Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A Pool Element (PE) is a server in the Reliable server pooling (RSerPool) framework. Reliable server pooling (RSerPool) is a computer protocol framework for management of and access to multiple, coordinated (pooled) servers. RSerPool is an IETF standard, which has been developed by the IETF RSerPool Working Group and documented in RFC 5351 to RFC 5356.In the terminology of RSerPool a server is denoted as a Pool Element (PE). In its Pool, it is identified by its Pool Element Identifier (PE ID), a 32-bit number. The PE ID is randomly chosen upon a PE's registration to its pool. The set of all pools is denoted as the Handlespace. In older literature, it may be denoted as Namespace. This denomination has been dropped in order to avoid confusion with the Domain Name System (DNS). Each pool in a handlespace is identified by a unique Pool Handle (PH), which is represented by an arbitrary byte vector. Usually, this is an ASCII or Unicode name of the pool, e.g. "DownloadPool" or "WebServerPool".