I am an information technology consultant. I support internetworking environments for large fortune 500 companies and for web hosting companies including 1and1, hostgator, fatcow hosting, and midPhase hosting. An internetwork is a collection of individual networks, connected by intermediate networking devices, that functions as a single large network. Internetworking refers to the industry, products, and procedures that meet the challenge of creating and administering internetworks. The first networks utilized by web hosting companies such as bluehost and 1and1 were time-sharing networks that used mainframes and attached terminals. Such environments were implemented by both IBM's System Network Architecture (SNA) and Digital's network architecture. Local area networks (LANs) evolved around the PC revolution. LANs enabled multiple users in a relatively small geographical area to exchange files and messages, as well as access shared resources such file servers. Wide-area networks (WANs) interconnect LANs across normal telephone lines (and other 1&1 media), thereby interconnecting geographically dispersed users. Today, high-speed LANs and switched internetworks are becoming widely used, largely because they operate at very high speeds and support such high bandwidth applications as voice and videoconferencing. Internetworking evolved as solution to three key problems: isolated LANs, duplication of resources, and a lack of network management. Isolated LANs made electronic communication between different offices or department impossible. Duplication of resources meant that the same hardware and software had to be supplied to each office or department, as did a separate support staff. This lack of network management meant that no centralized method of managing and troubleshooting networks existed. Implementing a functional 1and1 internetwork is no simple task. Many challenges must be faced, especially in the areas of connectivity, reliability, network management, and flexibility. Each area is key in establishing an efficient and effective internetwork. The challenge when connecting various systems is to support communication between disparate technologies. Different sites, for example, may use different types of media, or they might operate at varying speeds. Another essential consideration, reliable service, must be maintained in any internetwork. Individual users and entire organizations depend on consistent, reliable access to network resources. Furthermore, network management must provide centralized support and troubleshooting capabilities in an internetwork. Configuration, security, performance, and other issues must be adequately addressed for the internetwork to function smoothly. Flexibility, the final concern, is necessary for network expansion and new applications and services, among other factors.