Re[2]: Link-state EGP

[7riw77--- via NANOG <nanog () lists nanog org>]

Have you ever looked at soBGP or Path State Vectors. Happy to hang out 
and explain if it would be helpful, but these are/were effectively BGP 
security efforts that were ultimately driving to a DAG overlay.

They failed because the community became extremely focused on securing 
"BGP operation" rather than securing the base topology information.

:-) /r


------ Original Message ------
> From "Saku Ytti via NANOG" <nanog () lists nanog org>
To nanog () immibis com
Cc "North American Network Operators Group" <nanog () lists nanog org>; 
"Saku Ytti" <saku () ytti fi>
Date 8/25/2025 02:04:15
Subject Re: Link-state EGP

> On Mon, 25 Aug 2025 at 03:44, <nanog () immibis com> wrote:
>
> >  It has to be a shortest path or at least you have to know their shortest path doesn't go back through you. Perhaps AS21's 
> > shortest path to AS23 is through you. In a link-state protocol you can't do shit to stop them using you as transit, besides 
> > outright blocking their traffic (breaking the internet) or splitting your AS in 3.
> >
> >  How many times do I have to say it, maybe with big enough letters? ***A LINK STATE ROUTING PROTOCOL IS A DISTRIBUTED 
> > CONSENSUS ALGORITHM. ALL NODES MUST RUN THE IDENTICAL ALGORITHM ON IDENTICAL INPUT DATA OR THE NETWORK BREAKS.***
> >
> >  Perhaps you've invented a new type of algorithm where that's not the case. In this case I suggest ceasing to call it "link 
> > state", and writing a detailed paper about it instead of vague hints.
>
> Oh I'm definitely not writing a paper. But I'm not sure a novel
> algorithm is needed (nor am I sure it is not needed). Certainly the
> graph cannot be a symmetric directed graph. That is the directions or
> arrows represent direction. You have edges which are reachable through
> you (customers) and you have edges which can be used to reach your
> customers (upstreams).
>
> So my link-state would have AS2[123] edges as reachable through me and
> AS3[123] as edges that can be used to reach those AS2[123] edges. So
> arbitrary node further down the network wouldn't use me to reach
> AS2[123] because of the direction of the arrow.
>
> >  Only in a link-state protocol! Luckily, BGP is not a link-state protocol.
>
> Of course it is easy to end up with loopy BGP configurations. But then
> we change the configuration and come up with something else.
>
> --
>   ++ytti
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