Subject: Re: Thinking differently about names and addresses

From: "J. Noel Chiappa" <[email-masked]>
Date: Tue, 1 Apr 2003 16:26:47 -0500

> From: Keith Moore <[email-masked]>

    > HIP only solves part of the problem ... it doesn't provide any way of
    > mapping between that identity and an address where you can reach the
    > host.

A system doesn't have to provide mechanisms to look up mappings from
<any-name> to <any-other-name> to be useful; just because I can't (in general)
look up the mapping from an Ethernet address to an IP address doesn't mean
there's a fatal flaw in IPv4.

A directorized mapping need only exist *when you need to look up that mapping
for some good reason*. If you construct the protocol interactions such that
you don't *need* to be able to look up the "identity->address" mapping (which
is what HIP does - in general, by providing the identity->address mapping
used in any given transaction as part of the initiation thereof), there's no
problem.

Now, maybe what you meant to say is "there are cases A, B and C in the use of
HIP that I have identified where you need to be able to look up that mapping,
having only the identity in hand", that would be something to examine.

But to merely say "the system doesn't provide all possible mappings" is, as
we can see from my inital example above, not really a useful critique.

	Noel

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From: Keith Moore <[email-masked]>
Date: Tue, 1 Apr 2003 16:58:33 -0500

On Tue, 1 Apr 2003 16:26:47 -0500
"J. Noel Chiappa" <[email-masked]> wrote:

>     > HIP only solves part of the problem ... it doesn't provide any
>     > way of mapping between that identity and an address where you
>     > can reach the host.
> 
> <any-name> to <any-other-name> to be useful; 

agreed.  but it does need to provide such mechanisms in order to provide
useful endpoint identifiers.  without a mechanism to map the endpoint
identifier to an IP address, such identifiers are useless in referrals
between application components.

Keith

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From: John Stracke <[email-masked]>
Date: Tue, 01 Apr 2003 17:24:27 -0500

Keith Moore wrote:

>without a mechanism to map the endpoint
Not completely useless; they would prevent the problem of reaching the 
*wrong* endpoint.  This isn't much help if you have only one address for 
the endpoint you want; but, if you have a global and a local address for 
it, and you get the wrong HIP from the host that answers when you use 
the local address, then you know not to use that one.

-- 
/============================================================\
|John Stracke      [email-masked]                     |
|Principal Engineer|http://www.centive.com                   |
|Centive           |My opinions are my own.                  |
|============================================================|
|"God does not play games with His loyal servants." "Whoo-ee,|
|where have you *been*?" --_Good Omens_                      |
\============================================================/

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From: Rob Austein <[email-masked]>
Date: Tue, 01 Apr 2003 18:25:49 -0500

> between application components.

Correct, if you assume that there will be situations in which you only
have the endpoint identifier and you need the IP address.  That's not
the only conceivable way of passing around a referal, it's just the
one that's closest to being a drop-in replacement for a referal
mechanism based on raw IP addresess.

In other words, whether you need this particular mapping depends on
precisely how you intend to use the endpoint identifiers, which is
what I think Noel was saying.

---

From: Keith Moore <[email-masked]>
Date: Wed, 2 Apr 2003 18:05:09 -0500

> > > A system doesn't have to provide mechanisms to look up mappings
> > > from<any-name> to <any-other-name> to be useful; 
> > 
> > agreed.  but it does need to provide such mechanisms in order to
> > provide useful endpoint identifiers.  without a mechanism to map the
> > endpoint identifier to an IP address, such identifiers are useless
> > in referrals between application components.
> 

well, we've had people saying that you shouldn't pass around the IP
address.  obviously the new identifier doesn't help you avoid passing
around the IP address if you can't get the IP address from the
identifier.

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From: Keith Moore <[email-masked]>
Date: Wed, 2 Apr 2003 18:07:56 -0500

> >identifier to an IP address, such identifiers are useless in
> >referrals between application components.
> >
> *wrong* endpoint.  This isn't much help if you have only one address
> for the endpoint you want; but, if you have a global and a local
> address for it, and you get the wrong HIP from the host that answers
> when you use the local address, then you know not to use that one.

true.  but requiring apps to determine which of several potentially
ambiguous (or obsolete) addresses is the one that reaches the intended
peer by trial-and-error does not strike me as an efficient or
desirable strategy.