The Data link layer [also called layer 2] is responsible for moving a message from one computer or network device to the next computer or network device in the overall path from sender or receiver. It controls the way messages are sent on the physical media. Both the sender and receiver have to agree on the rules or protocols that govern how they will communicate with each other. A data link protocol determines who can transmit at what time, where a message begins and ends, and how a receiver recognizes and corrects a transmission error.
The data link layer performs two main functions, and therefore is often divided into two sublayers.
Logical link control [LLC] sublayer - The first sublayer is the data link layer’s connection to the network layer above it. At the sending computer, the LLC sublayer software is responsible for communicating with the network layer software
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The MAC sublayer software at the sending computer controls how and when the physical layer converts bits into the physical symbols that are sent down the circuit. At the receiving computer, the MAC sublayer software takes the data link layer PDU from the LLC sublayer, converts it into a stream of bits, and controls when the physical layer actually transmits the bits over the circuit. At the receiving computer, the MAC sublayer receives a stream of bits from the physical layer and translates it into a coherent PDU, ensures that no errors have occurred in transmission, and passes the data link layer PDU to the LLC sublayer.
Both the sender and receiver have to agree on the rules or protocols that govern how their data link layers will communicate with each other. A data link protocol performs three functions:
• Controls when computers transmit (media access control)
• Detects and corrects transmission errors (error control)
• Identifies the start and end of a message by using a PDU (message
2: Data Link Layer: It take care of errors in physical layer. The main aim of the data link layer is to controls the flow of frame synchronization and transmission protocol. The data link layer divided in to two types. They are Media Access Control (MAC) and Logical Link Control (LLC).
Layer 3: Network - The way that the data will be sent to the recipient device is determined in this layer. Logical protocols, routing and addressing are handled here.
The fifth layer is the session layer this establishes a connection,this layer makes and sets up the connection using co ordinates and could terminate conversations links. the session layer produces services that make authentication after an interruption and not only that but it can reconnect.and as well as the transporting layer it can also have the TCP and the UDP can provide services for all most all applications.An application layer is an abstraction layer that specifies the shared protocols and interface methods used by hosts in a communications network. The application layer abstraction is used in both of the standard models of computer networking; the Internet Protocol Suite (TCP/IP) and the Open Systems Interconnection model (OSI model).Although both models use the same term for their respective highest level layer, the detailed definitions and purposes are different.In TCP/IP, the application layer contains the communications protocols and interface methods used in process-to-process communications
• “Data Link -Whenever two or more nodes share the same physical medium (for example, several computers plugged
Information is composed into a unit (called an edge) and sent over a system to a destination that confirms its effective entry likewise deals with the stream or pacing at which information is sent.
gateway. When the data packets reach their destination, they fit back together to for the
This makes sure the data transferred is in the right order, error free and reliable from beginning to end. The Network Layer is the third layer of the model and its function is to interpret the network addresses into physical addresses and figure out how to direct them from the sender to the receiver. The next layer is the Data Link Layer, this is the second layer and it separates the data it receives from the Network layer into specific frames so they can be transmitted by the Physical layer. Frames are packages for moving data, they include the raw data, the sender and receiver’s addresses, as well as error checking and control information. This makes sure the frames are delivered to their destination without any problems. The physical layer is the first layer and the lowest, the protocols at this layer recognize and receive the frames from the Data Link layer. They also monitor data error and set data transmission
It is the software structure, which implements the communication function. The protocol architecture consists of a layered set of protocols, with one or more
Layer 4 is the transport layer and utilises common transport protocols to enable network communications. This may include the Transport Control Protocol (TCP) and Universal Data Protocol
The internet layer is built up of four core protocols: IP, IGMP, ICMP and ARP. Internet protocol (IP) is responsible for routing, IP addressing and breakdown/reassembly of data packets, address resolution protocol (ARP) is responsible for mapping an IP address to a device on the local network, internet control message protocol (ICMP) provides diagnostic information and error reports on lost packets, internet group management protocol (IGMP) controls who receives IP datagrams in a single transmission. The transport layer is built up of two core protocols: TCP and UDP. Transmission control protocol (TCP) sequences and acknowledges packets sent and their recovery when lost in transmission allowing the computer to make and maintain network conversations where applications exchange data, defined as a connection-oriented protocol meaning the connection is maintained until the programs has finished exchanging data. User datagram protocol (UDP) This is used to transfer small amounts of data when the use of error correction isn’t needed increasing the speed of the transmission, common in multi-player video games as the user will not need to receive packets of past events in the game so the error correction featured in (TCP) would be
Data Link Layer communicates two routers by means of physical channel. In Transport Layer the communication is achieved throughout a subnet.
The layer starts from 7 being the top layer and 1 being the lowest layer of the OSI model. Application layer- Serves as the window for users and application processes to access networks services like web browser (Internet explorer, Mozilla) protocols – DNS & SSH etc. Presentation layer- Translates data from the format send into the format that program can understand. Session Layer- Starts and end session and also keeps them isolated protocols- SMB,NFS, Socks and allows session establishment between processes running on different stations. Network- Determines addressing method for being transmitted. Transport- Defines ports and reliability protocols- TCP, UDP. Network- logical or IP addressing: Determines best path for the destination protocols- IPV4, IPV6, ICMP, IPsec. Data link- Contain data into a frame that contains a header with a destination. Switches, Mac addressing protocols- PPTP, Token Ring. Physical Link- Determines the hardware used and the method used for data transmission like cables, network interface cards, electrical
17. Which of the following answers list true facts about the data link layer of the TCP/IP? Two TCP/IP data-link protocols are Ethernet and PPP. Data-link protocols define addresses that
The transport layer: This layer determines how the packets are transported such as the order and what to do if there are errors. The purpose of this layer is to make sure the data be transported correctly. Besides, due to the limitation of physic (maximum IP packet size is 65535bits), the speed of transportation is limited. As a result, this layer needs break big data in to small packets. This can also collect small data into a big packet to reduce unnecessary transmission, which can improve the transmitting speed. Example protocols are TCP, UDP, SCTP.
A given layer in the OSI model generally communicates with three other OSI layers: the layer directly above it, the layer directly below it, and its peer layer in other networked computer systems. The data link layer in System A, for example, communicates with the network layer of System A, the physical layer of System A, and the data link layer in System B. The following figure illustrates this example.