Subject: Re: review of draft-ietf-node-req-bis

From: Ray Hunter <[email-masked]>
Date: Fri, 27 May 2011 14:39:11 +0200

>
> Message: 2
> Date: Thu, 26 May 2011 16:21:59 -0400
> From: Thomas Narten<[email-masked]>
> To:[email-masked]
> Subject: Re: review of draft-ietf-node-req-bis
> Message-ID:<[email-masked]>
>
> Going back to this...
>
> Jari Arkko<[email-masked]>  writes:
> <snip>
>
> New text:
>
>     12.3.  Stateful Address Autoconfiguration (DHCPv6) - RFC 3315
>
>     Because a single DHCP server can support devices on multiple links,
>     it is not necessary that every router support DHCPv6 directly.
>     However, in order to support DHCPv6 servers on other links, routers
>     SHOULD support relay agent functionality of DHCPv6 [RFC3315].
>     Routers MAY support full [RFC3315] or stateless [RFC4862] DHCPv6
>     server functionality as well.
>
> I'm on the fence wrt MAY/SHOULD on the recommendation above. I don't
> think every router needs to support DHCP, hence the MAY. But SHOULD is
> also not a MUST, so I'd be OK with SHOULD.
>
> Indeed, where one arguably should have a MUST is in relay agent
> functionality. SHould I elevate it?
>
> Thoughts?
>
> Thomas
>
>    

All from my own very very humble opinion based on experiences mainly in 
enterprise networks.

Many people have centralized DHCPv4 at least at the site level, if not 
the enterprise level, for very good and varied operational reasons (not 
just because they had to have them for allocating and registering names 
and addresses) and much of that functionality cannot currently be 
replaced by SLAAC alone (or any other widely deployed alternatives AFAIK).

I was reminded just the other day of the (humble) origins in bootp when 
someone walked into the office and wanted to set the Code 67 
boot_file_name and Code 66 boot_server in the DHCP scope for use by a 
server located on another remote site, which contacted the central DHCP 
server via DHCP relay.

DHCPv6 server on a router is definitely not a must. Probably not even a 
should. MAY is absolutely fine for me.

DHCPv6 relay on a router is definitely at least a SHOULD. Otherwise 
those centralized IPAM systems that exist today will not be able to 
function with IPv6: you will break existing functionality that 
enterprise network managers currently use to great extent.

On the other hand, a MUST for DHCP relay on routers seems to go way too 
far for me. DHCPv6 support is after all only a SHOULD for end nodes. And 
it may not even be turned on by default.

So what parameters are network operators expecting to set on an end node 
that is so important?

I'd like it to be otherwise, but the truth seems to be that the current 
consensus is that there is no consensus on a single mechanism of how to 
signal options and settings between a network manager/ service provider 
and an end node.

Personally, I won't buy a router without a DHCPv6 relay function. But 
then again in an SP environment with PD, where do you point DHCPv6 relay 
to by default to fetch content if it is a MUST? Does it serve local 
config parameters (set by the local admin to control e.g. printservers) 
or does it serve config parameters sent to the household end node 
systems by the Service Provider (which might be ignored by end nodes not 
running DHCPv6)? Who has the admin rights? Potential can of worms and 
source of conflict until the question is sorted out for each DHCPv6 
option of who can set the value and which source is authoritative.

So in summary, I'd settle for MAY for server, and SHOULD for relay. IMVVVVHO

regards,
RayH

---

From: RJ Atkinson <[email-masked]>
Date: Fri, 27 May 2011 18:51:05 -0400

Earlier Thomas Narten wrote in part:
> Let me ask a question. In IPv4, for typical SOHO routers, do they
> support DHCP relay agent functionality? (My guess is no.)

Small office routers, such as the one in my garage, 
generally include DHCP relay agent capability and 
also have DHCP server capability (both static & dynamic).

Low-cost home/consumer-electronics routers often
have DHCP server capability (at least dynamic DHCP, 
sometimes also static DHCP) but generally do not have 
DHCP relay agent capability.

> And what about configuring it?
> It is *not* plug and play, zeroconf magic...

Agreed.  

Note, however, that Dynamic DHCP server configuration 
can be done auto-magically in situations where the 
home router is performing NAT/NAPT-like transformations
and the interior is using some private address space 
(192.168.X.*/24 is popular for several IPv4 home/
consumer-electronics routers).  

For IPv6, something similar could be auto-magical
if ULAs were used on the interior, for example.

Cheers,

Ran