was predicted by a number of IT professionals. The actual allocations which pushed the number of routes above 512k was the announcement of about 15,000 new routes in short order, starting at 07:48 UTC. Almost all of these routes were to Verizon Autonomous Systems 701 and 705, created as a result of deaggregation of larger blocks, introducing thousands of new routes, and making the routing table reach 515,000 entries. The new routes appear to have been reaggregated within 5 minutes, but instability across the Internet apparently continued for a number of hours. Even if Verizon had not caused the routing table to exceed 512k entries in the short spike, it would have soon happened through natural growth. Route summarization is often used to improve aggregation of the BGP global routing table, thereby reducing the necessary table size in routers of an AS. Consider AS1 has been allocated the big address space of , this would be counted as one route in the table, but due to customer requirement or traffic engineering purposes, AS1 wants to announce smaller, more specific routes of , , and . The prefix does not have any hosts so AS1 does not announce a specific route . This all counts as AS1 announcing four routes. AS2 will see the four routes from AS1 (, , , and ) and it is up to the routing policy of AS2 to decide whether or not to take a copy of the four routes or, as overlaps all the other specific routes, to just store the summary, . If AS2 wants to send data to prefix , it will be sent to the routers of AS1 on route . At AS1's router, it will either be dropped or a destination unreachable ICMP message will be sent back, depending on the configuration of AS1's routers. If AS1 later decides to drop the route , leaving , , and , AS1 will drop the number of routes it announces to three. AS2 will see the three routes, and depending on the routing policy of AS2, it will store a copy of the three routes, or aggregate the prefix's and to , thereby reducing the number of routes AS2 stores to only two: and . If AS2 wants to send data to prefix , it will be dropped or a destination unreachable ICMP message will be sent back at the routers of