512k Day causes sporadic internet problems2014-08-13 09:44 by Philip
Tags: 512k day, BGP, outage, routing
Yesterday, many tier-one Internet service providers, and in turn, the last mile ISPs they support, experienced technical problems that resulted in bad service throughout the US and some parts of Canada. According to NANOG, and complaints tracker DownDetector, many Internet providers - including Level 3, AT&T, Cogent, Sprint, Verizon, and others - have suffered from serious performance problems at various times on Tuesday.
At first, several ISPs thought that the outage was due to local flooding, but apparently that's not the case. Rather, older routers and their inability to cope with the web's ever-growing routing table is to blame.
That's because today many so-called Border Gateway Protocol (BGP) routers need to store a map of the internet defining which IP address range belongs to which network. Due to the increasing scarcity of IPv4 space, registrars and ISPs assign smaller and smaller netblocks to customers, leading to a more and more fragmented topology. Many older routers are limited to store 512k entries, and the Internet's routing table has become large enough to reach this limit. Tuesday morning, it appears to have exceeded this limit for a short time.
For those with older routers who've been affected by the problems, Cisco has published guidelines on how to fix the issue. But this is just a fix, the real solution is to update your router. The routing table is only going to get larger over the next few years, until networks finally catch on to IPv6 and rely less on IPv4.
Read more -here-