Some data from the ARIN region, courtesy of Richard Jimmerson of ARIN: For the last several years ARIN has been registering AS numbers by issuing the lowest AS number we have in inventory to approved organizations. We ask those organizations if they would be willing to accept an AS number higher in the number range, and outside of the range that previously made up the 2-byte only AS number space.
In 2014 we found that nearly 27% of the organizations approved for an AS number elected to receive a 4-byte AS number rather than take the lowest AS number in our inventory. Several organizations unwilling to receive a 4-byte AS number have indicated to ARIN that their transit providers strongly state a preference that their customers use AS numbers from the traditional 2-byte AS number range. More recently, because of a lack of 2-byte AS numbers in the ARIN inventory, the AS number assignments we make are 4-byte AS numbers and outside of the range that previously made up the 2-byte only AS number space. For those organizations who come back to ARIN specifically stating a preference for a 2-byte AS number, we may be able to continue satisfying their requests using AS numbers that have recently been added to the ARIN AS number inventory through returns or revocations. Very recently ARIN received a new assignment of AS numbers from the IANA. Roughly 90 of those were from the 2-byte range. In 2014 there were 12 organizations that elected to receive a 4-byte AS number and later came back to ARIN to exchange it for a 2-byte AS number. Each of these organizations stated issues with their transit providers either unwilling or unable to accept the use of a 4-byte AS number by a customer. 2014 total AS numbers issued: 1,579 2014 4-byte AS numbers issued: 416 2014 2-byte AS numbers issued: 1,163 David R Huberman Principal, Global IP Addressing Microsoft Corporation
