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Glossary

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0-9

802
IEEE 802 (IEEE Std. 802-2001) is a family of standards for peer-to-peer communication over a LAN. These technologies use a shared-medium, with information broadcast for all stations to receive. The basic communications capabilities provided are packet-based. The basic unit of transmission is a sequence of data octets (8-bits), which can be of any length within a range that is dependent on the type of LAN.
Included in the 802 family of IEEE standards are definitions of bridging, management, and security protocols.
802.1x
IEEE 802.1x (IEEE Std. 802.1x-2001) is a standard for passing EAP packets over an 802.11 wireless network using a protocol called EAP Encapsulation Over LANs (EAPOL). It establishes a framework that supports multiple authentication methods.
IEEE 802.1x authenticates users not machines.
802.2
IEEE 802.2 (IEEE Std. 802.2.1998) defines the LLC layer for the 802 family of standards.
802.3
IEEE 802.3 (IEEE Std. 802.3-2002) defines the MAC layer for networks that use CSMA/CA. Ethernet is an example of such a network.
802.11
IEEE 802.11 (IEEE Std. 802.11-1999) is a medium access control (MAC) and physical layer (PHY) specification for wireless connectivity for fixed, portable, and moving stations within a local area. It uses direct sequence spread spectrum (DSSS) in the 2.4 GHz ISM band and supports raw data rates of 1 and 2 Mbps. It was formally adopted in 1997 but has been mostly superseded by 802.11b.
IEEE 802.11 is also used generically to refer to the family of IEEE standards for wireless local area networks.
802.11a
IEEE 802.11a (IEEE Std. 802.11a-1999) is a PHY standard that specifies operating in the 5 GHz U-NII band using orthogonal frequency division multiplexing (OFDM). It supports data rates ranging from 6 to 54 Mbps.
802.11a Turbo
IEEE 802.11a Turbo is a proprietary variant of the 802.11a standard from Atheros Communications. It supports accelerated data rates ranging from 6 to 108Mbps. Atheros Turbo 5 GHz is IEEE 802.11a Turbo mode. Atheros Turbo 2.4 GHz is IEEE 802.11g Turbo mode.
802.11b
IEEE 802.11b (IEEE Std. 802.11b-1999) is an enhancement of the initial 802.11 PHY to include 5.5 Mbps and 11 Mbps data rates. It uses direct sequence spread spectrum (DSSS) or frequency hopping spread spectrum (FHSS) in the 2.4 GHz ISM band as well as complementary code keying (CCK) to provide the higher data rates. It supports data rates ranging from 1 to 11 Mbps.
802.11d
IEEE 802.11d defines standard rules for the operation of IEEE 802.11 wireless LANs in any country without reconfiguration. PHY requirements such as provides frequency hopping tables, acceptable channels, and power levels for each country are provided. Enabling support for IEEE 802.11d on the access point causes the AP to broadcast which country it is operating in as a part of its beacons. Client stations then use this information. This is particularly important for AP operation in the 5GHz IEEE 802.11a bands because use of these frequencies varies a great deal from one country to another.
802.11e
IEEE 802.11e is a developing IEEE standard for MAC enhancements to support QoS. It provides a mechanism to prioritize traffic within 802.11. It defines allowed changes in the Arbitration Interframe Space, a minimum and maximum Contention Window size, and the maximum length (in kÁsec) of a burst of data.
IEEE 802.11e is still a draft IEEE standard (most recent version is D5.0, July 2003). A currently available subset of 802.11e is the Wireless Multimedia Enhancements (WMM) standard.
802.11f
IEEE 802.11f (IEEE Std. 802.11f-2003) is a standard that defines the inter access point protocol (IAPP) for access points (wireless hubs) in an extended service set (ESS). The standard defines how access points communicate the associations and reassociations of their mobile stations.
802.11g
IEEE 802.11g (IEEE Std. 802.11g-2003) is a higher speed extension (up to 54 Mbps) to the 802.11b PHY, while operating in the 2.4 GHz band. It uses orthogonal frequency division multiplexing (OFDM). It supports data rates ranging from 1 to 54 Mbps.
802.11i
IEEE 802.11i is a comprehensive IEEE standard for security in a wireless local area network (WLAN) that describes Wi-Fi Protected Access 2 (WPA2). It defines enhancements to the MAC Layer to counter the some of the weaknesses of WEP. It incorporates stronger encryption techniques than the original Wi-Fi Protected Access (WPA), such as Advanced Encryption Standard (AES).
The original WPA, which can be considered a subset of 802.11i, uses Temporal Key Integrity Protocol (TKIP) for encryption. WPA2 is backwards-compatible with products that support the original WPA
IEEE 802.11i / WPA2 was finalized and ratified in June of 2004.
802.11k
IEEE 802.11k is a developing IEEE standard for wireless networks (WLANs) that helps auto-manage network Channel selection, client Roaming, and Access Point (AP) utilization. 802.11k capable networks will automatically load balance network traffic across APs to improve network performance and prevent under or over-utilization of any one AP. 802.11k will eventually complement the 802.11e quality of service (QoS) standard by ensuring QoS for multimedia over a wireless link.
802.1Q
IEEE 802.1Q is the IEEE standard for Virtual Local Area Networks (VLANs) specific to wireless technologies. (See http://www.ieee802.org/1/pages/802.1Q.html.)
The standard addresses the problem of how to break large networks into smaller parts to prevent broadcast and multicast data traffic from consuming more bandwidth than is necessary. 802.11Q also provides for better security between segments of internal networks. The 802.1Q specification provides a standard method for inserting VLAN membership information into Ethernet frames.

