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

2. 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.

3. 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

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

5. 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

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

7. 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

8. 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

9. 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

10. 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

11. 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

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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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
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
The root server replies, not with the IP address of because the root server does not know, either; it replies with the IP address of another DNS server,
At this point, the client still does not know that IP address is , but the name resolution process is almost complete.
Finding the Right DNS Server for a Domain Name in Another Company 19
Figure 9-45

20. 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 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 and
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 ), 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

21. 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

22. 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 ( )
NAT Function on a Router 22
Figure 9-54

23. Network Layer Concepts with Scarce IPv4 Addresses
Example using private and public IP addresses
Three separate enterprises use PRIVATE networks based on
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
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 23
Figure 9-55

24. 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 B 16 C
256
All that begin ( , , , and so on, through )
Private IP Networks 24
Table 9-5

25. 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 )
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

26. 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

27. Questions? Comments? 27

28. 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

29. 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.