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RE: TCP/IP Terms

2002-10-06 16:31:04
Mastaka / Bill,

Michel Py wrote:
In terms of design, if you do TCP/IP *only* design, the TCP/IP model
is
probably enough. However, the Internet is not only TCP/IP. Carriers,
for
example, don't care much if their fiber transports TCP/IP or IPX or
voice or video or GigE.

Masataka Ohta wrote:
No.
Anything at or above transport layer is a layer internal to
end systems and has nothing to do with networking or network
protocols. Seperation of transport and application layers is
a overkill for a best effort network, though it may help
standardize the internal design of end systems such that
anything supported by kernel belong the transport layer. You
can check the reality that application and transport areas
of IETF are now almost identical, though, historically,
trasnsport area was working on protocols likely to be
implemented in kernel. In addition, defining a thin transport
layer may be useful over a hypothetical port-number-aware
network such as that supporting RSVP. However, forcibly
defining a session-layer-aware network is a layer violation.

I don't disagree for the upper part of the model, but all the examples I
have used in this thread were about the lower part of the model.


Michel Py wrote:
And, there are complex multi-protocol networks that a) don't
use only TCP/IP and b) would not be able to use the TCP/IP
model anyway because it's too simple.

Bill Cunnigham wrote:
* Would not be able to use TCP/IP.*
How can that be changed?

If I had to design a model it would be:

    Michel's           TCP/IP                OSI
      model             model               model
+--------------+  +---------------+  +---+--------------+
!              !  !               !  ! 7 ! Application  !
!              !  !               !  +---+--------------+
! Application  !  ! Application   !  ! 6 ! Presentation !
!              !  !               !  +---+--------------+
!              !  !               !  ! 5 ! Session      !
+--------------+  +---------------+  +---+--------------+
! Transport    !  ! Transport     !  ! 4 ! Transport    !
+--------------+  +---------------+  +---+--------------+
! Network      !  ! Internet      !  ! 3 ! Network      !
+--------------+  +---------------+  +---+------+-------+
! Logical Link !  !               !  !   ! Data ! LLC   !
+--------------+  ! Network       !  ! 2 ! Link +-------+
! Media Access !  ! Interface     !  !   !      ! MAC   !
+--------------+  !               !  +---+------+-------+
! Physical     !  !               !  ! 1 ! Physical     !
+--------------+  +---------------+  +---+--------------+

I understand that people that have used the TCP/IP model don't care much
of what's inside the Network Interface layer, but there is a bunch of
stuff there that could use layering. That's why, short of having my very
own model drawn above, I keep using the OSI one for
explanatory/educational purposes.

Michel.



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