Who's MAE and Why's She So Slow?
by Rob Robertson 11 Apr 1997



Q:  What happened yesterday? Our sysadmin said that MAE was having problems, so the East Coast was unbearably slow. What is MAE and is it a router or a backbone node? What gives?


A:  Although it's a sales mark of MFS Communications, the MAE acronym has practically become a generic term for public network exchange points and network access points (NAPs). But what are those, you ask? Well, let me explain.

Network access points were initially created by the National Science Foundation so ISPs could connect to the NSF-funded backbone in the early commercial days of the Net. Although used interchangeably with NAP, public network exchange point is a more generic term that better describes the current purpose of these entities: They are places where ISPs come to exchange traffic and routes (tell each other who's on their networks), and no longer places ISPs come to hook up to the Internet.

Physically, public network exchange points are usually switched LANs, where an ISP, for a fee, can acquire an Ethernet, FDDI, or ATM port, as well as some rack space for a router. But getting a connection to a network exchange point is only half the equation, because it just puts you on a LAN with a bunch of other ISPs. There's no guarantee they'll exchange traffic with you.

An agreement to exchange traffic is known as peering, and they can be difficult to get - especially with the bigger ISPs. Most of the larger ones demand that another ISP have connections (all the same speed) to at least four or five different public network exchange points before they'll consider a peering agreement. This prevents an ISP from connecting a fairly cheap line to one exchange point and getting a free ride off other ISPs with an expensive national backbone.

The history of MAEs

The original MAE, or Metropolitan Area Ethernet, was an Ethernet set up by MFS and a few ISPs in the Washington, DC, area to peer and exchange traffic in the early 1990s, when the National Science Foundation was getting out of the Internet backbone business. The MAE was very successful. At the time, the MAE was the center of the Internet universe - the one place where everyone came together and exchanged routes.

After this success, MFS and NASA opened a similar facility in Silicon Valley and dubbed it MAE-West. There are several other notable exchange points, such as the Sprint NAP in New Jersey, the Pacific Bell NAP in San Francisco, and a whole passel of new MAEs in major metropolitan areas. 

Some problems

Public network exchange points are a good thing, but they often suffer from traffic congestion. The bottlenecks usually occur when an ISP has more data to get out of the exchange point than its connection can handle. And with relatively few exchange points in the world, data can travel great physical distances before it gets to its ultimate destination. The most extreme example of this is Europe, which effectively has no public exchange point, so MAE-East in the United States must shoulder the burden. One way to solve this problem is to create more public network exchange points in more places around the globe. This would relieve the current load on many of the key NAPs, as well as utilize bandwidth better by keeping local bandwidth local and avoiding expensive and potentially overcrowded long-haul lines.

To avoid potentially congested NAPs, many ISPs currently rely on private network exchange points. Private network exchange points (or private peering points, as they are often called) are (as their name implies) invitation-only network exchange points. They're usually created when two ISPs conclude that they exchange a lot of traffic, and that it would be beneficial to both sides to avoid congestion at NAP points.