v6 subnet size for DSL & leased line customers

Iljitsch van Beijnum iljitsch at muada.com
Thu Dec 27 21:57:59 UTC 2007

On 27 dec 2007, at 20:26, Christopher Morrow wrote:

>> With IPv4, a lot of these features are developed by vendors and
>> (sometimes) later standardized in the IETF or elsewhere. With IPv6,
>> the vendors haven't quite caught up with the IETF standardization
>> efforts yet, so the situation is samewhat different. For instance,
>> SEND/CGA is excellent work, but we've only recently seen the first
>> implementations.

> first implementations, in a protocol that's 'fully baked' (according
> to ietf closing down the v6 WG) and been in 'production' for 15 years?

You suggest that I said that IPv6 has only recently seen the first  
implementations. I was talking about CGA/SEND, not IPv6 proper, which  
was standardized some 12 years ago.

> for features that have existed in the v4 network for 5+ years? ouch...
> This gets back to my point about having feature parity

Some of the "features" of IPv4 are actually glaring holes that some  
people have found a use for. Also, SEND is something that doesn't  
exist in IPv4 so your complaint doesn't apply here.

> and the fact
> that that is important. People have deployed rather large environments
> that require these features, not having them is a step backwards and
> painful for the operators in question.

Please direct your feature request to your favorite vendors...

>> What this all boils down to is that if you want to deploy DHCPv6 you
>> need to install software on a lot of systems and modify a lot of

> 'the largest deployed platform' already has this built-in, yes?  
> (vista/xp)

Vista: yes, it seems. XP, no so much. Windows XP can't even do DNS  
lookups over IPv6, which basically means that you can't use an XP  
machine on an IPv6-only network.

>> If you're going to do all that, it's easier to simply
>> configure this stuff manually. The only downside to that is that it's

> you are crazy... seriously, have you walked around to 10k or 50k
> machines or attempted to get helpdesky people to do the same? have you
> considered that this all works fine in v4, is tied into my OSS
> backends and is a part of my business process? Getting some new
> software (firefox is a fine example) deployed to 50k workstations is
> an overnight event... SMS (or whatever the new MS equivalent is) rolls
> out the software update, there are many other options (tivoli,
> ca-unicenter, custom-foo) which will also do this work for you,
> getting proper and dynamic setup of IP info (my earlier example of
> resolvers) isn't quite as simple unless you use dhcp.

It is wih IPv6: you just connect the ethernet cable and the RAs take  
care of the rest. _You_ _really_ _don't_ _need_ _DHCP_ _for_ _IPv6_.  
If you need extreme control then manual configuration will give you  
that, which may be appropriate in some cases, such as servers.

> just saying 'dhcpv6 isnt possible use autoconf' is never going to be
> acceptable.

Never said it isn't possible. But unlike with IPv4, where DHCP is the  
default answer unless you're really sure you need manual  
configuration, DHCPv6 isn't the default answer for IPv6.

>> That being said, please go to your vendors and tell them what you
>> need. Preferably at a high level, so they can provide the
>> functionality in the optimal way, rather than just revert back to the
>> IPv4 way of doing things.

> also be sure to let your standards body(s) know that some form of
> feature parity is relevant. I think often there is a missing message
> between operators and the other folks :( this clearly (to me atleast)
> seems like one of those areas.

Taken to its extreme "feature parity" means a search and replace of  
all IPv4 specs to make every instance of "32 bits" "128 bits" but not  
changing anything else. That's not what IPv6 is.

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