Chapter 2 Flashcards
Repeater
receives bit signals sent by the NIC and other devices, strengthens them (in part by filtering out electrical noise and cleaning the signal), and then “repeats” them to other parts of the network
hub
a multiport repeater
half-duplex, bandwidth shared
network bandwidth
amount of data that can be transferred in an interval (usually measured in bits per second (bps))
bandwidth sharing
when all computers connected to the hub must share the amount of bandwidth the hub provides
uplink port
port used to connect two hubs together or connect a hub to a switch
Switch
reads data in the message and determines which port the destination device is connected to, and forwards the message to only that port
full duplex, bandwidth dedicated to each port
Steps of switch operation
1: The switch receives a frame
2: The switch reads the source and destination MAC addresses
3: The switch looks up the destination MAC address in its switching table
4: The switch forwards the frame to the port where the computer owning the MAC address is found
5: The switching table is updated with the source MAC address and port information
Advantages of a switch over a hub
1: Each port gets dedicated bandwidth (instead of having to share bandwidth with all ports)
2: Can operate in full-duplex mode (can send and receive data simultaneously) while hubs can only operate in half-duplex mode (can send or receive data but not both at one time)
Access point
Heart of a wireless network, all communication passes through it, most places use a wireless router which combines the functions of an AP, a switch, and a router
similar to a wired hub
receiving device sends an acknowledgement to indicate successful reception
Sometimes sending station must send a request to send (RTS) message and receive a clear to send (CTS) message before transmitting
NIC/NIC driver tasks
provide a connection from computer to medium
Incoming messages: receives bit signals and assembles them into frames (verifies destination address , removes frame header and sends the resulting package to the network protocol)
Outgoing messages: receives packets from network protocol (creates frames by adding MAC addresses/error check)
Converts frames into bit signals suitable for the medium and then transmits them
MAC address
consists of two 24 bit hexadecimal numbers (24 bit manufacturer ID called OUI and 24 bit serial number assigned by the manufacturer)
NIC only permits inbound communications if the destination MAC address:
1: matches the NIC’s burned in address
2: is a broadcast address (ff-ff-ff-ff-ff-ff)
3: NIC is in a special mode called promiscuous
unicast frame
when the destination MAC address matches the BIA of a NIC (intended for a single computer)
broadcast frame
when the destination is the broadcast address (broadcast frames are intended to be processed by all computers on the network)
Promiscuous mode
turns off the gatekeeper functions and enables the NIC to process all the frames it sees
Things to consider when purchasing NIC
1: Select correct bus interface (bus connects the NIC to the motherboard)
2: NIC driver must be available for your OS
Wireless NICs
must be chosen according to type of Access Point (AP) being used
Typical are Wireless-n, 802.11ac or 802.11 a/b/g/n
The letters a, b, g, n, and ac refer to the wireless networking standard the device supports
Service set identifier (SSID)
the name assigned to the wireless network (used to connect wireless NICs to the network)
Router
device that enables multiple LANs to communicate with each other by forwarding packets from one LAN to another
Routers vs Switches
1: Routers connect LANs, switches connect computers
2: Routers work with logical (IP) addresses, switches work with physical (MAC) addresses
3: Routers work with packets, switches work with frames
4: Routers don’t forward broadcasts, switches do
5: Routers use routing tables, switches use switching tables
broadcast domain
the devices to which broadcast frames are forwarded
Default route
where to send a packet when the router doesn’t have an entry in its routing table
Network unreachable
Message sent when the network can’t be found and there is no default route
Default gateway
the IP address of the computer’s router (In a computer’s IP address configuration)
