[ih] TCP RTT Estimator

Greg Skinner gregskinner0 at icloud.com
Mon Mar 24 17:16:06 PDT 2025


On Mar 11, 2025, at 2:48 PM, Barbara Denny <b_a_denny at yahoo.com> wrote:
> 
> I don't recall ever hearing, or reading, about TCP transport requirements from the underlying network but I wasn't there in the early days of TCP (70s).?
> I have trouble thinking the problem with the congestion assumption? wasn't brought up early but I certainly don't know.
> barbara
>    On Tuesday, March 11, 2025 at 02:10:26 PM PDT, John Day <jeanjour at comcast.net> wrote:  
> 
> I would disagree. The Transport Layer assumes a minimal service from the layers below (actually all layers do). If the underlying layer doesn?t meet that normally, then measures are needed to bring the service up to the expected level.? Given that the diameter of the net now is about 20 or so and probably back then 5 or 6. Packet radio constituted a small fraction of the lower layers that the packet had to cross. Assuming packet radio didn?t have to do anything had the tail wagging the dog.
> 
> Of course the example some would point to was TCP congestion control assuming lost packets were due to congestion. That was a dumb assumption and didn?t take a systems view of the problem. (Of course, it wasn?t the only dumb thing in that design, it also maximized retransmissions.)
> 
> Take care,
> John Day
> 
>> On Mar 11, 2025, at 17:02, Barbara Denny via Internet-history <internet-history at elists.isoc.org> wrote:
>> 
>> I do view packet radio as a stress test for the protocol(s).? I think it is important to consider all the different dynamics that might come into play with the networks. 
>> I still need to really read Jack's message but there were also military testbeds that had packet radio networks.? I don't know what these users were trying to do. I was only involved if they experienced problems involving the network. My role was? to figure out why and then get it fixed (with whatever contractor that was working that part of the system, including BBN).
>> barbara 
>> 

For what it's worth, there was a discussion on this list back in 2016 about early TCP work and how packet radio networks were involved. [1] [2] Based on what I’ve been able to find, I would agree with John that most Internet traffic didn’t cross packet radio networks back then.  The Ft. Bragg testbed was one of the most used, as far as I can tell.

As for people who tried to deal with how inherent loss problems of packet radio networks affected TCP, I did find a comp.protocols.tcp-ip thread from 1987 on that subject.  [3] Jil Westcott, who contributed to the thread, also had email correspondence with Zaw-Sing Su in the Ft. Bragg PRNET simulation paper he wrote.

--gregbo

[1] https://elists.isoc.org/pipermail/internet-history/2016-August/thread.html
[2] https://elists.isoc.org/pipermail/internet-history/2016-September/thread.html
[3] https://groups.google.com/g/comp.protocols.tcp-ip/c/vuPqc12SLis/m/1GoOsEem954J


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