A

Access Point
An access point is the communication hub for the devices on a WLAN, providing a connection or bridge between wireless and wired network devices. It supports a Wireless Networking Framework called Infrastructure Mode.
When one access point is connected to wired network and supports a set of wireless stations, it is referred to as a basic service set (BSS). An extended service set (ESS) is created by combining two or more BSSs.
Ad hoc Mode
Ad hoc mode is a Wireless Networking Framework in which stations communicate directly with each other. It is useful for quickly establishing a network in situations where formal infrastructure is not required.
Ad hoc mode is also referred to as peer-to-peer mode or an independent basic service set (IBSS).
AES
The Advanced Encryption Standard (AES) is a symmetric 128-bit block data encryption technique developed to replace DES encryption. AES works at multiple network layers simultaneously.
Further information is available on the NIST Web site.

B

Basic Rate Set
The basic rate set defines the transmission rates that are mandatory for any station wanting to join this wireless network. All stations must be able to receive data at the rates listed in this set.
Beacon
Beacon frames provide the "heartbeat" of a WLAN, announcing the existence of the network, and enabling stations to establish and maintain communications in an orderly fashion. It carries the following information (some of which is optional):
Bridge
A connection between two local area networks (LANs) using the same protocol, such as Ethernet or IEEE 802.1x.
Broadcast
A Broadcast sends the same message at the same time to everyone. In wireless networks, broadcast usually refers to an interaction in which the access point sends data traffic in the form of IEEE 802.1x Frames to all client stations on the network.
Some wireless security modes distinguish between how unicast, multicast, and broadcast frames are encrypted or whether they are encrypted.
See also Unicast and Multicast.
Broadcast Address
See IP Address.
BSS
A basic service set (BSS) is an Infrastructure Mode Wireless Networking Framework with a single access point. Also see extended service set (ESS) and independent basic service set (IBSS).
BSSID
In Infrastructure Mode, the Basic Service Set Identifier (BSSID) is the 48-bit MAC address of the wireless interface of the Access Point.

C

CCMP
Counter mode/CBC-MAC Protocol (CCMP) is an encryption method for 802.11i that uses AES. It employs a CCM mode of operation, combining the Cipher Block Chaining Counter mode (CBC-CTR) and the Cipher Block Chaining Message Authentication Code (CBC-MAC) for encryption and message integrity.
AES-CCMP requires a hardware coprocessor to operate.
CGI
The Common Gateway Interface (CGI) is a standard for running external programs from an HTTP server. It specifies how to pass arguments to the executing program as part of the HTTP request. It may also define a set of environment variables.
A CGI program is a common way for an HTTP server to interact dynamically with users. For example, an HTML page containing a form can use a CGI program to process the form data after it is submitted.
Channel
The Channel defines the portion of the radio spectrum the radio uses for transmitting and receiving. Each 802.11 standard offers a number of channels, dependent on how the spectrum is licensed by national and transnational authorities such as the Federal Communications Commission (FCC), the European Telecommunications Standards Institute (ETSI), the Korean Communications Commission, or the Telecom Engineering Center (TELEC).
CSMA/CA
Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) is a low-level network arbitration/contention protocol. A station listens to the media and attempts to transmit a packet when the channel is quiet. When it detects that the channel is idle, the station transmits the packet. If it detects that the channel is busy, the station waits a random amount of time and then attempts to access the media again.
CSMA/CA is the basis of the IEEE 802.11e Distributed Control Function (DCF). See also RTS and CTS.
The CSMA/CA protocol used by 802.11 networks is a variation on CSMA/CD (used by Ethernet networks). In CSMA/CD the emphasis is on collision detection whereas with CSMA/CA the emphasis is on collision avoidance.
CTS
A clear to send (CTS) message is a signal sent by an IEEE 802.11 client station in response to an request to send (RTS) message. The CTS message indicates that the channel is clear for the sender of the RTS message to begin data transfer. The other stations will wait to keep the air waves clear. This message is a part of the IEEE 802.11 CSMA/CA protocol. (See also RTS.)

