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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: anycast (Re: .ORG problems this evening)
DGA> Date: Mon, 22 Sep 2003 18:32:19 -0400 DGA> From: David G. Andersen DGA> The whole problem with only listing two anycast servers is that DGA> you leave yourself vulnerable to other kinds of faults. Your DGA> upstream ISP fat-fingers "ip route 64.94.110.11 null0" and DGA> accidentally blitzes the netblock from which the anycast servers DGA> are announced. A router somewhere between customers and the And this is peculiar to anycast? DGA> anycast servers stops forwarding traffic, or starts corrupting And this is peculiar to anycast? DGA> transit data, without interrupting its route processing. DGA> packet filters get misconfigured.. And this is peculiar to anycast? DGA> Route updates in BGP take a while to propagate. Much longer DGA> than the 15ms RTT from me to, say, a.root-server.net. The application DGA> retry in this context can be massively faster than waiting 30+ seconds DGA> for a BGP update interval. If a location goes dark, that's a problem. With redundant machines locally anycasted and inter-location transport, it becomes a question of border router and peer reliability. DGA> The availability of the DNS is now co-mingled with the success DGA> of the magic route tweak code; the resulting system is a fair The availability of * is co-mingled with the success of the gear advertising its prefixes. The difference between standard multihoming and anycast is that the behind-the-scenes stuff happens to be on different machines in different locations. DGA> bit more complex than simply running a bunch of different DGA> DNS servers. God forbid that zebra ever has bugs... DGA> DGA> http://www.geocrawler.com/lists/3/GNU/372/0/ You assume zebra is the only option. Sure, it has bugs. So do Vendors C, J, and R. DGA> In contrast, talking to a few DNS servers gives you an end-to-end DGA> test of how well the service is working. So splay is bad? Eddy -- Brotsman & Dreger, Inc. - EverQuick Internet Division Bandwidth, consulting, e-commerce, hosting, and network building Phone: +1 785 865 5885 Lawrence and [inter]national Phone: +1 316 794 8922 Wichita _________________________________________________________________ DO NOT send mail to the following addresses : [email protected] -or- [email protected] -or- [email protected] Sending mail to spambait addresses is a great way to get blocked.
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