Re: [Ntp] Antw: Re: Antw: [EXT] NTPv5 Loop Detection without Stratum

[Hal Murray <[e-mail]>]

[e-mail] said:
> No, the loop avoidance algorithm only rejects a source if that source depends
> on the node itself. So, when having 4 servers A B C and D, if server A is a
> stratum 1 server, and servers B and C sync to server A, server D can still
> use all of A,B and C to synchronize. However, suppose it uses all 3, then at
> that point, it will no longer be accepted as a potential time source by node
> B or C, because these then see they were part of the source of D, and
> therefore reject. 

That brings up an interesting point.

What does loop mean?

The draft for NTPv5 is only the wire protocol.  It doesn't cover what goes on 
inside a server.  If a server latches on to the best upstream server and only 
uses any others for checking, then the topology is simple and loop would be 
easy to define.

Is that a reasonable assumption?  Do we need a section in the draft to collect 
assumptions about the internals of servers?

Consider the alternative where a server does some sort of weighting on the use 
of its upstream servers.  What does stratum mean?  Is loop well defined?

------

Do we want 2 different client/server packet modes/formats?  One for 
leaf-clients (SNTP) and another for the client side of servers?  Or maybe the 
same packet format but different descriptions of the way fields are used.

Or maybe even 2 separate RFCs.  The idea being that SNTP will be much easier 
to understand and we can target it for a longer lifetime.  In particular, it 
wouldn't have to say anything about loop detection.



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