D

DCF
The Distribution Control Function is a component of the IEEE 802.11e Quality of Service (QoS) technology standard. The DCF coordinates channel access among multiple stations on a wireless network by controlling wait times for channel access. Wait times are determined by a random backoff timer which is configurable by defining minimum and maximum contention windows. See also EDCF.
DHCP
The Dynamic Host Configuration Protocol (DHCP) is a protocol specifying how a central server can dynamically provide network configuration information to clients. A DHCP server "offers" a "lease" (for a pre-configured period of time-see Lease Time) to the client system. The information supplied includes the client's IP addresses and netmask plus the address of its DNS servers and Gateway.
DNS
The Domain Name Service (DNS) is a general-purpose query service used for translating fully-qualified names into Internet addresses. A fully-qualified name consists of the hostname of a system plus its domain name. For example, www is the host name of a Web server and www.usr.com is the fully-qualified name of that server. DNS translates the domain name www.usr.com to some IP address, for example 66.93.138.219.
A domain name identifies one or more IP addresses. Conversely, an IP address may map to more than one domain name.
A domain name has a suffix that indicates which top level domain (TLD) it belongs to. Every country has its own top-level domain, for example .de for Germany, .fr for France, .jp for Japan, .tw for Taiwan, .uk for the United Kingdom, .us for the U.S.A., and so on. There are also .com for commercial bodies, .edu for educational institutions, .net for network operators, and .org for other organizations as well as .gov for the U. S. government and .mil for its armed services.
DOM
The Document Object Model (DOM) is an interface that allows programs and scripts to dynamically access and update the content, structure, and style of documents. The DOM allows you to model the objects in an HTML or XML document (text, links, images, tables), defining the attributes of each object and how they can be manipulated.
Further details about the DOM can be found at the W3C.
DTIM
The Delivery Traffic Information Map (DTIM) message is an element included in some Beacon frames. It indicates which stations, currently sleeping in low-power mode, have data buffered on the Access Point awaiting pick-up. Part of the DTIM message indicates how frequently stations must check for buffered data.
Dynamic IP Address
See IP Address.

E

EAP
The Extensible Authentication Protocol (EAP) is an authentication protocol that supports multiple methods, such as token cards, Kerberos, one-time passwords, certificates, public key authentication, and smart cards.
Variations on EAP include EAP Cisco Wireless (LEAP), Protected EAP (PEAP), EAP-TLS, and EAP Tunnelled TLS (EAP-TTLS).
EDCF
Enhanced Distribution Control Function is an extenstion of DCF. EDCF, a component of the IEEE Wireless Multimedia (WMM) standard, provides prioritized access to the wireless medium
ESS
An extended service set (ESS) is an Infrastructure Mode Wireless Networking Framework with multiple access points, forming a single subnetwork that can support more clients than a basic service set (BSS). Each access point supports a number of wireless stations, providing broader wireless coverage for a large space, for example, an office.
Ethernet
Ethernet is a local-area network (LAN) architecture supporting data transfer rates of 10 Mbps to 1 Gbps. The Ethernet specification is the basis for the IEEE 802.3 standard, which specifies the physical and lower software layers. It uses the CSMA/CA access method to handle simultaneous demands.
Ethernet supports data rates of 10 Mbps, Fast Ethernet supports 100 Mbps, and Gigabit Ethernet supports 1 Gbps. Its cables are classified as "XbaseY", where X is the data rate in Mbps and Y is the category of cabling. The original cable was 10base5 (Thicknet or "Yellow Cable"). Some others are 10base2 (Cheapernet), 10baseT (Twisted Pair), and 100baseT (Fast Ethernet). The latter two are commonly supplied using CAT5 cabling with RJ-45 connectors. There is also 1000baseT (Gigabit Ethernet).
ERP
The Extended Rate Protocol refers to the protocol used by IEEE 802.11g stations (over 20 Mbps transmission rates at 2.4GHz) when paired with Orthogonal Frequency Division Multiplexing (OFDM). Built into ERP and the IEEE 802.11g standard is a scheme for effective interoperability of IEEE 802.11g stations with IEEE 802.11b nodes on the same channel.
Legacy IEEE 802.11b devices cannot detect the ERP-OFDM signals used by IEEE 802.11g stations, and this can result in collisions between data frames from IEEE 802.11b and IEEE 802.11g stations.
If there is a mix of 802.11b and 802.11g nodes on the same channel, the IEEE 802.11g stations detect this via an ERP flag on the access point and enable request to send (RTS) and clear to send (CTS) protection before sending data.
See also CSMA/CA protocol.

