Computer Network Reading Notes (1)

The computer network referred to here is Andrew S. tanenbaum's "Computer Networks" fourth edition, which had been roughly read once before, now it's time to study again and take some notes by the way.
A computer network is a set of independent computers connected by the same technology. So neither Internet nor WWW is a computer network, and WWW is a distributed system. In addition, pay attention to the differences and relationships between computer networks and distributed systems. In fact, distributed systems are software systems built on networks. Therefore, distributed systems have a high degree of cohesion and transparency. Therefore, the difference between the two lies in software (especially Operating Systems) rather than hardware.
B2C = business-to-consumer
Currently, two types of transmission technologies are widely used: 1. Broadcast-based connections (including broadcast and Multicast) and 2. Point-to-point connections (also called unicast ). The topological structure of a broadcast LAN can be divided into 1. bus Type (eg. ethernet is a non-centralized, bus-based broadcast network. ring Type (eg. the 802.5ibm licensing ring is a ring-based LAN, and FDDI is also used .) Man is composed of a LAN and a resource subnet (including a router and a transmission line.
A protocol is an agreement between the communication parties on how to communicate. Three elements of the Protocol: syntax, semantics, and time sequence (Time when the data should be transferred or retrieved by the receiver, information sorting, rate matching, etc ). The architecture refers to the hierarchy of computer communication networks, the set of protocols and interfaces between layers. The bottom three layers of the OSI model are in parallel, and the top four were in series. The formats of transmitted data are bit-> frame-> group-> tpdu-> spdu-> ppdu-> APDU.
Connection-oriented network: 1. x.25 and Frame Relay: In 1980s, frame relay was essentially a connection-oriented network without error control, flow control, and connection, therefore, the group will be submitted according to the sending order, which is very similar to a wide-area lan. The most important application is to connect the LAN in multiple office areas of the company. 2. ATM (Asynchronous Transfer Mode asynchronous transmission mode): ATM is widely used in telephone systems and is usually used for IP group transmission. Now it is mainly used for internal transmission.
802.1 LAN overview and architecture
802.2 Logical Link Control
802.3 Ethernet
802.4 Token Bus (temporarily used in the manufacturing industry for a while)
802.5 licensing ring (a technology IBM entered the LAN field)
802.6 dual-queue bus (early man)
802.7 Technical Consultation Group on Broadband Technology
802.8 Technical Consultation Group on Optical Fiber Technology
802.9 synchronous LAN (for real-time applications)
802.10 Virtual LAN and security
802.12 requirement priority (Hewlett-Packard's anylan)
802.13 unlucky figures, no one is willing to use them.
802.14 wired modulator (abolished)
802.15 personal region Network (Bluetooth)
802.16 Broadband Wireless
802.17 elastic grouping Ring