Wired Equivalent Privacy (WEP) is a security standard for wireless networks or WiFi. It was a part of the original IEEE 802.11 protocol. As wireless networks transmit data over radio waves, eavesdropping on wireless data transmissions is relatively easier than in wired networks connected by cables. WEP aims to provide the same level of security and confidentiality in wireless networks as in wired counterparts.Features of WEPWEP was introduced as a part of IEEE 802.11 standard in 1997.It was available for 802.11a and 802.11b devices.WEP uses encryption of data to make it unrecognizable to eavesdroppers.It uses RC4, a stream cipher, for ... Read More

Wi-Fi Protected Access (WPA) and Wi-Fi Protected Access 2 (WPA2) are security standards to protect network stations connected to WiFi networks. They were developed by WiFi Alliance for delivering sophisticated data encryption technologies and improved user authentication than the pre-existing Wired Equivalent Privacy (WEP).WiFi Protected Access (WPA)Wi-Fi Protected Access (WPA) was supported in IEEE 802.11i wireless networks and was proposed in 2004. It was backward-compatible with the existing WEP that led to its rapid, hassle-free adoption.The encryption method adopted in WPA is the Temporal Key Integrity Protocol (TKIP). TKIP includes per-packet key, integrity check, re-keying mechanism. It dynamically generates an ... Read More

The IEEE 802.11 standard, lays down the architecture and specifications of wireless local area networks (WLANs). WLAN or WiFi uses high frequency radio waves instead of cables for connecting the devices in LAN. Users connected by WLANs can move around within the area of network coverage.The 802.11 MAC sublayer provides an abstraction of the physical layer to the logical link control sublayer and upper layers of the OSI network. It is responsible for encapsulating frames and describing frame formats.MAC Sublayer Frame Structure of IEEE 802.11The main fields of a frame in WLANs as laid down by IEEE 802.11 are as ... Read More

Inter – frame SpacesInter − frame spaces (IFS) are waiting periods between transmission of frames operating in the medium access control (MAC) sublayer where carrier-sense multiple access with collision avoidance (CSMA/CA) is used. These are techniques used to prevent collisions as defined in IEEE 802.11-based WLAN standard (Wi-Fi).IFS is the time period between completion of the transmission of the last frame and starting transmission of the next frame apart from the variable back-off period.The diagram below shows the different types of inter − frame spacing starting from the shortest duration (highest priority) to the longest duration (lowest priority). Among these, ... Read More

Transmit opportunity (TXOP) is a MAC layer feature used in IEEE 802.11-based wireless local area network (WLAN). TXOP defines the time duration for which a station can send frames after it has gained contention for the transmission medium. By providing this contention-free time period, TXOP aims to increase the throughput of high priority data, such as voice and video.TXOP is available in Quality of Service as part of Enhanced Distributed Channel Access (EDCA).Working PrincipleTXOP operates in the following sequence of steps −When a station in the WLAN has frames to send, it waits till it’s Network Allocation Vector (NAV) decrements ... Read More

Extended inter-frame spacing (EIFS), is a waiting period used in MAC layer of IEEE 802.11-based wireless local area network standard (WLAN standard). It is an additional waiting period used in addition to the mandatory DISF technique in case of corrupted frames.DISF (Distributed coordination function inter-frame spacing) is inserted before sending frames to avoid collisions in areas where carrier-sense multiple access with collision avoidance (CSMA/CA) is used. EISF is used for erroneous frames.Functioning of EIFSIn normal delivery of frames, DISF waiting period is good enough. However, when a previously received frame is corrupted, the DISF waiting period proves to be insufficient. ... Read More

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) is a network protocol for carrier transmission that operates in the Medium Access Control (MAC) layer. CSMA/CA prevents collisions prior to their occurrence and is ideally used in wireless communications.Rate anomaly occurs when the performance of a high speed station is impaired due to a low speed station, thus reducing the average throughput of the entire wireless network.ExplanationThe CSMA/CA allows each station to send a single frame at a time. Before sending a frame, the station waits for a certain inter-frame spacing (IFS). Following the IFS, it sends the request to send ... Read More

Arbitration inter-frame spacing (AIFS), is an optional technique used to prevent collisions in IEEE 802.11e based WLAN standard (Wi-Fi), in the medium access control (MAC) layer. It determines the time interval that a station should wait before it sends its request frame, by prioritizing the stations based upon the Access Category, i.e. the type of data to be transmitted.Functioning of AIFSIn a wireless communication, it is very difficult to resolve collisions. So, collision avoidance schemes are used when multiple stations want to access the channels. Inter-frame spacing are inserted before transmissions for avoiding collisions. Unlike other inter-frame spaces, AISF assigns ... Read More

Cloud computing refers to a client-server computing framework where resources are managed in a centralized fashion. It is provided as a pay-per-use service. Cloud computing makes the system all-time accessible.Grid computing refers to a network of the same or different types of computers whose target is to provide an environment where a task can be performed by multiple computers together on a need basis. Each computer can work independently as well. Grid Computing is used internally by organizations.Read through this article to find out more about Cloud Computing and Grid Computing and how they are different from each other.What is ... Read More

A cluster computer refers to a network of same type of computers whose target is to work as one collaborative unit. Such a network is used when a resource-hungry task requires high-computing power or memory. Two or more same types of computers are clubbed together to make a cluster and perform the task.Grid computing refers to a network of same or different types of computers whose target is to provide an environment where a task can be performed by multiple computers together on need basis. Each computer can work independently as well.Read through this article to find out more about ... Read More