F

Frame
A Frame consists of a discrete portion of data along with some descriptive meta-information packaged for transmission on a wireless network. Each frame includes a source and destination MAC address, a control field with protocol version, frame type, frame sequence number, frame body (with the actual information to be transmitted) and frame check sequence for error detection. A Frame is similar in concept to a Packet, the difference being that a packet operates on the Network layer (layer 3 in the OSI model) whereas a frame operates on the Data-Link layer (layer 2 in the OSI model).

G

Gateway
A gateway is a network node that serves as an entrance to another network. A gateway also often provides a proxy server and a firewall. It is associated with both a router, which use headers and forwarding tables to determine where packets are sent, and a switch or bridge, which provides the actual path for the packet in and out of the gateway.
Before a host on a LAN can access the Internet, it needs to know the address of its default gateway.

H

HTML
The Hypertext Markup Language (HTML) defines the structure of a document on the World Wide Web. It uses tags and attributes to hint about a layout for the document.
An HTML document starts with an <html> tag and ends with a </html> tag. A properly formatted document also contains a <head> ... </head> section, which contains the metadata to define the document, and a <body> ... </body> section, which contains its content. Its markup is derived from the Standard Generalized Markup Language (SGML), which is defined in ISO 8879:1986.
HTML documents are sent from server to browser via HTTP. Also see XML.
HTTP
The Hypertext Transfer Protocol (HTTP) defines how messages are formatted and transmitted on the World Wide Web. An HTTP message consists of a URL and a command (GET, HEAD, POST, etc.), a request followed by a response.

I

IAPP
The Inter Access Point Protocol (IAPP) is an IEEE standard (802.11f) that defines communication between the access points in a "distribution system". This includes the exchange of information about mobile stations and the maintenance of bridge forwarding tables, plus securing the communications between access points.
IBSS
An independent basic service set (IBSS) is an Ad hoc Mode Wireless Networking Framework in which stations communicate directly with each other.
IEEE
The Institute of Electrical and Electronic Engineers (IEEE) is an international standards body that develops and establishes industry standards for a broad range of technologies, including the 802 family of networking and wireless standards. (See 802, 802.1x, 802.11, 802.11a, 802.11b, 802.11e, 802.11f, 802.11g, and 802.11i.)
For more information about IEEE task groups and standards, see http://standards.ieee.org/.
Infrastructure Mode
Infrastructure Mode is a Wireless Networking Framework in which wireless stations communicate with each other by first going through an Access Point. In this mode, the wireless stations can communicate with each other or can communicate with hosts on a wired network. The access point is connected to a wired network and supports a set of wireless stations.
An infrastructure mode framework can be provided by a single access point (BSS) or a number of access points (ESS).
Intrusion Detection
The Intrusion Detection System (IDS) inspects all inbound network activity and reports suspicious patterns that may indicate a network or system attack from someone attempting to break into the system. It reports access attempts using unsupported or known insecure protocols.
IP
The Internet Protocol (IP) specifies the format of packets, also called datagrams, and the addressing scheme. IP is a connectionless, best-effort packet switching protocol. It provides packet routing, fragmentation and re-assembly. It is combined with higher-level protocols, such as TCP or UDP, to establish the virtual connection between destination and source.
The current version of IP is IPv4. A new version, called IPv6 or IPng, is under development. IPv6 is an attempt to solve the shortage of IP addresses.
IP Address
Systems are defined by their IP address, a four-byte (octet) number uniquely defining each host on the Internet. It is usually shown in form 192.168.2.254. This is called dotted-decimal notation.
An IP address is partitioned into two portions: the network prefix and a host number on that network. A Subnet Mask is used to define the portions. There are two special host numbers:
There are a finite number of IP addresses that can exist. Therefore, a local area network typically uses one of the IANA-designated address ranges for use in private networks. These address ranges are:
10.0.0.0 to 10.255.255.255
172.16.0.0
to 172.31.255.255
192.168.0.0
to 192.168.255.255
A Dynamic IP Address is an IP address that is automatically assigned to a host by a DHCP server or similar mechanism. It is called dynamic because you may be assigned a different IP address each time you establish a connection.
A Static IP Address is an IP address that is hard-wired for a specific host. A static address is usually required for any host that is running a server, for example, a Web server.
IPSec
IP Security (IPSec) is a set of protocols to support the secure exchange of packets at the IP layer. It uses shared public keys. There are two encryption modes: Transport and Tunnel.
ISP
An Internet Service Provider (ISP) is a company that provides access to the Internet to individuals and companies. It may provide related services such as virtual hosting, network consulting, Web design, etc.

