i have always heard that atm is a layer 1 and 2(AAL) protocol myself
>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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