1. Prepared By E.Musa Alyaman1 Networking Theory Chapter 1

2. Prepared By E.Musa Alyaman2 Chapter 1 Outline What Is a Network? How Do Networks Communicate? Network Components - Data flow - Addressing Network Layers –TCP/IP Protocol Suite Layers –OSI Layers Internet Architecture –IP Datagram format –ICMP Major protocols 1. IP 2. ICMP 3. TCP 4. UDP Security Issues – Firewalls – Proxy Servers Chapter 1 Highlights

3. Prepared By E.Musa Alyaman3 What Is a Network ? Data communication is the transfer of data from one device to another via some form of transmission medium. A Network: is a set of communication devices connected by media links.

4. Prepared By E.Musa Alyaman4 What Is a Network ? Network card – hardware needed for a computer to talk to a network. The most common network card in use is the Ethernet card Router – machines that act as switches. Direct packets of data to the next “hop” across a network Hub – provides connections that allow multiple computers to access a network Gateway – connects one network to another

5. Prepared By E.Musa Alyaman5 How Do Networks Communicate? Connections between computers and devices: 1.Wires and cables – electricity sent 2.Infrared and RF (wireless) 3.Fiber-optics cable – use light Through this connection, data is carried between one point in the network to another, data represented as bits of information (“on” or “off”)

6. Prepared By E.Musa Alyaman6 Network Components Components: message, sender, receiver, medium, and protocol.

7. Prepared By E.Musa Alyaman7 Data flow Data flow between two devices can occur in one of three ways: simplex, half-duplex, or full-duplex.

8. Prepared By E.Musa Alyaman8 Simplex

9. Prepared By E.Musa Alyaman9 Half-duplex

10. Prepared By E.Musa Alyaman10 Full-duplex

11. Prepared By E.Musa Alyaman11 Addressing Each node represented by an address just as home address Manufacturer of NIC installed in every devices connected to network is responsible to ensure that no two card carry the same address and chooses a suitable addressing scheme

12. Prepared By E.Musa Alyaman12 Addressing Commonly used term for physical address: –Hardware address –Ethernet address –MAC address –NIC address Addresses are used to send information to the appropriate node Ethernet network cards are assigned a unique 48-bit number

13. Prepared By E.Musa Alyaman13 Sending a letter

14. Prepared By E.Musa Alyaman14 Data Transmission Using Packets Data will be divided into smaller packets and sent through network to reach its destination Packets may take different routes to reach the destination depending on the routing approach and congestion level of the network Mechanism to ensure no packets lost is available depending on the protocol used to send the data

15. Prepared By E.Musa Alyaman15 Data Transmission Using Packets Packets consist of header and data segment Header contains addressing information, checksum to ensure no error and other useful information needed for transmission over the network

16. Prepared By E.Musa Alyaman16 OSI model

17. Prepared By E.Musa Alyaman17 Advantages of Layering The Advantages of layering: 1.Simplify networking protocol by breaking them into smaller and manageable 2.Offers better flexibility The protocols that make up the TCP/IP suite have been carefully designed with the following major achievement: 1.Resource sharing between networks 2.Hardware and software independence 3.Reliability and robustness 4.“Good” protocols that are efficient and simple

18. Prepared By E.Musa Alyaman18 Internet layers The five-layer model provides guidelines for the development of universally compatible networking protocols.

19. Prepared By E.Musa Alyaman19 Summary of duties

20. Prepared By E.Musa Alyaman20 Major protocols 1.Internet Protocol (IP) Layer 3 protocol (network layer) Used to transmit data packet over the Internet The most widely used networking protocol in the world All networking hardware support IP Acts as a bridge between networks of different types Packet-switching network protocol – no “connections between” machines Information exchanged between 2 host in the form of IP packets – IP datagrams

21. Prepared By E.Musa Alyaman21 IPv4 Datagram Format Back

22. Prepared By E.Musa Alyaman22 IP Address To map between a physical network address and an IP address, Address Resolution Protocol (ARP) is used Four-byte (32 bits) address expressed in dotted decimal format 192.10.1.1 Classful IP Addresses (first octet) –Class A (1 - 126) –Class B (128 – 191) –Class C (192 - 223) What are IP addresses for yahoo/google/metalab? IP address are not designed with people in mind. Imagine textual- based name vs number-based name Mechanism to associate an easy-to-remember textual name with an IP address – hostname DNS (Domain Name System)

23. Prepared By E.Musa Alyaman23 Major Protocols 2.Internet Control Message Protocol (ICMP) ICMP (RFC 792) is used by hosts and routers to communicate network-layer information –Error reporting –Router signaling One of the mechanisms to ensure Internet Protocol runs error-free since IP provides no guarantee of datagram delivery. Example: –“Destination network unreachable” is a message sent when a host with a certain IP address cannot be found. –This message originated from a router and is sent when it was not able to find a path to the host.

24. Prepared By E.Musa Alyaman24 ICMP ICMP defines five error messages 1. Destination Unreachable 2. Parameter Problems 3. Redirect 4. Source Quench 5. Time Exceeded ICMP also supports informational message: Echo Request/Echo Reply ICMP is a useful protocol, however only few network application make use of it since its functionality is limited to diagnostic and error notification Famous application is ping which is used to determine if host is alive or inaccessible and the delay between sending a packet and receiving a response

25. Prepared By E.Musa Alyaman25 Major Protocols 3.Transmission Control Protocol –Layer 4 protocol that provides guaranteed delivery and ordering of bytes –Uses IP to send TCP segments –Contains additional information that allows it to order packets and resend them if error occurs –Has extra layer of abstraction, by using a communication port –Communication port – a numerical value ( 0 – 65535) used to distinguish one application or service from another

26. Prepared By E.Musa Alyaman26 Major Protocols 4.User Datagram Protocol (UDP) –Layer 4 protocol to send packets of data –Raw access to IP datagram is not really easy to determine which application a packet is for –Supports port number –Does not guarantee delivery of packets or will arrive in the correct order –Faster data delivery but without error checking feature –Video streaming etc.

27. Prepared By E.Musa Alyaman27 TCP/IP Suite HTTPSMTPFTPPOP3 TCPUDPICMP Internet Protocol

28. Prepared By E.Musa Alyaman28 Internet Application Protocols Telnet (port 23) File Transfer Protocol (port 20 & 21) Post Office Protocol Version 3 (POP3) (port 110) Internet Message Access Protocol (IMAP) (port 150) Simple Mail Transfer Protocol (SMTP) (port 25) HyperText Transfer Protocol (HTTP) (port 80) Network News Transport Protocol (NNTP) (port 119)

29. Prepared By E.Musa Alyaman29 Firewalls for Developers Firewalls good for network administrators but not to network developers Most corporate firewalls block direct UDP and TCP access and making these protocol unusable Hence, developers must make a choice – either use standard Internet protocols and ignore user who work behind firewalls or adapt software to proxy requests using protocols such a HTTP

30. Prepared By E.Musa Alyaman30 Chapter Highlights In this chapter, you have learned: What a network is How networks transmit information using packets and addresses The layers of the OSI Reference Model The major protocols of the Internet, including the Internet Protocol (IP), Internet Control Message Protocol (ICMP), Transmission Control Protocol (TCP), and User Datagram Protocol (UDP) The effect of firewalls and proxy servers on users and developers