Hi William, Sorry for jumping into the discussion, I just want to remind that Router and Host are different concept.
Routers are hosts too and figuring out ......
Take the definition from RFC2460:
router - a node that forwards IPv6 packets not explicitly
addressed to itself. [See Note below].
host - any node that is not a router. [See Note below].
Although they are both node - a device that implements IPv6.
Regards
Xiangsong
----- Original Message -----
From: "William Herrin" <bill at herrin.us>
To: "liu dapeng" <maxpassion at gmail.com> Cc: <mif at ietf.org> Sent: Tuesday, November 10, 2009 12:03 PM Subject: Re: [mif] Some thoughts
On Mon, Nov 9, 2009 at 10:11 PM, liu dapeng <maxpassion at gmail.com> wrote:Routers are hosts too and figuring out how to handle packets to multiple upstreams in different administrative domains is important there as well. Otherwise we limit ourselves to only the simplest case: where no component larger than a single host is a member of two networks. As often as not, that isn't the case. The entire local LAN can be a member of two upstream networks and it'd be nice if entire routed subsystems could be members of two networks.In my understanding, router normally does not have the multiple interfaces issue, since router is designed to forward packets across different interfaces and there is no default route issue in router. so what problems are you thinking that need to be solved?Hi, Starting from a post-multipath TCP world... The situation that jumps to mind is: 3 offices, A B and C. B connects to A with a T1. C connects to A with a T1. B connects to C with a T1. So they're connected in a triangle. A connects to the Internet with a DSL. B also connects to the Internet with a WiMax link. Server located at C called CS. It has an address from the DSL ISP and an address from the WiMax ISP. CS(DSL)->CA router->AC Router->DSL Router->Internet CS(WiMax)->CB router->BC Router->WiMax Router->Internet But if the CA T1 is down then: CS(DSL)->CA router->CB Router->BC Router->BA Router->AB Router->DSL Router->Internet And while CS has two addresses and network blocks, it has only one ethernet interface on which it talks to both the CA and CB routers. Following me? The routers in the picture have two different routing domains depending on the source address. Add an Internet cable modem to site C and now you have to handle 3 routing domains on every router in the system. But if you keep thinking about it, maybe you don't try to introduce routing domains at all. Maybe you introduce source+destation CIDR pairs instead of just destination CIDRs. So, the DSL at A offers 1.2.3.0/24+0.0.0.0/0, the WiMax at B announces 4.5.6.0/24+0.0.0.0/0 and the cable modem at C announces 7.8.9.0/24+0.0.0.0/0. On the flip side, the site-C routers announce 0.0.0.0/0+1.2.3.32/28, 0.0.0.0/0+4.5.6.32/28 and 0.0.0.0/0+7.8.9.32/28. Now there's just one routing domain and six routes which work sensibly in a dynamic routing protocol. And if CS gets hacked and tries to send a packet to 9.9.9.9 from the forged source address 8.8.8.8, the packet dies at the first router because there's no route for 8.8.8.8/32+9.9.9.9/32. Now if you go back and think of host CS the same way as the routers, CS has the following routes: 1.2.3.35/32+1.2.3.32/28->eth0 1.2.3.35/32+0.0.0.0/0->Router CA metric 2 1.2.3.35/32+0.0.0.0/0->Router CB metric 3 4.5.6.35/32+4.5.6.32/28->eth0 4.5.6.35/32+0.0.0.0/0->Router CB metric 2 4.5.6.35/32+0.0.0.0/0->Router CA metric 3 7.8.9.35/32+7.8.9.32/28->eth0 7.8.9.35/32+0.0.0.0/0->Cable Modem metric 1 127.0.0.0/8+127.0.0.0/8->loopback Or so goes my train of thought anyway... Regards, Bill Herrin -- William D. Herrin ................ herrin at dirtside.com bill at herrin.us 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/> Falls Church, VA 22042-3004 _______________________________________________ mif mailing list mif at ietf.org https://www.ietf.org/mailman/listinfo/mif
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