Found 496 Articles for Computer Engineering

TCP/IP Reference Model is a four-layered suite of communication protocols. It was developed by the DoD (Department of Defence) in the 1960s. It is named after the two main protocols that are used in the model, namely, TCP and IP. TCP stands for "Transmission Control Protocol" and IP stands for "Internet Protocol".The four layers in the TCP/IP protocol suite are −Host-to- Network Layer −It is the lowest layer that is concerned with the physical transmission of data. TCP/IP does not specifically define any protocol here but supports all the standard protocols.Internet Layer −It defines the protocols for logical transmission of ... Read More

The application layer (Layer 7) is the topmost layer of the OSI model. It specifies the interfaces and supports services to the end users for network access.The main functions of the application layer are as follows −It provides a virtual network terminal through which a user can log on to the remote host on the network.It provides facilities so that a user can access and retrieve files in a remote computer for local usage, as well as manage and store files on a remote computer from the local computer.It provides e-mail services.It helps to retrieve global information and services by ... Read More

The presentation layer (Layer 6) ensures that the message is presented to the upper layer in a standardized format. It deals with the syntax and the semantics of the messages.The main functions of the presentation layer are as follows −It encodes the messages from the user dependent format to the common format and vice versa, for communication among dissimilar systems.It is responsible for data encryption and decryption of sensitive data before they are transmitted over common channels.It is also responsible for data compression. Data compression is done at the source to reduce the number of bits to be transmitted. It ... Read More

The session layer (layer 5) is responsible for establishing, managing, synchronizing and terminating sessions between end-user application processes.The main functions of the session layer are as follows −It works as a dialog controller. It allows the systems to communicate in either half-duplex or full-duplex mode of communication.It is responsible for token management. Through this, it prevents the two users to simultaneously attempt the same critical operation.It synchronizes communication. It adds synchronization points or checkpoints in data streams for long communications. This ensures that data streams up to the checkpoints are successfully received and acknowledged. In case of any failures, only ... Read More

The transport layer (Layer 4) is responsible for delivery of an entire message from an application program on the source device to a similar application program on the destination device.The main functions of the transport layer are as follows −It delivers a message from a specific process of one computer to a specific process in another computer. The transport layer adds a port address to the header of the data packet.It divides a message into smaller segments such that each segment contains a sequence number along with the port address. It ensures that the segments arrive correctly at the receiver’s ... Read More

The network layer (Layer 3) controls the source to destination delivery of data packets across multiple hops (nodes). It controls the operation of the subnet.The main functions of the network layer are as follows −It is responsible for routing packets from the source host to the destination host. The routes can be based upon static tables that are rarely changed, or they can be automatically updated depending upon network conditions.The data link layer assigns the physical address locally. When the data packets are routed to remote locations, a logical addressing scheme is required to differentiate between the source system and ... Read More

The data link layer (Layer 2) converts the raw transmission facility provided by the physical layer to a reliable and error-free link.The main functions of the data link layer are as follows −It breaks up the stream of bits into data frames having sizes from a few hundred to a few thousand bytes.It ensures distribution of the frames to the different systems. For this, it adds a header to the frame containing the address of the sender and the receiver.In case of reliable connection, this layer ensures that the receiver sends an acknowledgement frame. In absence of acknowledgement frames, frame ... Read More

The physical layer (Layer 1) deals with transmission of individual bits from one node to another over a physical medium.The main functions of the physical layer are as follows −It defines the physical characteristics and functions of the physical devices and interfaces so that transmission can occur. It states the number of pins in each of the devices as well as the purpose of each pin.It lays out the transmission medium and type of signal for transmitting the bits, i.e., electrical pulses, optical pulses or radio signals.It defines the procedure of encoding of the bits, for example, how many volts ... Read More

OSI or Open System Interconnection model was developed by International Standards Organization (ISO). It gives a layered networking framework that conceptualizes how communications should be done between heterogeneous systems. It has seven interconnected layers. The seven layers of the OSI Model are a physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and application layer, as shown in the following diagram −The physical layer, data link layer and the network layer are the network support layers. The layers manage a physical transfer of data from one device to another. Session layer, presentation layer, and application layer ... Read More

In computer networks, reference models give a conceptual framework that standardizes communication between heterogeneous networks.The two popular reference models are −OSI ModelTCP/IP Protocol SuiteOSI ModelOSI or Open System Interconnection model was developed by International Standards Organization (ISO). It gives a layered networking framework that conceptualizes how communication should be done between heterogeneous systems. It has seven interconnected layers.The seven layers of the OSI Model are a physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and application layer. The hierarchy is depicted in the following figure −TCP / IP PROTOCOL SUITETCP stands for Transmission Control Protocol, while ... Read More