Sliding window protocols are data link layer protocols for reliable and sequential delivery of data frames. The sliding window is also used in Transmission Control Protocol. In these protocols, the sender has a buffer called the sending window and the receiver has buffer called the receiving window.In one – bit sliding window protocol, the size of the window is 1. So the sender transmits a frame, waits for its acknowledgment, then transmits the next frame. Thus it uses the concept of stop and waits for the protocol. This protocol provides for full – duplex communications. Hence, the acknowledgment is attached ... Read More

In reliable full - duplex data transmission, the technique of hooking up acknowledgments onto outgoing data frames is called piggybacking.Why Piggybacking?Communications are mostly full – duplex in nature, i.e. data transmission occurs in both directions. A method to achieve full – duplex communication is to consider both the communication as a pair of simplex communication. Each link comprises a forward channel for sending data and a reverse channel for sending acknowledgments.However, in the above arrangement, traffic load doubles for each data unit that is transmitted. Half of all data transmission comprise of transmission of acknowledgments.So, a solution that provides better ... Read More

Sliding window protocols are data link layer protocols for reliable and sequential delivery of data frames. The sliding window is also used in Transmission Control Protocol.In this protocol, multiple frames can be sent by a sender at a time before receiving an acknowledgment from the receiver. The term sliding window refers to the imaginary boxes to hold frames. Sliding window method is also known as windowing.Working PrincipleIn these protocols, the sender has a buffer called the sending window and the receiver has buffer called the receiving window.The size of the sending window determines the sequence number of the outbound frames. ... Read More

Vinton G. Cerf is known as the “Father of the Internet". He is the co-designer of the TCP/IP protocols and the architecture of the Internet. The US President, Bill Clinton presented the U.S. National Medal of Technology to Cerf and his colleague, Robert E. Kahn, for founding and developing the wonderful creation of the Internet in December 1997.The contribution of Cerf and his colleagues have been acknowledged and applauded all over the world. Today, we cannot imagine our lives without the Internet.Vint Cerf has been awarded many honorary degrees and prizes that include the Turing Award, the Presidential Medal of ... Read More

Positive Acknowledgement with Retransmission (PAR) is a group of error – control protocols for transmission of data over noisy or unreliable communication network. These protocols reside in the Data Link Layer and in the Transport Layer of the OSI (Open Systems Interconnection) reference model. They provide for automatic retransmission of frames that are corrupted or lost during transit. PAR is also called Automatic Repeat ReQuest (ARQ).PARs are used to provide reliable transmissions over unreliable upper layer services. They are often used in Global System for Mobile (GSM) communication.Working PrincipleIn these protocols, the receiver sends an acknowledgement message back to the ... Read More

Automatic Repeat ReQuest (ARQ) is a group of error – control protocols for transmission of data over noisy or unreliable communication network. These protocols reside in the Data Link Layer and in the Transport Layer of the OSI (Open Systems Interconnection) reference model. They are named so because they provide for automatic retransmission of frames that are corrupted or lost during transmission. ARQ is also called Positive Acknowledgement with Retransmission (PAR).ARQs are used to provide reliable transmissions over unreliable upper layer services. They are often used in Global System for Mobile (GSM) communication.Working PrincipleIn these protocols, the receiver sends an ... Read More

Simplex Stop – and – Wait protocol for noisy channel is data link layer protocol for data communications with error control and flow control mechanisms. It is popularly known as Stop – and –Wait Automatic Repeat Request (Stop – and –Wait ARQ) protocol. It adds error control facilities to Stop – and – Wait protocol.This protocol takes into account the facts that the receiver has a finite processing speed and that frames may get corrupted while transmission. If data frames arrive at the receiver’s end at a rate which is greater than its rate of processing, frames can be dropped ... Read More

Stop – and – Wait protocol is data link layer protocol for transmission of frames over noiseless channels. It provides unidirectional data transmission with flow control facilities but without error control facilities.This protocol takes into account the fact that the receiver has a finite processing speed. If data frames arrive at the receiver’s end at a rate which is greater than its rate of processing, frames be dropped out. In order to avoid this, the receiver sends an acknowledgement for each frame upon its arrival. The sender sends the next frame only when it has received a positive acknowledgement from ... Read More

The Simplex protocol is data link layer protocol for transmission of frames over computer network. It is hypothetical protocol designed for unidirectional data transmission over an ideal channel, i.e. a channel through which transmission can never go wrong.It is assumed that both the sender and the receiver are always ready for data processing and both of them have infinite buffer. The sender simply sends all its data available onto the channel as soon as they are available its buffer. The receiver is assumed to process all incoming data instantly. It is does not handle flow control or error control. Since ... Read More

Data Link Layer FrameA frame is a unit of communication in the data link layer. Data link layer takes the packets from the Network Layer and encapsulates them into frames. If the frame size becomes too large, then the packet may be divided into small sized frames. At receiver’ end, data link layer picks up signals from hardware and assembles them into frames.Fields of a Data Link Layer FrameA data link layer frame has the following parts:Frame Header: It contains the source and the destination addresses of the frame and the control bytes.Payload field: It contains the message to be ... Read More