Re: Generic anycast addresses...

[Mark Smith <[e-mail]>]

On Sun., 2 Jun. 2019, 00:05 Michael Richardson, <[e-mail]>
wrote:

>
> Mark Smith <[e-mail]> wrote:
>     >> hop 1 is the router at home, and hope 2 is the access router at my
> ISP, and
>     >> hop 3 is my ISP's core router connect to upstream peers.
>     >>
>     >> Should hop 1 (home router) or hop 2 (access node) were to blackhole
> route
>     >> fc00::/6 (ULA-R and ULA-C), would that affect your use case?  Or
> could the
>     >> anycast service possibly be at the ISP?
>
>     > I'm guessing you don't have internal ULA address space, which is why
> you're
>     > more successful than if you did.
>
> I do have a lot of ULA, but I didn't try from within those segments,
> because I
> was not at my office and I couldn't get there from the conference I was at.
>
>     >> Should home routers install routes to 2000::/3 when they see
> "default"
>     >> rather
>     >> than "::/0"?  I have made that argument, but I see the other point
> about
>     >> how limiting it could be in the future.
>
>     > A ULA address at an ISP would only be reachable to customers who
> only have
>     > GUA addresses.
>
>     > If a customer has ULA internally, a ULA source address would be
> preferred
>     > over a GUA source to reach an ISP ULA (anycast) destination. That ULA
>     > source address would cause the packet to be dropped by a BCP38
> filter at
>     > the ISP access router, assuming they have them, as they should.
>
>     > Even if the ISP doesn't have BCP 38 filters, the ISP's routing is
> very
>     > unlikely to have routes back to all customers' ULA address spaces.
>
> This is a good point you make.
> So should home routers do BCP38 filtering on their external interface?
> (Better to drop it early)
>
>     > So you need global scope anycast addresses for working source address
>     > selection. Except that defeats the goal of having anycast destined
> packets'
>     > travel being restricted to a domain smaller than global when that is
>     > required or desirable.
>
> Do you think we need another scope of address?
>

I think we need a formal, multi-scoped anycast address space.

Anycast also has enough properties in common with multicast that I think it
should be more than just a configured special case address within the
unicast address space. I think it should be a distinct class in between
unicast and multicast.

Unicast: 1:1
Anycast: 1:Any
Multicast: 1:Many


IPv6 Formal Anycast Addresses and Functional Anycast Addresses

https://tools.ietf.org/id/draft-smith-6man-form-func-anycast-addresses-00.txt


Regards,
Mark.



> --
> Michael Richardson <[e-mail]>, Sandelman Software Works
>  -= IPv6 IoT consulting =-
>
>
>
>