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

Class Agenda 2/16/16 Learning Objectives Unit 9 Quiz 2 today. Make up day for holiday Lesson Presentation and Discussions Lab Activities will be performed in class. Assignments will be given in class. Break times will be observed. Note: Submit all Assignment and labs due today.

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. 3

The Internet as a Network of Networks Internet Access Links from TCP/IP Networks, Large and Small 4 Figure 9-1

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 5 Figure 9-2

The Internet as a Network of Networks Connecting enterprises Typical Organizations Whose TCP/IP Networks Connect to the Internet 6 Figure 9-3

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 7 Figure 9-5

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 8 Figure 9-6

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 9 Figure 9-8

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 10 Figure 9-9

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 11 Figure 9-12

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 12 Figure 9-14

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 13

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 Access Multiplexer (DSLAM) for DSL frequencies DSL Using Multiple Frequencies over a Single Local Loop 14 Figure 9-18

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 15 Figure 9-22

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 16 Figure 9-26

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 Name Locations Served AfriNIC Africa APNIC Asia Pacific ARIN North America LACNIC Latin America, Caribbean RIPE NCC Europe, Middle East, Central Asia Regional Internet Registries (RIRs) 17 Table 9-4

Network Layer Concepts Before Scarce IP Addresses Routers receive packets and then send them to next router IP Forwarding (Routing) on Several ISP Routers 18 Figure 9-35

Network Layer Concepts Before Scarce IP Addresses DNS defines how world creates distributed database of hostnames and their addresses DNS server for each subdomain knows all hostnames and IP addresses for that subdomain Root DNS servers: Special DNS servers inside Internet know IP addresses of all DNS servers DNS defines protocol that servers use to ask among all DNS servers to find DNS server for right subdomain Following the steps in the Figure: Client A sends a DNS query to the DNS it knows, the DNS for subdomain ent- 2.com, at 128.1.9.9. The ent-2.com DNS server’s logic is that it does not know the answer, so ask some other DNS. (Each DNS would be configured to know the IP address of other DNS servers). The ent-2.com DNS server asks a DNS Root Server to resolve www.ent-1.com. The root server replies, not with the IP address of www.ent-1.com, because the root server does not know, either; it replies with the IP address of another DNS server, 1.1.9.9. At this point, the client still does not know that www.ent-1.com’s IP address is 1.1.1.1, but the name resolution process is almost complete. Finding the Right DNS Server for a Domain Name in Another Company 19 Figure 9-45

Network Layer Concepts with Scarce IPv4 Addresses Classless Interdomain Routing (CIDR): One method to deal with IP address depletion Used by IANA Each CIDR block is set of consecutive IP addresses unique in Internet (same as classful IP networks) The figure shows that process, noted as three steps, as follows: ISP1 had already requested a new CIDR block from IANA; the figure shows IANA assigning a new block, the entire class B network 128.1.0.0. Now ISP1 owns all addresses that begin 128.1, for the purpose of assigning CIDR blocks to ISP1’s customers. A company (Ent-1 in this case) wants to connect to the Internet, and they decide to use ISP1. The two companies talk, and Ent-1 submits paperwork that shows a need for 500 public IP addresses. ISP1 looks at the size of the request (500 addresses), as compared to the powers of 2 (64, 128, 256, 512, 1024, and so on.) ISP1 chooses a CIDR block just large enough to meet the need, in this case of size 512 (29). (As a reminder, the first and last IP addresses in the block are reserved.) The CIDR block in the figure includes all addresses that begin 128.1.0 and 128.1.1. Another company (Ent-2) asks for a CIDR block with 200 public IP addresses. This time, the ISP can assign a block of 256 addresses (all addresses that begin 128.1.2), to reduce wasted addresses. While the example shows the ISP assigning blocks that are a subset of a class B network, CIDR allows any grouping, as long as it aligns on boundaries based on powers of 2. IANA Assigns to ISP; ISP Assigns Smaller CIDR Block to Customer 20 Figure 9-49

Network Layer Concepts with Scarce IPv4 Addresses CIDR reduces routing table growth with route aggregation Example: ISP1 has 3 customers, each of which has CIDR block of public IP addresses Router R4 (part of ISP1’s network) has routes for each customer’s CIDR block CIDR Address Assignment Creates Larger Routing Tables 21 Figure 9-50

Network Layer Concepts with Scarce IPv4 Addresses NAT combines connections into one Example: Three real devices each connect to same real web server Router implementing NAT makes all three connections look like they come from single host (128.1.1.4) NAT Function on a Router 22 Figure 9-54

Network Layer Concepts with Scarce IPv4 Addresses Example using private and public IP addresses Three separate enterprises use PRIVATE networks based on 10.0.0.0 Each company uses different PUBLIC IP address block to access Internet The Figure shows some powerful concepts with NAT, as follows: Enterprises use a private IP network for host IP addresses throughout the Enterprise TCP/IP network, in this case, private class A IP network 10.0.0.0. Two (or more) Enterprises can use the exact same private IP networks, and the same exact IP addresses, with no problems in connecting to the Internet, with servers, and even with hosts in the other company. The device doing NAT, usually a router or firewall, uses some of the public CIDR block or IP network for NAT. The number of required public IP addresses is far lower than the number of necessary client IP addresses inside the Enterprise. In this case, each company uses a single public IP address. Three Enterprises Networks, Each Using Private Network 10.0.0.0 23 Figure 9-55

Network Layer Concepts with Scarce IPv4 Addresses Public and private IP addresses: RFC 1918 sets aside several private IP network address blocks Enterprise can pick private address block, assign IP addresses from that block, subnet that block, etc. Class Number of Networks Network IDs A 1 10.0.0.0 B 16 172.16.0.0 - 172.31.0.0 C 256 All that begin 192.168 (192.168.0.0, 192.168.1.0, 192.168.2.0, and so on, through 192.168.255.0) Private IP Networks 24 Table 9-5

Network Layer Concepts with Scarce IPv4 Addresses Router typically has defaults such as Dynamically uses one public IP address (from ISP) on WAN port Uses that one public IP for NAT Makes WAN port “outside” port for NAT Processes traffic coming in from LAN ports with NAT Picks one private IP network to use on LAN (typically 192.168.1.0) Acts as DHCP server on LAN ports to lease IP addresses to all hosts on LAN Acts as firewall, allowing Intranet clients to connect to Internet and preventing Internet clients from getting onto Intranet Various Roles of Consumer “Router” 25 Figure 9-59

Summary - This Chapter… Explained how individual devices, some home-based TCP/IP networks, corporate TCP/IP networks, and ISP TCP/IP networks connect to create the global Internet. Showed the typical devices and connections used in a connection from a corporate TCP/IP network and an ISP. Described how ISPs work together to create the Internet core. Generally described the layer 1 and 2 features used when connecting to an ISP using analog modems, DSL modems, and cable modems. 26

Questions? Comments? 27

Unit 9 Assignment Unit 9 Assignement 1: Internet Technologies Review - Complete chapter 9 multiple-choice questions. 2. Complete the Define Key Terms table. 3. Unit 9 Research Project 1: Network Design, Part 3. Reading Assignment. Read Chapter 10

Unit 9 Lab Lab 9.1: Broadband Internet Lab 9.2: Networks and Subnets Lab 9.3: Internet Protocol Version 6 (IPv6) Lab 9.4: Configuring an FTP Service Uncompleted Lab must be submitted in the next class.