On 10/27/2013 10:10 AM, Magnus Danielson wrote: > On 10/27/2013 02:42 PM, Tal Mizrahi wrote: >> Hi Danny, >> >>> That also means that the extension field MUST NOT be added by any >>> intermediate nodes if it does not exist. >> I am not sure we want to go there, for 2 reasons: >> >> 1. Let's not forget that the source and the intermediate node are in fact >> two modules in the same client/server (see Figure 1 in the draft). From an >> interoperability perspective it would be exactly the same if the source >> created the extension field, or the intermediate node did. Why would we >> mandate a specific implementation detail that would be completely >> transparent to the network? >> >> 2. A clock that receives an NTP message has no way of knowing whether an >> extension field was added by the source or by an intermediate node, and thus >> there is no way to enforce (enforce from a security perspective) the >> requirement you suggested. > I think this discussion would benefit from separating "interface node" > from "intermediate node" as these have different roles. The interface > node would add the output time-stamp of the sending node. If > intermediate nodes where allowed to add fields, we could have buffer > compensation in NTP just as in PTP's transparent clock.
I'm not sure that there's a real difference here. From a topological point of view the interface node and an intermediate node are just a node in the network. You are just calling it a different name. > At the same time, as long as there is no authentication on this, any > intermediate node can create any form of modification that the receiver > node will accept, malicious or unintentional. Hence, there is only so > much protection you can create in the semantics. > There's no protection whatsoever here. Danny _______________________________________________ TICTOC mailing list [email protected] https://www.ietf.org/mailman/listinfo/tictoc
