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Topic: Data link layer


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In the News (Sun 22 Nov 09)

  
  Data Communications - Data Link Protocols packet
Most of the data link protocols are derived from a data link protocol used in IBM’s SNA, called SDLC (Synchronous Data Link Control Protocol).
All are bit-oriented and all use bit stuffing for data transparency.
For both the router-router leased line connection and the dial-up host-router connection, some point-to-point data link protocol is required on the line for framing, error control and the other data link layer functions two such protocols are widely used in the internet, SLIP and ppp.
www.ligaturesoft.com /data_communications/data-link-protocols.html   (419 words)

  
  Data link layer - Wikipedia, the free encyclopedia
This is the layer which transfers data between adjacent network nodes in a wide area network or between nodes on the same local area network segment.
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.
Other data link layer protocols, such as HDLC, are specified to include both sublayers, although some other protocols, such as Cisco HDLC, use HDLC's low-level framing as a MAC layer in combination with a different LLC layer.
en.wikipedia.org /wiki/Data_link_layer   (701 words)

  
 The Data Link Layer.   (Site not responding. Last check: )
The second layer, Layer 2, the data link layer, is what enables hosts on the same link to communicate with each other.
Ethernet for example is a data link protocol that allows all hosts connected to the same link, hidden for example in a hub, to communicate with each other.
Layer 2 protocols hide the details of the physical layer to hosts; Ethernet for example allows communication over such media as copper, fibre, and air, and at speeds of 10Mb/s, 100Mb/s, and 1Gb/s.
www.ee.vt.edu /~wells/rapport/node9.html   (130 words)

  
 The Data Link Layer   (Site not responding. Last check: )
The main task of the data link layer is to take a raw transmission facility and transform it into a line that appears free of transmission errors in the network layer.
Since the physical layer merely accepts and transmits a stream of bits without any regard to meaning of structure, it is up to the data link layer to create and recognize frame boundaries.
Another issue that arises in the data link layer (and most of the higher layers as well) is how to keep a fast transmitter from drowning a slow receiver in data.
www2.rad.com /networks/1994/osi/datalink.htm   (268 words)

  
 CCNA Study Notes - OSI - Data Link Layer
Error notification alerts upper layer protocols that a transmission error has occurred, and the sequencing of data frames reorders frames that are transmitted out of sequence.
The Data Link layer uses a calculated value called the CRC (Cyclic Redundancy Check) that's placed into the Data Link trailer that's added to the message frame before it's sent to the Physical layer.
This is left for the upper layers to deal with, primarily on the Transport layer.
defoenet.com /ccna/osi_l2.html   (1380 words)

  
 NOAAPORT Data Link Layer Protocol
This field contains the data packet that is further defined in the SBN protocol.
The NBS encodes the data using nonreturn-to-zero (NRZ) encoding.
With this encoding method, only a minimal amount of clocking information is available in the data stream in the form of transitions on bit-cell boundaries, which do not allow for self-clocking.
www.nws.noaa.gov /noaaport/html/datalink.shtml   (419 words)

  
 Data link layer   (Site not responding. Last check: )
Data link layer has several functions to perform they are providing a well defined service to the network layer, determining how the bits of the physical layer are grouped into frames, dealing with transmission errors, regulating the flow of frames so that slow receivers are not swamped by fast senders, and general link management.
The principal service provided by the data link layer to the network layer is the transmission of data from the source network layer to destination network layer.
Data link layer also deals with the delivery of all frames to the network layer at the destination.
homepages.uel.ac.uk /u0214590/data.html   (548 words)

  
 The Data Link Layer Protocols
The purpose of the data link layer is to transfer blocks of data without error between two adjacent devices.
The implication of such a physical link is that the data bits are delivered in exactly the same order in which they are sent.
A data link protocol thus has to be designed to ensure an error-free transmission and also to achieve an efficiency of the data transfer as high as possible.
www.dsi.unive.it /~franz/reti/dll/Protocolli.html   (4436 words)

  
 The DataLink Layer   (Site not responding. Last check: )
The overall task of the data link layer is to make the physical line appear error free to the higher layers (this is usually called a virtual circuit).
Thus the higher layer of the protocol hierarchy can pass data down to the lower layers and be able to assume that if the message reaches the destination it will error free.
This property is called data transparency and means that the transmission of the data does not corrupt the data no matter what bit patterns (or characters) it contains (this is a non-trivial problem and is usually done by the hardware at the physical level).
www.cse.dmu.ac.uk /~cfi/Networks/DataLink/DataLink0.htm   (206 words)

