network administrators can tailor security needs to meet the wide range of security requirements for different users. Alcatel's IP Communications solutions integrate seamlessly in multi-vendor environments. They do not force customers into upgrading the data infrastructure to deploy proprietary voice solutions. Much like the Alcatel OnmiPCX 4400's standardbased approach enables customers to provide voice over any data network, the Alcatel family allows customers to provide a solid data foundation on any voice and video platform. Hub Multiport repeaters combine connectivity with the amplifying and retiming properties of repeaters. It is typical to see four, eight, 12, and up to 24, ports on multiport repeaters. This allows many devices to be cheaply and easily interconnected. Multiport repeaters are often called hubs, instead of repeaters, when referring to the devices that serve as the center of a star topology network. Hubs are very common interrietworking devices. Since the typical unmanaged hub only requires power and plugged in RJ-45 jacks, they are great for setting up a network quickly. Like the repeaters on which they are based, they only deal with bits, and are Layer I devices. Figure 2.9: HUB Fiber Optic Cable Fiber-optic cable is a networking medium capable of conducting modulated light transmissions. Compared to other networking media, it is more expensive. It is not susceptible to electromagnetic interference and is capable of higher data rates than any of the other types of networking media discussed here. Fiber-optic cable does not carry electrical impulses, as other forms of networking media that employ copper wire do. Signals that represent bits are instead converted into beams of light. Even though light is an electromagnetic wave, light in fibers is not considered wireless because the 27