Chapter 2 OSI reference model and TCP/IP model (continued)

Chapter 2 OSI reference model and TCP/IP model (continued)
3. TCP/IP model 3.1 the hierarchical network layer of TCP/IP is a key part of the TCP/IP system. Its main function is to enable the host to send information to any network and send it to the correct target. The network layer uses IP addresses to identify network nodes. The routing protocol is used to generate route information, and packet forwarding is implemented based on the routing information, so that packets can be accurately transmitted to the destination: use protocols such as ICMP and IGMP to help manage networks. The TCP/IP network layer functions very similar to the network layer. IGMP (Internet Control Message Protocol) is also considered as a network layer Protocol. ICMP provides management and control functions for IP networks through a set of predefined information transmitted over the Internet. A typical application of ICMP is to test the accessibility of IP networks. The transport layer provides end-to-end connections for applications on two hosts, enabling peer entities on the source and target hosts to perform sessions. The transport layer protocols in the TCP/IP protocol family mainly include TCP and UDP. TCP is connection-oriented, which ensures reliable transmission between the two ends of the communication and supports recovery in disorder, error retransmission, and traffic control. While UDP is connected, it provides non-reliability data transmission, and the reliability of data transmission is ensured by the application layer. The Application Layer TCP/IP model does not have a separate session layer and presentation layer, and its functions are integrated in the TCP/IP application layer. The Application Layer directly deals with users and applications, and provides interfaces to the software to enable the program to use network services. Network services include file transmission, file management, and email message processing. Typical application layer protocols include Telnet, FTP, SMTP, and SNMP. Network Interface Layer typical network interface layer technologies include common LAN technologies such as Ethernet, FDDI, and card ring. They are used for SLIP, HDLC, and PPP Technology for serial connection, and common Packet Exchange technologies such as X.25, frame relay, and ATM.