J

Jitter
Jitter is the difference between the latency (or delay) in packet transmission from one node to another across a network. If packets are not transmitted at a consistent rate (including Latency), QoS for some types of data can be affected. For example, inconsistent transmission rates can cause distortion in VoIP and streaming media. QoS is designed to reduce jitter along with other factors that can impact network performance.

L

Latency
Latency, also known as delay, is the amount of time it takes to transmit a Packet from sender to receiver. Latency can occur when data is transmitted from the access point to a client and vice versa. It can also occur when data is transmitted from access point to the Internet and vice versa. Latency is caused by fixed network factors such as the time it takes to encode and decode a packet, and also by variable network factors such as a busy or overloaded network. QoS features are designed to minimize latency for high priority network traffic.
LAN
A Local Area Network (LAN) is a communications network covering a limited area, for example, the computers in your home that you want to network together or a couple of floors in a building. A LAN connects multiple computers and other network devices such as storage and printers. Ethernet is the most common technology implementing a LAN.
Wireless Ethernet (802.11) is another very popular LAN technology (also see WLAN).
LDAP
The Lightweight Directory Access Protocol (LDAP) is a protocol for accessing on-line directory services. It is used to provide an authentication mechanism. It is based on the X.500 standard, but less complex.
Lease Time
The Lease Time specifies the period of time the DHCP Server gives its clients an IP Address and other required information. When the lease expires, the client must request a new lease. If the lease is set to a short span, you can update your network information and propagate the information provided to the clients in a timely manner.
LLC
The Logical Link Control (LLC) layer controls frame synchronization, flow control, and error checking. It is a higher level protocol over the PHY layer, working in conjunction with the MAC layer.

M

MAC
The Media Access Control (MAC) layer handles moving data packets between NICs across a shared channel. It is a higher level protocol over the PHY layer. It provides an arbitration mechanism in an attempt to prevent signals from colliding.
It uses a hardware address, known as the MAC address, that uniquely identifies each node of a network. IEEE 802 network devices share a common 48-bit MAC address format, displayed as a string of twelve (12) hexadecimal digits separated by colons, for example FE:DC:BA:09:87:65.
MDI and MDI-X
Medium Dependent Interface (MDI) and MDI crossover (MDIX) are twisted pair cabling technologies for Ethernet ports in hardware devices. Built-in twisted pair cabling and auto-sensing enable connection between like devices with the use of a standard Ethernet cable. (For example, if a wireless access point supports MDI/MDIX, one can successfully connect a PC and that access point with an Ethernet cable rather than having to use a crossover cable).
MIB
Management Information Base (MIB) is a database of objects used for network management. SNMP agents along with other SNMP tools can be used to monitor any network device defined in the MIB.
MSCHAP V2
Microsoft Challenge Handshake Authentication Protocol Version 2 (MSCHAP V2) provides authentication for PPP connections between a Windows-based computer and an Access Point or other network access device.
MTU
The Maximum Transmission Unit is the largest physical packet size, measured in bytes, that a network can transmit. Any messages larger than the MTU are fragmented into smaller packets before being sent.
Multicast
A Multicast sends the same message to a select group of recipients. Sending an e-mail message to a mailing list is an example of multicasting. In wireless networks, multicast usually refers to an interaction in which the access point sends data traffic in the form of IEEE 802.1x Frames to a specified set of client stations (MAC addresses) on the network.
Some wireless security modes distinguish between how unicast, multicast, and broadcast frames are encrypted or whether they are encrypted.
See also Unicast and Broadcast.

N

NAT
Network Address Translation is an Internet standard that masks the internal IP addresses being used in a LAN. A NAT server running on a gateway maintains a translation table that maps all internal IP addresses in outbound requests to its own address and converts all inbound requests to the correct internal host.
NAT serves three main purposes: it provides security by obscurity by hiding internal IP addresses, enables the use of a wide range of internal IP addresses without fear of conflict with the addresses used by other organizations, and it allows the use of a single Internet connection.
Network Address
See IP Address.
NIC
A Network Interface Card is an adapter or expansion board inserted into a computer to provide a physical connection to a network. Most NICs are designed for a particular type of network, protocol, and media, for example, Ethernet or wireless.
NTP
The Network Time Protocol assures accurate synchronization of the system clocks in a network of computers. NTP servers transmit Coordinated Universal Time (UTC, also known as Greenwich Mean Time) to their client systems. An NTP client sends periodic time requests to servers, using the returned time stamp to adjust its clock.

