Networking Devices
February 14 (Day); February 9 (Night)
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Network Interface Card (NIC):
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NICs are devices that enable a computer, server, printer, or other device to
receive and transmit data over a cable or other media.
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NICs contain a data transceiver, the devices that transmit and receive data.
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NICs are unusual in that they belong to both the Physical layer (because they
actually apply data signals to the wire) and the Data Link layer (because they can
assemble or disassemble frames).
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NIC Installation Issues:
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Access methods (ex. Ethernet vs. Token Ring)
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Network transmission speed (ex. 100 Mbps vs. 1 Gbps)
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Connector (ex. RJ-45)
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Motherboard compatibility (ex. PCI vs. ISA)
Repeaters:
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The purpose of the repeater is to regenerate and retime network signals to allow
them to travel a longer distance.
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Repeaters operate in the Physical layer because they have no means to interpret
the data they retransmit. They cannot improve or correct a bad or erroneous
signal – they merely repeat it.
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Since it cannot interpret data, it cannot route data to its destination.
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It has one input port and one output port.
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Rarely used on modern networks.
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A hub is a repeater with more than one output port (typically from 4-24) –
Hubs:
sometimes called a multiport repeater.
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Hubs operate at the Physical layer of the OSI model.
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Hubs are used on almost all network.
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Bridges:
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Bridges are devices that connect two network segments by analyzing incoming
frames and making decisions about where to direct them on each frame’s MAC
address.
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Bridges operate at the Data Link layer of the OSI Model.
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Bridges have a single input port and a single output port.
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The bridge works by maintaining a forwarding table of their MAC addresses and
their locations.
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To translate between two network segments, a bridge reads a frame’s destination
MAC address and decides to either forward it or filter it. If the bridge determines
that the destination is on another segment as the source address, it forwards the
data. If the destination is on the same segment as the source, it filters (drops) the
data.
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Switches:
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Switches are multiport bridges. They can have up to 24 ports.
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Switches operate at Data Link layer.
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Switches have an internal processor, an operating system, and memory.
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Bridges and switches create collision domains.
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A router is a multiport connectivity device that directs data on a network.
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Routers operate at the Network layer of the OSI Model.
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Routers use the logical address of data to determine which network or segment of
Router:
network to route the data.
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A typical router has a processor, an operating system, memory, input and output
jacks for different types of connector, and a management console.
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Routers are very intelligent. They can determine the fastest path from one point
to another. They can also reroute traffic if the preferred path is down.
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Gateway:
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Gateways are combinations of networking hardware and software that connects
two dissimilar kinds of networks. Gateways connect two systems that use
different formatting, protocols, or architecture.
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Gateways actually repackage information so that it can be read by another
system. They are usually quite slow.
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Gateways operate at multiple layers of the OSI Model.
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Gateways are usually broken down by function:
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E-mail gateway – translates one type of e-mail to another
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Voice/data gateway – connects the part of the network that handles data
traffic with the part of the network that handles voice traffic.
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Internet – allows and manages access between LANs and the Internet