First, the layer-4 protocol is defined as follows:
The fourth layer, application layer:
Application layer and the layer of the OSI reference model expression corresponds.
Internet application layer protocol comprises Finger, Whois, FTP (File Transfer Protocol), Gopher, HTTP (hypertext transfer protocol), Telent (Remote Terminal Protocol), the SMTP (Simple Mail Transfer Protocol), the IRC (Internet relay session), NNTP (network News transfer protocol), etc.
The third layer, the transport layer:
Transport layer corresponds to the transport layer of the OSI reference model, which provides two-end communication services.
In which the TCP protocol (Transmission Control Protocol) provides reliable stream transport service, UDP protocol (Use Datagram Protocol) provides unreliable datagram service user.
A second layer, network layer:
The network layer corresponds to the network layer of the OSI reference model. Responsible for packaging, addressing and routing data. It also includes Internet Control Message Protocol (Internet Control Message Protocol, ICMP) is used to provide network diagnostics information.
Protocol: This protocol contains an IP layer, RIP protocol (Routing Information Protocol, Routing Information Protocol), ICMP protocol.
The first layer, network interface layer
Network interface layer comprises a cooperative protocol IP data transmitted over the existing network media for.
Protocols: ARP, RARP
Two, seven protocol is defined as follows:
┌───────┐
│ │ ← seventh layer application layer
├───────┤
│ presentation layer │
├───────┤
│ session layer │
├────── ─┤
│ transport layer │
├───────┤
│ network layer │
├───────┤
│ data link layer │
├───────┤
│ │ ← a first physical layer layer
└───────┘