O

OSI
The Open Systems Interconnection (OSI) reference model is a framework for network design. The OSI model consists of seven layers:

P

Packet
Data and media are transmitted among nodes on a network in the form of packets. Data and multimedia content is divided up and packaged into packets. A packet includes a small chunk of the content to be sent along with its destination address and sender address. Packets are pushed out onto the network and inspected by each node. The node to which it is addressed is the ultimate recipient.
Packet Loss
Packet Loss describes the percentage of packets transmitted over the network that did not reach their intended destination. A 0 percent package loss indicates no packets were lost in transmission. QoS features are designed to minimize packet loss.
PHY
The Physical Layer (PHY) is the lowest layer in the network layer model (see OSI). The Physical Layer conveys the bit stream - electrical impulse, light or radio signal -- through the network at the electrical and mechanical level. It provides the hardware means of sending and receiving data on a medium, including defining cables, NICs, and physical aspects.
Ethernet and the 802.11 family are protocols with physical layer components.
PID
The Process Identifier (PID) is an integer used by Linux to uniquely identify a process. A PID is returned by the fork() system call. It can be used by wait() or kill() to perform actions on the given process.
Port Forwarding
Port Forwarding creates a `tunnel' through a firewall, allowing users on the Internet access to a service running on one of the computers on your LAN, for example, a Web server, an FTP or SSH server, or other services. From the outside user's point of view, it looks like the service is running on the firewall.
PPP
The Point-to-Point Protocol is a standard for transmitting network layer datagrams (IP packets) over serial point-to-point links. PPP is designed to operate both over asynchronous connections and bit-oriented synchronous systems.
PPPoE
Point-to-Point Protocol over Ethernet (PPPoE) is a specification for connecting the users on a LAN to the Internet through a common broadband medium, such as a single DSL or cable modem line.
PPtP
Point-to-Point Tunneling Protocol (PPtP) is a technology for creating a Virtual Private Network (VPN) within the Point-to-Point Protocol (PPP). It is used to ensure that data transmitted from one VPN node to another are secure.
Proxy
A proxy is server located between a client application and a real server. It intercepts requests, attempting to fulfill them itself. If it cannot, it forwards them to the real server. Proxy servers have two main purposes: improve performance by spreading requests over several machines and filter requests to prevent access to specific servers or services.
PSK
Pre-Shared Key (PSK), see Shared Key.
Public Key
A public key is used in public key cryptography to encrypt a message which can only be decrypted with the recipient's private or secret key. Public key encryption is also called asymmetric encryption, because it uses two keys, or Diffie-Hellman encryption. Also see Shared Key.

Q

QoS
Quality of Service (QoS) defines the performance properties of a network service, including guaranteed throughput, transit delay, and priority queues. QoS is designed to minimize Latency, Jitter, Packet Loss, and network congestion, and provide a way of allocating dedicated bandwidth for high priority network traffic.
The IEEE standard for implementing QoS on wireless networks is currently in-work by the 802.11e task group. A subset of 802.11e features is described in the WMM specification.

R

RADIUS
The Remote Authentication Dial-In User Service (RADIUS) provides an authentication and accounting system. It is a popular authentication mechanism for many ISPs.
RC4
A symmetric stream cipher provided by RSA Security. It is a variable key-size stream cipher with byte-oriented operations. It allows keys up to 2048 bits in length.
Roaming
In IEEE 802.11 parlance, roaming clients are mobile client stations or devices on a wireless network (WLAN) that require use of more than one Access Point (AP) as they move out of and into range of different base station service areas. IEEE 802.11f defines a standard by which APs can communicate information about client associations and disassociations in support of roaming clients.
Router
A router is a network device which forwards packets between networks. It is connected to at least two networks, commonly between two local area networks (LANs) or between a LAN and a wide-area network (WAN), for example, the Internet. Routers are located at gateways-places where two or more networks connect.
A router uses the content of headers and its tables to determine the best path for forwarding a packet. It uses protocols such as the Internet Control Message Protocol (ICMP), Routing Information Protocol (RIP), and Internet Router Discovery Protocol (IRDP) to communicate with other routers to configure the best route between any two hosts. The router performs little filtering of data it passes.
RSSI
The Received Signal Strength Indication (RSSI) an 802.1x value that calculates voltage relative to the received signal strength. RSSI is one of several ways of measuring and indicating radio frequency (RF) signal strength. Signal strength can also be measured in mW (milliwatts), dBms (decibel milliwatts), and a percentage value.
RTP
Real-Time Transport Protocol (RTP) is an Internet protocol for transmitting real-time data like audio and video. It does not guarentee delivery but provides support mechanisms for the sending and receiving applications to enable streaming data. RTP typically runs on top of the UDP protocol, but can support other transport protocols as well.
RTS
A request to send (RTS) message is a signal sent by a client station to the access point, asking permission to send a data packet and to prevent other wireless client stations from grabbing the radio waves. This message is a part of the IEEE 802.11 CSMA/CA protocol. (See also RTS Threshold and CTS.)
RTS Threshold
The RTS threshold specifies the packet size of a request to send (RTS) transmission. This helps control traffic flow through the access point, and is especially useful for performance tuning on an access point with a many clients.

