Dataling Layer
This layer deals with getting data across a specific medium and individual links by providing one or more data link connections between two network entities. End points are specifically identified, if required by the Network layer Sequencing. The frames are maintained in the correct sequence and there are facilities for Flow control and Quality of Service parameters such as Throughput, Service Availability and Transit Delay.
The Data link layer performs the error check using the Frame Check Sequence (FCS) in the trailer and discards the frame if an error is detected. It then looks at the addresses to see if it needs to process the rest of the frame itself or whether to pass it on to another host. The data between the header and the trailer is passed to layer 3. The MAC layer concerns itself with the access control method and determines how use of the physical transmission is controlled and provides the token ring protocols that define how a token ring operates. The LLC shields the higher level layers from concerns with the specific LAN implementation. The LLC layer controls frame synchronization, flow control and error checking.
We can also say, that the Data Link layer frame puts in the hardware addresses of both the source node and the next directly connected network device. The Layer is responsible for communications between adjacent network nodes. Hubs and switches operate at the Data Link Layer.
Standards which operate at the Data Link Layer include: Ethernet, Wi-Fi, Frame Relay, ATM, and PPP.
Next function of datalink layer is to reserve unoverload recipient with data from sender. This named flow control. It ensure , that data are send just, when the recipient is able to accept them. For expample- compensatory memory, he doesn´t do another work.
This layer have 2 big group of Request. idle RQ, stop&wait RQ and continous RQ. Continous RQ minimalize time losses thnaks Go-back-N technik.
In this layer we use sliding window method. It means, that by continous RQ rise o window. You can send just specific maximal count of framework. In the window are still unconfirmed framework. When recipient confirm it, the window dissolve.
he only reference and tutorial on the market covering all the major data link protocols in use in industry. (Data link protocols (DLPs) manage the flow of data across a communications path and ensure that this traffic arrives error-free at the receiving machine.) Examines relative merit and pros/cons of each. Covers both synchronous and asynchronous protocols as well as WAN and LAN links. Protocols covered include: LAPD, LAPB, LEEE LAN Link Protocols, LAPM, Frame Relay, Internet Link Protocols, SDLC as well as wireless link protocols. The value of these protocols for their underlying network technologies is examined; for example the relationship of LAPD to ISDN nets or LAPB to X.25 nets. For programmers, engineers, project managers responsible for designing, installing, and maintaining communication systems using data link protocols.
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