[e2e] TCP Framing

[Cannara]

This is interesting David, having known the people at Parc and being still
older, the idea that packet networking began with those meetings is, as you'll
agree, incorrect.  Since "unreliable" was used in packet networking as
equivalent to "datagram" for years before those meetings, and books describing
UDP even later used "unreliable", perhaps as a matter of ethical choice, I can
only say that the choice of "user" as a modifier for a user-invisible protocol
component underscores how arbitrary many choices of terms in the TCP/IP family
have been.  

The idea of "best effort" is also a hard one to support, since "best" is very
much open to interpretation, especially by a receiver who got nothing, or
something trashed.  If "best effort" is a euphemism for datagram, then it's no
wonder some folks thought the imaginitive naming, adopted as you say, was
objectionable.  The problem that "user" and "best-effort" raise is that they
mean nothing and add nothing to pre-existing terms, such as datagram.

Actually, since UDP at least checksums a datagram, it could well have been
called "CDP", for "checksummed datagram protocol", thus being much clearer to
"users" in its purpose and capability.  

Alex


"David P. Reed" wrote:
> 
> At 09:01 AM 3/26/01 -0800, Cannara wrote:
> >Craig, this has been a common test for years, to see how old a "network-
> >knowledgeable" student is.  Ask the what UDP means.  Prior to the interesting
> >RFC Jeremy produced the "U" stood for just what it stands for in all other
> >families of protocols that have datagram services -- "unreliable".  Somehow
> >some Internet folks seemed to become sensitive, almost ashamed, of that very
> >accurate and truthful engineering label, and turned to seek a "u"-word that
> >had marketability.  I've yet to meet a user who knowingly "uses" a datagram
> >protocol.  You're younger than I thought!
> 
> Alex - Craig may be young, but then I must be ancient at only 49.  Anyway,
> I was there at the meeting where we created UDP (and split TCP into the TCP
> and IP layers), in Marina del Rey in winter '77/'78.  We called it the
> "User Datagram Protocol" from the first, and the reason was to distinguish
> it from the IP layer, which was the "datagram protocol" not well tuned for
> users, since you couldn't demux sensibly on the "protocol" field to the
> correct "user process" aka "application program instance".  (I won't bore
> you with the radical idea that we had tried to force into TCP of using a
> 64-bit process-specific address in IP, rather than a machine specific
> address - but memory cost a few pennies per bit then, so we were viewed as
> dangerously profligate).
> 
> Now there may have been some in the years after that that called it
> "Unreliable ...", but I'd suggest that only those who had fought against
> the idea that a base datagram function was useful would have stooped to
> that kind of propaganda.  Those of us who fought for a datagram protocol
> (the PARC people, Danny Cohen and the speech people, and the LAN people
> like me) used the term "best efforts", not "unreliable", to describe the
> delivery reliability of IP and UDP.
> 
> - David
>