  
 Role of the Data-link layer   (Site not responding. Last check: )
We have seen that the Physical layer is responsible for actually transmitting bits over a transmission medium and in general a bit stream given from the higher layer is coded and modulated to do this.
An important function of the Data-link layer is the establishment of reliable and efficient communication with another Data-link layer peer.
The Data-link layer in the receiver extracts the data and passes the data to its Network layer.
www.cs.mu.oz.au /353/notes/node53.html   (199 words)

  
 OSI Model - Data Link Layer
The data link Layer is the second layer of the OSI model.
The data link layer organizes the pattern of data bits into frames before transmission.
The Ethernet Adaptor's primary job at the data link layer is to transmit Ethernet frames onto the wire.
www.inetdaemon.com /tutorials/theory/osi/data_link.shtml   (281 words)

  
 AX.25 Amateur Packet-Radio Link-Layer Protocol
The AX.25 Link- Layer Protocol is designed to provide this service, independent of any other level that may or may not exist.
Link layer packet radio transmissions are sent in small blocks of data, called frames.
Any information in the I field shall be passed along the link transparently, except for the zero-bit insertion (see 2.2.6) necessary to prevent flags from accidentally appearing in the I field.
www.tapr.org /pub_ax25.html   (8552 words)

  
 Data Link Layer and IEEE
RFC 1042 defines the IP to link layer data encapsulation for networks using the IEEE 802 standards.
The 802 standards define the two lowest levels of the seven layer network model and primarily deal with the control of access to the network media.
The network media is the physical means of carrying the data such as network cable.
www.comptechdoc.org /independent/networking/guide/netieee.html   (1039 words)

  
 Webopedia: The 7 Layers of the OSI Model
Control is passed from one layer to the next, starting at the application layer in one station, proceeding to the bottom layer, over the channel to the next station and back up the hierarchy.
This layer formats and encrypts data to be sent across a network, providing freedom from compatibility problems.
This layer provides transparent transfer of data between end systems, or hosts, and is responsible for end-to-end error recovery and flow control.
www.webopedia.com /quick_ref/OSI_Layers.asp   (822 words)

  
 Data Link Layer
Data link layer algorithms may be embedded in the network hardware (rather than running as software process on a machine).
Assume a single link from A to B. Assume service provided by physical layer is that it will deliver bits to B in the order in which they are sent.
Data link layer sends frames - small fixed (or max) length pieces of data.
www.compapp.dcu.ie /~humphrys/Notes/Networks/data.link.html   (1931 words)

  
 Data Link Layer Protocols
The remote Network Layer peer should receive the identical message generated by the sender (e.g., if the data link layer adds control information, the header information must be removed before the message is passed to the Network Layer).
The Network Layer wants messages to be delivered to the remote peer in the exact same order as they are sent.
Nonetheless, the ISO reference model suggests that the data link layer provide such a service, and we now examine the protocols that provide such a service.
www.cs.wpi.edu /~cs4514/b98/week3-dllprot/week3-dllprot.html   (1228 words)

  
 Data-Link Layer - 2   (Site not responding. Last check: )
Concerned with the transmission of data between two directly connected devices across a single link.
Data has to be free of all errors to be useful.
Builds on the transmission facility provided by the physical layer to transform it into a link that appears to the network layer above to be free of transmission errors.
www.eeng.dcu.ie /~murphyj/tc2/dc2000/tsld018.htm   (72 words)

  
 Data Link Layer Processing © AA VERSTRAETE   (Site not responding. Last check: )
The data link is the last layer in the protocol suite that treats the data as a logical data string held in the computer's main memory and processed by the communication's software.
Peer-to-peer dialogue (dotted line): The sending and receiving data link layers confirm any transmission protocol conventions that may be required to transfer the message to the next network node.
The data link layer takes posession of the protocol data unit that has been received by the data communications equipment [DCE] operating at the physical layer.
www.smeal.psu.edu /misweb/datacomm/ID/OSI_RDL.HTM   (207 words)

