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 of Networked 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

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6 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

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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 Transferred on 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 Transferred on 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 Models of Networking

29 Conceptual Models of Networking

30 Conceptual Models of 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 servers Routers move packets between network segments and they maintain a routing table to identify how to reach various network IDs