Menoufia University Computer and Network Security Basics Lecture 2 PDF

Menoufia University Faculty of Electronic Engineering Department of Computer Science and Engineering Computer and Information Security (CSE 316) Lecture 2 Computer and Network Security Basics Presented By Dr.Marwa Sharaf...

Menoufia University Faculty of Electronic Engineering Department of Computer Science and Engineering Computer and Information Security (CSE 316) Lecture 2 Computer and Network Security Basics Presented By Dr.Marwa Sharaf el-Din Department of Computer Science and Engineering Faculty of Electronics Engineering Menoufia University 10/15/2024 1 Types of Networks The two most common types of network infrastructures are: 1. Local Area Network (LAN) 2. Metropolitan Area Network (MAN) 3. Wide Area Network (WAN). Local Area Networks (LAN) ✓ Local Area Network (LAN): An individual network usually spans a single geographical area, providing services and applications to people within a common organizational structure, such as a single business, campus or region. Metropolitan Area Networks (MAN) ✓ Metropolitan Area Network (MAN): is a group of LANs that are interconnected within small area. Wide Area Networks (WAN) ✓ Wide Area Networks (WANs): are LANs separated by geographic distance are connected by a network known as a Wide Area Network (WAN). Network Types 6 The Internet ✓ The Internet is defined as a global mesh of interconnected networks. Intranet and Extranet Connecting Remote Users to the Internet  Reference Models 10/15/2024 10 Reference Models ▪ A framework (guideline) for network implementation and troubleshooting. ▪ Divides complex functions into simpler components. Importance of reference model: ✓Vendor interoperability “standardization”. ✓Better understanding of data transfer. Reference model types : ✓Open System Interconnection (OSI). ✓TCP/IP (DOD Model) Reference Models & Interoperability problem ✓ In the mid-1980s, the network technologies that had been created with a variety of different hardware and software implementations. ✓ Each company that created network hardware and software used its own company standards. ✓ Therefore, many of the new network technologies were incompatible with each other. ✓ Need: Achieve open interconnection between multi vendors ✓ Solution : OSI-RM. OSI Model ✓ It standardizes network components to allow multiple vendor development and support. ✓ It allows different types of network hardware and software to communicate with each other. S/W ✓ It prevents changes in one layer from affecting other layers. S/W H/W ✓ It divides network communication into smaller parts to make learning it easier to understand. Protocol in Network Communication ✓ Protocol are the rules that govern communications. ✓ Protocol suite is a group of inter-related protocols that are necessary to perform a communication function. ✓ TCP/IP Model and Protocol Suite is an open standard. No one company controls it. ✓ Governed by IETF Working Groups with standards proposed using Request for Comments (RFCs). Protocol Suites and Standards ✓Early days – branded network equipment and protocols. ✓Now – Industry standards ✓Institute of Electrical and Electronics Engineers (IEEE) ▪ Develops standards in telecommunications, information technology and power generation. ▪ Examples: 802.3 (Ethernet), 802.11 (WLAN) ✓Internet Engineering Task Force (IETF) ▪ Internet standards ▪ RFCs (Request for Comments) ▪ Example: TCP, IP, HTTP, FTP OSI-RM OSI Model 17 Layer 7: The Application Layer 7 Application It’s the S\w on our pcs that is used to represent a user 6 Presentation interface to the network & 5 Session so aids the user to make 4 Transport applications. 3 Network Examples: 2 Data Link Email (SMTP,POP3) Web browsers (HTTP) 1 Physical FTP Telnet Application Layer Application Layer : Network Application HTTP , HTTPS , FTP , SMTP , TELNET , DHCP , POP3 FTP HTTP SMTP S Text POP3 Hyper Simple Male File Transfer Transfer Transfer Post Office 19 Protocol Protocol Protocol Secure Protocol Layer 6: The Presentation Layer 7 Application This layer is responsible 6 Presentation for presenting the data in the proper format. 5 Session 4 Transport Examples: ASCII, AVI,JPG,…. 3 Network 2 Data Link 1 Physical Presentation Layer Application Translation ASCII 10 MB Hello ! Presentation 72 101 108 108 111 1010111100110101 How Are U ? 32 33 32 11 72 111 119 32 65 114 101 Data Compression 32 85 32 63 32 10 3 MB 100101 21 Data Encryption SSL 011000 Secure Socket Layer Layer 5: The Session Layer 7 Application Ensure that all information required for opening a 6 Presentation session is available. 5 Session Give orders for: 4 Transport establishment, management, and termination of the 3 Network session. 