A useful Glossary of Terms for wired and wireless networking
A group of wireless networking standards, also known as Wi-Fi, set by the Institute of Electrical and Electronics Engineers (IEEE).
A supplement to the IEEE 802.11 WLAN specification that describes radio transmissions at a frequency of 5 GHz and data rates of up to 54 Mbps.
A supplement to the IEEE 802.11 WLAN specification that describes radio transmissions at a frequency of 2.4 GHz and data rates of up to 11 Mbps.
A supplement to the IEEE 802.11 WLAN specification that describes radio transmissions at a frequency of 2.4 GHz and data rates of up to 54 Mbps.
802.11h supports Dynamic Frequency Selection (DFS) and Transmit Power Control (TPC) requirements to ensure coexistence between Wi-Fi and other types of radio frequency devices in the 5 GHz band.
An IEEE standard specifying security mechanisms for 802.11 networks. 802.11i makes use of the Advanced Encryption Standard (AES) block cipher. The standard also includes improvements in key management, user authentication through 802.1X and data integrity of headers.
A taskgroup of the IEEE 802.11 committee whose goal is to define a standard for high throughput speeds of at least 100Mbps on wireless networks. The standard is expected to be ratified by 2009. Some proposals being fielded by the taskgroup include designs for up to 540 Mbps. Multiple-Input-Multiple-Output (MIMO) technology, using multiple receivers and multiple transmitters in both the client and access point to achieve improved per formance is expected to form the basis of the final specification.
An IEEE standard for MAC layer frame tagging (also known as encapsulation). Frame tagging uniquely assigns a user- defined ID to each frame. It also enables a switch to communicate VLAN membership information across multiple (and multi-vendor) devices by frame tagging.
AES (Advanced Encr yption Standard)
A data encryption scheme that uses three different key sizes (128-bit, 192-bit, and 256-bit). AES was adopted by the U.S. government in 2002 as the encryption standard for protecting sensitive but unclassified electronic data.
Describes the establishment and maintenance of the wireless link between devices. (If security is enabled, the devices cannot do anything but exchange security credentials with this link).
The process that occurs after association to verify the identity of the wireless device or end user and allow access to the network.
The central par t of a large network that links two or more sub-networks. The backbone is the primar y data transmission path on large networks such as those of enterprises and ser vice providers. A backbone can be wireless or wired.
The maximum transmission capacity of a communications channel at any point in time. Bandwidth, usually measured in bits per second (bps), determines the speed at which information can be sent across a network. If you compare the communications channel to a pipe, bandwidth represents the pipe diameter and determines how much data can flow through the pipe at any one time. The greater the bandwidth, the faster data can flow.
The transmission rate of binar y symbols (‘0’ and ‘1’), equal to the total number of bits transmitted in one second. bps (Bits per second) A measure of data transmission speed across a network or communications channel; bps is the number of bits that can be sent or received per second. It measures the speed at which data is communicated and should not be—but often is—confused with bytes per second (Bps, in this reference the B is capitalized while in bps lower case is used). While “bits” is a measure of transmission speed, “bytes” is a measure of storage capacity.
A wireless device that connects multiple networks together. Broadband A comparatively fast Internet connection possessing suf ficient bandwidth to accommodate multiple voice, data and video channels simultaneously. Cable, DSL and satellite are all considered to be broadband channels; they provide much greater speed than dial-up Internet access over telephone wires. BSS (Basic Ser vice Set) When a WLAN is operating in infrastructure mode, each access point and its connected devices are called the Basic Ser vice Set.
A specific portion of the radio spectrum—the channels allotted to one of the wireless networking protocols. For example, 802.11b and 802.11g use 14 channels in the 2.4 GHz band, only 3 of which don’t overlap (1, 6, and 11). In the 5 GHz band, 802.11a currently has 12 channels, none of which overlap.
CoS (Class of Service)
A category based on the type of user, type of application, or some other criteria that QoS systems can use to provide differentiated classes of service.
Carrier Sense Multiple Access/Collision Avoidance. The principal media access control strategy used in 802.11 networks to avoid data collisions. It is a “listen before talk” method of minimizing collisions. The network node checks to see if the transmission channel is clear before a data packet is sent. (See collision avoidance, CSMA/CD).
Customer Sense Multiple Access/Collision Detection. The principal media access control strategy used to manage traf fic and reduce noise on wired Ethernet networks. It allows a network device to transmit data after detecting a channel is available. If two devices transmit data simultaneously, the sending device detects the collision of data packets and retransmits after a random time delay. (See collision avoidance, CSMA/CA).
DC Power Module
Modules that convert Alternate Current (AC) power to Direct Current (DC) for the operation of electronic and computer equipment. Depending on the manufacturer and product, these modules can range from typical “wall wart” transformers that plug into a wall socket to larger, enterprise-level Power-Over-Ethernet systems that inject DC power into the Ethernet cables to provide power to the access points.
