On 3/19/09 at 8:17 AM -0400, Keith Moore wrote:
Lixia Zhang wrote:
I believe that people in general agree that applications should not
use IP address for referrals.
I don't know which people you're referring to there, but that's
absolutely not the case for application developers. In the current
internet, use of IP addresses for referrals is essential.
That IP addresses are currently essential for referral is not
mutually exclusive with the idea that applications should not use IP
addresses for referrals. IP addresses fail for referrals in a vast
number of cases including 1918 addresses, firewalled networks,
certain asymmetric routing cases, etc. Given the current state of the
network, you can neither recommend nor completely forbid the use of
IP addresses for referrals in applications. (And nowhere in what
Lixia said was the statement that applications MUST NOT use IP
addresses for referrals.)
And in fact every application that uses DNS does exactly that.
I think that's a rather narrow view of where DNS falls in the architecture.
It's all well and good to imagine a world where there would be a
clear ID-LOC separation. But we've never created such a world, and
we don't currently have an ID-LOC mapping layer that is good enough
to use by all applications.
Yup. In part, that's what LISP is about. But I actually think it's
incorrect to talk about having "an ID-LOC mapping layer good enough
to use by all applications". If we're talking about the ideal world,
applications should almost never need to use the mapping layer; they
should be able to simply use the ID (without touching the LOC) and
let the routing system deal with finding a LOC for the ID. That an
application would have to actually deal with the mapping is an
artifact of the current state of affairs where neither the LOC (IP
address) or ID (DNS) is good enough to allow the application to do
what it needs to do.
DNS falls short in many ways. And as long as there is not a
universal mapping layer that is aware of things like NATs and
mobility, and for that matter as long as there are devices that
impose arbitrary limitations on traffic flow (e.g. connections have
to be initiated from "inside"), there will be a need for
applications to deal explicitly with IP addresses. Sure it's ugly
but it's the best that applications can do.
I'm guessing we're in violent agreement, but NATs and mobility and
"traffic flow limiters" actually make it impossible (viewing it from
the other end) to use IP addresses: Giving a reference to myself
using my own IP address when I am behind a NAT is useless; using a
name, if one is available, is the only way to go. (And I still agree
with your above paragraph.)
pr
--
Pete Resnick <http://www.qualcomm.com/~presnick/>
Qualcomm Incorporated - Direct phone: (858)651-4478, Fax: (858)651-1102
_______________________________________________
Ietf@xxxxxxxx
https://www.ietf.org/mailman/listinfo/ietf