S

Shared Key
A shared key is used in conventional encryption where one key is used both for encryption and decryption. It is also called secret-key or symmetric-key encryption.
Also see Public Key.
SNMP
The Simple Network Management Protocol (SNMP) was developed to manage and monitor nodes on a network. It is part of the TCP/IP protocol suite.
SNMP consists of managed devices and their agents, and a management system. The agents store data about their devices in Management Information Bases (MIBs) and return this data to the SNMP management system when requested.
SSID
The Service Set Identifier (SSID) is a thirty-two character alphanumeric key that uniquely identifies a wireless local area network. It is also referred to as the Network Name. There are no restrictions on the characters that may be used in an SSID.
Static IP Address
See IP Address.
STP
The Spanning Tree Protocol (STP) an IEEE 802.1 standard protocol (related to network management) for MAC bridges that manages path redundancy and prevents undesirable loops in the network created by multiple active paths between client stations. Loops occur when there multiple routes between access points. STP creates a tree that spans all of the switches in an extended network, forcing redundant paths into a standby, or blocked, state. STP allows only one active path at a time between any two network devices (this prevents the loops) but establishes the redundant links as a backup if the initial link should fail. If STP costs change, or if one network segment in the STP becomes unreachable, the spanning tree algorithm reconfigures the spanning tree topology and reestablishes the link by activating the standby path. Without spanning tree in place, it is possible that both connections may be simultaneously live, which could result in an endless loop of traffic on the LAN
Subnet Mask
A Subnet Mask is a number that defines which part of an IP address is the network address and which part is a host address on the network. It is shown in dotted-decimal notation (for example, a 24-bit mask is shown as 255.255.255.0) or as a number appended to the IP address (for example, 192.168.2.0/24).
The subnet mask allows a router to quickly determine if an IP address is local or needs to be forwarded by performing a bitwise AND operation on the mask and the IP address. For example, if an IP address is 192.168.2.128 and the netmask is 255.255.255.0, the resulting Network address is 192.168.2.0.
The bitwise AND operator compares two bits and assigns 1 to the result only if both bits are 1. The following table shows the details of the netmask:
IP address
192.168.2.128
11000000 10101000 00000010 10000000
Netmask
255.255.255.0
11111111 11111111 11111111 00000000
Resulting network address
192.168.2.0
11000000 10101000 00000010 00000000
Supported Rate Set
The supported rate set defines the transmission rates that are available on this wireless network. A station may be able to receive data at any of the rates listed in this set. All stations must be able to receive data at the rates listed in the Basic Rate Set.

T

TCP
The Transmission Control Protocol (TCP) is built on top of Internet Protocol (IP). It adds reliable communication (guarantees delivery of data), flow-control, multiplexing (more than one simultaneous connection), and connection-oriented transmission (requires the receiver of a packet to acknowledge receipt to the sender). It also guarantees that packets will be delivered in the same order in which they were sent.
TCP/IP
The Internet and most local area networks are defined by a group of protocols. The most important of these is the Transmission Control Protocol over Internet Protocol (TCP/IP), the de facto standard protocols. TCP/IP was originally developed by Defense Advanced Research Projects Agency (DARPA, also known as ARPA, an agency of the US Department of Defense).
Although TCP and IP are two specific protocols, TCP/IP is often used to refer to the entire protocol suite based upon these, including ICMP, ARP, UDP, and others, as well as applications that run upon these protocols, such as telnet, FTP, etc.
TKIP
The Temporal Key Integrity Protocol (TKIP) provides an extended 48-bit initialization vector, per-packet key construction and distribution, a Message Integrity Code (MIC, sometimes called "Michael"), and a re-keying mechanism. It uses a RC4 stream cipher to encrypt the frame body and CRC of each 802.11 frame before transmission. It is an important component of the WPA and 802.11i security mechanisms.
ToS
TCP/IP packet headers include a 3-to-5 bit Type of Service (ToS) field set by the application developer that indicates the appropriate type of service for the data in the packet. The way the bits are set determines whether the packet is queued for sending with minimum delay, maximum throughput, low cost, or mid-way "best-effort" settings depending upon the requirements of the data. The ToS field is used by the U.S. Robotics Professional Access Point to provide configuration control over Quality of Service (QoS) queues for data transmitted from the AP to client stations.

