Subject: FW: [Hist Trivia] IP Protocol Layers

From: "Polinsky, Steven" <[email-masked]>
Date: Tue, 17 Jul 2001 17:24:38 -0400

Dave Clark refers to the IP layer and the TCP layer in RFC817:

"The TCP layer, as well as the IP layer, performs a  demultiplexing
function ...."

He also cites: 1]  Cohen  and  Postel,  "On  Protocol  Multiplexing",  Sixth
Data Communications Symposium, ACM/IEEE, November 1979, 

Steven

Steven M. Polinsky
Goldman, Sachs & Co.
180 Maiden Lane
New York, NY 10038
212-902-3669 | Fax: 212-493-0107

-----Original Message-----
From: Timothy J. Salo [mailto:[email-masked]] 
Sent: Tuesday, July 17, 2001 3:59 PM
To: [email-masked]
Subject: [Hist Trivia] IP Protocol Layers

Can anyone point me to an early reference describing the Internet
protocol layers in IP terms, rather than OSI terms?

One recent text used the following terms.  However, I don't know whether
this description has a long history, or is simply revisionist history.

	Application
	Transport (TCP, UDP)
	Internet (IP, etc.)
	Network Interface (LAN and WAN technologies).

By 1983 the Internet protocols were already being recast in OSI terms.
Vint Cerf, in "The DoD Internet Architecture Model", described the
following layers:

	Application
	Utility
	Transport
	Internetwork
	Network
	Link
	Physical

In May 1979, Jon Postel in IEN-94 ("Internet Protocol Handbook"; it was
small then - 1209 bytes) use the following layers:

>                        Internet Protocol Handbook
>                            Table of Contents
> 
> Gateway Level
>    Internet Datagram Protocol                                     IEN-80
>    Gateway Routing: An Implementation Specification               IEN-30
> 
> Host Level
>    User Datagram Protocol                                         IEN-88
>    Transmission Control Protocol                                  IEN-81
>    Multiplexing Protocol                                          IEN-90
> 
> Application Level
>    Name Server Protocol                                           IEN-89
>    Internet Message Protocol                                      IEN-85
> 
> Appendices
>    Protocol Options                                               IEN-92
>    Address Mappings                                               IEN-91
>    Assigned Numbers                                               IEN-93

Does anyone have a pointer to an early, more "traditional", non-OSI 
description of the TCP/IP protocol layers?

(By the way, I found the concept behind RFC 157, "Invitation to the Second
Symposium on Problems in the Optimization of Data Communications Systems",
rather interesting.  I must admit that I hadn't thought of submitting
spam as an RFC.)

Thanks,
	-tjs

---

From: [email-masked] (Sean Doran)
Date: Wed, 18 Jul 2001 03:39:56 +0200 (CEST)

Radia Perlman asks:

| One of the things I've been meaning to chase down is ... why did anyone
| think "Transport" was a good name for layer 4?

So that we could have the excellent seven-words-for-seven-layers mnemonic,
All People Should Talk Nicely Like Padlipsky, of course.

	Sean.

PS - his book is back @ outofprint.com... (it makes a great gift for X.25ers)

---

From: [email-masked] (Sean Doran)
Date: Wed, 18 Jul 2001 03:47:18 +0200 (CEST)

Apart from being beaten up by invoking ghosts of "mean people", I have also
been told that I meant "backinprint.com", will let you find Padlipsky's
book via a simple author search.

Also, I guess I was a bit obtuse - the book itself has some of Radia's
answers inside, along with some first-class ranting and excellent summaries
of debates along time ago by people who are ancient & venerable now (ho ho ho).

	Sean. (sorry)

---

From: [email-masked]
Date: Wed, 18 Jul 2001 14:04:10 -0500

>Hmm, so ftp-packets get better with age?

AOL seems to think so....
;-)

---

From: "J. Noel Chiappa" <[email-masked]>
Date: Wed, 18 Jul 2001 22:42:55 -0400

> From: Steve Deering <[email-masked]>

    > We used to use "gateway" instead of "router" (and a few still do),
    > and I always thought the change to the "router" term was due to some
    > sort of OSI political correctness. If not OSI, who gets credit for
    > imposing the "router" jargon on the IP world? Was it the DEC folks
    > (mostly Radia?)?

