[ih] ARPAnet Type 3 packets (datagrams)

[John Day]

As with most early attempts they don't quite fit the categories that 
coalesce later.  The ARPANET was not as pure connection as X.25, but 
not pure datagram either.  Although, I remember one evening around 
74-75 Danthine sitting in my living room insisting that the ARPANET 
was not a datagram network!  ;-)  But then that was Danthine.

Did the Xmas lock up occur because they were multi-packet control 
messages and not subject to the end-to-end RFNM in NCP?

If I remember right, weren't there also hop-by-hop RFNMs in the 
IMP-IMP protocol?

Which brings up another question.  I had always thought that X.25 
originated mostly with the French PTT.  I have heard stories that the 
Telenet guys had a strong hand in its design.  What is the case?

At 0:32 -0500 2009/11/26, Vint Cerf wrote:
>Richard, ARPANET was not circuit switched in the traditional sense 
>of the word. Packets were dynamically routed. There was end/end RFNM 
>for flow control (that actually inhibited use of things like the 
>TCP/IP window in the NCP protocol). Buffer space was reserved at the 
>far end to deal with reassembly lockup. "get a block" "got a block" 
>handshake assured that no multi-packet message would be initiated 
>without adequate space in the destination IMP.  There was no 
>priority for type 3 packets. there was priority for ARPANET (IMP 
>level) control packets.
>
>
>On Nov 25, 2009, at 7:16 PM, Richard Bennett wrote:
>
>>That really is ironic. If the circuit-switched service in ARPA and 
>>X.25 was good for anything at all, it should have been good for 
>>voice, but I'm guessing you guys tried voice over datagram over 
>>circuits and found it didn't work worth crap, probably because of 
>>high loss rates and excessive queuing inside the ARPANET. I also 
>>wonder of the type 3 service didn't have the effect of boosting the 
>>priority of voice packets in some way.
>>
>>Vint Cerf wrote:
>>>the type 3 packets were explicitly used for real-time packet voice 
>>>and later packet video experiments. This would have been in the 
>>>1975 time frame (but Danny Cohen and Steve Casner would know for 
>>>sure as they were at ISI; Lincoln Labs was also involved and we 
>>>used their packet digitizers/compressors. Duane Adams managed the 
>>>packet voice activity during the time I was at DARPA so I am 
>>>copying him too. I don't seem to have steve casner's email but I 
>>>think he is now at PARC.
>>>
>>>vint
>>>
>>>
>>>
>>>
>>>On Nov 25, 2009, at 6:05 PM, Richard Bennett wrote:
>>>
>>>>I've discussed this issue recently with a key member of the IMP 
>>>>team at BBN and he (unsurprisingly) has a very different 
>>>>recollection of the facts. A datagram mode was added to the IMP 
>>>>and to X.25 switches fairly early. Datagrams appeared on research 
>>>>networks well before TCP/IP was defined; CYCLADES had them in 
>>>>1972.
>>>>
>>>>The BBN people have not been able to tell me whether the NWG ever 
>>>>took advantage of the datagram mode in the IMP; that was outside 
>>>>their department.
>>>>
>>>>RB
>>>>
>>>>Bob Braden wrote:
>>>>>
>>>>>My memory was that BBN included type 3 (Uncontrolled or "raw") 
>>>>>messages in the IMP protocol as an experiment, which they then 
>>>>>considered too dangerous to use . BBN disabled them at (almost?) 
>>>>>all hosts (almost?) all the time, I believe.  TCP/IP used 
>>>>>standard reliably-delivered IMP traffic. But the facility must 
>>>>>have been enabled for the packet voice experiments shown in that 
>>>>>marvelous video.
>>>>>
>>>>>My memory on this point is hazy, but probably Vint can correct 
>>>>>me. When Barry Leiner became (D)ARPA Program Manager for the 
>>>>>Internet research program, he became determined that BBN should 
>>>>>try using Type 3 IMP-IMP packets for normal TCP/IP flows. He 
>>>>>complained to the ICCB/IAB that BBN was resisting.  He insisted 
>>>>>that the experiment be tried for 24 hours. Unfortunately I don't 
>>>>>recall that the experiment ever happened;
>>>>>it is more than possible that BBN stone-walled his demand.
>>>>>
>>>>>Bob Braden
>>>>>'
>>>>>
>>>>
>>>>--
>>>>Richard Bennett
>>>>Research Fellow
>>>>Information Technology and Innovation Foundation
>>>>Washington, DC
>>>>
>>>
>>
>>--
>>Richard Bennett
>>Research Fellow
>>Information Technology and Innovation Foundation
>>Washington, DC