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NT1210 Introduction to Networking

NT1210 Introduction to Networking. Unit 9: Chapter 9, The Internet. Objectives. Identify the major needs and stakeholders for computer networks and network applications. Identify the classifications of networks and how they are applied to various types of enterprises.

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NT1210 Introduction to Networking

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  1. NT1210 Introduction to Networking Unit 9: Chapter 9, The Internet

  2. Objectives • Identify the major needs and stakeholders for computer networks and network applications. • Identify the classifications of networks and how they are applied to various types of enterprises. • Explain the functionality and use of typical network protocols. • Analyze network components and their primary functions in a typical data network from both logical and physical perspectives. 2

  3. Objectives • Differentiate among major types of LAN and WAN technologies and specifications and determine how each is used in a data network. • Explain basic security requirements for networks. • Plan and design an IP network by applying subnetting skills. • Assess a typical group of devices networked to another group of devices through the Internet, identifying and explaining all major components and their respective functions. 3

  4. Objectives • Relate how different technologies are used to access the Internet. • Define how IP routing is used in the Internet to move data from source to destination. • Define classless routing. • Evaluate the need for NAT, PAT, CIDR, and IPv6 in current networks. 4

  5. The Internet as a Network of Networks Internet Access Links from TCP/IP Networks, Large and Small Figure 9-1 5

  6. The Internet as a Network of Networks • Internet Service Providers (ISPs) create Internet core • Creates physical network for IP packets to travel between enterprises and individual users The Internet Core, with Multiple Service Providers Figure 9-2 6

  7. The Internet as a Network of Networks • Connecting enterprises Typical Organizations Whose TCP/IP Networks Connect to the Internet Figure 9-3 7

  8. The Internet as a Network of Networks • Connecting to Internet edge: Part of Internet topology between ISP and customer (sits at edge of both networks) Comparing an Enterprise and ISP Network Figure 9-4 8

  9. The Internet as a Network of Networks • From network layer perspective: Internet access link acts like any other WAN link between routers T3 Serial Link Connection to the Internet Figure 9-5 9

  10. The Internet as a Network of Networks • Securing Internet edge: Enterprises use many security measures and devices to make Internet connection more secure • Firewalls • Intrusion Prevention Systems (IPS) • Example: Firewall sits in path that all packets take; IPS sits outside path so LAN switch forwards packets to IPS and it analyzes packets and watches for signs of problems An Example Case of Using an Enterprise Firewall and IPS Figure 9-6 10

  11. The Internet as a Network of Networks • Typical rules for enterprise firewall • (Default): Allow inside clients to reach outside servers in Internet • (Default): Disallow outside clients from sending packets to inside servers, unless another rule allows packet • (New Rule): Allow outside clients to connect to the two public web servers in DMZ • Example: Two attempts from users in Internet to connect to two different servers in enterprise Firewall Allowing Connections to Public Web Servers Only Figure 9-7 11

  12. The Internet as a Network of Networks • Each WAN technology creates connection between user’s device and ISP • WAN connection might connect user’s device directly to WAN or may use router (not shown in example) Four Main Options for Individual Internet Access Figure 9-8 12

  13. The Internet as a Network of Networks • Connecting Customers to ISP Point-of-Presence (PoP): Each ISP has to create connections • Connections between ISP’s customers and ISP PoP • Connections between all ISP’s PoPs create ISP’s own network and allow all of customers to send packets to one another • Connections to other ISP networks form Internet core which allows all Internet hosts everywhere to send packets to each other • To create effective Internet access service, ISP needs number of PoPs in different locations ISP Point-of-Presence (PoP) Concept with Customer Access Figure 9-9 13

  14. The Internet as a Network of Networks • Example: Typical PoP with access routes using direct link to distribution router which connects to rest of ISP’s network Example of Dividing Responsibilities Inside an ISP PoP Figure 9-10 14

  15. The Internet as a Network of Networks • Connecting PoPs to create ISP network example • ISP might put two more routers at centralized site and use 10-Gbps Ethernet or SONET equivalent (called OC-192) on all links (center of graphic) Connecting All ISP PoP Routers to Create an ISP TCP/IP Network Figure 9-11 15

  16. The Internet as a Network of Networks • ISPs work together to create Internet core • Internet core connects all ISPs to all other ISPs (sometimes directly; sometimes indirectly) • Result: All ISPs can send packets to hosts connected to every other ISP Creating the Internet Core: Connections Between Large ISPs Figure 9-12 16

