OSI Model question...

[Andrew Murgas]

Here's some more, courtesy of "The CNE-4 Study Guide"

The Network Layer serves to support communication between logically 
separate networks. This layer is concerned with the following:

Addressing - logical network addresses
and services addresses. 

Circuit, message and packet switching

Route discovery and route selection

Connection services which include Network Layer flow control, Network
layer error control, and packet sequence conrol

And of course, Gateway services.

The Transport layer facilitates reliable message delivery between processes
running on network devices. This layer addresses the following topics:

Addressing and the use of connection identifiers and transaction identifiers

Service-requestor-initiated and service provider initiated address/name 
resolution

Message segment development

Connection services, including segment sequencing, Transport layer error 
control, and end-to-end flow control.

----------------------------

The Network layer's purpose is to move data to its specific destination while
the Transport layer's purpose is responsible for sending and receiving 
messages between a process on one computer and the corresponding process on
another.

HTH


Andrew R. Murgas                               Suburban Library System
Information Technology Specialist              murgasa at sls.lib.il.us
Pergamentum init, exit Pergamentum
..................................................


On Wed, 29 Jan 1997, Deanna P. Denk wrote:

> Here it is ... straight from the book BUSINESS DATA COMMUNICATIONS, 3rd
> edition by David A. Stamper, Benjamin/Cummings Publishing Company, Inc.,
> 1991. (It's a text book I keep at my desk. I knew some of this for a
> test once, but have long forgotten it. Thanks for causing me to read
> some of this book again.) Hope this is helpful.
> 
> The network layer is responsible for end-to-end routing.
> It performs three major functions: routing, network control, and
> congestion control. The network layer must be aware of alternate paths
> in the network and choose the best one. Which path depends on a variety
> of factors, some of which are congestion, number of intervening nodes,
> speed of links and so onl.
> 
> The transport layer is involved in end-to-end transmission services and
> assists the session layer in establishing the connection for a session.
> The transport layer may accept messages of any length; however, the
> communications link may have limitations regarding message size. The
> transport layer must segment these large messages into smaller
> transmissions blocks and establish sequence numbers for each. The
> transport layer is responsible for end-to-end sequence number control
> and error detection and recovery. For example, if a segment of a long
> message is lost, the transport layer effects recovery to ensure correct,
> complet message transfer.
> 
> Another service that may be provided by the transport layer is
> addressing. 
> 
> -- 
> Deanna P. Denk
> Internet Trainer/Consultant
> denkd at interaccess.com
> http://homepage.interaccess.com/~denkd/deanna.html
> 
> "I'm not unemployed, I'm a consultant"  -- Dogbert
> 
> 
> jkaminski at BROOK.EDU wrote:
> > 
> >  Now something different:
> > 
> > sorry for change of subject, but can someone explain (simply, w/ examples)
> > the difference between the Transport Layer and the Network Layer in the
> > 7 layer OSI model??
> > 
> > Thanks in advance!!
> > 
> > ********************
> > John C. Kaminski
> > Serials/WWW
> > www.brook.edu/lib/lib_hp.htm
> > The Brookings Institution
>