The entire Harvard computer network went down for nearly three hours Friday following a routine system update by the Faculty of Arts and Sciences (FAS) Network Operations.

"[Friday's] outage appears to be one of the largest network outages we have ever experienced," wrote Franklin M. Steen, director of FAS computer services, in an e-mail message.

According to Steen, FAS Network Operations have been upgrading the server regularly over the last six months. Friday morning, however, Network Operations encountered unexpected difficulties.

Operations posted two messages to the Harvard newsgroup explaining the problems. The first message explained that the program allowing computers on the network to generate unique addresses suddenly failed Friday. This meant that both e-mail and all Internet sites based in the Harvard system were inaccessible.

The message went on to say that Operations believed the problems to be resolved by 10 a.m.

However, the updates to routers completed earlier in the day left remaining problems that caused the network to crash just before noon.

"The network was up and down for several hours until it finally went down altogether," said Steen. "For a while most connectivity was lost. For other times, only access to the FAS systems was lost."

The long interruption of Internet service disturbed many students' work.