[ih] when did APRANET -TIPs become known as -TACs

[Karl Auerbach]

It annoyed me that IPv6 did not adopt the Fletcher checksum that was 
used in ISO/OSI TP[1234] and CLNP.  (Or perhaps even a Hamming error 
correcting code.)

(At first glance the Fletcher checksum looks like a computational burden 
with expensive machine operations, such as integer multiplies, but there 
are both full and incremental algorithms for it that are quite 
efficient, avoid expensive machine instructions, and fast.  And the 
Fletcher checksum does catch byte big-endian/little-endian reversals, or 
what was called in the early days of Unix the "nUxi" [pairs of bytes 
reversed] problem.)

We now live in a world where jumbograms - and large path MTU values, on 
the order of 8K+, are rather common.  And those larger packets are more 
likely to get hit with a burst of line noise than were the shorter 
packets of days gone by.  But that revives the old debate whether to do 
error checks/correction on a per-link basis or end-to-end basis (in 
addition to per-link checks/correction.)  (Those of us who were burned 
by the old Sun S-bus has no parity check, coupled with Suns NFS using 
zero as null UDP checksum, kinda cling to the end-to-end check side of 
the argument.  [When I was at Sun a critical machine had an 
S-Bus/Ethernet path that became noisy and the effect caused the major 
source code repository used for all Sun code to become corrupted.  It 
was a mess to clean up.])

     --karl--


On 9/28/25 4:26 PM, John Day via Internet-history wrote:
> No one took those seriously.
> TP0 was for CCITT SGVIII, TP1 was for CCITT SGVII, TP2 was for the Brits who had to use X.25, and TP3 was for the Germans.
>
> No one paid them any mind. The real focus was on TP4 which was a major advance because it adopted Watson’s insight on synchronization which made it much simpler and more secure.
>
> Take care,
> John
>
>> On Sep 28, 2025, at 19:21, Dave Crocker <dhc at dcrocker.net> wrote:
>>
>> On 9/28/2025 4:13 PM, John Day via Internet-history wrote:
>>> The OSI vision was, if anything, Ethernet (an ISO standard), CLNP, TP4, and ACSE.
>> That sounds reasonable, except for TP0, TP1, TP2, and TP3.
>>
>>
>>
>> and the various CONS alternatives to CLNP.
>>
>> OSI went for the union of everybody's wish lista.  The Internet went for the intersection.
>>
>> d/
>>
>> -- 
>> Dave Crocker
>>
>> Brandenburg InternetWorking
>> bbiw.net
>> bluesky: @dcrocker.bsky.social
>> mast: @dcrocker at mastodon.social