Date: Mon, 26 Jan 2004 07:57:01 -0600 From: "Randall R. Stewart (home)" <randall@stewart.chicago.il.us> To: Juan Rodriguez Hervella <jrh@it.uc3m.es> Cc: freebsd-net@freebsd.org Subject: Re: Two ISP lines Message-ID: <40151CAD.9080502@stewart.chicago.il.us> In-Reply-To: <200401231843.14422.jrh@it.uc3m.es> References: <200401191533.i0JFXUDE050449@soth.ventu> <40106D1A.3000902@stewart.chicago.il.us> <200401231843.14422.jrh@it.uc3m.es>
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Juan Rodriguez Hervella wrote: >Just some questions about this paper: > >"(...) Note that this route has to be at the same level of the tree, i.e. >the code cannot return a less specific match or a more specific >match (...)" > >Question: I don't understand why if you are looking for an alternate >route you aren't allowed to retrieve a more specific route. This doesn't >make sense to me. If you are routing packets using a route when >there is a more specific match, you aren't doing "longest prefix match".\ > When you first ask for a route.. you get the longest prefix match. So you are at say a depth in the tree of N. If you try to go to a lower level in the tree (say N-1) then you could be going to the wrong place... I suppose one could go to a N+ level in the tree.. i.e. more specific match (assuming that maybe a new route was added lower in the tree).. but I never contemplated that aspect much because it would be more of a corner case I think... It would also make the code a bit more complex as well :-> > >Another question: if ISP-1 goes down, and you use this feature of >alternatives routes, this still doesn't fix the communication problem. Unless >you make something with the source addr. of the multihomed site's >packets, the reply packets will be lost in the faulty ISP, imho. > Ahh.. it is true that SOME ISP's do ingress filtering.. for TCP this would be a problem.. But for SCTP (a multi-homed protcol) this is NOT a problem.. the SCTP association would just use the source address of the outbound interface (since the association is made up of a SET of addresses on each side and a port on each side).... Now there are still ISP's that do NOT filter (I have one that does and one that does not :->)... R > >Regards. > > > > >On Friday 23 January 2004 01:38, Randall R. Stewart (home) wrote: > > >>Andrea/all: >> >>An interesting question... the following link has >>some thoughts along these lines... and something >>for the BSD community to think upon... >> >>http://www.sctp.org/what_is_alt_route >> >>TCP could definetly use something like the above (with Itojun's Multi-path >>updates as well).. it would give more reliability to even a singly >>homed protocol such as TCP :-> >> >>R >> >>Andrea Venturoli wrote: >> >> >>>Ok, I asked already asked something similar to this in the past, but it's >>>not the same thing... maybe it's a trivial question... >>>If I had two lines to the Internet: how would I use both? >>>Could I just provide two default routes? How? >>>What algorithm would be used to choose among the two? >>>What if one failed? >>> >>>bye & Thanks >>> av. >>> >>> >>> >>>_______________________________________________ >>>freebsd-net@freebsd.org mailing list >>>http://lists.freebsd.org/mailman/listinfo/freebsd-net >>>To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" >>> >>> > > > -- Randall R. Stewart 815-477-2127 (office) 815-342-5222 (cell phone)
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