Error Recovery In Data Link Layer
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be challenged and removed. (June 2013) (Learn how and when to remove this template message) OSI model by layer 7. Application layer NNTP SIP SSI DNS FTP Gopher HTTP NFS NTP SMPP SMTP SNMP Telnet DHCP Netconf more.... 6. Presentation layer error control in data link layer MIME XDR 5. Session layer Named pipe NetBIOS SAP PPTP RTP SOCKS SPDY 4. error detection in data link layer Transport layer TCP UDP SCTP DCCP SPX 3. Network layer IP IPv4 IPv6 ICMP IPsec IGMP IPX AppleTalk X.25 PLP 2. Data
Error Correction In Data Link Layer
link layer ATM ARP IS-IS SDLC HDLC CSLIP SLIP GFP PLIP IEEE 802.2 LLC MAC L2TP IEEE 802.3 Frame Relay ITU-T G.hn DLL PPP X.25LAPB Q.921 LAPD Q.922 LAPF 1. Physical layer EIA/TIA-232 EIA/TIA-449 ITU-T V-Series I.430
Data Link Layer Error Checking
I.431 PDH SONET/SDH PON OTN DSL IEEE 802.3 IEEE 802.11 IEEE 802.15 IEEE 802.16 IEEE 1394 ITU-T G.hn PHY USB Bluetooth RS-232 RS-449 v t e The data link layer or layer 2 is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between adjacent network nodes in a wide area network (WAN) or between nodes on the same local area network data link layer protocols (LAN) segment.[1] The data link layer provides the functional and procedural means to transfer data between network entities and might provide the means to detect and possibly correct errors that may occur in the physical layer. The data link layer is concerned with local delivery of frames between devices on the same LAN. Data-link frames, as these protocol data units are called, do not cross the boundaries of a local network. Inter-network routing and global addressing are higher-layer functions, allowing data-link protocols to focus on local delivery, addressing, and media arbitration. This way, the data link layer is analogous to a neighborhood traffic cop; it endeavors to arbitrate between parties contending for access to a medium, without concern for their ultimate destination. When devices attempt to use a medium simultaneously, frame collisions occur. Data-link protocols specify how devices detect and recover from such collisions, and may provide mechanisms to reduce or prevent them. Examples of data link protocols are Ethernet for local area networks (multi-node), the Point-to-Point Protocol (PPP), HDLC and ADCCP for point-to-point (dual-node) connections. In the Internet Protocol Suite (TCP/IP), the data link layer functionality is contained within the link layer, the lowest layer of the descriptive model. Contents 1 Overview 2 Sublayers 2.1 Logical link control sublayer 2.2 Media access control sublayer 3
called frames. Note that frames are nothing more than ``packets'' or ``messages''. By convention, we'll use the term ``frames'' when discussing DLL packets. Sender checksums the frame and sends checksum together with data. The checksum allows the
Data Link Layer Devices
receiver to determine when a frame has been damaged in transit. Receiver recomputes the data link layer ppt checksum and compares it with the received value. If they differ, an error has occurred and the frame is discarded. Perhaps return data link layer protocols list a positive or negative acknowledgment to the sender. A positive acknowledgment indicate the frame was received without errors, while a negative acknowledgment indicates the opposite. Flow control. Prevent a fast sender from overwhelming a slower receiver. https://en.wikipedia.org/wiki/Data_link_layer For example, a supercomputer can easily generate data faster than a PC can consume it. In general, provide service to the network layer. The network layer wants to be able to send packets to its neighbors without worrying about the details of getting it there in one piece. At least, the above is what the OSI reference model suggests. As we will see later, not everyone agrees that the data link https://web.cs.wpi.edu/~cs4514/b98/week3-dll/week3-dll.html layer should perform all these tasks. Design Issues If we don't follow the OSI reference model as gospel, we can imagine providing several alternative service semantics: Reliable Delivery: Frames are delivered to the receiver reliably and in the same order as generated by the sender. Connection state keeps track of sending order and which frames require retransmission. For example, receiver state includes which frames have been received, which ones have not, etc. Best Effort: The receiver does not return acknowledgments to the sender, so the sender has no way of knowing if a frame has been successfully delivered. When would such a service be appropriate? When higher layers can recover from errors with little loss in performance. That is, when errors are so infrequent that there is little to be gained by the data link layer performing the recovery. It is just as easy to have higher layers deal with occasional lost packet. For real-time applications requiring ``better never than late'' semantics. Old data may be worse than no data. For example, should an airplane bother calculating the proper wing flap angle using old altitude and wind speed data when newer data is already available? Acknowledged Delivery: The receiver returns an acknowledgment frame to the sender indicating that a data frame was pro
data-link layer in The Network Encyclopedia. data-link layer Layer 2 of the Open Systems Interconnection (OSI) reference model, which converts frames of data into raw bits for the http://www.thenetworkencyclopedia.com/entry/data-link-layer/ physical layer and is responsible for framing, flow control, error correction, and retransmission of frames. MAC addresses are used at this layer, and bridges and network interface cards (NICs) operate at this layer. The data-link layer establishes and maintains the data link for the network layer above it. It ensures that data is transferred reliably between two stations on the network. A number of protocols data link can be implemented at this layer depending on whether you are establishing local area network (LAN) or wide area network (WAN) connections between stations. Data-link protocols are responsible for functions such as addressing, frame delimiting and sequencing, error detection and recovery, and flow control. For LANs, the Project 802 standards of the Institute of Electrical and Electronics Engineers (IEEE) separate the data-link layer into data link layer two sublayers: The logical link control (LLC) layer, the upper of the two layers, which is responsible for flow control, error correction, and resequencing functions for connection-oriented communication, but which also supports connectionless communication The media access control (MAC) layer, the lower of the two layers, which is responsible for providing a method for stations to gain access to the medium Graphic D-5. Data-link layer. Examples of data-link protocols for local area networking include the following: IEEE 802.3, which provides the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) access method for baseband Ethernet networks IEEE 802.5, which provides the token-passing access method for baseband token ring implementations For WANs, data-link layer protocols encapsulate LAN traffic into frames suitable for transmission over WAN links. Common data-link encapsulation methods for WAN transmission include the following: Point-to-point technologies such as Point-to-Point Protocol (PPP) and High-level Data Link Control (HDLC) protocol Multipoint technologies such as frame relay, Asynchronous Transfer Mode (ATM), Switched Multimegabit Data Services (SMDS), and X.25 Featured DHCP Maintenance Guide RAID RAID 0 RAID 1 RAID 5 Migrating Apache to IIS Migrating with the IIS Tool Migrating web sites manually Configu
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