I beg to differ. Most UDP based protocols do not have this requirement. If they did, it would not be the case that in the (mumble mumble) years since the invention of the UDP protocol and the sockets interface, that the interface even provided the ability for the application to to do this within the interface within the last few years.
The UDP protocol itself has no such requirement. Although the Hosts requirements RFC says that a host SHOULD provide a mechanism to do it, until IPv6 came along, few systems actually did. The only way to guarantee it was using the awful "bind every interface" trick that the reference implementation uses. The "RPC protocol" itself (RFC 1050) does not have this requirement. I do not know why the original designers of UDP did not include this requirement. I suspect they did not foresee the security requirements we have today. Or perhaps they had a good reason. But in any case the NTPv3 spec does not have the requirement in it. If I recall correctly, the NTPv4 spec does have the requirement, but I also recall commenting on this ages ago, comments that were ignored. I don't disagree that UDP should have the requirement, but it does not, and as such I do object to gratuitously adding the requirement to NTP, which has complicated the code base to no end. Of course, as I said above, it is now possible to implement this cleanly on many OS's, which would allow us to simplify the code immensely. But until such support is universal, that won't happen. Brian David L. Mills wrote: > Guys, > > In both the NTPv4 specification and reference implementation the > destination address used by the client when mobilizeing the association > and sending the request must match the source address when receiving the > response. This is a property of all RPC protocols known to me that use > addresses to match requests with responses. This is so obvious a > requirement that maybe the specification doesn't make it clear enough. > > Dave > > Brian Utterback wrote: >> [EMAIL PROTECTED] wrote: >> >>> Are there any clear requirements in NTP/SNTP RFC docs about the UDP >>> source address in >>> all responses the same as the UDP target address in the original >>> requests? >>> I doubt it would be a UDP requirement because this is domain of upper >>> protocols. >> >> >> >> Yes and no. The basic protocol does not require it. The reference >> implementation does require it. The Autokey crypto authentication >> scheme currently requires it, but there has been some discussion >> recently about the nature of that requirement and whether it could >> be relaxed, but I don't see that discussion going anywhere in this >> regard. >> >> Brian Utterback _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
