The main difference between HDLC and PPP is that HDLC is a bit-oriented protocol for communication over a point to point and multipoint links, while PPP is a byte-oriented protocol for communication over a point to point links.
HDLC is a code-transparent synchronous data link layer protocol that depends on bits. In contrast, PPP is a data link layer communication protocol that helps to establish a direct connection between two nodes. Let’s look at the difference between HDLC and PPP in more detail in this article.
Key Areas Covered
Data Link Layer, HDLC, I-frame, Multiclass PPP, Multilink PPP, PPP, S-frame, U-frame
What is HDLC
HDLC stands for High-Level Data Link Control. It is a bit-oriented code transparent synchronous data link layer protocol. The International Organization for Standardization (ISO) developed it. Moreover, it supports both connection-oriented and connectionless services.
HDLC frame consists of information, address bits, control bits and flag bits. It also has a Frame Check Sequence (FCS). Furthermore, it allows the receiver to detect errors that occurred while transmitting the frame; for example, bit losses and bit swapping. The receiver calculates FCS and checks with the sender’s FCS. If these are different, the receiver can send a negative acknowledgement to the sender. After receiving a negative acknowledgement or after a time out for a positive acknowledgement, the sender cans transmit the frame again.
Moreover, there are three types of HDLC frames. The information frame or I-frame helps to transport user data from the network layer. Also, it provides flow and error control methods. The supervisory frame or S-frame allows flow and error controlling when a station does not have data to send. These frames do not have information fields. Furthermore, U-frames allow link management.
What is PPP
PPP stands for Point to Point Protocol. It is a data link layer; a byte-oriented communication protocol. It is capable of connecting two routers directly without any host or networking device in the middle. Furthermore, the PPP frame consists of one or more bytes. It has bytes for flag, address, control, payload and FCS.
Moreover, PPP provides services such as connection authentication, transmission encryption, and compression. It is possible to use PPP over various physical networks like serial cable, phone lines, trunk lines and cellular telephone, radio links, fibre optic links (SONET). Moreover, Internet Service Provider (ISP) uses PPP for customer dial-up access to the internet.
Besides, there are various types of PPP. First, multilink PPP provides a way of distributing traffic over a set of distinct PPP connections. It avoids running multilink PPP multiple times on the same link. For example, we can use it to connect a home computer to an Internet Service Provider using two traditional 56k modems. Meanwhile, multiclass PPP allows each class of traffic using a separate sequence number space and reassembly buffer.
Difference Between HDLC and PPP
HDLC is a bit-oriented code-transparent synchronous data link layer protocol developed by ISO. But, PPP is a data link layer communication protocol used to establish a direct connection between two nodes.
HDLC stands for High-Level Data Link Control, while PPP stands for Point to Point.
HDLC is a bit-oriented protocol, whereas PPP is a byte-oriented protocol. Thus, this is the main difference between HDLC and PPP.
Moreover, another important difference between HDLC and PPP is that HDLC supports point to point and multipoint links, whereas PPP only supports point to point links.
Furthermore, there is no authentication mechanism in HDLC, while there is authentication in PPP. Hence, this is also a difference between HDLC and PPP.
Besides, HDLC cannot be used with non-cisco devices, while PPP can be used with non-cisco devices.
The main difference between HDLC and PPP is that HDLC is a bit-oriented protocol for communication over a point to point and multipoint links while PPP is a byte-oriented protocol for communication over a point to point links. In brief, HDLC is bit oriented while PPP is byte oriented.
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