Subject: Re: v6 (was Re: -current sendmail cancer in IPv4-only kernel)
To: Sean Doran <>
From: Jonathan Stone <jonathan@DSG.Stanford.EDU>
List: current-users
Date: 05/08/2000 18:01:50
In message <>, Sean Doran writes:

>Feico Dillema <> writes:

>> Second, with IPv6 an attempt is made to change the way
>> packet routing is performed and addresses are structured
>> in order to make routing on defaultless backbone routers
>> much more simpler (by building a hierarchical addressing
>> structure).
>What?!?!?!?!  It's Just CIDR, precisely as in IPv4.  And
>with all the pluses AND minuses of CIDR.  There is
>absolutely nothing different about routing IPv4 and IPv6.
>Please note that this was said by Steve Deering in an IETF 
>message with Message-Id: <v04220801b52d488e05ee@[]>
>(I do like that Message-ID, from Dr. IPv6!)
>  Yes, that's right.  If I understand correctly, you are upset by the
>  imprecise shorthand of saying "this is an advantage of IPv6 over IPv4"
>  and would prefer that we were careful always to say "this is an advantage
>  of the IPv6 addressing plan over the addressing plan of the existing IPv4
>  Internet, an advantage of starting fresh".  Fair enough.
>More concisely, "the only difference between the IPv4 and
>IPv6 routing plan is that there are almost no
>currently-used IPv6 addresses, and therefore no routing
>swamp (yet)".

I'm not sure this is correct.  The IPv6 addressign archtitecture seems
to add levels of hierarchy.

With IPv4 CIDR, if you get a big enough block (say an /18) and enough
clue to become a BPG peer, one can advertise one's own CIDR block.
Via multiple ISPs, should one choose.

As best I undrstand things, you can't do that with IPv6: Instead one
has to multi-home all hosts with multiple addreses, one from each ISP.
Failover after a back-hoe takes out one ISP becomes, uh, interesting.
This is a very real concern to some people.

(Of course, I may be misinformed, or mis-understanding.)

But other than that: yes, you're right. IPv6 has the pros and cons
of CIDR.  Renumbering, for example.

>> This is not inherent to IPv6 (it merely facilitates it),
>> although it is currently the only addressing
>> architecture designed and implemented, if experience or
>> need dictates other addressing architecture could be
>> added.

But surely with just as much pain as adding them to IPv4, modulo
differences in the allocated space at the point the features are added.
(I'm thinking of  Deering multicast as a possible example).

Anyways,  this isn't exactly on-topic here.
Can we move it ot tech-net, at least?