What is the Use of HDLC Protocol?


Category: Computer Network

What is the Use of HDLC Protocol?

If you are unfamiliar with HDLC protocol, you might be confused about its uses and benefits. HDLC protocol uses a standard pattern to mark each frame. This pattern is confusing for the receiver, which is why it uses a technique known as bit stuffing. The method involves adding a zero after five consecutive ones. This is done to avoid a problem called the transparency problem. HDLC uses full duplex communication, a flow control mechanism, physical layer clocking, and synchronization.


HDLC is a high-speed transmission standard developed by IBM. The HDLC protocol is a variant of the SDLC protocol. It uses bit-stuffing as a key to avoid signal corruption. After the start flag, the transmitter inserts an extra 0 bit after five consecutive ones. The receiver performs the inverse function, monitoring the bit stream after a start flag. If the sixth bit is zero, the receiver deletes it.

The HDLC protocol also prevents bit-stuffing by limiting the number of consecutive bits with the same value. The procedure is implemented by creating a lookup table of 256 locations and addressing each of them with 8 incoming bits. The table’s locations are listed in Appendix B. They include the bit-stuffing flag, an abort flag indicator, reception shift data, and start/stop flag indicator. The variables are redundant, but the inclusion of them eases implementation.

HDLC protocol can handle bit-stuffing and frame stuffing. The process is similar to byte-stuffing, with the receiver inserting an escape byte into the outgoing character stream. It’s completely transparent to the network layer and is often used in networks where the incoming data is duplicated. It’s important to note, however, that this method is not suitable for all situations.

HDLC is a synchronous serial line, and it’s faster than its asynchronous counterparts. It uses a technique known as bit-stuffing, whereby a transmitting side inserts a 0 every time 5 consecutive ones are transmitted. The receiver then makes a decision based on the next bit it receives. If the receiver sees a stuffed bit, the corresponding change is in the frame.

In this procedure, the transmitting unit adds a prestored sequence of bits to queue D. For example, if an RNB value is 11.111, it will be added to queue D in the next cycle. In this way, bit-stuffing with HDLC protocol requires additional data storage capacity. If the transmitting unit does not have enough space, it will perform the corresponding operations.

Error control

The HDLC protocol is a standardized protocol used to transfer data over wireless networks. It provides an extended address field, which is one or more bytes long, as well as error control features. HDLC frames contain a Frame Check Sequence, which enables high levels of physical error control and allows transmission of frame data that is deemed to be valid. HDLC frames are also made up of one or two bytes of information, called bytes.

HDLC frames are transmitted over both asynchronous and synchronous serial links. In both cases, the data is encoded to avoid flag sequences within the frame. The frame delimiter, or flag bytes, is unique for each frame, and may mark the beginning or end of the next frame. In synchronous and asynchronous links, this delimiter is binary “01111110”.

Each HDLC frame contains data and control information. I-frames contain the first bit of the control field (0), which is reserved for system management. HDLC frames exchange error control information between communicating devices. HDLC frames can contain up to six fields, including a beginning flag field, a destination address field, a control field, information, and a frame check sequence (FCS).

High-Level Data Link Control is a synchronous data-link layer protocol that uses bit-oriented code. It was developed by the International Organization for Standardization (ISO) and standardized as ISO/IEC 13239:2002. It is also a major transport protein for cholesterol in the body. It is believed to protect the body from a variety of diseases by transporting cholesterol from the arteries to the liver.

HDLC is a synchronous communication protocol at the Data Link Layer in the Open Systems Interconnection (OSI) reference model. HDLC allows for data-transmission transparency, error detection, and flow control. HDLC also helps manage the pace of data transmission. Its usage in data-link networks is widely accepted, and it is commonly used in a data link network. This protocol is commonly used in the OSI model layer.

Flow control

HDLC protocols use synchronous serial transmission, which means that there is no way for any error to occur during the transmission of the data. In HDLC protocol, the information frame consists of a header and user data, and it also has a frame check sequence (FCS), which is a result of a mathematical computation performed at the sending and receiving side of the link. The FCS frame indicates whether any bits in the transmission have changed, which indicates an error.

A frame sent through HDLC has a source address and a destination address. The frame can be one or several bytes in length, depending on the requirements of the network. The HDLC protocol has two distinct types of frames: supervisory and piggyback. The former enables error control, while the latter is more suitable for flow control. The latter contains a set of features that may vary from device to device.

HDLC supports multi-protocol environments. Each HDLC frame may contain up to seven fields. The header contains a starting flag, an address field, a control field, information, and a frame check sequence. Some Cisco devices have an additional protocol field. The format of this frame is described in the following table:

The HDLC protocol is a bit-stream communication protocol that uses an embedded 32-bit CRC byte for error correction. Frames are composed of a flag byte, control information, and data bits. The CRC byte is used to detect errors in the data. In addition to this, the HDLC protocol has a sliding window that allows a transmitter to transmit until its window is full. This option is faster and more flexible than the former.

HDLC protocols support full and half duplex communication lines. They are also designed for point-to-point networks. They provide code-transparent data transmission. HDLC supports three types of frames, and the control field in each frame determines which type of message is transmitted. In the supervisory mode, the primary station can respond to the secondary station, while the HDLC protocol uses two types of frames. Its data transfer protocol is the preferred choice for many applications.


HDLC is a bit-oriented, network-layer protocol that uses a control field that has bits that are used to stuff flags. Its first bit in the control field is always 0, and it is mostly used for system management. HDLC frames have up to six fields: start flag, address, control, information, and frame-check sequence. There is also a control field in the header that indicates what the protocol is doing.

This protocol is very easy to configure and use. The encapsulation command sets the interface to HDLC. HDLC is set as the default on serial interfaces, but you can also manually change this setting. HDLC is not as flexible as PPP, however. PPP supports many advanced features that HDLC doesn’t. It supports both PAP and CHAP authentication. In addition, it can carry multiple layers of data simultaneously.

HDLC is one of the most widely used internet protocols. It’s part of the Layer 2 industry communication reference model. Layer 1 is a physical level, while Layer 3 is higher level knowledge about networks. HDLC encapsulates Layer 3 frames and adds data link control information. This way, security is guaranteed even between devices that are thousands of miles apart. HDLC is a secure protocol, which has many benefits. It also provides full-duplex communication.

HDLC uses a bit-stream protocol called a header. It uses a 32-bit checksum to correct error messages. HDLC frames consist of a flag byte, address, and control information. The header includes a CRC byte. HDLC works in a full-duplex mode, which means that data can be transmitted and received continuously without waiting for acknowledgement. It also provides a flow control mechanism and physical layer clocking.

Despite its name, HDLC supports authentication via PPP. The protocol also supports CHAP authentication. PPP authentication, on the other hand, is not supported by non-cisco devices. Its underlying protocol is Link Control Protocol (LCP), which provides dynamic addressing. The protocol uses the PPP encapsulation to avoid compatibility issues. In addition, PPP does not have a mechanism for error detection.

Leave a Comment