  17. The Internet as a Network of Networks • Tier 2 ISPs rely on connections to Tier 1 ISPs for some of their connections to Internet • Tier 2 ISPs connect to one or more Tier 1 ISPs rather than connecting to ALL Tier 1 ISPs across globe Connectivity Between Tier 1 and Tier 2 ISPs Figure 9-13 17

  18. The Internet as a Network of Networks • Other providers of Internet services: Companies who provide services available through Internet • Web hosting • Search engines • Social media • Cloud services Other Service Providers Connected to the Internet Figure 9-14 18

  19. The Internet as a Network of Networks • Other providers of Internet services • Web Hosting: Customer picks URL for its website, creates content for website, and puts website files onto servers that sit at web hosting company • Search Engine: Computers inside service provider’s network have programs that act like web browsers, systematically getting copy of every web page they can find on Internet • Social Media: Service provider that builds web servers that provide framework for users to add their own content (text, photos, video, apps) • Cloud Services: Large variety of services available through Internet 19

  20. The Internet as a Network of Networks • Web hosting example: Company website (www.example.com) exists on servers owned by web hosting company • When user browses to www.example.com, packets flow to/from servers at web hosting company Hosting a Web Site at a Web Hosting Service, Not in the Enterprise’s IP Network Figure 9-15 20

  21. Internet Access Technologies • Phone line and analog modem (Layers 1 and 2) Internet access: When customer calls, Telco passes call to ISP PoP over phone line not being used at moment • Example: Two ISP customers with analog modems • If ISP wants to support many concurrent users in PoP, they need many modems • Once dialed in, users’ PCs can send and receive bits with ISP through R1 Two ISP Customers Using Analog Modems and Analog Phone Lines Figure 9-16 21

  22. Internet Access Technologies • PPP and DHCP: Together they help customer’s PC learn its public IP address, subnet mask, default gateway, and IP addresses of DNS servers so PCs can access Internet Role of PPP on a Analog Dial-up Circuit to an ISP Figure 9-17 22

  23. Internet Access Technologies • Using analog phone lines for Internet access • Analog modems use symmetric speeds: Upstream speed (from customer to ISP) same as downstream speed (from Internet to customer) • For most Internet applications, more bytes flow downstream than upstream • Asymmetric service with faster downstream speeds actually works better 23

  24. Internet Access Technologies • Using analog phone lines for Internet access Comparison Points: Analog Modem Table 9-1 24

  25. Internet Access Technologies • Digital technologies from Telcos: Integrated Services Digital Network (ISDN) and Digital Subscriber Line (DSL) • DSL requires changes to devices at end of local loop cabling, including device in Telco CO • Traditional CO voice switch does not know what to do with DSL higher frequencies, so CO needs DSL AccessMultiplexer(DSLAM) for DSL frequencies DSL Using Multiple Frequencies over a Single Local Loop Figure 9-18 25

  26. Internet Access Technologies • Line splitter allows both analog phone and DSL modem to connect to same phone line and transmit simultaneously Home Cabling and Devices for DSL Figure 9-19 26

  27. Internet Access Technologies • DSLAM uses Frequency Division Multiplexing (FDM) to separate voice and data frequencies in same electrical signal • DSLAM does not process data or voice; just passes data or voice off to correct device (router or traditional voice switch) DSLAM Multiplexes Voice to the PSTN and Data to the ISP Figure 9-20 27

  28. Internet Access Technologies • DSL uses Data Link protocol PPP (Point-to-Point Protocol) to move data (IP packet encapsulated in PPP frame) to DSLAM which then moves PPP frame to ISP router PPP Encapsulated IP Packets Going from Home to ISP Router over DSL Figure 9-21 28

  29. Internet Access Technologies • Differences and similarities between analog and DSL modems Internet Access Link Comparison Points: Analog and DSL Table 9-2 29

  30. Internet Access Technologies • Cable TV and cable modem: Cable modem uses different frequency channels than those used for video (TV) • Cable Internet service just like another TV channel • Instead of video, channel sends data Cable Internet Using Multiple Frequencies over a Single Circuit on Co-axial Cable Figure 9-22 30

  31. Internet Access Technologies • Cable modem example: Cable modem feed comes from same cable as TV connection Home Cabling and Devices for Cable Internet Figure 9-23 31

  32. Internet Access Technologies • Fiber to the Neighborhood (FTTN): Fiber goes to front of neighborhood with coaxial rest of way to houses • Fiber to the Curb (FTTC): Fiber goes into neighborhood and is buried at curb (closer to homes) Hybrid Fiber Coax (HFC) and Fiber-to-the-Curb (FTTC) Figure 9-24 32

