[ntpwg] draft minutes from Vancouver NTP WG meeting

[Danny Mayer]

Rob Seaman wrote:
> On Dec 23, 2007, at 11:38 AM, Danny Mayer wrote:
> 
>> Consider the Interplanetory Internet for example. Sending a packet  
>> from a spacecraft orbiting Mars to a station on Earth, for example,  
>> has very long delays AND asymmetry since the  returned packet will  
>> be returned from a different location on Earth than when it arrived  
>> AND the position of the spacecraft will have changed.
> 
> This is a different problem regime.  The light time delay is highly  
> predictable, whether or not it is asymmetric.  The general issue of  
> "world coordinate systems" and space-time coordinates is quite active  
> in the astronomical computing community - you can benefit from side  
> channel information about the relative positions of the endpoints of  
> each link.
> 

I forgot to comment on this one. The packet follows the geodesic which
is a 4-dimensional path so you cannot just locate the 3-d coordinates of
each endpoint and calculate the distance between them.

Danny