1. HTML 2 as the text markup language for pages. HTTP as the Document delivery protocol 3. Uniform Resource Locator (URL) that specifies the URL where the document locates WWW is the name of the client application used by Web browsers to browse hypertext. It is now used to refer to the collection of these series, also known as Web for short. The TCP/IP protocol family is divided into four layers: application layer, transport layer, network layer and data link layer. 1. Application layer: The application layer determines the communication activities when providing application services to users. Including FTP, DNS, and HTTP 2. Transport layer: The transport layer transfers data between two computers connected to the network. At the transport layer, there are two different protocols: Transmission Control Protocol (TCP) and User Data Protocol (UDP). 3. Network layer (also known as network interconnection layer) : The network layer is used to process packets flowing across the network. A packet is the smallest unit of data transmitted over a network. This layer defines the path (the so-called transport route) through which the packets are sent to each other’s computers. 4. Link layer (also known as data link layer, network interface layer) : It deals with the hardware part of the network. ** Example diagram of client and server communication:

Byte stream serviceByte Stream Service (Byte Stream Service) divides a chunk of data into data packets for easy transmission.Five, three-wayhandshakingAfter sending a packet using TCP, TCP does not ignore the situation after transmission. It must confirm whether the packet was successfully delivered to the other party. The TCP flag is used during the handshakeSYN(the synchronize) andACK(acknowledgement). The sender first sends a packet with the SYN flag to the peer. After receiving the packet, the receiving end sends a packet with the SYN/ACK flag to confirm the packet. Finally, the sender sends back a packet with an ACK flag, indicating the end of the handshake. If the handshake is interrupted, the TCP protocol sends the same packets in the same order again.

Vi. The relationship between various protocols and HTTP protocol:

                               

7. A URI is a locator identifier of a resource represented by a protocol scheme. A protocol scheme is the name of the protocol type used to access the resource.