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Re: [RRG] some musings on PI v. PA, and assumptions, requirements, and tradeoffs



	Geoff,

> Dino Farinacci wrote:
> >>On Fri, Jul 13, 2007 at 01:38:21PM -0400, Scott Brim wrote:
> >>>Dave, I'm missing what's new here.  Having a PI allocation means news
> >>>of available paths to you can be carried further (all over) in BGP
> >>>space without being aggregated, so people are aware of you further
> >>>away and may take different paths to reach you.  Good but costly.
> >>
> >>    I was just trying to point out that there are folks
> >>    (service providers of a sort) for whom the grail of
> >>    aggregation doesn't seem like an advantage.
> >>
> >>    Dave
> >
> >This is a really important point. That is, "the sorts" are willing to 
> >pay for slots in everyone's routing table (read: it costs them nothing) 
> >because they get better convergence. Having said that, a Loc/ID split 
> >solution provides no value in this case of multihoming.
> >
> >And if their servers are stationary, there isn't a mobility case where a 
> >Loc/ID split solution would help.
> 
> Haven't we been round this particular mulberry bush a few times already? 
>   Yes, the routing system offers the path of least resistance when 
> attempting to solve a number of issues, and thats because routing 
> solutions are invariable simple and (today) cheap. And the Loc/ID split 
> seems to be a pretty massive solution for something that does not appear 
> to be a commonly accepted problem in the first place. So yes, we 
> continue to use the routing system for multi-homing, traffic engineering 
> and similar. It just works.
> 
> The only concern I've heard voiced that seems to me to be a real issue 
> in all this is the question "what if we all did that?" Are there numbers 
> for "we all" that appear to be beyond the capability of the technology 
> curve? Are there numbers for "we all" that might even be beyond the 
> capability of the protocol? If so, then we probably need some kind of 
> plan B, and it does appear to me that if you want to get out of the 
> tyranny of incrementalism then you need to consider something a little 
> more fundamental in terms of network architectures when you start to 
> look at what would make a Plan B effective. For me this path is where 
> the split loc/ID approaches start to gain traction. 

	Agreed, but as you know, even that isn't a consensus
	position (that a plan B will be needed, or if it is, that
	loc/ID split would be the solution). 

> But to be clear, the split loc/ID approach does not appear to
> me to be a viable tactical response to routing inflation in the
> near term future. 

	Guess it depends on what "near term" means, but I do
	agree that some of the ideas that have been bouncing
	around to improve various aspects of the current routing
	system (i.e., BGP) seem more near/immediate term.

	However, as I've said on various occasions, if we can
	improve the performance of BGP (again, along all of the
	various dimensions we've been discussing), we should be
	doing that in any event.

	Dave

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