RE: Let's Focus on Moving Forward Re: V6 still not supported re: 202203261833.AYC

["Pascal Thubert \(pthubert\) via NANOG" <nanog () nanog org>]

Hello Matthew

At the moment the draft has a general architecture, and it will take the right minds and experience to turn a model 
into a live network. Considering what the people in this list have already built, it’s no gigantic leap to figure they 
can build that too. Most of the building blocks that are implicit or TBD in the draft exist already.

About linking ASN to realms, that’s Eduard’s view, I’ll let him answer. The draft is not like that, all existing ASN 
and IP addresses can be reused in every new realm, and there does not need to be any mapping. If people find a need or 
a reason to add constraints, that’s beyond me at this time, and against the natural philosophy of minimizing 
interdependences to maintain design freedom in each realm. The draft has one and one only dependency, that surface of 
the shaft is common to all realms.

To your point, and unrelated to ASNs, the shaft can be physically distributed. Each physical place would announce 
240.0.0.0/6, and the nearest alive would attract the traffic. See it as as many IXPs. In the current draft, there’s 
only one shaft that links all realms. And there’s a single realm number for each realm that is advertised in every 
physical instances of the shaft. All that is a  simplification to highlight the design.

As the shaft lives on, a realm may be multihomed, the shaft might be subnetted to interconnect only specific realms, or 
to be advertised differently in different geographies. And then the subnets will need to be injected in the realms. The 
way around a breakage can be DNS, or BGP.

All this is possible, you’ve already done it, and it’s really your play. We build the car, you drive it. Happy that you 
start figuring out how you prefer it to happen. While we figure out protocols to renumber more efficiently, fix source 
address selection, extend the NATs, you name it. There’s work for all and at every phase. But at this stage of the 
discussion, I favor the 10 miles view to get a shared basic understanding.

On the side, I’d be happy to learn how you solved a situation like the one below, if there’s any article / doc?

Keep safe;

Pascal

From: Matthew Petach <mpetach () netflight com>
Sent: mardi 5 avril 2022 0:29
To: Vasilenko Eduard <vasilenko.eduard () huawei com>
Cc: Pascal Thubert (pthubert) <pthubert () cisco com>; Nicholas Warren <nwarren () barryelectric com>; Abraham Y. Chen 
<aychen () avinta com>; Justin Streiner <streinerj () gmail com>; NANOG <nanog () nanog org>
Subject: Re: Let's Focus on Moving Forward Re: V6 still not supported re: 202203261833.AYC



On Mon, Apr 4, 2022 at 10:41 AM Vasilenko Eduard via NANOG <nanog () nanog org<mailto:nanog () nanog org>> wrote:
240.0.01.1 address is appointed not to the router. It is appointed to Realm.
It is up to the realm owner (ISP to Enterprise) what particular router (or routers) would do translation between realms.

Please forgive me as I work this out in my head for a moment.

If I'm a global network with a single ASN on every populated continent
on the planet, this means I would have a single Realm address; for
the sake of the example, let's suppose I'm ASN 42, so my Realm
address is 240.0.0.42.  I have 200+ BGP speaking routers at
exchange points all over the planet where I exchange traffic with
other networks.

In this new model, every border router I have would all use the
same 240.0.0.42 address in the Shaft, and other Realms would
simply hand traffic to the nearest border router of mine, essentially
following a simple Anycast model where the nearest instance of the
Realm address is the one that traffic is handed to, with no way to do
traffic engineering from continent to continent?

Or is there some mechanism whereby different instances of 240.0.0.42
can announce different policies into the Shaft to direct traffic more
appropriately that I'm not understanding from the discussion?

Because if it's one big exercise in enforced Hot Potato Routing with
a single global announcement of your reachability...

...that's gonna fail big-time the first time there's a major undersea
quake in the Strait of Taiwan, which cuts 7/8ths of the trans-pacific
connectivity off, and suddenly you've got the same Realm address
being advertised in the US as in Asia, but with no underlying connectivity
between them.

https://www.submarinenetworks.com/news/cables-cut-after-taiwan-earthquake-2006

We who do not learn from history are doomed to repeat it...badly.   :(

Matt