Subject: ISP using dynamic address/prefix

From: Pekka Savola <[email-masked]>
Date: Wed, 23 Apr 2003 11:52:54 +0300 (EEST)

Majordomo was too smart and blocked this message because it believed it 
was a administrative request due to the words used.

Let's try with a slightly different subject/body.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
---------- Forwarded message ----------
Date: Wed, 16 Apr 2003 15:47:21 +0300 (EEST)
From: Pekka Savola <[email-masked]>
To: [email-masked]
Cc: Robert Elz <[email-masked]>
Subject: reasons for ISP changing address/prefix

Hello all,

A point inherited from another thread: why do the ISP's today force the 
users use dynamic address/prefix for intermittent connectivity?

Let's try to look at the possible reasons first, and after that, look 
again to see if the situation is any different with IPv6 (at least for 
some things yes, I believe for some others no).

Depending how much discussion this incites, writing a short I-D
summarizing this issue should probably be a good idea.  I can do it if it
seems warranted.

On Wed, 16 Apr 2003, Robert Elz wrote:
>   | Note: in today's world, it seems to me that almost all of these cases are
>   | really those of intermittent connectivity.
> 
> Of changing connectivity, whether intermittent, or not.   Right now
> (as of this instant I mean) my connections rarely last much more than
> an hour or so (then restart fairly quickly).   Every time I connect I
> get a different address.   You can be dead sure that that address has
> no bearing at all on the addressing I am using on my internal net.

This is outside of the scope of the original topic but let's consider 
this a bit.

Why would an operator change the prefix/address?  A few possible reasons
spring to mind:

 - make it more difficult for people to run servers in their "low-end" 
connectivity services (and wasting bandwidth and what not)

 - addresses are a relatively scarce resource and especially in cases
where the users do not need them all the time, it's easier to explain this 
to RIR's in address applications and you need a smaller block

 - in cases where the users do not need them all the time, it's
easier&simpler to just have a pool of addresses, and associate the user
with one only when required

 - one could also cite privacy reasons but I believe that's mostly only 
an excuse for another reason

 - the user has no incentive to get a more expensive connection or a 5$/mo 
upgrade for static addresses if everyone gets them for free

 - one might have to keep a real database of user<->IP mappings (both in 
the backend like RADIUS and possible RIPE-whois like databases) if they 
were assigned statically

More of them?

Some of these are bogus and can be argued of course, but let's just 
collect a list of reasons first.

Going a bit to the IPv6 side already:

> We might like to pretend that we can stop providers from doing that, but we
> cannot.

Well, I agree with you to a degree here that we cannot _assume_ that there 
will not be providers that provide you with a changing prefix.  But with 
proper work and education, if we can manage most of them to do the right 
thing, we just might be able to make this problem a bit smaller.  Then, a 
little bit less extensive mechanisms to cope with this case might be 
acceptable.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings

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