  33. Internet Access Technologies • HeadEnd: CATV (cable access TV) company’s equivalent of Telco’s Central Office (CO) • Has space to hold various devices, including those that connect to ends of HFC cables CMTS and Head End Multiplexes Video and Data Figure 9-25 33

  34. Internet Access Technologies • Differences and similarities between cable Internet, DSL, analog modems Internet Access Link Comparison Points Table 9-3 34

  35. Internet Access Technologies • Wireless Telco and 4G: Wireless WAN technology supports many devices (mobile phones, tablets, laptops or other computers) • Devices can have built-in wireless WAN card or can use wireless WAN expansion card Wireless WAN Examples Figure 9-26 35

  36. Internet Access Technologies • Consumer Internet-access technologies use cabling already in most homes; makes it inexpensive and affordable Enterprise WAN Options Used as Internet Access Technologies Figure 9-27 36

  37. Short Break Take 10 37

  38. Network Layer Concepts Before Scarce IP Addresses • Individual IP addresses must be unique to each host connected to Internet before they can send or receive IP packets • Hosts use IP addresses based on class A, B, or C networks • Addresses can not be assigned randomly • Organized IP addresses helps routers to build usable routing tables of networks • Makes routing tables shorter and routing more efficient 38

  39. Network Layer Concepts Before Scarce IP Addresses • Many different organizations (typically part of some not-for-profit organization) work together to assign IP addresses for Internet worldwide • IANA: Part of ICANN (Internet Corporation for Assigned Names and Numbers) works with five worldwide regional organizations to manage address assignment process Regional Internet Registries (RIRs) Table 9-4 39

  40. Network Layer Concepts Before Scarce IP Addresses • Early days of Internet: Original rule for assigning addresses was for each company to use one classful IP network for its network • When company wanted to connect to Internet, it applied to IANA for classful network • IANA reviewed application and assigned network ID IANA Assigned Classful IP Network Numbers Figure 9-29 40

  41. Network Layer Concepts Before Scarce IP Addresses • IANA IP network assignments followed these general rules: • Only assign network IDs not yet assigned to any other enterprise • Assign class of network just large enough to meet need of enterprise • At end of process, each enterprise had public address that fell into class A, B, or C • IP address from public network could be used to send packets to any other network in Internet Enterprises Subnet their One Classful IP Network Figure 9-30 41

  42. Network Layer Concepts Before Scarce IP Addresses • Example of SOHO address assignment in early days: ISP1 reserved class C network 200.2.2.0 • When PC2 and PC3 connect to ISP, they are given addresses by ISP1 router Assigning IP Addresses to SOHO PCs Figure 9-31 42

  43. Network Layer Concepts Before Scarce IP Addresses • Border Gateway Protocol (BGP): Internet IP routing protocol • Prefers routes through less expensive links • Creates large routing tables BGP: Choosing Routes (Indirectly) Based on Business Rules Figure 9-32 43

  44. Network Layer Concepts Before Scarce IP Addresses • In Internet core, routing tables have grown to over 400,000 routes • So BGP built to be better able to handle larger numbers of routes Scale of Internet Routing Tables: Large Enterprise Vs. Internet Core Routers Figure 9-33 44

  45. Network Layer Concepts Before Scarce IP Addresses • Once classful network has been assigned to company, all routers in Internet core need to know how to forward packets so they can reach ISP connected to company Internet Routing: IP Routes to Each Classful IP Network Figure 9-34 45

  46. Network Layer Concepts Before Scarce IP Addresses • Routers receive packets and then send them to next router IP Forwarding (Routing) on Several ISP Routers Figure 9-35 46

  47. Network Layer Concepts Before Scarce IP Addresses • Single-homed connection means that enterprise has only one WAN link connecting to ISP Single-Homed Connection with Default Route Figure 9-36 47

  48. Network Layer Concepts Before Scarce IP Addresses • Dual-homed Internet connection means enterprise has two (or more) connections to Internet • Gives enterprise choice of where to send Internet packets • Default route might not work well in suchnetwork designs Inefficient Routes With Dual-homed Internet Connections Figure 9-37 48

  49. Network Layer Concepts Before Scarce IP Addresses • Dual-homed example: Enterprise uses BGP between itself and both ISP1 and ISP2 • ISP2’s router would advertise routes for networks 22.0.0.0 and 23.0.0.0, and routers R1 and R2 view route to Internet through ISP2 as better route Partial BGP Updates Figure 9-38 49

  50. Network Layer Concepts Before Scarce IP Addresses • Example: User device connects to Internet without using router • Host has OS that includes TCP/IP software • IP software includes concept of default router • When connected to Internet, host’s default router setting refers to ISP router Default Routers and Default Routes Figure 9-39 50

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