[ntpwg] ntpwg Updated NTPv4 Protocol Specification/timestamp location

[David L. Mills]

Stuart,

That's the beauty of it. Herbie and Sue don't care. The delays are still 
reciprocal and the fact Sue's delays are one packet longer doesn't matter.

Dave

UART VENTERS wrote:

> Dave,
>
>
>>> Where's the beef?
>>
>
> Fair enough.
>
> I think it's in 2 places, one technical and one philosophical.
>
> We appear to be in agreement the Media Herbie and Driver Sue (much 
> better names, thanks) built spec compliant implementations.
> If we connect them together with a zero length cable and assume Sue 
> and Herbie's time references are aligned,
> then consider what happens when Sue's client sends a request to 
> Herbie's server.
>
> Sue's T1 timestrike is at the end of packet, Herbie's T2 is at the 
> start of packet. This makes T2 happen about 1 packet time before T1.
> So T2-T1 is about minus 1 packet.
>
> Now for the response.
> Herbie's T3 is at the start of packet, Sue's T4 is at the end. This 
> makes T4 happen about 1 packet time after T3.
> So T4-T3 is about plus 1 packet.
>
> In other words, the reciprocal delay is mismatched by about 2 packet 
> times.
>
>
> Regards,
>
> Stuart
>
>
> ps, The other beef is in your first 3 words (All three citizens). 
> Pesky should not be included in the list of folks who have to read the 
> spec and sweat over matching the delays.
>
> pps, The above is a CP1 story. There is a similar story for CP2.
>
> ppps, You're right, life is much easier in the fpga. It lets me put 
> the whole implementation in one place. I'm very impressed at what you 
> have been able to achieve especially considering the variety of 
> platforms that ntpd runs on.
>
>