Routing table that shaken the United States

Last week, the interruption of Internet services in the United States and elsewhere certainly shows that some Tier1 providers' Internet router's Border Gateway Protocol (BGP) routing tables have become too large.As a result, such routers could no longer control the Internet traffic.

BGP is the most important protocol on the Internet.In BGP, each routing domain is specified as an autonomous system (AUTONOMOUS SYSTEM).The BGP is used to find the shortest route, that is, a route that minimizes the number of hops of the AS between the hosts.The Tier1 network can be accessed to the entire Tier1 Internet BGP routing table.Usually, the Tier1 network, such as the three major Tier1 Internet Service Providers (ISP) (Level 3, NTT, Teliasonera), offers 10 to 100 Gbps Internet connections to Tier2 ISPs and end ISPs.

To record such a high -speed connection, the top -level router creates a path map.This map is stored in a special memory called 3 -value associative memory (TCAM).It's okay so far.The problem is that some old routers, TCAM, can only handle 512,000 routes.Insufficient TCAM resources in routers, as Cisco explained in May 2014, the network faces a decrease in performance, routing unstable, and availability issues.

According to BGPMON, which monitors the traffic of the upper network, 2587 autonomous systems have stopped functioning.This was caused by "15,000 new prefix added to the global routing table".The total number of BGP maps was slightly below 500,000, but this number is a Cisco router made of Tier1 that is not upgraded, which is enough to exceed the TCAM capacity.rice field.And this caused a big confusion throughout the Internet.

According to BGPMON's calculation, almost all of these 15,000 new prefixes, which were to exceed the router, were derived from Verizon."Network engineer and founder of BGPMON's founder Andree Toonk said," Because of something that happened inside Verison, these prefix consolidation did not work well, and as a result, many new routes have been added to the global routing table.This temporarily reached 515,000 routing tables, causing problems with old Cisco routers. "

Fortunately, Mr. Toonk said, "Verizon has quickly solved the problem of this consolidation failure, so there is no problem now, but the routing table on the Internet continues to be enlarged and immediately reaches the upper limit of 512,000 cases.It will be. "

We asked Verizon to comment on this, but no answer was obtained by the release of this article.