MIS 4342 Ch 6
Ethernet
A formal standard commonly used in LANs. Two types: -IEE 802.3 = developed by the IEEE (institute of electrical and electronics engineers) -Shared Ethernet = traditional ethernet. --Ethernet is a two layer protocol, so it operates at the data link layer.
overlay network
A network (usually a WLAN) used to supplement a primary network (usually a wired LAN).
channel
A specific radio frequency used in wireless communication. --Used in WLANs so that the various APs in the Local Area (cordless phones, computers, yada yada yada) don't interfere with each other
Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
A system used in contention networks. The network interface unit listens for the presence of a carrier before attempting to send and detects the presence of a collision by monitoring for a distorted pulse.
directional antenna
Antenna on an AP projects a signal only in one direction
layer-2 switch
Because the switch uses the Ethernet address to decide which port to use and because Ethernet is a data link layer or layer-2 protocol, this type of switch is called a ____.
1GbE
Gigabit per second (1,000,000,000 bits per second)
frame
Group of data bits having bits at each end to indicate the beginning and end of the frame --Contain source addresses, destination addresses, frame type identifiers, and a data message.
logical topology
How the network works conceptually, similar to the data flow of a DFD or a logical ERD
physical topology
How the the network is physically installed, similar to physical DFDs and ERDs.
resource sharing
Refers to one computer sharing a hardware device (eg. printer) or software package with other computers on the network to save costs.
LAN metering software
One approach to controlling the number of copies of a particular software package is to use LAN Metering Software.....prohibits using more copies of a package than there are installed licenses.
Power over Ethernet (POE)
Power Over Ethernet. An access point in LANs that does not need an external power supply.
Wired Equivalent Privacy (WEP)
-One wireless security technique -the AP requires the user to have a key in order to communicate with it
distributed coordination function (DCF)
-The first media access control method -also called physical carrier sense method because it relies on the ability of computers to physically listen before they transmit -each frame in CSMA/CA is sent using stop-and-wait ARQ.
point coordination function (PCF)
-The second media access control technique -(also called the virtual carrier sense method).
clear to transmit (CTS)
-message sent back from a Request to Transmit -specifying the amount of time for which the circuit is reserved for the requesting computer.
Wi-Fi
-wireless Ethernet -the commercial name for a set of stan- dards developed by the IEEE 802.11 standards group
dedicated-server LAN
A category of LANs where one or more computers are permanently assigned as network servers. --ideal for handling very large files and databases --the servers usual operating system (eg. windows) is replaced by a network operating system (eg. Linux) --different types of dedicated servers include: mail servers, datatabase servers, and web servers.
software audit
SPA performs these. It is a program that checks the number of illegal software copies on LANs. Whistleblowers are rewarded, and violators are brought to court.
hub
Serve two purposese 1)provide an easy way to connect network cables. They are like junction boxes that permit new computers to connect to the network....by connecting wires into ports. 2)they serve as repeaters that counteract attenuation in transmission signals.
server farm
Servers are sometimes organized into a large set of servers on one part of the network called a CLUSTER or Server Farm.
shielded twisted-pair (STP)
Shielded Twisted-Pair. --is only used in special areas that produce electrical interference (eg. Hospitals by an MRI scanners, or factories near heavy machinery)
small office, home office (SOHO)
Small Office, Home Office
Software Publishers Association (SPA)
Software Publishers Association
network profile
Specifies what resources on each server are available on the network for use by other computers and which devices or people are allowed what access to the network.
topology
The basic geometric layout of the network...the way computers on the network are interconnected. Two types: Logical Topology & Physical Topology
fragment-free switching
The switch examines the first 64 bytes (which contain all the header information for the frame) and if all the header data appears correct, the switch presumes that the rest of the frame is error free and begins transmitting.
Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)
This protocol is similar to the Carrier Sense Multiple Access (CSMA) with Collision Detection (CD) protocol. Whereas CSMA/CD sends a data packet and then reports back if it collides with another packet, CSMA/CA sends a small preliminary packet to determine whether the network is busy. If there is a collision, it is with the small packet rather than with the entire message. CA is thought to be more efficient because it reduces the time required to recover from collisions.
unshielded twisted-pair (UTP) cable
Unshielded Twisted-Pair. --Is of Low cost
Extensible Authentication Protocol (EAP)
WEP keys are produced dynamically
lightweight directory services (LDAP)
When a client wishes to view available resources or access them, it sends a message using an industry standard (LDAP) to the Active Directory Service (ADS) Domain Controller
beacon frame
contains all the necessary information for a NIC to associate with it.
site survey
determines the feasibility of the desired coverage, the potential sources of interference, the current locations of the wired network into which the WLAN will connect, and an estimate of the number of APs required to provide coverage
symmetric multi-processing (SMP)
enables one server to use up to 16 CPUs.
print server
handle print requests on the LAN --by offloading this job from the main LAN, the server in turn becomes more efficient
software piracy
obtaining/using software in an illegal way --North America has the lowest rate of software piracy. (28%) --piracy is on the decline but still exceeds 75% in some areas of the world
collision
of signals, causes jamming to occur
cable plan
plan to instal cable usually during the construction of a building
access point (AP)
point where a computer connects to the network. Generally hubs and switches
switched Ethernet
primary networks for LAN
storage area network (SAN)
A LAN solely devoted to data storage.
bus topology
(A LAN using a hub) - all computers are connect to one half duplex circuit running the length of the network (bus). All Frames from any computer flow onto the central cable and through it to all computers on the LAN.
