At 02:19 PM 7/17/2001, Radia Perlman - Boston Center for Networking wrote:
I think TCP and IP were all one layer at one point. It's possible
the old IEN's, (which I'd heard would be on-line "soon" if
That is my understanding, too: In the beginning there was only TCP.
During on-going discussions between the ARPA research and the Xerox PARC
research folks, the need for separating out IP functionality became apparent.
I don't know the dates for this architectural transition.
Transport (TCP, UDP)
Internet (IP, etc.)
Network Interface (LAN and WAN technologies).
The idea of intermediate "upper" layers has periodically been
played with in the Internet realm, such as with XDR and RPC, and again more
recently with BEEP. A range of efforts that standardize on an application
infrastructure, such as with XML, encourage viewing this as a real
architectural enhancement. Hence we probably need to wedge a layer between
transport and applications. I prefer to call it session; others will
likely prefer presentation.
Dave Crocker <mailto:dcrocker(_at_)brandenburg(_dot_)com>
Brandenburg InternetWorking <http://www.brandenburg.com>
tel +1.408.246.8253; fax +1.408.273.6464