1. Transmission Control Protocol (TCP) Internet Protocol (IP)

2. Network Layers The communication process that takes place over a network is made up of a series of different layers. The TCP/IP protocol stack is generally considered to be made up of four layers. The TCP/IP Protocol Stack Applications Transport Network Data Link TELNET, FTP, Email, SMTP, POP3 & We b browsing (HTTP) Transmission Control Protocol (TCP) Internet Protocol (IP) Device driver and interface card Four layers of the TCP/IP control stack

3. The TCP/IP protocol stack TELNET Client Web Browser Application Layer TCP Layer Port No: 1045 TCP Layer Port No: 1035 Network or IP Layer: 195.112.56.7 210.34.56.78 Link Layer: 12-4D-6A-22-75-A2 16-88-6F-22-35-BB TELNET Server Web Server TCP layer Port no 23 TCP layer Port no 80 Network or IP Layer: 210.34.56.78 195.112.56.7 Link Layer 16-88-6F-22-35-BB 12-4D-6A-22-75-A2 Gateway Router Network Gateway Physical Layer IP: 195.112.56.7 IP: 210. 34.56.78 Transport Layer Network Layer Physical Link Layer

4. 1. Application Layer This layer deals with the particular network application: - Hypertext Transfer Protocl (HTTP) - File Transfer Protocol (FTP) - Simple mail Transfer Protocol (SMTP) -Simple Network Management Protocol (SNMP) -Domain Name System (DNS) -TELNET The TCP/IP Protocol Stack TELNET Client Web Browser Application Layer TELNET Server Web Server IP: 195.112.56.7 IP: 210. 34.56.78 Encodes data into a format that can be understood.

5. 2. Transport Layer The ‘end to end principle’ of the Internet means that the two end points (the hosts) are responsible for establishing, supervising and maintaining the connection. The TCP/IP Protocol Stack Transport Layer TCP Layer Port No: 1045 TCP Layer Port No: 1035 TCP layer Port no 23 TCP layer Port no 80 TCP Software IP: 195.112.56.7IP: 210. 34.56.78

6. 2. Transport Layer Splits the data to be sent into packets. Identifies each data packet with an order number. Acknowledges receipt of packets Resends packets if they are not acknowledged. Provides either a reliable or unreliable connection from host to host, depending on which protocol is being used. Designates a port number The TCP/IP Protocol Stack What is its main purpose?

7. 2. Transport Layer The TCP/IP Protocol Stack Ports TCP Software IP: 195.112.56.7IP: 210. 34.56.78 Ports When connections are made ports are allocated to provide different services. These ports are in the range of 1024 - 4095 Port 80: Web Server Port 23: TELNET server The combination of IP address and port number is known as a socket

8. 3. Network Layer The TCP/IP Protocol Stack Network or IP Layer Passed down from the TCP/IP layer, the ‘network’ layer is responsible for addressing the packets: Source IP address Destination IP address The packets are then passed down to the ‘data link’ layer The reverse process also happens with the data link layer passing packets to the network (IP) layer.

9. 4. Data Link Layer The TCP/IP Protocol Stack Received from the network layer, the ‘data link’ layer adds source and destination hardware addresses to packets. It then despatches the packets onto the local cable. In an Ethernet Local area network (LAN) hardware addresses are Ethernet card addresses or Media Access Control (MAC) addresses. These addresses would have to include the address of the gateway, which links the host to the Internet. Link Layer

10. Data What does a packet look like? Data Source MAC Address: 00:30:BD:19:OB:09 Gateway MAC Address: 00:30:BD:19:OB:09 Source IP Address: 195.112.56.7 Source IP Address: 210.34.56.78 Source Port No: 1045 Destination Port No: 1 Data Link Layer IP TCP Packet Sequence No: 1 (An Ethernet frame contains an IP packet, a TCP packet and payload data) (Encapsulation)