  
 Data Link Layer Components   (Site not responding. Last check: )
The data link layer consists of drivers that directly handle communication with the physical medium.
Once a link is established, an ID/password pair is sent repeatedly by the peer to the authenticator until authentication is acknowledged or the connection is terminated.
The PPP link can serve as an additional network interface apart from the existing default network interface, or it can be the default network interface on the target, causing PPP to serve as a network back end for the target server on the host.
www.ia.agh.edu.pl /personal/pszwed/kss-lab/wind-docs/vxworks/netguide/c-dll.html   (8027 words)

  
 Networking Technology - Questy's study guide   (Site not responding. Last check: )
The Data Link layer deals with issues on a single segment of the network, the Network layer deals with issues spanning networks.
The lower sub-layer of the Data Link layer, the Media Access Control (MAC), performs Data Link layer functions related to the Physical layer, such as controlling access and encoding data into a valid signaling format.
The upper sub-layer of the Data Link layer, the Logical Link Control (LLC), performs Data Link layer functions related to the Network layer, such as providing and maintaining the link to the network.
www.computerguru.net /tech/netw31.htm   (532 words)

  
 PC Hardware reviews, overclocking, news - Master a network: Layer II 1/5
As data from the Application layer travels down the Layer stack, it is broken down into smaller units and each unit receives additional information (headers and trailers).
You place the letter (data from upper layers) into an envelope and on the envelope you write the friend's address (the destination address).
I've stated earlier that the Data Link Layer is where the network topology is defined.
www.pchardware.ro /Articles/article.php?id=124   (521 words)

  
 LAN Data Link Layer Protocols - CIF | Ethernet | FDDI | GARP | GMRP | GVRP | LLC | Multiprotocol over ATM | SNAP | SRP ...
The Data Link Layer defines how data is formatted for transmission and how access to the network is controlled.
IP datagrams are sent on IEEE 802 networks encapsulated within the 802.2 LLC and SNAP data link layers and the 802.3, 802.4 or 802.5 physical network layers.
CIF specifies how the ATM layer protocols can be made to work over the existing LAN framing protocols in such a way that the operation is transparent to an application written to an ATM compliant API.
www.protocols.com /pbook/lan.htm   (1957 words)

  
 Data-Link Layer   (Site not responding. Last check: )
The data-link layer provides error-free transfer of data frames from one computer to another over the physical layer.
Establishment and termination of logical links (virtual-circuit connection) between two computers identified by their unique network adapter addresses.
Instead, reliable data delivery is provided by protocols operating at the transport layer.
www.microsoft.com /resources/documentation/Windows/2000/server/reskit/en-us/cnet/cnfh_osi_ltkh.asp?frame=true   (217 words)

  
 What is Data-Link layer? - a definition from Whatis.com
- The Data-Link layer is the protocol layer in a program that handles the moving of data in and out across a physical link in a network.
The Data-Link layer is layer 2 in the Open Systems Interconnect (OSI) model for a set of telecommunication protocols.
The Data-Link layer ensures that an initial connection has been set up, divides output data into data frames, and handles the acknowledgements from a receiver that the data arrived successfully.
searchnetworking.techtarget.com /sDefinition/0,,sid7_gci211899,00.html   (334 words)

  
 NETBOOK - Q & A on Data Link Layer in OSI   (Site not responding. Last check: )
Q: The Data Link layer of the OSI model is sometimes subdivided into a media access control (MAC) and a logical link control (LLC) layer.
For example, in X.25, a link layer frame includes a sequence number, and the receiver must acknowledge each frame.
The difference between layer 2 communication and higher layers arises from the span: layer 2 only guarantees communication between two directly-connected machines (e.g., over a serial line), whereas higher-layer protocols provide end-to-end guarantees.
www.netbook.cs.purdue.edu /othrpags/qanda114.htm   (242 words)

  
 Chapter 6: Data Link Layer
The data link layer manages point to point communication and frames data for the physical layer to send over the media.
The Media Access Control (MAC) sublayer handles coordination of and contention for use of the media (particularly important in shared media situations), while the Logical Link Control (LLC) layer is an interface between MAC and the network layer (layer 3).
Error detection is performed by adding additional information to the data which might allow the receiver to recognize an error.
telecomm.boisestate.edu /is380.f97/datalink.htm   (453 words)

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