[address-policy-wg] Summary TLD Anycast Allocation Policy

On 4-apr-05, at 18:18, Andreas Bäß/Denic wrote:

> 1. Is there a need for anycasting at all ?

> I was surprised to see this question on the list.
> I think that anycasted nameservers are an accepted standard and there
> is no need to discuss pros and cons anymore.

Well, certainly not here. But if this is your question, answering it is 
easy: no, there is no NEED. Whether it's useful in a particular case is 
something different.

> 2. /32 vs. /48 V6 prefix - routability aspect

There are incorrect documents published which suggest that filtering at 
/32 is ok. After changing these documents and waiting some time this 
should no longer be an issue.

BTW, from RFC 3513:

2.6 Anycast Addresses

[...]

    For any assigned anycast address, there is a longest prefix P of that
    address that identifies the topological region in which all
    interfaces belonging to that anycast address reside.  Within the
    region identified by P, the anycast address must be maintained as a
    separate entry in the routing system (commonly referred to as a "host
    route"); outside the region identified by P, the anycast address may
    be aggregated into the routing entry for prefix P.

    Note that in the worst case, the prefix P of an anycast set may be
    the null prefix, i.e., the members of the set may have no topological
    locality.  In that case, the anycast address must be maintained as a
    separate routing entry throughout the entire internet, which presents
    a severe scaling limit on how many such "global" anycast sets may be
    supported.  Therefore, it is expected that support for global anycast
    sets may be unavailable or very restricted.

> 3. /32 vs. /48 V6 prefix - address conservation aspect

> There is no question that a /32 is quite a big block and that this
> sacrifice
> to "ensure" reachability from most network places is worth it.

There is at least a question here, even if we agree on the answer.

However, it's not simply whether it's worth it or not, it's a question 
of doing the right thing. If we start changing allocation policies to 
accommodate laziness on the part of router operators, where does it 
end?

> I don't think that sharing an assignment between multiple TLDs if they
> outsource
> their operation to an anycasting DNS provider should be a must to 
> separate
> TLD operations from each other and that the extra address space spent 
> is a
> good
> thing keeping in mind the limited number of TLDs where talking about.

Disagree. Resource conservation should be the default, this should only 
be changed when there is clear evidence that this is problematic.

> Any comments or suggestions?

Yes. I want to see a specific plan from the TLD community about what 
they want to do here. "Give us the prefixes" isn't good enough for me.