Subject: Advertising prefixes rather than addresses

From: Ralph Droms <[email-masked]>
Date: Thu, 26 Jul 2001 16:58:45 -0400

Bernie Volz wrote:

>    At another time we also discussed using the server to just
>    advertise prefixes and allowing the client to generate the
>    addresses? What about adding a "P" bit (next to the "T"-temporary
>    bit) to indicate that this is a prefix from which the client should
>    generate an address (or simply allowing it to do so if the
>    link-identifier field is all 0's).

Sounds like a reasonable idea - anyone have a strong reaction (either 
positive or negative)?

- Ralph

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From: Josh Littlefield <[email-masked]>
Date: Thu, 26 Jul 2001 17:13:33 -0400

I used to think this was a reasonable idea.  But I thought it was killed by
this group a while ago as unnecessary.  If you want stateless autoconfig,
then use that and not DHCP.  If the router advertisement tells you to do
stateful autoconfig (DHCP), then having DHCP tell you to do stateless
autoconfig on a prefix (essentially this proposal) doesn't seem right.  The
server can always just generate for a client the address it would generate
for itself (supposedly on some subset of the allowable prefixes).

--
=====================================================================
Josh Littlefield                                  Cisco Systems, Inc.
[email-masked]                                      250 Apollo Drive
tel: 978-244-8378  fax: same               Chelmsford, MA  01824-3627

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From: Bernard Aboba <[email-masked]>
Date: Thu, 26 Jul 2001 14:09:56 -0700 (PDT)

This is just duplicating functionality that is already in stateless
autoconfig. Presumably you'd use DHCPv6 for addressing if you wanted to do
it statefully. So I don't see the need or purpose of this.

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From: Jitesh N Verma <[email-masked]>
Date: Fri, 27 Jul 2001 19:32:17 +0530 (IST)

What can't we have this functionality in DHCP??
1) Stateless autoconfiguration through router advertizement has already
hijacked half of the DHCP's usefulness.
2) SLP guys have hijacked the idea of Service Location from DHCP.
3) DNS guys are thinking of putting a mini DHCP in the DNS.

Everybody is trying to hijack the DHCP functionality. Why can't we implement
a functionality which is DHCP's own domain (The address allocation)?? I am
not saying that it should be included in the next draft. It may be deferred,
but it should be considered by the working group.

- Jitesh

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From: Jim Bound <[email-masked]>
Date: Fri, 27 Jul 2001 12:08:06 -0400 (EDT)

Let me try to give supportive example of permitting bernies request. we
have discussed this before too and in many places.

the sysadm wants control over the entire network space and at a central
location for IPv6 and to do that from servers.  this means for whatever
reason stateless will not be used for address configuration.  The the
routers set the M and O bits and the clients must use dhcpv6.

but the sysadm wants to use the autoconfig benefit of ipv6 where by the
client configures their address using prefix from the server.  then the
same code to generate an address as in stateless can be reused too as a
note and DAD etc..  thats why it is reasonable.

but if we want the server database to have all addresses a client has from
a prefix then one of two things must happen.

1.; client sends the completed addresses back to the server with the low
order bits used (we cannot hard code that is only 64bits for IPv6 fyi as
that is just one addressing scheme supported today).

2. Or client must always send link-local address in dhcpv6 msg hdr as the
server could use that to concatenate the address assuming all other bits
are owned by the server for the prefix (I think we can assume that) for
that link.

OR 

the server only keeps prefixes for the client.

/jim

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From: "Charles E. Perkins" <[email-masked]>
Date: Fri, 27 Jul 2001 09:30:39 -0700

Hello,

As I was one of the SLP guys, I have to point out
that this is a totally inaccurate characterization.
SLP works a lot different than DHCP, we didn't steal
anything from DHCP and there was never any Service
Location feature in DHCP.  Maybe instead you were
thinking of some specific options for things like
DNS server addresses.  That is a lot different.

Charlie P.