I don't know how much of the credit^H^H^H^Hblame belongs to me, but I was
one of the people who pushed hard for that switch in terminology.

My reasoning had nothing to do with OSI (which I disliked about as much as
a certain later alternative, to calibrate you :-), but had to do with the
fact that to the then-great-unwashed (I mean, it was the early '80's - who
knew about the Internet? :-) a "gateway" was some sort of service
translation box, e.g. to convert Novell Netware email to DECNet email, or
whatever.

I reckoned it would be easier to explain to people how this new-fangled
Internet thing worked if we didn't have to erase all the wrong ideas that
automatically paged into their brain when we said the word "gateway".

	Noel

---

From: Vernon Schryver <[email-masked]>
Date: Thu, 19 Jul 2001 09:05:01 -0600 (MDT)

> From: Jon Crowcroft <[email-masked]>

> ...
> i also like the fact that MOST fancy things we do in traffic treatment
> (firewall, diff/int serv, header compression, checksum) ignore this
> layering rubbish idea and look at the whole packet and the whole state
> of the systems where you need to......creating articifical monitor
> security/concurrency boundary crossings in component software was a
> terrible thing, and many modern OSs have got a long way away from
> it....
>
> on reflection (pun intended):
> layering is a clothing methodology for people who live in fractal climates
> not a design pattern for correct or efficient communications
> systems....

Yes, but without the ISO layering terminology, what would we have done
with all of the time wasted arguing with layering priests about what
is impossible or sinful?  Without the layer labels, how would legions
of the pointy haired, salescritters, and people who implement TCP by
installing software on PCs prove their expertise?

Without the layering religion, much of the steam in the GOSIPs might
not have been generated.  Do you remmeber the endless educational lectures
from experts informing us that the OSI suite was inevitiable and desirable,
mostly because it had proper layering unlike that ad hoc DDN stuff?

A serious case can be made that the 7 layer model did more harm than
good by helping the congenitally or willfully clue challenged pretend
to be knowlegable and authoritative.  Without the simplistic view of
networking required by the 7 layer model, the experts might have been
forced to find other areas to plow.

It's not that the good in layering needed to be invented by the ISO
and then imported into the rest of the network universe.  The notion
of software and hardware modularity had already had its 15 minutes of
being the panacea among the CASE gurus by 1976.  (Yes, I know that
species of psuedo-expert didn't call itself that then and doesn't
today.)

Vernon Schryver    [email-masked]

---

From: Vernon Schryver <[email-masked]>
Date: Thu, 19 Jul 2001 09:05:01 -0600 (MDT)

---

From: "Christian Huitema" <[email-masked]>
Date: Thu, 19 Jul 2001 09:33:06 -0700

> A serious case can be made that the 7 layer model did more 
> harm than good by helping the congenitally or willfully clue 
> challenged pretend to be knowlegable and authoritative.  
> Without the simplistic view of networking required by the 7 
> layer model, the experts might have been forced to find other 
> areas to plow.

I concur. The 7 layer model had its most harmful impact where it is most used, which is in education. By the late 80's, a pretty standard curriculum was to have a 7 session networking course, with one session per layer. This was quite convenient for the naïve teaching assistant who had a general computer science background but no specialisation in networking. It was also quite wrong, since it manufactured generations of students who believed that the OSI layering was somehow logical, when in fact it was the result of accomodating diverse pre-existing systems, such as X.25 or teletext.

The basic failure was to "teach the standards" rather than "teach the technology." If you teach the technology, then you deal with algorithms and scaling issues, and there is plenty to teach and learn: retransmission algorithms and the use of timers, various approaches to congestion control, name resolution, resource allocation algorithms, marshalling and un-marshalling, synchronization and time, and many more. If you teach the standard, then you content yourself with whatever a committee picked. Worse still, in many case the committees' decisions were grounded in political compromise and cloaked in technicalities. In many cases, the students got such a distorted view that you litteraly need to make them "unlearn OSI" before they can do productive networking work.

