Communication method between hosts
- Client-Server (C/S): The client is the requester of the service, and the server is the provider of the service.
- Peer-to-peer (P2P): Does not distinguish between clients and servers.
Circuit switching and packet switching
1. Circuit Switching
Circuit switching is used in telephone communication systems. Before two users want to communicate, a dedicated physical link needs to be established, and the link is always occupied during the entire communication process. Since the transmission line cannot be used all the time in the communication process, the utilization rate of circuit switching on the line is very low, often less than 10%.
2. Packet switching
Each packet has a header and a tail, containing control information such as source address and destination address. The simultaneous transmission of multiple packets on the same transmission line will not affect each other, so multiple packets are allowed to be transmitted simultaneously on the same transmission line, that is Said packet switching does not need to occupy the transmission line.
In a post office communication system, after the post office receives a mail, it first stores it, and then forwards the mails of the same destination to the next destination together. This process is the store-and-forward process, and packet switching also uses the store-and-forward process.
Computer network performance index
- Rate: refers to the transfer rate of data, also known as data rate or bit rate, the unit is bit/s (b/s or bps);
- Bandwidth: In a computer network, the network bandwidth represents the "highest data rate" that a channel in the network can pass in a unit of time;
- Throughput: represents the actual amount of data passing through a certain network (or channel or interface) in a unit of time;
- Latency: Refers to the time required for data to be transmitted from one end of the network to the other end. Including transmission delay, propagation delay, processing delay and queuing delay;
- Delay bandwidth product: Delay bandwidth product = propagation delay * bandwidth;
- Round trip time RTT: the time required for a two-way exchange of information on the Internet;
Computer network architecture
- Application layer: specific network applications are completed through the interaction between application processes. The protocols of the application layer are http, https, ftp, etc.
- Transport layer: Responsible for providing general data transmission services for the communication between processes in two hosts. The transport layer has two protocols, TCP and UDP. TCP provides connection-oriented and reliable data transmission services. The unit of data transmission It is a message segment, UDP provides a connectionless, best-effort data transmission service
- Network layer: Responsible for providing communication services for different hosts on the packet switching network
- Data link layer: Determine a link
for data transmission between two hosts, and provide communication services. - Data link layer: Determine a link for data transmission between two hosts
- Physical layer: consider how to transmit the data bit stream on the transmission medium