802.11i
(also called WPA2) is the newest, most secure type of WLAN security.
Active Directory Service (ADS)
(by microsoft) in the NOS client Software which provides information about resources on the network that are available to the users (ie. shared printers, files, or application software)
collision detection (CD)
1. Collision detection in the CSMA (Carrier Sense Multiple Access) protocol for LANs. 2. Carrier detect occurs when a modem detects a carrier signal to be received.
10 GbE
10 Gigabits per second
40 GbE
40 Gigabits per second
domain controller
A type of Active Directory Service (ADS) server that can also act as a Domain Name System (DNS) server
fiber-optic cable
Cable that is even thinner than UTP wire. It is small and light weight, but has high capacity. --usually used for BNs (backbone networks), but is beginning to be used for LANs
peer-to-peer network
Don't require a dedicated server. All computers act as both client and server. --popular in application layer software file sharing on the internet
probe frame
During active scanning, a NIC transmits a special frame called ____.
omnidirectional antenna
The antennas on an access point transmit in all directions simultaneously.
network-attached storage (NAS)
NOT like a server computer, but instead is a small processor with large disk space that only responds to requests for files and data.
network interface card (NIC)
Network Interface Card. --Used to connect the computer to the network cable in a wired network and is one part of the physical layer connection among the computers in the network. In a wireless network, the NIC is a radio transmitter --Virtually all desktop computers have a wired NIC, and virtually all laptops have a wireless NIC. Wireless NIC can be bought for desktops
network operating system (NOS)
Network Operating System. Software that controls the network. Every NOS provides two sets of software: -one that runs the Network Server(s) (performs functions associated with data link, network, and application layers as well as working with the computers operating system). -and one that runs on the network clients (performs functions associated with the data link and network layers and works with application software).
Wireless LAN (WLAN)
Wireless Local Area Network. --Uses radio transmissions to send data between the NIC and AP. --usually operate in two frequency ranges: 2.4 GHz and 5 GHz.
10/100/1000 Ethernet
a hybrid that can run at any of these three speeds.
Wi-Fi Protected Access (WPA)
a newer, more secure type of security
file server
allow many users to share the same set of files on a common, shared disk drive
virtual carrier sense
also called point coordination function
802.11a
an obsolete, legacy technology, and no new products are being developed. Under perfect conditions, it provides eight channels of 54 Mbps each with a maximum range of 50 meters or 150 feet. Speeds of 20 Mbps at 50 foot ranges are more common in the face of interference such as drywall or brick walls.
802.11g
another obsolete, legacy technology, but many organiza- tions still use it. Under perfect conditions, it provides three channels of 54 Mbps each with a maximum range of 150 meters or 450 feet, although in practice both the speed and range are lower.
802.11b
another obsolete, legacy technology. Under perfect condi- tions, it provides three channels of 11 Mbps each with a maximum range of 150 meters or 450 feet, although in practice both the speed and range are lower.
information sharing
refers to having users access the same data files, exchange information via email, or use the internet.
request to transmit (RTS)
requests permission to transmit and to reserve the circuit for the sole use of the requesting computer for a specified time period
1000Base-T
run at 1 Gbps and are sometimes called 1 GbE
physical carrier sense method
same thing as the distributed coordination function (DCF)
100Base-T
standard ethernet used today
10Base-T
standard that revolutionized Ethernet and made it the most popular type of LAN in the world.
forwarding table
table lists the Ethernet address of the computer connected to each port on the switch.
MAC address filtering
the AP permits the owner to provide a list of MAC addresses (i.e., layer-2 addresses)
802.11n
the latest version of Wi-Fi that most firms use (or are in the process of installing). Under perfect conditions, it provides three channels of about 200 Mbps each with a maximum range of 150 meters or 450 feet,
bottleneck
the part of the network that is restricting the data flow.
warchalking
the practice of writing symbols in chalk on sidewalks and walls to indicate the presence of an unsecured WLAN
cut-through switching
the switch begins transmitting before it has received the entire frame.
store and forward switching
the switch does not begin transmitting the outgoing frame until it has received the entire incoming frame and has checked to make sure it contains no errors.
latency
the time it takes a device from receiving a frame to transmitting it
shared Ethernet
traditional ethernet
redundant array of inexpensive disks (RAID)
using several smaller disks rather than 1 large disc. -used for large volumes of data
IEEE 802.3
version of Ethernet is slightly different from the original version but the differences are minor
cabling
wires that connect everything in an LAN system
twisted-pair cable
wiring in which two conductors of a single circuit are twisted together for the purposes of canceling out electromagnetic interference (EMI) from external sources;