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Access point (AP)

In a wireless local area network (WLAN), an access point is a station that transmits and receives data (sometimes referred to as a transceiver). An access point connects users to other users within the network an also can serve as the point of interconnection between the WLAN and a fixed wire network. Each access point can serve multiple users within a defined network area; as people move beyond the range of one access point, they are automatically handed over to the next one. A small WLAN may only require a single access point; the number required increases as a function of the number of network users and the physical size of the network.

From: http://searchmobilecomputing.techtarget.com/definition/access-point

Wireless access point

In computer networking, a wireless access point (WAP) is a networking hardware device that allows a Wi-Fi compliant device to connect to a wired network. The WAP usually connects to a router (viaa wired network) as a stand alone device, but it can also be an integral component of the router itself. A WAP is differentiated from a hotspot, which is the physical location where Wi-Fi access to a WLAN is available.

Introduction

Prior to wireless networks, setting up a computer network in business, home or school often required running many cables through walls and ceilings in order to deliver network access to all of the network-enabled devices in the building. With the creation of the wireless access point, network users are now able to add devices that access the network with few or no cables. A WAP normally connects directly to a wired Ethernet connection and the WAP then provides wireless connection using radio frequency links for other devices to utilize that wired connection. Most WAPs support the connection of multiple wireless devices to one wired connection. Modern WAPs are built to support a standard and receiving data using these radio frequencies. Those standards and the frequencies they use are defined by the IEEE. Most APs use IEEE 802.11 standards.

Communication Processors (Networking)

The widespread perception of communication processors (CPs) is that they are general-purpose devices from a family of equipment types, including feeder multiplexers, packet assembler/disassemblers (PADs), terminal servers, and protocol converters. In the typical IBM mainframe environment, however, system administrators usually take a much narrower view, limiting the definition to FEPs, establishment controllers, and network gateway controllers.

Even though most mainframe central processors include parallel circuits and clocking mechanisms to handle I/O in a quasi-parallel fashion, they still consume a significant percentage of available CPU cycles for specialized, high-overhead, front-end applications. This has motivated system designers to find ways to offload these support processes onto less expensive resources. This motivation gave rise to the introduction of communications processor technology.

These special-purpose computers are designed to manage to complexities of computer communications such as protocol processing, data format conversion, data buffering and routing, error checking and correction, and network control. Depending on the environment, vender, or configuration, communications processors are commonly referred to as front-end processors (FEPs), local/remote concentrators or hubs, communication servers, gateway switches, intelligent routers, and controllers.

The market for communications processors is fully mature and dominated by one product, the IBM 3475 Communication Controller. Lately the term communications processor has been used increasingly to refer to network add-in boards for both PC and VMEbus system. The concept is the same - that these boards offload communications functions from the CPU.

Functions

The traffic management responsibilities of CPs include establishing, maintaining, and controlling any communications sessions between a host computer and dataterminal equipment (DTE), switching devices, other hosts (peer-to-peer), and intranet and Internet activities. Several venders have enhanced their CP offerings by adding features that include utilities for response time monitoring, event logging, terminal status indication, system administration, and diagnostic testing.

The original communication processors were relegated to mainframe systems. However, the advent of client/server computing and network topologies brought with them new, modernized devices for communications connectivity. Instead of a processor dedicated to servicing a single, central host, these newer communications servers offer front end for any number of processors connected via a local or enterprise-wide network.

Communications servers allow any piece of data communication equipment supporting the EIA-232 standard (terminals, modems, printers, hosts, and personal computers) to attach to a network. In some configurations, several operate concurrently in the same network, thereby providing an extensive range of communications services.

Communications processors, on the other hand, are generally classed by their range of features, flexibility, and capabilities. These include the number and types of host interfaces and protocols supported, aggregate bandwidth, and the types of terminal equipment and other devices supported. Creating an optimum configuration generally entails customizing the CP application software according to the functional and operational requirements of the system. This process, called System Generation (SYSGEN), prompts users through a series of questions about the desired configuration and estimates of data traffic. The result of this atrocity is a customized, resident program and associated tables that are automatically loaded and run each time the processor is initialized.

Communications processors support a number of protocols, including OSI, TCP/IP, IBM’s SNA/SDLC and 3270/3780 BSC, Ethernet, Fast Ethernet, token-ring, FDDI, ATM, X.25, frame relay, SONET, and Digital Equipment’s DECnet, and Local Area Transport (LAT) protocols. Anumber of CPs is able to operate in a multi-stack environment, supporting and translating multiple protocols concurrently.

From: http://what-when-how.com/networking/communications-processors-networking/

Pre-shared Key

In cryptography, a pre-shared key (PSK) is a shared secret which was previously shared between the two parties using some secure channel before it needs to be used.

To build a key from shared secret, the key derivation function is typically used. Such systems almost always use symmetric key cryptographic algorithms. The term PSK is used in Wi-Fi encryption such as Wired Equivalent Privacy (WEP), Wi-Fi Protected Access (WPA), where the method is called WPA-PSK or WPA2-PSK, and also in the Extensible Authentication Protocol (EAP), where it is known as EAP-PSK. In all these cases, both the wireless access point (AP) and all clients share the same key.

The characteristics of this secret or keyare determined by the system which uses it; some system designs require that such keys be in a particular format. It can be a password, a pass phrase, or a hexadecimal string. The secret is used by all systems involved in the cryptographic processes used to secure the traffic between the systems.

Crypto systems rely on one or more keys for confidentiality. One particular attack is always against keys, the brute force key search attack. A sufficiently long, randomly chosen, key can resist any practical brute force attack, though not in principle if an attacker hassufficient computational power. Unavoidably, however, pre-shared keys are heldby both parties to the communication, and so can be compromised at one end, without the knowledge of anyone at the other. There are several tools available to help one chose strong passwords, though doing so over any network connection is inherently unsafe as one cannot in general know who, if anyone, may be eavesdropping on the interaction. Choosing keys used by cryptographic algorithms is somewhat different in that any pattern whatsoever should be avoided, as any such pattern may provide an attacker with a lower effort attack than brute force search. This implies random key choice to force attackers to spend as much effort as possible; this is very difficult in principle and in practice as well. As a general rule, any software except a cryptographically secure pseudorandom number generator should be avoided.

From: https://en.wikipedia.org/wiki/Pre-shared_key