2 Data Link 1 Physical Session Layer Application Presentation Server Session Computer Authentication Who Are U ? Tracking Downloading files. You don’t have Authorization A permission to access this page 29 Layer 4: The Transport Layer Responsible for actual 7 Application mechanism of: 1. Establishment of connection. 6 Presentation 2. Management of connection: 2.1) segmentation. 5 Session 2.2) sequencing. 4 Transport 2.3) end-to-end check. 2.4) error detection &correction. 3 Network 2.5) flow control. 3. Termination of connection. 2 Data Link 1 Physical Examples: TCP (Transmission Control Protocol). UDP (User Datagram Protocol). Transport Layer Application Segmentation Data Presentation Flow Control Session Error Control Port , Port , Port , Seq. Seq. Seq. Transport Data Unit Data Unit Data Unit 25 Transport Layer Application Segmentation The Speed Internet Presentation Of Server is : 150 Mbps Flow Control Session Error Control 5 Mbps Transport Computer Server 50 Mbps 26 The Speed Internet of Computer is : 5 Mbps Transport Layer Application Port , Port , Port , Segmentation Seq. Seq. Seq. Data Unit Data Unit Data Unit Presentation Flow Control Automatic Repeat Request Session Error Control Checksum Transport Port , Port , Seq. Seq. 27 Data Unit Data Unit TCP : Transmission Control Protocol UDP : User Datagram Protocol Layer 3: The Network Layer 7 Application Responsible for: 1. End-to-end delivery. 6 Presentation 2. Logical addressing. 5 Session EX: 4 Transport IPv4,IPv6,IPX,APPLETALK 3 Network 3. Routing (choose the best 2 Data Link path to destination.) EX: RIP,OSPF,IS-IS,EIGRP 1 Physical Network Layer Application Logical Address Sender Receiver IP1 IP2 Presentation Routing Path Determine Segment Session IP1 & IP2 Transport Packets 29 Network Network Layer Application Logical Address Presentation Routing Path Determine Facebook 192.168.1.8 Session 255.255.255.0 192.168.1.5 Transport 192.168.1.8 30 Network Network Network 2 Packets 1 192.168.1.7 Mobile 192.168.1.5 Laptop Network Types Application Logical Address Sender Presentation Routing Path Determine 1 Session 2 Transport 6 3 31 5 Network Receiver 4 Layer 2: The Data Link Layer 7 Application 6 Presentation Responsible for: 5 Session 1. Hop-to hop data delivery. 2. Hop-to-hop addressing 4 Transport (MAC Address in Ethernet). 3 Network 3. Hop-to-hop error detection 2 Data Link 4. Hop-to-hop flow control. 1 Physical Data Link Application MAC 1 : Sender Data Packet Presentation MAC 2 : Receiver MAC 1 MAC 2 IP 1 & IP2 Segment Tail Session Transport Frame Network Data Link 33 Layer 1: The Physical Layer 7 Application 6 Presentation It’s responsible for all 5 Session Physical properties of the 4 Transport network : 1. Cable length. 3 Network 2. Cable type. 2 Data Link 3. Bit rate. 4. Voltage levels. 1 Physical 5. H/W interface types. Physical Application Presentation Hi ! Transport Layer Session Packet Transport Sender IP Receiver IP Segment Network Layer Network Frame Data Link Sender Receiver 35 MAC MAC Packet FCS Data Link Layer 5V 1 Physical Frame Like : 10111001100110011111001010 0 Physical Convert it to : Electric Signal Layers with TCP/IP and OSI Model Compare OSI and TCP/IP model TCP/IP Model How each layer is implemented The Application Layer The Transport Layer Connection oriented, reliable service Connectionless, unreliable service The Internet Layer The Network Access Layer L2 LAN technologies : Ethernet , Tokenring , FDDI L2 WAN technologies : Point-to-Point (HDLC PPP) , Frame relay , X.25 ,ATM ARP, RARP, Proxy ARP PORTS URL Converted TO IP By DNS IP:PORT Destination PORT : 80 12.154.26.1:80 Source PORT : 35012 HTTP 80 Computer SMTP 25 SERVER FTP 21 IP:PORT Destination PORT : 35012 15.81.3.52:35012 Source PORT : 80 42 TCP vs UDP 43 TCP vs UDP 44 TCP vs UDP 45 Repeater Repeater : Regenerate incoming electrical signal In physical devices [Ethernet , WIFI]. We use repeater in distance limitation in LAN. 46 HUB 1 2 47 3 HUB 48 HUB (layer1 –physical ) 49 Bridge 50 Bridge l2 51 SWITCH(l2-datalink) 52 ROUTER(l3-networklayer) 192.168.1.0 10.2.3.0 53 Firewall 54 Firewall 55 BUS Topology 56 Star Topology 57 Ring Topology 58 Mesh Topology 59 Encapsulation Encapsulation is the process of adding control information as it passes down through the layered model. Data Link IP TCP HTTP Data Link Data Trailer Header Header Header Header Server HTTP Data Decapsulation Data Link IP TCP HTTP Data Link Data Trailer Header Header Header Header Client HTTP Data Protocol Data Unit (PDU) Protocol Data Unit (PDU) is The form that a piece of data takes at any layer. At each stage of the process, a PDU has a different name to reflect its new appearance. PDUs are named according to the protocols of the TCP/IP suite. ✓ Data - The general term for the PDU used at the Application layer ✓ Segment - Transport Layer PDU ✓ Packet - Internetwork Layer PDU ✓ Frame - Network Access Layer PDU ✓ Bits - A PDU used when physically transmitting data over the medium PDU in Peer to peer communication