The following text is copyright 1998 by Network World, permission is hearby given for reproduction, as long as attribution is given and this notice is included.

Why we do what we do

By Scott Bradner

Massachusetts is running out of phone numbers -- again! Less than a year ago two new area codes were carved out of the two area codes which have been serving eastern Mass for a number of years. But we are now told that the newly created area codes may run out of numbers as early as the year 2000.

Massachusetts currently has 5 area codes. Five area codes could theoretically support 49,999,995 phone lines. Even if one were to assume a good penetration of office phones, fax machines, cell phones and second lines to support teenagers, the ability to support 50 million phone lines should not be all that confining in a state whose total population was 6,016,425 people in 1990. And now they want to add support for 20 milion additional lines! I don't think that many people have suddenly decided that shoveling snow is a fun task.

The basic reason for this clear inefficiency is that the phone number assignment rules are severely limited by the technology of the phone system. If I wanted to start up a new cell phone service in an existing area code I would go to the phone number assignment authority (see for more information) and if I met their requirements I would be assigned a block of phone numbers for my use. The minimum sized block of numbers that can be assigned is 10,000. this is the case even if I actually only have 10 customers. This process can result in very ineffecent use of the potential number space. This problem, combined with the demand, the Boston Globe reports that there were 57 requests for phone number blocks in one of the Mass. area codes during the week of May 11th, means more area codes are on the way.

The Internet used to assign IP addresses in fixed sized blocks like this, with block sizes of 256 hosts (class-C), 65 thousand hosts (class-B) or 17 million hosts (class-A), but this changed a few years back with the development of classless inter-domain routing (CIDR). The Internet address assignment organizations (the American Registry for Internet Numbers (ARIN) serves this hemisphere and southern Africa) now assign IP addresses in power-of-two sized blocks. The size of an assignment is based on the actual size of the organization, backed up by concrete documentation. (ARIN's web page is

The change in assignment procedures has dramatically moved back the time when the Internet will actually run out of IP addresses and thus the time when a switch to IPv6 will be forced by address exhaustion. There are other reasons that organizations may want to migrate to IPv6 but it seems that it will not be a forced marriage.

I hope the phone system learns how to be more efficient because I'd just as soon not change numbers but the problem may cure itself if the projected Internet take-over of the phone system happens soon enough.

disclaimer: Neither ARIN (where I'm a board member) nor Harvard (where I have an ambiguous title) do anything with phone numbers except try to remember a few of them.