What about -ATM ? how do you put this monster into the organized model?
>>>Brian
>From: "Chuck Larrieu" <[EMAIL PROTECTED]>
>Reply-To: "Chuck Larrieu" <[EMAIL PROTECTED]>
>To: <[EMAIL PROTECTED]>
>Subject: RE: Connection(less) services
>Date: Sat, 20 May 2000 07:24:57 -0700
>
>I saw an interesting statement in a book I was browsing recently: Ray
>Horak,
>in Communications Systems and Networks, calls UDP a layer seven protocol
>while TCP is a layer four protocol. When I saw that, I immediately went to
>my Radcom world of Protocols poster, and read their definition of layer
>four, which does indeed say "reliable" I have not seen it argued this way
>before, but I understand where the author is coming from. If layer four is
>reliable, and UDP is not, it cannot be layer four.
>
>I know some folks warn about trying to crunch everything into the OSI
>model.
>I believe the purpose of studying the model is 1) to provide a structured
>view of data communications 2) a means of structuring a troubleshooting
>methodology 3) so one can at least be conversant with the terminology when
>listening to all the presentations about what hardware or software operates
>at what layer. I myself have begun to look at the world using a variant of
>the ip model- physical/data link, network, transport, everything else.
>Someone else on the group once suggested a box with four sections -
>connection, connectionless on one axis and reliable, unreliable on the
>other. As his learning process he would place a protocol into each section
>based on the intersection. TCP = connection, reliable; frame relay PVC =
>connection, unreliable, and so on.
>
>Chuck
>
>-----Original Message-----
>From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of
>Howard C. Berkowitz
>Sent: Friday, May 19, 2000 8:42 PM
>To: mikey; [EMAIL PROTECTED]
>Subject: Re: Connection(less) services
>
> >According to the OSI model, layer 3 is connectionless and layer 4 is
> >connection oriented. However, one must remember that the OSI model is
> >theoretical.
>
>And the OSI model has been extended by ISO, considerably beyond the
>simple seven layers. Unfortunately, the extensions, such as the
>internal organization of the network layer, the object-oriented
>refinements of the application layer, management, etc., are rarely
>presented.
>
> >Specific protocol implementations do not necessarily adhere to
> >the OSI model.
>
>Actually, the main OSI Reference Model defined in ISO 7498 was
>connection-oriented at all levels. Connectionless operation was
>described in one of the Annexes to 7498 -- can't tell you the
>specific annex number from memory.
>
>In the actual OSI protocol suite, CLNP was the connectionless network
>layer protocol, and the connection-mode network protocol was a
>particular X.25 subset.
>
> >
> >Example: TCP and UDP are both layer 4, one is connection oriented the
>other
> >is connectionless. Also, take a look at the IPX stack, it does not map
> >nicely to the OSI model.
>
>
>Quite correct.
>
> >
> >mikey
> >Oscar Rau <[EMAIL PROTECTED]> wrote in message
> >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> > > When you look at TCP and UDP applications, they are placed
> > > in the Transport layer of the OSI model. Some of the Cisco
> > > certification literature suggests that connection oriented
> > > services and connectionless services are handled by Layer 3
> > > which is the network layer.
> > >
> > > Which layer is primarily responsible for connection oriented
> > > and connectionless services?
> > >
> > > Thank you in advance.
> > > --
> > >
> > > Oscar Rau
> > > [EMAIL PROTECTED]
> > >
> > > ___________________________________
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