Linux Networking and Security

1. Linux Networking and Security Chapter 1

2. Networking Fundamentals • Explain the purposes and development of computer networking • Identify common types of networking hardware • Describe how networking software operates • Understand when popular networking protocols are used • Define network routing and describe the purpose of popular routing protocols

3. The Development ofNetworked Computers • Connecting computers and related devices in a local area network (LAN) provides: • Ability to share information instantly • Automation of data-processing tasks that involve multiple computer systems • More efficient utilization of network resources • Trends contributing to network capability • Network capability added to personal computers • Reduced cost of UNIX-based server computers • Explosive Internet growth and accessibility

4. Network Types

5. Network Types

6. Network Types • Peer-to-peer • Computers act as both client and server on the network • There is no reliance on a centralized server to provide access to data and other resources • Compared to a centralized client-server model, peer-to-peer is decentralized, meaning any host can communicate with any other host • Linux is thought of as a peer-to-peer operating system

7. Network Types

8. Creating a Network

9. Creating a Network

10. Creating a Network

11. Networking Technologies • Ethernet • Most widely used technology • Varies in transmission speed, or bandwidth • Token-ring • Uses a token to identify which computer on the network has the right to transmit data • Each workstation must be connected to a multistation access unit (MAU) • Not as fast as Ethernet, and may be more expensive

12. Networking Technologies • Fiber Distributed Data Interface (FDDI) • Reliable, but slower and costlier than Ethernet • Arcnet • Reliable, but slower token-passing technology • Asynchronous Transfer Mode (ATM) • high-speed, very reliable and very expensive used for Internet backbones • Wireless LAN (WLAN) • No cables used to connect nodes to the network • Data is transmitted via radio signals of infrared

13. Networking Technologies

14. Networking Technologies

15. Cabling a Network

16. Cabling a Network • Unshielded Twisted Pair (UTP) • made of several pairs of wires encased in plastic • Comes in six categories, with CAT 6 being the highest quality and speed • UTP is relatively inexpensive, but is susceptible to interference from other electrical signals • Shielded Twisted Pair (STP) • Similar to UTP, but includes a metallic shielding around each pair of wires • Shielding protects from electrical interference, but is more expensive than equivalent quality UTP

17. Cabling a Network • Fiber-optic • A specialized solution using light pulses rather than electrical pulses to transmit data • Extremely fast transmission speeds and is immune to electrical interference • Most secure system, but most expensive too • Coaxial Cable (coax) • Was popular, but overtaken by UTP • Used for cable modems

18. Choosing Cable • Choosing transmission media (cable) means making trade-offs between: • Cost of physical cable and its installation • Maximum and typical speed • Susceptibility to interference • Expanding the network over time (scalability) • If a legacy system (existing wiring) is present: • Consider utilization of any existing cable and its ability to handle present and future network traffic • Consider usage by intended network workstations

19. Last Mile Options

20. How Data is Transferredon a Network • Data is transferred across a network as a series of electronic or light pulses • These on/off pulses are interpreted as data, bits and bytes which are organized into packets • A packet refers to a collection of data with identifying information for network travel • Packets are different sizes based on the network type being used and are no larger than the Maximum Transfer Unit (MTU) of the network • If more than the MTU must be send, additional packets are used

21. How Data is Transferredon a Network • Each packet is organized into two parts: • The payload is the data to be transferred • The header defines how the parts of the network should handle the data • Ethernet transmits data packages using a system called contention • Throughput refers to how much payload information can be transmitted on a network

22. Network Topologies

23. Network Topologies

24. Network Topologies

25. Network Topologies

26. Connecting Multiple Networks

27. Networking Software • A network-capable operating system is required in order to use networking hardware • In networking, different tools are required for different tasks • Networking is built on a host of networking tools and mist of these tools are protocols • A protocol is a formalized set of rules for communication

28. Conceptual Modelsof Networking

29. Conceptual Modelsof Networking

30. Conceptual Modelsof Networking • The software used to maintain each protocol is often called a protocol stack • Transport layer protocols can be: • Connectionless, or stateless, which sends each packet without regard to whether any other packet was received by the destination computer • Connection oriented, or stateful, which maintains information about which packets have been correctly received by the destination computer

31. The Internet Protocol

32. The Internet Protocol

33. IP Addressing • IP works by assigning a unique address to every computer on the Internet • IP Addressing is a scheme that allows each network device to have a unique ID number • An IP address is assigned to each computer network card or network device • Each address is 32 bits long, made up of four 8-bit numbers separated by periods (dotted-quad) • Addresses have two parts: a network ID and a host ID

34. IP Addressing

35. IP Addressing

36. Broadcast and Multicast Addressing • To transmit data to every device on the network, use the broadcast address • A special IP address where the host ID is all 1’s • These types of messages are used chiefly for system administration purposes • To transmit data to multiple specific hosts, use multicasting • Used when data needs to go to a subset of the devices on the network • True mulitcasting is not supported by the Internet yet, but its use is expected to increase

37. IPv6 • Replacement to current IP version (IPv4) which is rapidly running out of addresses • IPv6 uses 128 bits per IP address • IPv6 includes these enhancements over IPv4: • Will make multicasting more workable • Allows dynamic configuration of networks • Allows routers to make more intelligent routing decisions • IPv6 requires more sophistication in the infrastructure components of the Internet

38. Transport Protocols

39. Name Services • Are Application-layer software programs that let a computer provides names in place of IP addresses, also called name resolution. • A domain name refers to a collection of computers , usually on the same network, that can be accessed using a common name • The name service used by the Internet is Domain Name Service (DNS)

40. Transmission Control Protocol • The workhorse of the Internet, in that all of the services utilized rely on TCP as their transport protocol • These include HTTP, SMTP, FTP and Telnet • TCP is connection oriented and therefore guarantees delivery of each data packet • TCP provides application transport services using ports, which are numbers that are associated with network-capable applications

41. Transmission Control Protocol

42. User Datagram Protocol • UDP provides fast, connectionless service • Provides a similar service to IP, but with addition of port numbers • Applications that use UDP include name servers and network management utilities • The UDP header includes four fields: • Source and destination ports • Message length and checksum

43. Application Protocols

44. Routing Concepts

45. Routing Concepts

46. Routing Concepts • Routers use a routing table and a routing algorithm to decide where to send packets • Routing tables consist of at least three items: • Network ID for which a route is being stored • The network interface through which the network ID can be reached • The IP address of the upstream router that handles the listed network ID • Routing tables may contain: • Routing algorithm, or engine, that determines how to process a packet sent to the router

47. Chapter Summary • Networks allow users to work more efficiently • Client-server technology assumes intelligent systems • Networking hardware sends data over transmission media, where data collections are called a packets • Network topologies (bus, star, ring) define the physical and logical layout of a network • Many types of transmission media are available • Modern networks use different layers of software to handle the different aspects of managing a network • The OSI and Internet models are two important conceptual layered models of networking

48. Chapter Summary • Networking protocols can be connection oriented (guaranteed data delivery) or connectionless • IP addressing can be defined with or without using classes, but always consist of network and host IDs • Fragmentation allows packets with different MTU sizes to be routed across intermediate networks • IPv6 will provide more addresses and many additional features (over IPv4) as it is rolled out • Broadcasting and multicasting provide special methods of sending IP packages to multiple hosts simultaneously

49. Chapter Summary • Name services convert between IP addresses and human-readable domain names • TCP, UDP and ICMP are Transport-layer protocols • Many application protocols are used as part of network-aware programs such as Web servers and email servers • Routers move packets between network segments and they maintain a routing table to identify how to reach various network IDs