Data link Layer overview of computer network--Data link layer using point-to-point channel and three basic problems

1. Data link and frame.

(1) A link is a physical line between two adjacent nodes . When data needs to be transmitted on a single line, some communication protocols are needed to control the data, and the hardware and software that implement these protocols are combined with the physical lines to form the data link. The way to do this is for example a network adapter.

(2) frame is when the network layer down the IP datagram, the data link layer to the IP datagram encapsulation, that is, plus the header and tail, also constitute a frame.

2. Three basic questions

(1), packaged into frames.

Plus the header and the tail. A significant function of the first and the tail is to frame the bounding, so that the receiver can know the part of a frame. The first frame delimiter is the SOH, and the hexadecimal encoding is 0x01. The trailing frame delimiter is EOT, and hexadecimal encoding is 0x04. Next there is the maximum Transmission Unit MTU, which is the upper limit of the data part length.

(2), transparent transmission

Transparent transmission refers to a frame in which a text file consists of any character that can be transferred from the keyboard, regardless of the type of input. However, when the data section is a control character, it is necessary to precede the control character with the ESC character, which is hexadecimal encoded as 0x1b.

(3), error detection

　　　　　　

Data link Layer overview of computer network--Data link layer using point-to-point channel and three basic problems