On Tue, May 5, 2015 at 10:48 AM, Joe Touch <to...@isi.edu> wrote: > > > On 5/5/2015 10:23 AM, Larry Kreeger (kreeger) wrote: > ... >>> IP is a protocol. v4 and v6 are versions. >> >> While I completely agree architecturally, when it comes down to >> implementations, the only downside I see are that it uses multiple Next >> Protocol code points. > > Here are the primary downsides: > > a) multiple codepoints at the top level > > b) the need to continually add new codepoints for new versions > > c) (and this is the big one) > NO savings in processing, in fact, it makes processing worse > > Not only do you need to find the version (as codepoint or within the IP > header), but if you have the same information in two places you now need > to verify that the two match and decide what to do when they don't. > If they don't match the packet should dropped-- this behavior is already implemented.
> I.e., a person with one watch always knows what time it is; a person > with two watches is never sure. > To follow through with your analogy, a person with one watch can give the time but has no way to say that it is correct. A person with two watches can not only give the time but also an assurance that the time is correct (when the times on the watches match). Redundant information in a packet is the basis for verifying the packet against corruption. Since, the IPv6 version number is not protected by any IP layer checksum, a single bit flip can change an IPv4 packet into an IPv6 packet without detection. With version specific code-points we have another method to detect this corruption. > There is simply NO utility in copying information that is equally easily > available and it ONLY invites error. > > Joe > > _______________________________________________ > nvo3 mailing list > nvo3@ietf.org > https://www.ietf.org/mailman/listinfo/nvo3 _______________________________________________ nvo3 mailing list nvo3@ietf.org https://www.ietf.org/mailman/listinfo/nvo3
