| Author |
Message |
J. Clarke
Guest
|
 Posted:
Thu Apr 14, 2005 12:25 pm Post subject:
Re: OSI Model |
|
|
CJ wrote:
| Quote: | "Al Dykes" <adykes@panix.com> wrote in message
news:d3kgvq$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:d3heph0dnm@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) |
|
| Back to top |
|
 |
CJ
Guest
|
| Posted:
Thu Apr 14, 2005 12:50 pm Post subject:
Re: OSI Model |
|
|
"Al Dykes" <adykes@panix.com> wrote in message
news:d3kgvq$ha5$1@panix5.panix.com...
| Quote: | In article <aHg7e.780$Cz3.87456@monger.newsread.com>,
CJ <chrisj@illicom.net> wrote:
"J. Clarke" <jclarke.usenet@snet.net.invalid> wrote in message
news:d3heph0dnm@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? |
|
| Back to top |
|
|
Al Dykes
Guest
|
| Posted:
Thu Apr 14, 2005 1:06 pm Post subject:
Re: OSI Model |
|
|
In article <yGt7e.1537$5I5.73913@newshog.newsread.com>,
CJ <chrisj@illicom.net> wrote:
| Quote: | "Al Dykes" <adykes@panix.com> wrote in message
news:d3kgvq$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:d3heph0dnm@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. |
|
| Back to top |
|
|
Vincent C Jones
Guest
|
| Posted:
Thu Apr 14, 2005 3:32 pm Post subject:
Re: OSI Model |
|
|
In article <d3lprv$8il$1@panix5.panix.com>, Al Dykes <adykes@panix.com> wrote:
| Quote: | In article <yGt7e.1537$5I5.73913@newshog.newsread.com>,
CJ <chrisj@illicom.net> wrote:
"Al Dykes" <adykes@panix.com> wrote in message
news:d3kgvq$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:d3heph0dnm@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 |
|
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|
|
Al Dykes
Guest
|
| Posted:
Thu Apr 14, 2005 9:40 pm Post subject:
Re: OSI Model |
|
|
In article <d3lrdr0hml@news3.newsguy.com>,
J. Clarke <jclarke.usenet@snet.net.invalid> wrote:
| Quote: | CJ wrote:
"Al Dykes" <adykes@panix.com> wrote in message
news:d3kgvq$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:d3heph0dnm@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. |
|
| Back to top |
|
|
J. Clarke
Guest
|
| Posted:
Thu Apr 14, 2005 9:48 pm Post subject:
Re: OSI Model |
|
|
Al Dykes wrote:
| Quote: | 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:d3kgvq$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:d3heph0dnm@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) |
|
| Back to top |
|
|
Rich Seifert
Guest
|
| Posted:
Fri Apr 15, 2005 12:27 am Post subject:
Re: OSI Model |
|
|
In article <d3msqk22n3s@news4.newsguy.com>,
"J. Clarke" <jclarke.usenet@snet.net.invalid> wrote:
| Quote: | 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 |
|
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|
|
CJ
Guest
|
| Posted:
Fri Apr 15, 2005 3:14 am Post subject:
Re: OSI Model |
|
|
"Al Dykes" <adykes@panix.com> wrote in message
news:d3lprv$8il$1@panix5.panix.com...
| Quote: | In article <yGt7e.1537$5I5.73913@newshog.newsread.com>,
CJ <chrisj@illicom.net> wrote:
"Al Dykes" <adykes@panix.com> wrote in message
news:d3kgvq$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:d3heph0dnm@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
| Quote: | 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. |
|
|
| Back to top |
|
|
Albert Manfredi
Guest
|
| Posted:
Fri Apr 15, 2005 7:22 pm Post subject:
Re: OSI Model |
|
|
"CJ" <chrisj@illicom.net> wrote:
| Quote: | 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 |
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glen herrmannsfeldt
Guest
|
| Posted:
Sat Apr 16, 2005 8:45 pm Post subject:
Re: OSI Model |
|
|
Albert Manfredi wrote:
| Quote: | "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.
| Quote: | 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.
| Quote: | 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 |
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| Back to top |
|
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grep
Guest
|
| Posted:
Sat Jun 11, 2005 12:20 am Post subject:
Re: OSI Model |
|
|
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:
| Quote: | 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
|
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