U

UDP
The User Datagram Protocol (UDP) is a transport layer protocol providing simple but unreliable datagram services. It adds port address information and a checksum to an IP packet.
UDP neither guarantees delivery nor does it require a connection. It is lightweight and efficient. All error processing and retransmission must be performed by the application program.
Unicast
A Unicast sends a message to a single, specified receiver. In wireless networks, unicast usually refers to an interaction in which the access point sends data traffic in the form of IEEE 802.1x Frames directly to a single client station MAC address on the network.
Some wireless security modes distinguish between how unicast, multicast, and broadcast frames are encrypted or whether they are encrypted.
See also Multicast and Broadcast.
URL
A Uniform Resource Locator (URL) is a standard for specifying the location of objects on the Internet, such as a file or a newsgroup. URLs are used extensively in HTML documents to specify the target of a hyperlink which is often another HTML document (possibly stored on another computer). The first part of the URL indicates what protocol to use and the second part specifies the IP address or the domain name where that resource is located.
For example, ftp://ftp.usrobotics.com/downloads/myfile.tar.gz specifies a file that should be fetched using the FTP protocol; http://www.usrobotics.com/index.html specifies a Web page that should be fetched using the HTTP protocol.

V

VLAN
A virtual LAN (VLAN) is a software-based, logical grouping of devices on a network that allow them to act as if they are connected to a single physical network, even though they may not be. The nodes in a VLAN share resources and bandwidth, and are isolated on that network. The U.S. Robotics Professional Access Point supports the configuration of a wireless VLAN. This technology is leveraged on the access point for the "virtual" guest network feature.
VPN
A Virtual Private Network (VPN) is a network that uses the Internet to connect its nodes. It uses encryption and other mechanisms to ensure that only authorized users can access its nodes and that data cannot be intercepted.

W

WAN
A Wide Area Network (WAN) is a communications network that spans a relatively large geographical area, extending over distances greater than one kilometer. A WAN is often connected through public networks, such as the telephone system. It can also be connected through leased lines or satellites.
The Internet is essentially a very large WAN.
WDS
A Wireless Distribution System (WDS) allows the creation of a completely wireless infrastructure. Typically, an Access Point is connected to a wired LAN. WDS allows access points to be connected wirelessly. The access points can function as wireless repeaters or bridges.
WEP
Wired Equivalent Privacy (WEP) is a data encryption protocol for 802.11 wireless networks. All wireless stations and access points on the network are configured with a static 64-bit (40-bit secret key + 24-bit initialization vector (IV)) or 128-bit (104-bit secret key + 24-bit IV) Shared Key for data encryption. It uses a RC4 stream cipher to encrypt the frame body and CRC of each 802.11 frame before transmission.
Wi-Fi
A test and certification of interoperability for WLAN products based on the IEEE 802.11 standard promoted by the Wi-Fi Alliance, a non-profit trade organization.
WINS
The Windows Internet Naming Service (WINS) is a server process for resolving Windows-based computer names to IP addresses. It provides information that allows these systems to browse remote networks using the Network Neighborhood.
Wireless Networking Framework
There are two ways of organizing a wireless network:
WLAN
Wireless Local Area Network (WLAN) is a LAN that uses high-frequency radio waves rather than wires to communicate between its nodes.
WMM
Wireless Multimedia (WMM) is a IEEE technology standard designed to improve the quality of audio, video and multimedia applications on a wireless network. Both access points and wireless clients (laptops, consumer electronics products) can be WMM-enabled. WMM features are based on is a subset of the WLAN IEEE 802.11e draft specification. Wireless products that are built to the standard and pass a set of quality tests can carry the "Wi-Fi certified for WMM" label to ensure interoperability with other such products. For more information, see the WMM page on the Wi-Fi Alliance Web site: http://www.wi-fi.org/OpenSection/wmm.asp.
WPA
Wi-Fi Protected Access (WPA) is a Wi-Fi Alliance version of the draft IEEE 802.11i standard. It provides more sophisticated data encryption than WEP and also provides user authentication. WPA includes TKIP and 802.1x mechanisms.
WPA2
WiFi Protected Access (WPA2) is an enhanced security standard, described in IEEE 802.11i, that uses Advanced Encryption Standard (AES) for data encryption.
The original WPA uses Temporal Key Integrity Protocol (TKIP) for data encyrption. WPA2 is backwards-compatible with products that support the original WPA.
WPA2, like the original WPA, supports an Enterprise and Personal version. The Enterprise version requires use of IEEE 802.1x security features and Extensible Authentication Protocol (EAP) authentication with a RADIUS server.
The Personal version does not require IEEE 802.1x or EAP. It uses a Pre-Shared Key (PSK) password to generate the keys needed for authentication.
WRAP
Wireless Robust Authentication Protocol (WRAP) is an encryption method for 802.11i that uses AES but another encryption mode (OCB) for encryption and integrity.

X

XML
The Extensible Markup Language (XML) is a specification developed by the W3C. XML is a simple, flexible text format derived from Standard Generalized Markup Language (SGML), which is defined in ISO 8879:1986, designed especially for electronic publishing.
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