The gateway in a network that a computer will use to access another network if a gateway is not specified for use. In a network using subnets, a default gateway is the router that for wards traf fic to a destination outside of the subnet of the transmitting device.
DHCP (Dynamic Host Configuration Protocol)
A protocol for dynamically assigning IP addresses from a predefined list to nodes on a network. When they log on, network nodes automatically receive an IP address from a pool of addresses ser ved by a DHCP. The DHCP ser ver provides (or leases) an IP address (to a client for a specific period of time. The client will automatically request a renewal of the lease when the lease is about to run out. If a lease renewal is not requested and it expires, the address is returned to the pool of available IP addresses. Using DHCP to manage IP addresses simplifies client configuration and ef ficiently utilizes IP addresses.
Any large corporation, business or organization. The enterprise market can incorporate office buildings, manufacturing plants, warehouses and research and development facilities, as well as large colleges and universities.
The most popular international standard technology for wired Local Area Networks (LANs). It provides from 10 Mbps transmission speeds on basic 10BastT Ethernet networks to 100 Mbps transmission speeds on Fast Ethernet networks, 1000 Mbps on Gigabit Ethernet, and 10,000 Mbps on 10 Gigabit Ethernet.
A legacy term for 100Mbps Ethernet. At this writing, Gigabit and 10 Gigabit are Faster and Fastest.
FCC (Federal Communications Commission)
US wireless regulatory authority. The FCC was established by the Communications Act of 1934 and is charged with regulating Interstate and International communications by radio, television, wire, satellite and cable.
The Federal Information Processing Standard that defines the requirements of security technologies used in the handling and processing of information within government agencies.
A system of software and/or hardware that resides between two networks to prevent access by unauthorized users. The most common use of a firewall is to provide security between a local network and the Internet. Firewalls can make a network appear invisible to the Internet and can block unauthorized and unwanted users from accessing files and systems on the network. Hardware and software firewalls monitor and control the flow of data in and out of computers in both wired and wireless enterprise, business and home networks. They can be set to intercept, analyze and stop a wide range of Internet intruders and hackers.
Software routines that are embedded as read-only memory (ROM) in a computer chip or hardware device to prevent modification of the routines. Unlike random access memory (RAM), read-only memory stays intact in the absence of electrical power. Startup routines and low-level input/output instructions are stored in firmware.
In the wireless world, a gateway is an access point with additional software capabilities such as providing NAT and DHCP. Gateways may also provide VPN support, roaming, firewalls, various levels of security, etc.
The international unit for measuring frequency equivalent to the older unit of cycles per second. One megahertz (MHz) is one million hertz. One gigahertz (GHz) is one billion hertz. The standard U.S. electrical power frequency is 60 Hz; 802.11a devices operate in the 5 GHz band; 802.11b and g devices operate in the 2.4 GHz band.
IEEE Institute of Electrical and Electronics Engineers
A global technical professional society and standardssetting organization serving the public interest and its members in electrical, electronics, computer, information and other technologies.
IP (Internet Protocol)
The basic communications protocol of the Internet. (See IP address, TCP/IP). IP address Internet Protocol address. IP Version 4, the most widely used Internet protocol, provides 32-bit number that identifies the sender or receiver of information sent across the Internet. An IP address has two par ts: The identifier of the par ticular network on the Internet and the identifier of the particular device (which can be a ser ver or a workstation) within that network. The newer IP, Version 6, provides a 128-bit addressing scheme to support a much greater number of IP addresses. (See DHCP, DNS, IP).
ISO Network Model
A model developed by the International Standards Organization that defines seven levels, or layers, in a network. By standardizing these layers and the interfaces that connect them, different portions of a given protocol can be modified or changed as technologies advance or systems requirements are altered. The seven layers are, beginning at the lowest layer: • Layer 1 – Physical • Layer 2 – Data Link • Layer 3 – Network • Layer 4 – Transport • Layer 5 – Session • Layer 6 – Presentation • Layer 7 – Application
The time variation of a periodic signal in electronics and telecommunications. Jitter may be observed in characteristics such as the frequency of successive pulses, the signal amplitude, or phase of periodic signals.
A unit of digital information equal to 1024 bytes.
Kbps (Kilobits per second)
A unit of data transfer rate equal to 1024 bits per second.
A system of connecting PCs and other devices within the same physical proximity for sharing resources such as an Internet connections, printers, files and drives. When Wi-Fi is used to connect the devices, the system is known as a wireless LAN or WLAN.
MAC (Media Access Control) Address
A unique hardware number that identifies each device on a network. A device can be a computer, printer, etc.
MAN (Metropolitan Area Network)
A data network, typically operated by a municipality or communications carrier that provides high-speed service within a geographical area such as a college campus, town or city. A MAN is larger than a Local Area Network (LAN) but smaller than a Wide Area Network (WAN).
A communications network with at least two pathways to each node, forming a net-like organization. When each node is connected to ever y other node, the network is said to be fully meshed. When only some of the nodes are linked, switching is required to make all the connections and the network is said to be par tially meshed, or partially connected.
