Re: Comments on IPv6 Prefix Subdelegation

> From: Fred Baker <fred@cisco.com>
> Date: Thu, 30 Jul 2009 04:04:23 -0400
> To: Mikael Abrahamsson <swmike@swm.pp.se>
> Cc: <draft-ietf-v6ops-ipv6-cpe-router@tools.ietf.org>,
> <draft-donley-ipv6-cpe-rtr-use-cases-and-reqs@tools.ietf.org>, IETF IPv6
> Mailing List <ipv6@ietf.org>
> Subject: Re: Comments on IPv6 Prefix Subdelegation
> 
> On Jul 30, 2009, at 9:21 AM, Mikael Abrahamsson wrote:
>> On Thu, 30 Jul 2009, Fred Baker wrote:
>>> Um, what does a router do? Look at the example in the text and ask
>>> yourself if you want an average user (my canonical "average user"
>>> being my daughter, who wanted me to come to her house to install a
>>> camera on her computer so she could use it on Skype - "did you try
>>> plugging it in?") manually installing routes in each of the four
>>> routers when they could in fact learn them from each other directly?
>> 
>> So, looking at this from another angle, namely deployment. I'm a
>> router engineer, I support the use of routing protocols as much as
>> the next router engineer, but I think a good question to ask is
>> whether most home CPE vendors think RIP for IPv6 is hard to
>> implement, or if this is something they consider easy?
>> 
>> If it's easy to implement RIP for IPv6 then I'm a proponent for that
>> model.
> 
> Linksys and Cisco (which in this context represent completely separate
> product lines, one based on ODM sources and one based on IOS) both
> support RIP; the IOS products support all relevant IGPs.
> 
>> Fred, (just checking) the model you're advocating then is that
>> DHCPv6-PD from the main home CPE (with WAN connection) hands out
>> subnets which are then announced to all home gateways via RIP(v6) ?
> 
> What I am suggesting is that:
> 
>    a) DHCPv6-PD is very likely used by the ISP to delegate a prefix
>       to the CPE (although I know of providers that would prefer to
>       use an option on an RA to do this)
>    b) the CPE router installs a default route to its upstream (duh)
>    c) the CPE assigns some of the implied /64s to its interfaces as
>       described in 2.1 and 2.2
>    d.1) in a home with one router, that being the CPE, we're done
> 
[jjmb] the above is the most likely the near term typical use case.

[jjmb] the items below are more advanced.  How far do we need to go with the
below?  Seems to me that we should enumerate some fundamental mechanisms
that can be used for sub-delegation.  We probably need to make sure we cover
how routes are distributed within the home.
>    d.2) <something> may, in cases like the 2.3 case, sub-delegate
>         prefixes by some algorithm to other routers in the SOHO/SMB.
>    e) in a SOHO/SMB with multiple CPEs or with internal routing,
>       routers will need to communicate within the SOHO/SMB about
>       routes. For that, I would suggest the use of an IGP routing
>       protocol as opposed to manual static configuration.
> 
> As I observed Tuesday in v6ops, (d.2) is largely undefined; one could
> use DHCP-PD, but one could also imagine something akin to or using RFC
> 2894, or other approaches. Section 2.3 clearly has the allocation
> process (which could be in the CPE Router and probably is, but doesn't
> have to be) have some notion of a map of the SOHO/SMB; 2.3 is tree
> structured and therefore pretty simple (the CPE allocates a /63 to
> each of three downstream routers), but a network with a cut-set of two
> (which I would hope any self-respecting SMB would deploy) would need
> something more comprehensive. For example, in
> 
>                     /-------+-/   /
>                     prefix:2|     |
>                         +---+--+  |
>                         |Office|  |
>                         |RTR 1 +--+                 --
>                         +---+--+  |  +-------+     /
>                     prefix:3|     |  |CPE RTR|    |
>                     /-------+-/   +--+ISP 1  +------ ISP 1
>                                   |  +-------+    |
>                     /-------+-/   |p               \
>                     prefix:4|     |r                --
>                         +---+--+  |e
>                         |Office|  |f
>                         |RTR 2 +--+i
>                         +---+--+  |x
>                     prefix:5|     |:                --
>                     /-------+-/   |0 +-------+     /
>                                   |  |CPE RTR|    |
>                     /-------+-/   +--+ISP 2  +------ ISP 2
>                     prefix:6|     |  +-------+    |
>                         +---+--+  |                \
>                         |Home  |  |                 --
>                         |RTR   +--+
>                         +---+--+  |
>                     prefix:7|     |
>                     /-------+-/   /
> 
>                            Figure 3: Complex SOHO
> 
> if prefix:6 and prefix:0 are in fact the same wired network or 802.11
> SSID, we would want the "Home Router" to figure that out and use
> prefix:0 without trying to allocate ...:6 to it.
> 
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