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Navigation: Home > Hardware Info Library and Tips
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This page has been provided to help shed some light on the importance of each type of device that is commonly installed in or available for today's computers.
Hubs A hub is a small rectangular box, often constructed mainly of plastic, that receives its power from an ordinary wall outlet. A hub joins multiple computers (or other network devices) together to form a single network segment. On this network segment, all computers can communicate directly with each other. Ethernet hubs are by far the most common type, but hubs for other types of networks (such as USB) also exist. Included in a hub is a series of RJ-45 ports that each accept a network cable from another device. There can be as few as four or five ports (the last port being reserved for "uplink" connections to another hub or similar device) to as many as eight, 12, 16, and even 24 ports. Hubs are low-level devices in the OSI network layer model. At this layer, hubs do not read any of the data passing through them and are not aware of sending or receiving device. Essentially, a hub simply receives incoming packets, possibly amplifies the electrical signal, and broadcasts these packets out to all devices on the network (including the one that sent the packet!). Technically speaking, three different types of hubs exist:
Passive hubs do not amplify the electrical signal of incoming packets before broadcasting them out to the network. Active hubs, on the other hand, will perform this function -- a function that is also present in a different type of dedicated network device called a repeater. Some people use the terms concentrator when referring to a passive hub and multiport repeater when referring to an active hub. Intelligent hubs add extra features to an active hub that are of particular importance to businesses. An intelligent hub typically is stackable (built in such a way that multiple units can be placed one on top of the other to conserve space). It also typically includes remote management capabilities via SNMP and virtual LAN (VLAN) support.
Repeaters Network repeaters regenerate incoming signals. On physical media like Ethernet, data transmissions can only span a limited distance before the quality of the signal degrades. Repeaters attempt to preserve signal integrity and extend the distance over which data can safely travel.
The actual network devices that serve as repeaters are usually referred to by another name. Active hubs, for example, are sometimes called multiport repeaters but usually these are simply referred to as hubs.
Routers A router is a physical device that joins multiple networks together. Technically, a router is a "layer 3 gateway," meaning that it connects networks (as gateways do), and that it operates at the network layer of the OSI model. The home networker typically uses an Internet Protocol (IP) router. An IP router such as a DSL or cable modem router joins the home's local area network (LAN) to the wide-area network (WAN) of the Internet. By maintaining configuration information in a piece of storage called the "routing table," routers also have the ability to filter traffic, either incoming or outgoing, based on the IP addresses of senders and receivers. Some routers allow the home networker to update the routing table from a Web browser interface. DSL and cable modem routers typically combine the functions of a router with those of a switch in a single unit.
Switches A switch is a small device that joins multiple computers together at a low-level network protocol layer. Technically, switches operate at layer two (Data Link Layer) of the OSI model. Switches look nearly identical to hubs, but a switch generally contains more "intelligence" (and a slightly higher price tag) than a hub. Unlike hubs, switches are capable of inspecting the data packets as they are received, determining the source and destination device of that packet, and forwarding that packet appropriately. By delivering messages only to the connected device that it was intended for, switches conserve network bandwidth and offer generally better performance than hubs.
Like hubs, switches primarily are available for Ethernet, come in a range of port configurations starting with the four- and five-port models, and support 10 Mbps Ethernet, 100 Mbps Ethernet, or both.
Gateways "Gateway" is a generic term for an internetworking system (a system that joins two networks together). Gateways can be implemented completely in software, completely in hardware, or as a combination of the two. Depending on their implementation, gateways can operate at any level of the OSI model from application protocols to low-level signaling. Because a gateway by definition appears at the edge of a network, related functionality like firewalling tends to exist at the same location. Related: | |||||||
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