But two critical errors allowed Pakistan’s action to echo around the globe for at least a brief period on Sunday afternoon, according to Martin A. Brown, a data engineer at the Renesys Corporation, an Internet monitoring company, which posted a timeline of the incident on its Web site.

As part of its effort to block YouTube within the country, Pakistan Telecom created a dummy route that essentially discarded YouTube traffic, sending it into what Internet experts call a black hole.

Pakistan Telecom then made an error by announcing that dummy route to its own telecommunications partner, PCCW, based in Hong Kong, shortly before noon New York time on Sunday, according to Renesys.

PCCW then made a second error, accepting that dummy route for YouTube and relaying it to other Internet providers around the world.