[ih] ARPAnet Type 3 packets (datagrams)

[Richard Bennett]

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