Networking and Internet 3.pdf

Networking and Internet CO1201 - Introduction to Computer Systems June 2022 Deshan Kalupahana  From the last lecture 2 Deshan Kalupahana  DNS Put all together...

Networking and Internet CO1201 - Introduction to Computer Systems June 2022 Deshan Kalupahana  From the last lecture 2 Deshan Kalupahana  DNS Put all together Web Database DHCP Internet 3 Deshan Kalupahana  DNS Put all together Web Database DHCP ISP Internet 4 Deshan Kalupahana Today’s topics Open System Interconnection (OSI) model. Network troubleshooting 5 Deshan Kalupahana  OSI Model 6 Deshan Kalupahana Before OSI Model How a courier service process a package from a ○ Source to ○ Destination 7 Deshan Kalupahana Before OSI Model Books Books Package Package Address Address Set address Check address Sender station Receiver station Sending Receiver airport Sender airport 8 Deshan Kalupahana Before OSI Model Books Books Package Package Address Set address Address Check address Sender station Intermediate station Receiver station Sending Sending Intermediate airport Receiver airport Sender airport 9 Deshan Kalupahana  Before OSI Model Books Books Package Package Address Set address Address Check address Sender station Intermediate station Receiver station Sending Sending Receiver port Sender airport 10 Deshan Kalupahana  Before OSI Model Books Intermediate station Package Address Set address Address Sender station Sender airport Transit 11 Deshan Kalupahana  OSI model Describe a procedure to communicate computer systems over a network. It consist of seven layers. Categorizes the functionality of the network. 12 Deshan Kalupahana  OSI Model Sender / Receiver / source Destination Data reception Data transmission 13 Deshan Kalupahana  OSI Model : Physical layer Physical connection between devices. 1. Wired Copper coaxial cable Copper twisted pair Unshielded twisted pair (UTP) Shielded twisted pair (STP) Optic fiber 2. Wireless Radio waves With different frequencies. 14 Deshan Kalupahana  OSI Model : Data Link Layer Handles device to device communication. Data in frame format. Data exchange using MAC address of the devices. ○ Media Access Control Devices ○ Layer 2 switches. 15 Deshan Kalupahana  OSI Model : Network Layer Handles source to destination communication The IP Addresses are handled in this layer. ○ Uses Internet Protocol (IP) Data is in packet format. Data is routed based on IP address. Devices ○ Routers ○ Layer 3 switches. 16 Deshan Kalupahana  OSI Model : Transport Layer Handles the communication within applications. TCP and UDP ared used. ○ Transmission Control Protocol (TCP) ○ User Datagram Protocol (UDP) Data is in segment format. Application layer data are divided into segments in the transport layer. 17 Deshan Kalupahana  Transport Layer A port number is assigned at this layer ○ To identify the application running on the device. Port number Service/ Application 80 HTTP 443 HTTPS 20 FTP - (File Transfer Protocol) 53 DNS 67/68 DHCP 25 SMTP (Simple Mail Transfer Protocol) 22 SSH (Secure Shell) - For remote login 18 Deshan Kalupahana  Transport Layer : Eg: - ○ 192.168.1.10:80 -> HTTP request ○ 10.24.25.6:22 -> SSH request 19 Deshan Kalupahana  OSI Model : Last Layers Session Layer ○ Handles the session for an application. ○ Eg: Keep user login for certain period of time. Presentation Layer ○ Convert data to visible format by the application layer. ○ Eg: Convert set of text in HTML to viewable format in a web browser. Covert set of data to view in a video game. Application Layer 20 Deshan Kalupahana  OSI Model: Application Layer User directly interacts with program in application layer. Eg:- ○ Access Facebook via Web browser. ○ Upload a file to dropbox. ○ Playing an online video game. 21 Deshan Kalupahana  OSI Model : Upload a File Sender / Receiver / source Destination File File Segments Segments Packets Packets Frames Frames....0101010111.... Bit stream Bit stream 22 Deshan Kalupahana  OSI Model : Conversion of Payload 23 Deshan Kalupahana  OSI Model : Conversion of Payload 24 Deshan Kalupahana  OSI Model : Example 192.168.1.100 /24 192.168.2.100 /24 25 Deshan Kalupahana  OSI Model : Example 192.168.1.100 /24 192.168.2.100 /24 192.168.1.254 /24 192.168..254 /24 26 Deshan Kalupahana  Try to map Books Intermediate station Package Address Set address Address Sender station Sender airport Transit 27 Deshan Kalupahana  Network Troubleshooting 28 Deshan Kalupahana  Basic Commands ipconfig ping nslookup tracert 29 Deshan Kalupahana  ipconfig Retrieve network interface(s) information. ○ IP address ○ Network mask ○ Default gateway ○ MAC address ○ DNS addresses 30 Deshan Kalupahana  Ipconfig / ifconfig 31 Deshan Kalupahana  ping Check the connectivity with other device. ping host_ip_address or URL Example ○ ping 192.168.1.100 ○ ping www.google.com ○ ping localhost (ping to the same device) 32 Deshan Kalupahana  ping 33 Deshan Kalupahana  nslookup DNS resolution Can retrieve IP address for a given domain name. nslookup domain_name Eg: ○ nslookup sjp.ac.lk 34 Deshan Kalupahana  nslookup 35 Deshan Kalupahana  tracert / traceroute Displays the packet routing path. Shows only devices working with Network Layer. tracert URL or IP address. Eg: ○ tracert www.google.com ○ tracert 8.8.8.8 36 Deshan Kalupahana  tracert 37 Deshan Kalupahana  This lecture OSI Model ○ 7 layers Network troubleshooting ○ ipconfig ○ ping ○ nslookup ○ tracert 38 Deshan Kalupahana  Next Lecture Computer Security ○ Network Security ○ System Security 39 Deshan Kalupahana