of devices such as switches, routers, load balancers, and firewalls and installs these functions as virtual machines in servers. Is used as an adjunct to software-defined networks (SDNs). non-blocking Switches that have enough capability for each connected device to communicate at the same time up to the full speed of the port to which it is connected. number pooling Allows local carriers to share a "pool" of telephone numbers within the same exchange. Number pooling is a way to allocate scarce telephone numbers more efficiently. Without pooling, a single local telephone company has rights to the entire 10,000 block of telephone numbers, but it might only use a portion of the block. OSS (Operation and Support Service) Hardware and software that carriers use for billing, maintenance, and changes to customer features. packet switching A network technique that routes data in units called packets. Each packet contains addressing and error- checking bits as well as transmitted user data. Packets from a transmission can be routed individually through a network such as the Internet and be assembled at the end destination. PAN (Personal Area Network) Operates over small areas within rooms and buildings. Bluetooth and RFID are examples of PANs. PBX (Private Branch Exchange) Computerized, onsite telephone system located at an organization's premises. PBXs route calls both within an www.TechnicalPDF.com organization and from the outside world to people within the organization, and vice versa. PCS (Personal Communications Service) Originally referred to 2G digital mobile services that use spectrum in the higher frequencies. PCS (or DCS in Europe) is now used in the industry to refer to all 2G cellular access technologies. peer-to-peer network Distributes intelligence over devices in the network instead of relying on central computers. Peer-to-peer networks are often used to download free music and movies from the Internet. In addition, companies such as Skype use the technology for voice calls and other services. petabyte (P