The noticeable problem we faced, was traffic on the Telstra network destined for our IP's was being routed overseas, and back to us, then the traffic back to Telstra was going domestically. Usually this wouldn't have been such a problem for the average user, but since port 80 traffic was timing out, we believe one leg of the traffic flow was somehow missing Telstra's caching proxy, but I've had no confirmation on this, so it's only theoretical. Nick Larsen Network Technician ZeroOne (NZ) Limited 0800 ZEROONE www.zeroone.co.nz -----Original Message----- From: Joe Abley [mailto:jabley@ca.afilias.info] Sent: Thursday, 19 July 2007 2:46 a.m. To: Anton Smith Cc: nznog@list.waikato.ac.nz Subject: Re: [nznog] Telstra contact - BGP advertisements On 18-Jul-2007, at 06:30, Anton Smith wrote: > How many operators out there are using strict RPF? > > With a lot of interconnection points around the place to me it seems a > bit harsh to use strict RPF. > > And in fact, I wonder if Telstra Clear are using it, since a lot of > times I notice broken connectivity due to what appears to be > asymmetric > routing, and I then have to work around it. I think two useful things to remember are: 1. All routing is asymmetric, in general. 2. "Strict-mode" RPF is inappropriate to apply to an interface if the thing at the other end has other connectivity to the Internet. Unless you are absolutely convinced that the device at the far end is not multi-homed, applying strict-mode RPF is an error (and presumably should be corrected just like any other error). So, if $carrier has applied strict-mode RPF checks to their interface facing you, and you are multi-homed, you need to call them to report their configuration error so it can be corrected. If they doubt the existence of the error, point them at RFC 3704/BCP 84. However, if the path from A in your network to B elsewhere is not the same as the path from B back to A, then that's normal, and the observed asymmetry (in isolation) is no reason for a change. (If one or both of the paths is congested, or has some other problem, then obviously those are still problems that might deserve escalation.) Joe _______________________________________________ NZNOG mailing list NZNOG@list.waikato.ac.nz http://list.waikato.ac.nz/mailman/listinfo/nznog _______________________________________________ NZNOG mailing list NZNOG@list.waikato.ac.nz http://list.waikato.ac.nz/mailman/listinfo/nznog