A signal processing technology that uses multiple receivers and multiple transmitters in both the client and access point to achieve data throughput speeds of 100Mbps.
NAT (Network Address Translation)
A network capability that enables multiple of computers to dynamically share a single incoming IP address from a dial-up, cable or DSL connection. NAT takes a single incoming public IP address and translates it to a new private IP address for each client on the network. (See DHCP, IP address).
OFDM (Orthogonal Frequency Division Multiplexing)
The way that 802.11n, 802.11a and 802.11b subdivide each radio channel into narrower frequency ranges. It achieves higher performance than the spread spectrum techniques of 802.11b by splitting a data stream into multiple narrowband streams that are sent in parallel. Each one can use simpler modulation than would be required for the complete data stream, making the signal less vulnerable to interference or multipath effects.
The radio frequency range which wireless devices use to communicate with one another. Most devices use the 2.4 GHz range. (i.e. the operating frequency for 802.11g and Bluetooth is 2.4 GHz).
Data sent over a network is broken down into many small pieces—packets—by the Transmission Control Protocol layer of TCP/IP. Each packet contains the address of its destination as well the data. Packets may be sent on any number of routes to their destination, where they are reassembled into the original data. This system is optimal for connectionless networks, such as the Internet, where there are no fixed connections between two locations.
QoS (Quality of Service)
Required to support wireless multimedia applications and advanced traf fic management. QoS enables Wi-Fi access points to prioritize traf fic and optimize the way shared network resources are allocated among dif ferent applications. Without QoS, all applications running on dif ferent devices have equal opportunity to transmit data frames. That works well for data traf fic from applications such as web browsers, file transfers, or e-mail but it is inadequate for multimedia applications. Voice over Internet Protocol (VoIP), video streaming, and interactive gaming are highly sensitive to latency increases and throughput reductions and require QoS. QoS extensions for 802.11 networks will be addressed in the upcoming IEEE 802.11e standard.
The distance covered by a wireless network or radio device. Depending on the environment and the type of antenna used, Wi-Fi signals can have a range of up to a mile. RC4 An encryption cipher designed RSA Data Security. It allows key lengths up to 1024 bits and is a component in many encryption schemes, including SSL, WEP, and TKIP.
Wireless high-speed Internet service provided by satellites. Some satellite broadband connections are two-way—up and down. Others are one-way, with the satellite providing a high-speed downlink and then using a dial-up telephone connection or other land-based system for the uplink to the Internet.
SNMP (Simple Network Management Protocol)
A standard protocol that regulates network management over the Internet. SNTP (Simple Network Time Protocol) A simplified version of NTP. SNTP can be used when the ultimate performance of the full NTP implementation described in RFC 1305 is not needed or justified.
Subnetwork (or Subnet)
An IP address range that is part of a larger address range. Subnets are used to subdivide a network address of a larger network into smaller networks. Subnets connect to other networks through a router. Each individual wireless LAN will typically use the same subnet for all of its clients.
A network device that controls network usage to prevent data collisions and insures optimal network performance. A switch acts as a network traffic cop: Rather than transmitting all the packets it receives to all ports, as a hub does, a switch transmits packets to only the receiving port.
The underlying technology of Internet communications. While IP handles the actual deliver y of data, TCP tracks the data packets to ef ficiently route a message through the Internet. Every computer in a TCP/IP network has its own IP address that is either dynamically assigned at star tup (See DHCP) or permanently assigned as a static address. All TCP/IP messages contain the address of the destination network, as well as the address of the destination station. This enables TCP/IP messages to be transmitted to multiple networks (subnets) within an organization or worldwide. For example, when a user downloads a web page, TCP divides the page file on the web ser ver into packets, numbers the packets, and for wards them individually to the user’s IP address. The packets may be routed along dif ferent paths before reaching the user’s address. At the destination, TCP reassembles the individual packets, waiting until they have all arrived to present them as a single file.
Usually measured in bps, Kbps, Mbps or Gbps, throughput is the amount of data that can be sent from one location to another in a specific amount of time.
The amount of power used by a radio transceiver to send the signal out. Transmit power is generally measured in milliwatts, which you can convert to dBm.
WAN Wide Area Network (WLAN)
A data communications network that spans large local, regional, national or international areas and is usually provided by a public carrier (such as a telephone company or service provider).The term is used to distinguish between phone-based data networks and Wi-Fi networks. Phone networks are considered WANs and Wi-Fi networks are considered Wireless Local Area Networks.
WiMAX (Worldwide Interoperability for Microwave Access)
Refers to the 802.16 standard being developed by the IEEE to provide a wireless coverage of up to 31 miles. It operates in the 2 to 11 GHz bands and enables connectivity without a direct line-of-sight to a base station although line-of-site is probably required to achieve connectivity at the distance of 31 miles. It provides shared data rates up to 70 Mbps, which, according to WiMAX proponents, is enough bandwidth to simultaneously support more than 60 businesses and hundreds of homes.
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