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The data link layer packs bits which have been moved by the Physical Layer, into frames, so that each frame is distinguishable from another whiles being transmitted to destination.
A point-to-point connection between two computers or devices consists of a wire in which data is transmitted as a stream of bits. However, these bits must be framed into discernible blocks of information. Framing is a function of the data link layer which provides a way for a sender to transmit a set of bits that are meaningful to the receiver. Ethernet, token ring, frame relay, and other data link layer technologies have their own frame structures. Frames have headers that contain information such as error-checking codes.
There are three different types of framing, each of which provides a way for the sender to tell the receiver where the block of data begins and ends:
- Byte-oriented framing Computer data is normally stored as alphanumeric characters that are encoded with a combination of 8 bits (1 byte). This type of framing differentiates one byte from another. It is an older style of framing that was used in the terminal/mainframe environment. Examples of byte-oriented framing include IBM's BISYNC protocol.
- Bit-oriented framing This type of framing allows the sender to transmit a long string of bits at one time. IBM's SDLC (Synchronous Data Link Control) and HDLC (High-level Data Link Control) are examples of bit-oriented protocols. Most LANs use bit-oriented framing. There is usually a maximum frame size. For example, Ethernet has a maximum frame size of 1,526 bytes. The beginning and end of a frame is signaled with a special bit sequence (01111110 for HDLC). If no data is being transmitted, this same sequence is continuously transmitted so the end systems remain synchronized.
- Clock-based framing In a clock-based system, a series of repetitive pulses are used to maintain a constant bit rate and keep the digital bits aligned in the data stream. SONET (Synchronous Optical Network) is a synchronous system in which all the clocks in the network are synchronized back to a master clock reference. SONET frames are then positioned within the clocked stream.
The advantage of using frames is that data is broken up into recoverable chunks that can easily be checked for corruption. If a problem occurs during the transmission and some frames get corrupted, only the lost frames will be retransmitted, and not the entire set of data.
The usual approach and prime purpose of the Data Link Layer is to break the bit stream up into discrete frames for the purpose of Error Detection or Correction
By Louis Khim Burns
What else can I help you with?
Which OSI layer handles framing and routing?
Framing is done at the Data Link layer (Layer 2). Routing is done at the Network layer (Layer 3).
What is the role of the data link layer protocols in data transmission?
The role is to transfer frames to packets
Do frame encapsulate packet or packete encapsulate frames?
Frames are encapsulating packets. The data link layer makes framing and provide this service to the layer above layer "the network layer".
Do frame encapsulate packet or do packet encapsulate frame?
Frames are encapsulating packets. The data link layer makes framing and provide this service to the layer above layer "the network layer".
Suppose transmission channels become virtually error free.Is the data link layer still needed?
The data link layer is still needed for flow control over the transmission channel and for framing the data. In a multiple access medium such as a LAN, the data link layer is required to coordinate access to the shared medium among the multiple users.
Do frame encapsulate packet or packet encapsulate frame?
Frames are encapsulating packets. The data link layer makes framing and provide this service to the layer above layer "the network layer".
Bridge is used in which OSI layer?
Layer 2 (Data Link Layer) http://compnetworking.about.com/cs/internetworking/g/bldef_bridge.htm
Which of the following framing methods support arbitrary sized characters at the data link layer?
At the data link layer, framing methods that support arbitrary sized characters include byte-oriented protocols like PPP (Point-to-Point Protocol) and character-oriented protocols such as HDLC (High-Level Data Link Control). These methods allow for variable-length data frames, accommodating different sizes of characters or data packets. In contrast, fixed-size framing methods, such as Ethernet, are limited to specific frame sizes, making them less flexible for arbitrary-sized characters.
How data link layer works in wireless network?
In a wireless network, the data link layer manages the communication between devices over the radio frequency medium. It is responsible for framing data packets, addressing, and error detection and correction. This layer utilizes protocols like IEEE 802.11 (Wi-Fi) to handle medium access control (MAC), which ensures that multiple devices can share the same frequency without data collisions. Additionally, the data link layer establishes a reliable link by managing signal quality and retransmissions when necessary.
How a data link layer composed and how does it provide its services?
The data link layer is composed of two sublayers: the Logical Link Control (LLC) layer and the Media Access Control (MAC) layer. The LLC manages communication between the network layer and MAC, providing framing, error detection, and flow control, while the MAC layer controls how data packets are placed on and retrieved from the physical medium. It ensures proper access to the shared medium, manages addressing and encapsulation, and handles collision detection and avoidance in network environments. By performing these functions, the data link layer ensures reliable and efficient data transfer over the physical network.
Bits are packaged into frames at which layer of the OSI model?
Data link layer
Which layer is represented by frames?
The data link layer (layer 2) and the physical layer (layer 1) use the constructed frame.
