A wide area network accelerator (WAN accelerator) is a hardware component, a software, or an appliance executing in a virtualized environment that provides caching and optimization of WAN services. A WAN accelerator is also called a WAN optimizer or application accelerator.Working PrincipleA WAN accelerator provides services to speed up information flow between the end users for imparting better network experience. Its target is to reduce the data volume to be transmitted. So, it compresses data and uses data deduplication techniques. The accelerator caches duplicate data and sends references of them when they are needed multiple times instead of resending the ... Read More

Protocols in the data link layer are designed so that this layer can perform its basic functions: framing, error control and flow control. Framing is the process of dividing bit - streams from physical layer into data frames whose size ranges from a few hundred to a few thousand bytes. Error control mechanisms deals with transmission errors and retransmission of corrupted and lost frames. Flow control regulates speed of delivery and so that a fast sender does not drown a slow receiver.Types of Data Link ProtocolsData link protocols can be broadly divided into two categories, depending on whether the transmission ... Read More

Cyclic Redundancy Check (CRC)Cyclic Redundancy Check (CRC) is a block code that was invented by W. Wesley Peterson in 1961. It is commonly used to detect accidental changes to data transmitted via telecommunications networks and storage devices.CRC involves binary division of the data bits being sent by a predetermined divisor agreed upon by the communicating system. The divisor is generated using polynomials. So, CRC is also called polynomial code checksum.Before sending the message over network channels, the sender encodes the message using CRC. The receiver decodes the incoming message to detect error. If the message is error-free, then it is ... Read More

A polynomial code is a linear code having a set of valid code words that comprises of polynomials divisible by a shorter fixed polynomial is known as generator polynomial.They are used for error detection and correction during the transmission of data as well as storage of data.Types of Polynomial CodesThe types of polynomial codes are:Cyclic Redundancy CodeBose–Chaudhuri–Hocquenghem (BCH) CodesReed–Solomon CodesRepresentation of Bit Strings with PolynomialsThe code words, which are essentially bit strings, are represented by polynomials whose coefficients are either 0 or 1. A 𝑘 – bit word is represented by a polynomial ranging from 𝑥0 to 𝑥𝑘−1. The order ... Read More

Fletcher checksum is an error – detection technique that uses two checksums to determine single-bit errors in a message transmitted over network channels. It is a block code technique that was devised by John G. Fletcher in 1970s at Lawrence Livermore Labs, USA.The checksums are created based on the data values in the data blocks to be transmitted and appended to the data. When the receiver gets this data, the checksums are re-calculated and compared with the existing checksums. A non-match indicates an error.The error-detection capabilities of this method is nearly same as that of Cyclic Redundancy Check (CRC) but ... Read More

The arrangement of keys in a typing keypad that we have today is nearly a century and half old. Initially, in the olden days the typewriter machines did have the keys arranged alphabetically but because the machines were too slow in comparison to the speed at which users learned to master them, it presented a different problem.Swift UsersThe users turned out to be way faster than the machines and this resulted in the mechanical character arms getting jumbled up all over. Therefore, the makers of typewriters in response to customer experience and feedback designed a completely new keyboard where the ... Read More

Interleaving is a tool that is used to enhance existing error correcting codes so that they can be used to perform burst error corrections as well.Most error correcting codes (ECCs) are designed to correct random errors, i.e. error caused by additive noise that is independent of each other. Burst error are the errors that occur in a sequence or as groups. They are caused due to defects in storage media or disruption in communication signals due to external factors like lightning etc. Interleaving modifies the ECC or does some processing on the data after they are encoded by ECCs.Interleaving ProcedureDuring ... Read More

A parity bit is a check bit, which is added to a block of data for error detection purposes. It is used to validate the integrity of the data. The value of the parity bit is assigned either 0 or 1 that makes the number of 1s in the message block either even or odd depending upon the type of parity. Parity check is suitable for single bit error detection only.The two types of parity checking areEven Parity − Here the total number of bits in the message is made even.Odd Parity − Here the total number of bits in ... Read More

Errors and Error DetectionWhen bits are transmitted over the computer network, they are subject to get corrupted due to interference and network problems. The corrupted bits leads to spurious data being received by the receiver and are called errors.Error detection techniques are responsible for checking whether any error has occurred or not in the frame that has been transmitted via network. It does not take into account the number of error bits and the type of error.For error detection, the sender needs to send some additional bits along with the data bits. The receiver performs necessary checks based upon the ... Read More

Errors and Error DetectionWhen bits are transmitted over the computer network, they are subject to get corrupted due to interference and network problems. The corrupted bits leads to spurious data being received by the receiver and are called errors.Error detection techniques are responsible for checking whether any error has occurred or not in the frame that has been transmitted via network. It does not take into account the number of error bits and the type of error.For error detection, the sender needs to send some additional bits along with the data bits. The receiver performs necessary checks based upon the ... Read More