TCP/IP protocol cluster Basics

TCP/IP protocol cluster BASICS (1) network interface layer: the basic layer of the model, responsible for sending and receiving data frames (frame is an independent network information transmission unit ). The Network Interface Layer places frame data on the network or retrieves frames from the network. (2) network layer: encapsulate data into IP data packets, and run necessary routing algorithms to effectively find the optimal route tree Internet Protocol IP address reaching the target host: addressing and routing packet Address Resolution Protocol ARP between the host and the network: Obtain the host hardware address in the same physical network (3) control session transmission control protocol TCP between the two hosts: it provides reliable communication connections for reference programs and is suitable for User Datagram Protocol UDP when a large amount of data is transmitted at a time: Provides connectionless communication, suitable for transmitting small data at a time (generally less than 520 bytes). reliability can be achieved by the application layer 21/tcp FTP File Transfer Protocol 22/tcp SSH Secure Login, file transfer (SCP) and port redirection 23/tcp Telnet insecure text Transfer 25/tcp SMTP Simple Mail Transfer Protocol (E-mail) 80/tcp HTTP Hypertext Transfer Protocol (WWW) DNS protocol analysis (DNS) ), DNS uses a distributed database mapped to each other by domain name and IP address, so that the easy-to-remember domain name replaces the boring IP address. A host that provides domain name resolution services to hosts over the Internet is a DNS server. DNS is based on the UDP protocol in the IP protocol and the port number is 53. Currently, DNS Distributed queries generally use recursive or recursive iterations to obtain domain names and corresponding IP addresses. (1) host A application 1 transfers data to the application layer protocol with an application layer header. If http is used, an HTTP packet is added. (2) the application layer submits the data to the transport layer, and adds the data packet header (TCP/UDP) of the transport layer based on the transport layer protocol. The information involves the port of the sender and the receiving host (3) the Transport Layer transfers data to the IP layer and adds the ip address packet header (struct iphdr), which mainly involves the original IP address and the target ip address. (4) The ip layer delivers data to the data layer and adds a data link layer packet header, which mainly includes the source MAC address and target MAC address, if it is not in the same CIDR block, it should be the next-hop MAC address.