> From: [email protected]
Hi, thanks for those comments - most of them seem desirable, although I may
have some comments later. One thing that caught my eye quickly:
> 11.2.1 Why not use DNS:
> imho DDT has been developed to blow up the LISP work. Right?
This makes no sense, either organizationally, or technically. First, on the
non-technical front, the people who proposed DDT are the same people who did
LISP origially. Why would they want to blow up their own system? Second, I
cannot see how the selection of DDT is a crippling blow, technically.
Replacement of the ALT with 'something better' was necessary; the reasons
aren't given in detail in the draft (which is intended for a future audience,
not today/yesterday, which is why the details were left out). It turned out
that what I saw as the worst problem with ALT (traffic hot-spots at the root)
turned out to not be a problem yet (although in the long run, it would have
been a major problem). Rather, the problem that was starting to appear with
the ALT (I gather, from a brief conversation) was simply the configuration
management - one had to configure all the tunnels, etc, etc.
> The given explanations do not convince me.
As to why DDT was preferred to a DNS-based system (the people at Cisco
actually prototyped one, to see how it would do, compared to DDT), I can
assure you that the reasons given in the document are a reasonable short
summary of an extended discussion that went on over a couple of days.
Needless to say, everyone who participated in that discussion will have their
own views as to the strengths and weaknesses of each, and some people may
have a different take on the benefits of DDT (and indeed, there were some
people who actually preferred the DNS-based approach), but I tried to
summarize the reasoning as best I could in the short amount of space I felt I
could devote to the question.
(Perhaps a longer, more detailed discussion of why DDT is better than a
DNS-based alternative would be in order in the DDT spec, but I don't think
it's proper in an introduction to the entire system.)
I think in general the overall cost/benefit was felt to favour DDT - the cost
being the necessity to write code and specs, and the benefit being that we
didn't have to kludge anything, to adopt a system that was designed for a
different use; we could do a system that was exactly what was best for LISP.
You may disagree with that, and agree with those who preferred the DNS-based
system. But that's your judgement - the judgement of me, and a number of
others, goes the other way.
Noel
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