Chapter 02 Network Hardware Essentials

Repeater

A network device that takes incoming signals and regenerates, or repeats, them to other parts of the network.

Hub

A network device that performs the same function as a repeater but has several ports to connect a number of devices; sometimes called a multiport repeater.

Network bandwidth

The maximum amount of data that can be transmitted between devices in a specified unit of time; usually measured in bits per second.

Throughput

A measurement of the amount of data successfully transferred over a given period of time, including protocol headers, and taking into account any delays, such as the time gap between a device completing the transmission of one packet and starting transmission of the next packet.

Propagation delay

The time between the moment a device like a hub or switch receives data on one port and the moment it transmits the data out another port.

Latency

The cumulative delays among all devices between the source and destination device during data transfer across a network.

Buffering

A process in which a device has to temporarily store outgoing or incoming packets while other packets are being processed by the operating system.

Goodput

The amount of useful data that is transferred in a given time; not taking into account protocol headers. Goodput is measured in bytes per second.

Bandwidth sharing

A network design in which interconnecting devices allow only one connected device to transmit data at a time, thus requiring devices to share available bandwidth.

Uplink port

A designated port on a hub or switch used to connect to another hub or switch without using a crossover cable.

Switch

A network device used to interconnect multiple computers. It reads the destination MAC address of an incoming frame to determine on which switch port the destination device is located.

Switching table

A table containing MAC address and port pairs that a switch uses to determine which port to forward frames it receives. Also called the MAC address table.

MAC address table

A table containing MAC address and port pairs that a switch uses to determine which port to forward frames it receives. Also called the switching table.

Flooding

A process in which a switch forwards the frame to all connected ports except the one on which the frame was received.

Dedicated bandwidth

A property of switches in which each port's bandwidth is dedicated to the devices connected to the port.

Full-duplex mode

A communication mode in which a device can simultaneously transmit and receive data on the same cable connection. Switches can operate in full-duplex mode, but hubs can't.

Half-duplex mode

A communication mode in which a device can send or receive data but can't do both simultaneously. Hubs operate only in half-duplex mode; switches can operate in both half-duplex and full-duplex modes.

Uplinking

Making a connection between devices such as two switches, usually for the purpose of expanding a network.

Access point (AP)

A wireless device that serves as the central connection point of a wireless LAN and mediates communication between wireless computers.

Request to send (RTS)

A signal used in wireless networks indicating that a computer has data ready to send on the network.

Clear to send (CTS)

A signal an AP generates in response to a request-to-send signal. A CTS signal indicates that the computer that sent an RTS can transmit data.

Network interface card (NIC)

A device that creates and mediates the connection between a computer and the network medium.

Broadcast frame

A network message intended to be processed by all devices on a LAN; it has the destination address FF:FF:FF:FF:FF:FF.

Unicast frame

A network message addressed to only one computer on the LAN.

Promiscuous mode

An NIC operational mode in which the NIC reads and processes all frames rather than reading and processing only broadcast frames or unicast frames addressed to the NIC. Protocol analyzer software sets a NIC to promiscuous mode so that all network frames can be read and analyzed.

Service set identifier (SSID)

The name assigned to a wireless network that is configured on the wireless access point.

Router

A device that enables LANs to communicate with one another by forwarding packets from one LAN to another. Routers also forward packets from one router to another when LANs are separated by multiple routers.

Broadcast domain

The scope of devices to which broadcast frames are forwarded. Router interfaces delimit broadcast domains because they don't forward broadcasts, whereas switches and hubs do.

Local network

A network that is directly connected to the router.

Remote network

A network that can only be reached by going through one or more routers.

Default route

A routing table entry that tells a router where to send a packet with a destination network address that can't be found in the routing table.

Default gateway

The address configured in a computer's IP address settings specifying the address of a router to which the computer can send packets addressed to devices on other networks.