything as to when I would ever use it with the exception of being asked in
a job interview.

And if you can't really answer my question, then don't talk down to me.



, in
> computers and telecom you will routinely be presented with information
> structured with in a conceptual model described by ISORM. It ain't
> rocket science or magic. it encourages apples-apples comparisions
> which make learning faster and less error prone.
>
> As for real products and systems, Any product that says it implements
> an X.something standard is something out of the ISO and to some degree
> is part of OSI. There are lots of X roducts in major use. Go to any
> tech library and look in _Newton's Telecom Dictionary_ under X....
> and you'll find several pages of X.nnn standards.
> --
> a d y k e s @ p a n i x . c o m
>
> Don't blame me. I voted for Gore.
Anonymous
April 15, 2005 11:22:30 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

"CJ" <chrisj@illicom.net> wrote:

> Uh..yes, I've been working in IT for more than 6 years. And I know
> the OSI model, although the TCP/IP model seem more relevant, I have
> NEVER needed to count on that info for anything practical or NEVER has
> anyone provided anything as to when I would ever use it with the
> exception of being asked in a job interview.

Frankly, I'm puzzled. I've always treated the OSI 7-layer model as a
fairly obvious structure to use, as a way of understanding what's going
on. It has nothing to do with the specific protocol stack. It works just
fine with the IP family of protocols. I'd ignore any historic
association the OSI model might have with any particular protocol stack.
That misses the point entirely.

How does it help? For example, if someone advertizes a really fancy
Ethernet switch, with all manner of GARP and GMRP support, IEEE 802.1Q,
what have you, where does this fit in your network architecture? Do you
get all confused trying to figure it out? I know lots of people who DO
get all confused by something like this.

But no, this should not be confusing, because you know that this fancy
switch is just a layer 2 device, which sits under your IP routers (which
are layer 3 devices). This should be instinctive. So you know right away
that this switch in no impacts on your IP subnet architecture, although
it might give you some additional flexibility within each Ethernet
catenet that interconnects your routers.

Or if some switch vendor advertizes a switch with really cool single
mode WDM fiber optic interface ports, how does that impact on your
network? Once again, the OSI model makes it obvious. A lot of folk get
confused by such WDM devices, and start believing that they're somehow
the answer to all their networking woes. But someone who has grasped the
OSI model will know instinctively the difference between hype and
reality.

Or if someone sells you an application to install in your PC, how does
that impact the network structure? Well, once you've determined what
Transport layer the application depends on, you can very quickly
determine whether or not your underlying network will work for you.

Just about anything we do depends on some logical structure.
Understanding how a car works depends on a logical structure. You
separate drivetrain from engine from suspension from wheels and tires
from body structure from controls. You know right away that those $1000
wheels someone wants to sell you will not increase the engine
horsepower, for example. By themselves, they won't improve your
cornering capability, your acceleration, or your top end.

Bert
Anonymous
April 16, 2005 5:45:36 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Albert Manfredi wrote:

> "CJ" <chrisj@illicom.net> wrote:

>> Uh..yes, I've been working in IT for more than 6 years. And I know
>> the OSI model, although the TCP/IP model seem more relevant, I have
>> NEVER needed to count on that info for anything practical or NEVER has
>> anyone provided anything as to when I would ever use it with the
>> exception of being asked in a job interview.

Well, considering that the seven layers were a compromise between
six and eight, one shouldn't take them too literally.

> Frankly, I'm puzzled. I've always treated the OSI 7-layer model as a
> fairly obvious structure to use, as a way of understanding what's going
> on. It has nothing to do with the specific protocol stack. It works just
> fine with the IP family of protocols. I'd ignore any historic
> association the OSI model might have with any particular protocol stack.
> That misses the point entirely.

To me, the lower layers seem fairly obvious, and easy to keep apart.
The higher layers I find much harder to understand the distinctions
being made. Certainly for IP/ethernet the separation between two and
three doesn't seem so hard, with IP being only one of the possibly
ethernet protocols. I tend to believe that ICMP should be layer four,
but many seem to believe layer three.

> How does it help? For example, if someone advertizes a really fancy
> Ethernet switch, with all manner of GARP and GMRP support, IEEE 802.1Q,
> what have you, where does this fit in your network architecture? Do you
> get all confused trying to figure it out? I know lots of people who DO
> get all confused by something like this.

(snip)

-- glen
June 10, 2005 9:14:07 PM

Archived from groups: comp.dcom.lans.ethernet,microsoft.public.certification.networking (More info?)

There are basically three reasons you need to know the OSI model, if
you're going to work in networking:

1. You need to know the parlance of the field. Network Engineers
commonly talk about things in terms of OSI layers - it's just how we
talk. Engineers will talk about equipment in terms of layers. i.e.
"Yeah, it's a layer 3 device, but it does layer 4 filtering." If you
don't know what that means... well, then you don't know what that means.

2. It helps to understand a lot about data communications, in general,
and the abstraction that takes place between layers. In other words, I
don't care how you do it, as long as it accepts these inputs and
provides those outputs. Each layer is built on that idea.

3. You will look really stupid in a job interview for a networking
position, if the interviewer asks you to explain what you know about the
OSI model and you scratch your head and say, "Uh, I know it has 7
layers..." And don't think they won't ask. I've done and been on plenty
of technical interviews, and it usually comes up.

Just my thoughts...

grep

CJ wrote:
> I studied the OSI model, but nobody could ever tell me why I need to know
> it.
> The answer I always got was "you definitely need to know the OSI model" but
> when I ask why I always get "you just do".
>
> Can anyone tell me why I need to know it and how I would apply the
> knowledge? Perhaps a lab exercise or something??
>
> Thanks,
> CJ
>
>
!