RE: [dhcwg] Order of occurence of DHCPv6 options

["Bernie Volz (EUD)" <[e-mail]>]

Vijay:

The problem is how to mandate this in a reasonable way. We never know what future options will be defined and even you and I don't agree on the order of the options. And, servers and clients MUST NOT depend on this order (since new "more important" options might be defined in the future).

So, I think if anything we could give a general recommendation as to WHY certain options should be added earlier in a message. But that's as far as we can go, IMHO.

BTW, if you follow the rules for building the messages as documented, the server identifier and client identifier do appear early in the messages.

- Bernie

-----Original Message-----
From: Vijayabhaskar A K [mailto:[e-mail]]
Sent: Monday, June 17, 2002 6:19 AM
To: 'Bernie Volz (EUD)'; [e-mail]
Subject: RE: [dhcwg] Order of occurence of DHCPv6 options


Hi Bernie,

The requirement here is PERFORMANCE. Assume there are 1000 requests passing
through a server which are NOT intended to be handled by this server. This
will happen since most of the messages are Multicast only. This is not the
corner case situation as you said, this will happen in most of the cases.
There is nothing wrong in mandating this. This is something like specifying
these options in a fixed mesg header. The server/client will ignore the
remaining
option field, if there is any error in the mesg header.

All of the above, the relay should be lightweight, if the admin has
configured
the relay to load balance based on Elapsed time option and how bad the
performance will be if the relay has to search for this option by parsing
the whole message.

> the above might not even apply (for example, if a client or
> server always decodes all options to validate the packet,
> it won't save anything).

Then, this is a poor implementation. If the first option itself is
erraneous, (for ex. auth itself fails), then there is no need to
parse remaining stuff. We should leave these kind of implementation
as corner case and go on mandating options' order of occurence.

~ Vijay

-----Original Message-----
From: Bernie Volz (EUD) [mailto:[e-mail]]
Sent: Saturday, June 15, 2002 11:06 PM
To: '[e-mail]'; [e-mail]
Subject: RE: [dhcwg] Order of occurence of DHCPv6 options


Vijay:
On the order of options, we chose specifically NOT to specify this. There
really is no
requirement or overwhelming reason to do this. Putting some options earlier
than others
improves performance in some situations so it will be wise for clients (and
servers) to
do this, but it is difficult to specify this and a client and server MUST
assume the
worst anyway.
For example, I'd argue that putting the Server Identifier option first (or
very early)
is best since it allows all servers that receive this (except for the
intended one) to
drop the packet almost immediately. Rather than having to look through 4
options, won't
it be better if these servers only had to look at 1 option (the first).
Though, having said that there is no reason to require this and depending on
how a client
or server processes packets, the above might not even apply (for example, if
a client or
server always decodes all options to validate the packet, it won't save
anything).
So, we specifically decided not to specify option ordering and I think that
is a wise
decision.


Regarding the other issues, some clean-up for the draft will be required to
remove and
fix items based on the final status codes/option usage.
- Bernie
-----Original Message-----
From: Vijayabhaskar A K [mailto:[e-mail]]
Sent: Saturday, June 15, 2002 1:31 PM
To: [e-mail]
Subject: [dhcwg] Order of occurence of DHCPv6 options


I think, we need to fix the order of options occuring in DHCPv6 messages
for better processing of the messages.
1. Elapsed Time option - Since based on this value only, the relay/server is
going to decide the policy of reply.
2. Status Code - In the case of Failure, this message can be directly
ignored
3. Authentication option - If authentication fails, nothing is needed to
be processed.
4. server-id - If the server id doesn't match, server can ignore it.
5. client-id - If the client id doesn't match, client can ignore it.
6. Rapid commit - Based on this, the server can determine whether it need
to send Advertise or Reply.


If any of these options are occuring, then they MUST occur in this order.
----------------------------------------------------------------------------
--
ConfNoMatch and AddrUnavail are nowhere used. It can be removed.
AuthFailed is also nowhere used. We need to add text saying if the
server/client is not able to authenticate the other, then they
should send reply with error code AuthFailed set.
----------------------------------------------------------------------------
--
R-forw.    *                        *     *      *      *
R-repl.    *                        *     *      *      *
Why Authentication, User class, Vendor class, Vendor specific options
are needed in Relay-fwd and Relay-reply message.
~Vijay


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