[ih] Internet addressing history section

[Grant Taylor]

On 2/16/19 7:16 PM, Joe Touch wrote:
> Message transfer latency (the only one that matters, IMO), is a 
> combination of:
> 	- generation latency
> 	- propagation latency
> 	- computational latency
> 	- aggregation latency
> 	- multiplexing latency
> 
> (I recently gave a tutorial on this at Sigcomm, and it was the focus of 
> my thesis 25+ yrs ago)

Is there a recording?  }:-)

> These contribute to the overall latency of different communication 
> technologies in various ways. I’m glad that you noticed that such 
> latency is *of a message* (of size X), rather than an independent property 
> (i.e., just asking “what’s the latency?” cannot be answered).

:-)

> It also takes longer than it looks like it should across modems and RF 
> links, sometimes because of coding delays (aggregation latency above) 
> and channel access latencies.

Agreed.

Assuming that some of the coding delays are related to serial data going 
into a buffer but not filling it, so the modem times out and sends a 
partial buffer.  I wonder if different designs with different buffering 
or some sort of push / flush signal might help things.  But that's more 
complexity which drives price up.

> FWIW, propagation delay has gone up (from coax LANs @0.8c to twisted 
> pair @0.6c) then down (newer twisted pair approaches 0.8c again) and 
> fiber is 0.65c. WiFi is very close to 0.99c

I think that's signal in medium.  If I'm reading your statement 
correctly, the number closer to 1.0c is better.

Is that 0.8c 10Base2 or 10Base5?

The 0.8c for coax vs 0.6c for twisted pair matches experiences that I 
remember.  Coax seemed slightly faster than twisted pair.  People 
thought I was crazy seeing as how both were 10Base<something> and 10 Mbps.



-- 
Grant. . . .
unix || die