nanog mailing list archives
Re: SYN floods continue
From: Vadim Antonov <avg () quake net>
Date: Wed, 11 Sep 1996 15:12:48 -0700
Vern Paxson <vern () ee lbl gov> wrote:
In my Internet end-to-end routing study I found that fully 50% of the pairs of paths through the Internet had a major asymmetry at the end of 1995.
Sure, but where the asymmetry is? Certainly not on tail circuits of single-homed customers :) Moreover, multi-homed non-transit networks still announce all routes to all places; i.e. the filtering i was talking about will still work. It breaks on transit networks, i.e. the backbones; but people who run backbones are presumeably clueful enough to disable the filtering on backbone links, and leave it on on customer tail links.
"Major" meaning: visited at least one different city in the two directions. (30% visited at least one different AS.) This was a significant increase over the same figure for the end of 1994, 30%. So it may be quite hard to make and keep Internet routing symmetric.
Routing *must* be symmetrical within IGP only networks if metrics in different directions are symmetrical. When the packets leave the routing domain, that's another story. Again, the rule is "dont accept packets from an interface if there's no route for their source addresses pointing back to the same interface". Note that that route does not have to be the best one -- just that the router gets it from somewhere. --vadim - - - - - - - - - - - - - - - - -
Current thread:
- Re: SYN floods continue, (continued)
- Re: SYN floods continue Michael Dillon (Sep 11)
- Re: SYN floods continueg Avi Freedman (Sep 11)
- Re: SYN floods continue Steven L. Johnson (Sep 11)
- Re: SYN floods continueh Avi Freedman (Sep 12)
- Re: SYN floods continue Sean Donelan (Sep 11)
- Re[2]: SYN floods continue Pat Calhoun (Sep 11)
- Re: SYN floods continue Vadim Antonov (Sep 11)
- Re: SYN floods continue Justin W. Newton (Sep 11)
- Re: SYN floods continue Vern Paxson (Sep 11)
- Re: SYN floods continue alex (Sep 11)
- Re: SYN floods continue Vadim Antonov (Sep 11)
- Re: SYN floods continue Jim Forster (Sep 13)
- Re: SYN floods continue Perry E. Metzger (Sep 13)
- Re: SYN floods continue Jim Forster (Sep 13)
- Re: SYN floods continue Michael Dillon (Sep 11)