[EMAIL PROTECTED] wrote:
From: "Vijay K. Gurbani" <[EMAIL PROTECTED]>
Jeroen van Bemmel wrote:
> Vijay,
> It's not only IPv6: what about 127.0.0.1 versus 127.000.000.1?
Jeroen: Pedantically speaking, you are probably right. But
in practice we do not generally see leading zeros in an IPv4
octet.
Even worse, in some places, including some early RFCs, the leading
zero is used to indicate that the octet is represented in octal!
But I think Jeroen's point is actually well-taken, when comparing
representations of IP addresses (not DNS names), the comparison is
implicitly of the address represented, not the textual
representation. And this applies in IPv4 as well as IPv6.
In regard to loop detection, there are two approaches: (1) Whatever
attempts to detect loops can canonicalize the addresses before
comparing them or whatever. (2) Since there are a limited number of
likely representations of any address, having different entities use
different representations will only delay loop detection, not prevent
it. And loops will be detected even if address comparisons have
occasional false negatives.
Given that a particular IP address might serve many, many different
URI's (think about the outsourced case), I doesn't seem to me that this
would be a very good assumption. It might be perfectly reasonable for
a method to traverse from IP address A and then back through IP address
A again without being a loop since it might be outsource1.com through
outsource2.com which is legal, right? This case certainly comes up with
email and is actually really common(*).
It seems that the conclusion of Vijay and my violent agreement is that
the entity inserting the URI better keep things consistent as the loop
detector ought to just consider these things as opaque blobs.
Mike
(*) modulo DNSBL considerations.
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