A router is a multiport connectivity device that can integrate LANs and WANs running at different transmission speeds and using a variety of protocols. Routers operate at the Network layer (Layer 3) of the OSI Model. Routers have been slower than switches or bridges because they pay attention to information in Layers 3 and higher, such as protocols and logical addresses. Consequently, unlike bridges and Layer 2 switches, routers are protocol-dependent.They must be designed or configured to recognize a certain protocol before they can forward data transmitted using that protocol.
As is the case with bridges, traditional standalone LAN routers are being replaced by Layer 3 switches that support the routing functions. The concept of routing remains extremely important, however, and everything described in the remainder of this section also applies to Layer 3 switches. Standalone routers are still the technology of choice for connecting remote offices using WAN technology.
A bridge device filters data traffic at a network boundary.Bridges have a single input and a single output port.They differ from repeaters in that they can interpret the data they retransmit.
Bridges reduce the amount of traffic on a LAN by dividing it into two segmentsBridges operate at the data link layer (Layer 2) of the OSI model. Bridges inspect incoming traffic and decide whether to forward or discard it. An Ethernet bridge, for example, inspects each incoming Ethernet frame - including the source and destination MAC addresses, and sometimes the frame size - in making individual forwarding decisions.
Network repeaters regenerate incoming electrical, wireless or optical signals. With physical media like Ethernet or Wi-Fi(wireless media), 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.
Repeaters operate in the Physical layer of the OSI Model and, therefore, have no means to interpret the data they retransmit. For example, they cannot improve or correct a bad or erroneous signal; they merely repeat it. In this sense, they are not “intelligent” devices. Since they cannot read higher-layer information in the data packets, repeaters cannot direct data to their destination. Instead, repeaters simply regenerate a signal over an entire segment. It is up to the receiver to recognize and accept its data.
A repeater is limited not only in function, but also in scope.A repeater contains one input port and one output port, so it is capable of receiving and repeating only the data stream. Furthermore, repeaters are suited only to bus topology networks. The advantage to using a repeater is that it allows you to extend a network inexpensively.
Answered by
Nagendra
at
4:16 AM on October 15, 2008
