Disruptive technological change has occurred at the protocol and network levels as well. Two notable examples include: The Internet—the realization of a revolutionary communications paradigm—which introduced a new, highly flexible network architecture and protocols, and ultimately enabled myriad new applications and services; and Packetization of voice and video, such as voice over Internet Protocol (VoIP), which provides voice communications with greater flexibility and efficiency and has opened up opportunities for application innovation beyond the boundaries of the public switched network. At the level of applications, the Internet in turn has provided a unique laboratory for the creation of innovative applications—e-mail, instant messaging, collaboration, World Wide Web (WWW) browsers and servers, electronic auctions, and business to business (B2B) and business to consumer (B2C) electronic commerce—that have changed consumer behavior and business interaction. Audio and video have expanded as well, from traditional cable broadcast networks to digital cable systems to switched video on the Internet, file sharing, and pay-per-view. Traditional telephony has also been transformed over time. Out-of-band signaling protocols for the public switched telephone network, such as the current global standard Common Channel Signaling System No. 7 (SS7), have made possible the modern worldwide public telephone network by supporting such features as worldwide direct dialing, wireless roaming, local number portability, and toll-free calling. Telephony has also branched out into new application areas: voice over packet, wireless telephony, and integrated voice/data applications are industry-shaping developments.