Cost-effectivenesss of highly-accurate clocks for NTP

Lamar Owen lowen at pari.edu
Mon May 16 16:02:04 UTC 2016


On 05/15/2016 01:05 PM, Eric S. Raymond wrote:
> I'm not used to thinking of IT as a relatively low-challenge environment! 

I actually changed careers from broadcast engineering to IT to lower my 
stress level and 'personal bandwidth challenge.'  And, yes, it worked.  
In my case, I'm doing IT for radio and optical astronomy, and at least 
the timing aspect is higher-challenge that most IT environments.

> You're implicitly suggesting there might be a technical case for 
> replacing these T1/T3 trunks with some kind of VOIP provisioning less 
> dependent on accurate time synch. Do you think that's true? 

While I know the question was directed at Mel specifically, I'll just 
say from the point of view of a T1 voice trunk customer that I hope to 
never see it go to a VoIP solution.  VoIP codecs can have some serious 
latency issues; I already notice the round-trip delay if I try to carry 
on a conversation between our internal VoIP system and someone on a cell 
phone.  And this is before codec artifacting (and cascaded codec 
scrambling) is counted.  Can we please keep straight μ-law (A-law if 
relevant) lossless DS0 PCM timeslices for trunklines so we get at least 
one less lossy codec cascade?  Or have you never experimented with what 
happens when you cascade G.722 with G.729 with G.726 and then G.711 and 
back?  Calls become mangled gibberish.

I would find it interesting to see how many carriers are still doing 
large amounts of SONET, as that is the biggest use-case for 
high-stability timing.



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