Re: [Idr] draft on virtual aggregation
Robert Raszuk <raszuk@juniper.net> Fri, 11 July 2008 11:32 UTC
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Date: Fri, 11 Jul 2008 04:29:21 -0700
From: Robert Raszuk <raszuk@juniper.net>
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To: Paul Francis <francis@cs.cornell.edu>
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Subject: Re: [Idr] draft on virtual aggregation
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Hi Paul, >> True that some networks do not have the core ... the network can be >> meshed edges or more specifically meshed POPs. >> >> A very simple observation can be made that you can use a tunnel from >> the >> edge to one router (per POP for example) do IP lookup then encapsulate >> to the exit point. In that scenario your edge routers are free from >> carrying full table and due to shift in the place where single IP >> lookup >> is done and switching decision determined. > > This would overload that one router, as well as create a point of failure. > So you'd need to increase the capacity of that router, plus replicate > it for failure. It needs to be noticed that this one router can be any of today's edge router as if current edge handles full Internet table in FIB. The gain is that all other edge routers do not any more keep state in FIB. Reg single point of failure ... of course not. Two such routers (per POP or in small AS per network) would anycast common next hop and we would relay on IGP for failure detection and even for data packets in flight redirection. > So in essence you are designing a core architecture. The point > behind VA is that you don't force ISPs to change their architecture and Disagree 100%. VA is what I described + dividing the address space into chunks. > upgrade their routers to deal with table growth. Plus anyway you can't do > this for your edge routers that peer with ISPs that require the full routing > table, so this fix is quite limited. Why not ? Remember we are dealing with FIB only. (My idea works with RIB as well using multihop ebgp session, but let's focus on FIB). Why ASBRs peering with ISPs would require to store all the routes in FIB ? Core/POP full nodes would attract all traffic make switching decision then encapsulate and ship. It is very much the same as Lixia's APT model except no mapping plane is needed :). >> It is clearly not true that vendors today have any issues in delivering >> boxes which could keep today's Internet table and at least allow for >> 5-10 time it's grow. I know at least two of them which have been >> shipping such routers for few years now. > > Yes I understand that there are routers that can hold 5x or 10x the current > table. Your company makes them. How long will these routers last, given the > "end-game" of IPv4 address allocation? 5 years ago the new generation of > routers looked like they could handle a lot of table growth, but now they > have run out of space and yet ISPs want to keep them. If one have bought an ISP class router 5 years ago there is no reason to upgrade now capacity wise. 5 years ago internet table were about 130K today is 270K src: http://www.cidr-report.org/ Those routers 5 years ago were already design and ready to handle 1-2M routes and not due to expectation of Internet growth ... due to requirement for L3VPN deployments. > Basically you are > telling them that the solution is simple---buy your latest product. And to > not worry about growth because you'll have yet another product for them a few > years down the road. This is exactly what this draft is trying to avoid. If we compare Internet to Highways your draft still is trying to keep old Trabants going ... moreover bunch of them. It seems that they may be at some point became an obstacle on the road and it may be much better to find other uses for them then carrying passengers. What I proposed is to keep all of those still running on the edge while based the >> And such architecture does not require dividing address space in any >> chunks and can be deployed today on any exiting hardware without >> waiting >> for any new protocol extensions. > > I'm not sure what you mean by "such architecture". But many existing routers > in the field today cannot realistically use the kind of trick you mention > above to manage FIB size. Rather, they resort to simply dropping some > fraction of routes, for instance. What would be a single reason why at least pair of routers in any ISP could not carry full Internet table today in FIB ? I know quite a few ISP & SP networks worldwide and can't find any such example. Rest of the edge routers could function just fine without even slight need to drop anything. My proposal is a special case of yours ... So saying that routers in the field can not support this means that your proposal suffers from the same. The overall idea is good it is just I want to make sure that in whatever form this work goes forward ISP MUST be allowed to have single VA as well. And that would not require any new protocol extension as BGP could inject such default route today with next hop being APR. That means that the extended community attribute you are proposing should be optional as well. > To be clear, we are talking about one new attribute, zero changes to the data > plane, zero changes to the existing BGP decision process....just some rules > for automatically setting up tunnels and new address aggregates (virtual > prefixes). Better to do this now well before the next generation of routers > runs out of FIB. My concern is not about adding new attribute. The concern is about the additional deployment, operational and troubleshooting difficulties it will introduce. Having forwarding boxes partitioned with different information (which will have to be statically managed by hand) is very error prone. It also have other consequences including the need redesign on behavior of fast reroute technics or HA features. It is not the steady state of operation where things go out of control. Cheers, R. _______________________________________________ Idr mailing list Idr@ietf.org https://www.ietf.org/mailman/listinfo/idr
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- Re: [Idr] draft on virtual aggregation Robert Raszuk
- Re: [Idr] draft on virtual aggregation Paul Francis
- Re: [Idr] draft on virtual aggregation Paul Francis
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