Computer network learning notes (1)

For the following information, refer to "Computer Network (5th )".

I. Development of Computer Networks

1. "Three networks": telecom network, cable TV network, and computer network. Among them, the fastest growing core is the computer network

2. The network is composed of several nodes and links connecting these nodes.

3. The Internet is the "network", and the Internet is the largest Internet (Internet) today)

4. Host host, not just a computer.

Note the differences between the node and the node, although all are translated by node.

Note the differences between Internet and Internet

 

Three stages of Internet development:

1) The development from a single network ARPANET to the Internet became a standard protocol on ARPANET in 1983.

2) the second stage is characterized by the establishment of a three-level Internet

3) The third stage is characterized by the gradual formation of a multi-layer ISP-structured Internet

The formal Internet standards include the following four phases:

1) Internet Draft (internetdraft)-This stage is not yet an RFC document.

2) recommended standard (proposedstandard)-from this stage to become an RFC document.

3) Draft Standard)

4) Internet standard (internetstandard)

 

Note: RFC documentation in Section 6

 

Internet:

 

1) The edge part consists of all hosts connected to the Internet. This part is directly used by users for Communication (Transfer Data, audio or video) and resource sharing.

(2) The core part consists of a large number of networks and routers connected to these networks. This part provides services for the edge part (providing connectivity and exchange ).

 

Note: Computer Communication mainly refers to the communication between programs on different computers.

At the edge of the Internet is all hosts connected to the Internet. These Hosts are also called end systems)

 

The communication methods between programs running in the end system at the edge of the network can be divided into two categories:

1) customer/Server mode: C/S mode, emphasizing customer service and Server

 

2) peer-to-peer connection mode: P2P mode, which does not distinguish between customer service and server. Each communication Party is equivalent. It can be either a server or a customer.

 

Note: both the client and server are the two application processes involved in the letter.

Ii. Classification of computer networks

1. Definition of Computer Network

There is no precise definition of computer networks.

A simplest definition: a set of interconnected and autonomous computers. Note that autonomy here refers to an independent computer with its own hardware and software, which can be used separately.

2. There are many computer network types, and there is no unified classification method. The following is a simple classification from two perspectives.

 

By "size", that is, the size (scale), that is, the scope of the action

 

1. Wan)

 

2. Man)

The most famous man is a cable TV network.

 

3. Lan)

A private network, typically inside or near a building, such as a home, office, or factory. Lan is widely used to connect PCs and electronic consumer products so that they can share resources (such as printers) and exchange information. When a LAN is used by a company, it is called an enterprise network.

 

Expansion: Lan can be further divided into wireless LAN and wired LAN.

One standard of a wireless LAN is IEEE 802.11, commonly known as WiFi. Most wired LAN uses copper wires as transmission media, and many optical fiber cables are used now, IEEE 802.3, commonly known as Ethernet, is the most common wired LAN so far. Compared with wireless LAN, wired LAN outperforms all of them in terms of performance, because it is easier to send signals through wires or optical fiber cables than to send signals through air.

 

4. Personal Area Network (PAN), with a range of about 10 MB, allows devices to communicate around one. For example, connect a peripheral electronic device to a computer via wireless connection, for example, connect a mobile phone to a computer via Bluetooth. Pan can also be built using other short-range communication technologies.

 

 

 

By user

Public Network: pay-as-you-go, also known as public network

Private Network: a department or industry that is built for a special job and does not provide external services

 

Computer network performance indicators

1. Speed

 

The rate at which data is transmitted over a channel, also known as the data rate or bit rate.

Note: The rate is rated or nominal.

2. bandwidth

The bandwidth in the communication is the bandwidth of the signal, in Hz, etc.

Bandwidth on the computer network refers to the maximum data rate

 

3. Throughput

Throughput indicates the data volume of a network (or channel or interface) per unit time.

Throughput is limited by the bandwidth of the network or the rated rate of the network.

 

4. latency

Total latency = transmission latency + propagation latency + Processing latency + queuing latency

 

Note: For high-speed network links, we only increase the data transmission rate rather than the bit transmission rate on the link. Therefore, optical fiber transmission speed is faster, rather than faster transmission speed (lower than copper wire)

 

5. latency bandwidth product

 

Latency bandwidth product = transmission latency * bandwidth

The meaning is: the amount of data that has not reached the destination in the Link Channel

6. Utilization

1) The channel utilization rate indicates that a channel is used for a period of several percent (with data passed ). The usage of completely idle channels is zero.

2) network utilization is the weighted average value of channel utilization across the network.

Note: high channel or network utilization may cause a large latency.

 

 

 

 

Computer network learning notes (1)