[homenet] referrals [ tunnels as way to disambiguate .local]

[Brian E Carpenter <[e-mail]>]

> I get the impression that if NAT didn't exist, then
> draft-carpenter-referral-ps would server no purpose.  Is this draft
> entirely motivated by problems caused by NAT?

I don't think so. There are other causes of disjoint address space,
which existed even before we had NAT or specialised firewalls -
router ACLs for example. Certainly NAT is the major cause today (and
NPTv6 will propagate the problem into IPv6). v4-only and v6-only
islands will probably arise too.

Regards
   Brian

On 08/08/2012 19:39, Curtis Villamizar wrote:
> In message <[e-mail]>
> Brian E Carpenter writes:
>  
>> On 07/08/2012 20:11, Michael Thomas wrote:
>>> On 08/07/2012 11:46 AM, Kerry Lynn wrote:
>>>> On Mon, Aug 6, 2012 at 9:39 PM, Evan Hunt <[e-mail]> wrote:
>>>>> Tunnels are okay, but to use them, but has to get the DNS search order
>>>>> and the DNS server list right, and that's walled garden territory.
>>>>> *If* we are going to turn each home into a walled garden, then let's be
>>>>> aware that we are doing that.
>>>> I'm of the opinion that in a "walled garden" scenario, the tunnel
>>>> endpoint may
>>>> be the only resource that needs a global name / address.
>>> Just checking, but we all think that naming is a separate issue
>>> from reachability, right?
>>  
>> It certainly is. But see http://tools.ietf.org/html/draft-carpenter-referral-ps
>> especially section 4.2 "FQDNs are not sufficient".
>>  
>>    Brian
> 
> 
> Brian,
> 
> MIF may be trying to solve the problem the wrong way.  Providing a
> mapping of DNS to loopback address has long been used (by routers) to
> provide a stable reachable address.  The routing cost to reach that
> loopback interface (which can change many times for an active
> connection) is used to determine which physical interface gets used to
> reach the loopback.  For example if one interface is connected to an
> ethernet which gets isolated due to a router failure, the other
> interface is used because routing tells us that one of them is
> unreachable.
> 
> Multihoming of course pokes holes in the routing tables and causes
> some routing table bloat.  This has always been a problem and IPv6
> does nothing to improve the situation that existed in IPv4 two decades
> ago with a lot of small providers and large enterprises using dual
> provider multihoming.
> 
> If we are concerned with hosts that have multiple interfaces both
> leading to parts of the homenet, that is easily solved.  Multihomed
> homenets is a whole different problem, but solvable if redundancy is
> to the same provider.  A conditional static route can be advertised
> within the provider, with these routes having limited scope (for
> example using BGP communities).  If this practice were to become
> commonplace (I doubt it, no consumer provider has that sort of
> redundancy in the last mile), then the provider would have to limit
> the scope of these more specific routes to a small subset of their own
> topology.
> 
> I get the impression that if NAT didn't exist, then
> draft-carpenter-referral-ps would server no purpose.  Is this draft
> entirely motivated by problems caused by NAT?
> 
> Curtis
>