Re: Generic anycast addresses...

[Bob Hinden <[e-mail]>]

Ted,

> On Jul 12, 2019, at 8:19 AM, Ted Lemon <[e-mail]> wrote:
> 
> On Jul 12, 2019, at 8:14 AM, Bob Hinden <[e-mail]> wrote:
>>   Anycast addresses are allocated from the unicast address space, using
>>   any of the defined unicast address formats.  Thus, anycast addresses
>>   are syntactically indistinguishable from unicast addresses.  When a
>>   unicast address is assigned to more than one interface, thus turning
>>   it into an anycast address, the nodes to which the address is
>>   assigned must be explicitly configured to know that it is an anycast
>>   address.
> 
> Sorry, the distinction here is that we’re talking about well-known anycast addresses being used for resource discovery or edge probing, not anycast addresses generally.
> 
> So yes, of course anycast addresses can just be unicast addresses, and can come either from an org’s delegated prefix or from a global IANA prefix.   However, this isn’t always what we want; in the case of SRP, it’s better if it doesn’t leave the site, for example, so a unique local address would be a better choice than something in 2001::/16.   But we don’t have a mechanism for allocating well-known anycast addresses out of the unique local address space.

Understood, but the way you wrote your email, it sounded like you were surprised about their properties.

I am fine if someone wanted to write a draft to define the centrally assigned ULAs, and how they would work for this purpose. The hard part is to decide how the allocations and registration work.   I would be happy to discuss this with you in Montreal.

Bob







>