-- Christian Huitema

---

From: Bob Braden <[email-masked]>
Date: Mon, 23 Jul 2001 23:05:33 GMT

*> From [email-masked]  Tue Jul 17 13:21:47 2001
  *> Date: Tue, 17 Jul 2001 14:58:35 -0500 (CDT)
  *> From: "Timothy J. Salo" <[email-masked]>
  *> To: [email-masked]
  *> Subject: [Hist Trivia] IP Protocol Layers
  *> X-Loop: [email-masked]
  *> 
  *> Can anyone point me to an early reference describing the Internet
  *> protocol layers in IP terms, rather than OSI terms?
  *> 
  *> One recent text used the following terms.  However, I don't know whether
  *> this description has a long history, or is simply revisionist history.
  *> 
  *> 	Application
  *> 	Transport (TCP, UDP)
  *> 	Internet (IP, etc.)
  *> 	Network Interface (LAN and WAN technologies).

Tim,

This is the Internet protocol stack as understood by the creators of
TCP/IP.  It is documented (at least) in section 1.1.3 ("Internet
Architecture") of RFC 1122, a document that encapsulates a great deal
of the early wisdom on the Internet protocols.

Note, however, that RFC 1122 deliberately "OSIzed" the terminology
by using "Link Layer" instead of "Network Interface".  Also, the
term "transport" was imported from OSIland; we did not really have
a name for that layer. See RFC 793, for example.

  *> 
  *> By 1983 the Internet protocols were already being recast in OSI terms.
  *> Vint Cerf, in "The DoD Internet Architecture Model", described the
  *> following layers:
  *> 
  *> 	Application
  *> 	Utility
  *> 	Transport
  *> 	Internetwork
  *> 	Network
  *> 	Link
  *> 	Physical
  *> 
  *> In May 1979, Jon Postel in IEN-94 ("Internet Protocol Handbook"; it was
  *> small then - 1209 bytes) use the following layers:

These were not layers, they were categories.

  *> 
  *> 
  *> >                        Internet Protocol Handbook
  *> >                            Table of Contents
  *> > 
  *> > Gateway Level
  *> >    Internet Datagram Protocol                                     IEN-80
  *> >    Gateway Routing: An Implementation Specification               IEN-30
  *> > 
  *> > Host Level
  *> >    User Datagram Protocol                                         IEN-88
  *> >    Transmission Control Protocol                                  IEN-81
  *> >    Multiplexing Protocol                                          IEN-90
  *> > 
  *> > Application Level
  *> >    Name Server Protocol                                           IEN-89
  *> >    Internet Message Protocol                                      IEN-85
  *> > 
  *> > Appendices
  *> >    Protocol Options                                               IEN-92
  *> >    Address Mappings                                               IEN-91
  *> >    Assigned Numbers                                               IEN-93
  *> 
  *> Does anyone have a pointer to an early, more "traditional", non-OSI 
  *> description of the TCP/IP protocol layers?
  *> 
  *> (By the way, I found the concept behind RFC 157, "Invitation to the Second
  *> Symposium on Problems in the Optimization of Data Communications Systems",
  *> rather interesting.  I must admit that I hadn't thought of submitting
  *> spam as an RFC.)

!? Hardly spam.  The early RFCs were used for all sorts of informal notes
and announcements among the small set of early participants in the ARPAnet.
There are several one-line RFCs that announce meetings, for example.

Bob Braden

  *> 
  *> Thanks,
  *> 	-tjs
  *>

---

From: "J. Noel Chiappa" <[email-masked]>
Date: Tue, 24 Jul 2001 13:27:03 -0400

> I.e., layering is, IMO at least, a model. Fine for describing
    > things, but not necessarily a good blueprint for an implementation.

Yes, but this is hardly news in the IETF - or at least, it *ought not* to
be news. See RFC-817, "Modularity and Efficiency in Protocol
Implementation", July 1982 - about 20 years ago.

I also wonder why the notion that the functional modularization of the
architecture/specification might differ from that of particular
implementations is something some people seem not to have internalized -
this idea dates all the way back to the IBM 360 line of the early 1960's.

	Noel