point-of-presence (POP)

Contributor(s): Oswaldo Mesias

On the Internet, a point-of-presence (POP) is an access point from one place to the rest of the Internet. (POP also stands for the e-mail Post Office Protocol; see POP3.) A POP necessarily has a unique Internet Protocol (IP) address. Your Internet service provider (ISP) or online service provider (such as AOL) has a point-of-presence on the Internet and probably more than one. The number of POPs that an ISP or OSP has is sometimes used as a measure of its size or growth rate. 

A POP may actually reside in rented space owned by the telecommunications carrier (such as Sprint) to which the ISP is connected. A POP usually includes routers, digital/analog call aggregators, servers, and frequently frame relays or ATM switches.

This was last updated in July 2007

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"A POP necessarily has a unique Internet Protocol (IP) address. "

This is true for unicast and broadcast routing, which are the most common methods. However, for anycast routing (widely used by DNS providers), the same IP address is advertised by multiple POPs.