1-persistent CSMA is an aggressive version of Carrier Sense Multiple Access (CMSA) protocol that operates in the Medium Access Control (MAC) layer. Using CMSA protocols, more than one users or nodes send and receive data through a shared medium that may be a single cable or optical fiber connecting multiple nodes, or a portion of the wireless spectrum.In 1-persistent CSMA, when a transmitting station has a frame to send and it senses a busy channel, it waits for the end of the transmission, and transmits immediately. Since, it sends with a probability 1, the name 1 – persistent CSMA is ... Read More

Non-persistent CSMA is a non – aggressive version of Carrier Sense Multiple Access (CMSA) protocol that operates in the Medium Access Control (MAC) layer. Using CMSA protocols, more than one users or nodes send and receive data through a shared medium that may be a single cable or optical fiber connecting multiple nodes, or a portion of the wireless spectrum.In non-persistent CSMA, when a transmitting station has a frame to send and it senses a busy channel, it waits for a random period of time without sensing the channel in the interim, and repeats the algorithm again.AlgorithmThe algorithm of non-persistent ... Read More

Link Control Protocol (LCP) is a part of Point – to – Point Protocol (PPP) that operates in the data link layer. It is responsible for establishing, configuring, testing, maintaining and terminating links for transmission. It also imparts negotiation for set up of options and use of features by the two endpoints of the links.Working PrincipleWhen PPP tries to communicate, it sends out LCP packets prior to the establishment of connections over the point – to – point link. The LCP packets check the communication line to ascertain whether it can sustain the data volume at the required speed. Accordingly, ... Read More

Serial Line Internet Protocol (SLIP) is a simple protocol that works with TCP/IP for communication over serial ports and routers. They provide communications between machines that were previously configured for direct communication with each other.For example, a client may be connected to the Internet service provider (ISP) with a slower SLIP line. When a service is required, the client places a request to the ISP. The ISP responds to the request and passes it over to the Internet via high speed multiplexed lines. The ISP then sends the results back to the client via the SLIP lines.SLIP was developed by ... Read More

Synchronous optical networking (SONET) is a physical layer protocol for transmitting multiple digital bit streams over optical fiber links that form the backbone of the communication networks. Packet-over-SONET (POS) is a standard that maps IP packets into SONET frames. To implement this mechanism, Point – to – Point Protocol (PPP) runs on IP routers. Point – to – Point Protocol (PPP) is a data link layer protocol that is used to transmit data between two directly connected (point-to-point) computers. It is a byte-oriented protocol that is widely used in broadband communications having heavy loads and high speeds.The following diagram shows ... Read More

The data link protocols operate in the data link layer of the Open System Interconnections (OSI) model, just above the physical layer.The services provided by the data link protocols may be any of the following −Framing − The stream of bits from the physical layer are divided into data frames whose size ranges from a few hundred to a few thousand bytes. These frames are distributed to different systems, by adding a header to the frame containing the address of the sender and the receiver.Flow Control − Through flow control techniques, data is transmitted in such a way so that ... Read More

Selective repeat protocol, also called Selective Repeat ARQ (Automatic Repeat reQuest), is a data link layer protocol that uses sliding window method for reliable delivery of data frames. Here, only the erroneous or lost frames are retransmitted, while the good frames are received and buffered.It uses two windows of equal size: a sending window that stores the frames to be sent and a receiving window that stores the frames receive by the receiver. The size is half the maximum sequence number of the frame. For example, if the sequence number is from 0 – 15, the window size will be ... Read More

In data communications, when a receiver receives a message, it sends an acknowledgement back to the sender to notify it about correct receipt of the message. Cumulative acknowledgement is a process in which the receiver sends a single acknowledgement in response to a finite number of frames received. Through this, the receiver acknowledges that it has correctly received all previous frames or packets. When the sender receives an acknowledgement for frame n, it understands correct delivery of frames n – 1, n – 2 and so on.Cumulative acknowledgement is used along with sliding window protocols. It reduces the time and ... Read More

Dynamic channel allocation are schemes for allotting shared network channels to competing users in a dynamic manner as per their requirements. The users may be base stations, access points or terminal equipment which are allotted channels from a central pool. There are a number of methods for dynamic channel allocation. The key assumptions of these methods are −Independent Traffic − It is assumed that the users are independent of each other, i.e. each user has to send or receive data which is independent of the data transmission of the other users in the network system. Each user has a program ... Read More

When there are more than one user who desire to access a shared network channel, an algorithm is deployed for channel allocation among the competing users. Dynamic channel allocation encompasses the channel allocation schemes where channels are allotted to users dynamically as per their requirements, from a central pool.Working PrincipleIn dynamic channel allocation schemes, frequency channels are not permanently allotted to any user. Channels are assigned to the user as needed depending upon the network environment. The available channels are kept in a queue or a spool. The allocation of the channels is temporary. Distribution of the channels to the ... Read More