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

2. Class Agenda 11/13/15 Learning Objectives Quiz 2 Exams to day.
Make up day for holiday
Lesson Presentation and Discussions
Lab Activities will be performed in class.
Assignments will be given in class.
Break Times. 10 Minutes break in every 1 Hour.
Note: Submit all Assignment and labs due today.

3. Objectives
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.
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
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 7
Figure 9-6

8. 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 8
Figure 9-8

9. 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 9
Figure 9-9

10. 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 10
Figure 9-12

11. 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 11
Figure 9-14

12. 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 12

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 13
Figure 9-18

14. 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 14
Figure 9-22

15. 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 15
Figure 9-26

16. Short Break
Take 10 16

17. 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 17

18. 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) 18
Table 9-4

19. 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 19
Figure 9-29

20. 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 20
Figure 9-30

21. 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 21
Figure 9-32

22. 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 22
Figure 9-34

23. Network Layer Concepts Before Scarce IP Addresses
Routers receive packets and then send them to next router
IP Forwarding (Routing) on Several ISP Routers 23
Figure 9-35

24. Network Layer Concepts Before Scarce IP Addresses
To create globally unique hostnames, process relies on domain names
With this format, names exist as characters with periods in between
Subdomain: Last part of name
Format and Examples Using Domain Names 24
Figure 9-41

25. Network Layer Concepts Before Scarce IP Addresses
To ensure unique hostnames throughout Internet, company or individual must register subdomains with IANA-authorized company
If requested name not already in use, agency registers name so no other entity can use it
IANA/Others Approve Subdomain Registrations 25
Figure 9-42

26. Network Layer Concepts Before Scarce IP Addresses
Hostnames on LANs follow domain name format, too
Administrative process ensures no two hostnames will ever be same
Enterprises must not duplicate names inside company
IANA/Others Approve Subdomain Registrations 26
Figure 9-43

27. 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 27
Figure 9-45

28. Network Layer Concepts with Scarce IPv4 Addresses
IPv4 address exhaustion
Became clear by late 1980s that world would run out of IPv4 addresses with current IP class plan
Original address assignment plan had problems in part because of sizes of classful IP networks and number of each that existed
Class
Number of Networks
Size (Number of Host Addresses) A
126
224 – 2 (>16,000,000) B
16,384
216 – 2 (>65,000) C
2,097,192
28 – 2 (254)
Number and Sizes of Classful IP Networks 28
Table 9-4

29. Network Layer Concepts with Scarce IPv4 Addresses
Graph: Number of estimated Internet hosts 1984 – 1992
Data derived primarily from RFC 1296, which collected growth data in part because of IP address exhaustion problem
Approximate Number of Hosts Connected to the Internet, 29
Figure 9-48

30. 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 30
Figure 9-49

31. 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 31
Figure 9-50

32. Network Layer Concepts with Scarce IPv4 Addresses
Network Address Translation (NAT): Way to translate multiple PRIVATE addresses to single PUBLIC address for Internet access
Hosts with Public IP Addresses Connected to Servers in the Internet 32
Figure 9-52

33. Network Layer Concepts with Scarce IPv4 Addresses
Three different connections from one host
Server maps IP address for each connection
One Client Host with Three Application Connections 33
Figure 9-53

34. 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 34
Figure 9-54

35. 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 35
Figure 9-55

36. 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 36
Table 9-5

37. 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” 37
Figure 9-59

38. 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. 38

39. Summary - This Chapter…
Compared and contrasted analog modems, DSL, and cable as Internet access technologies.
Explained IP routing in the Internet, in the direction from Enterprise towards the Internet and from the Internet towards an Enterprise.
Listed the typical steps that occur when a client needs to do name resolution for a hostname that exists in a different DNS subdomain.
Compared and contrasted the public IP address assignment process that was used before IP address exhaustion, and after the introduction of CIDR. 39

40. Questions? Comments? 40

41. Unit 9 Assignment Complete chapter 9 multiple-choice questions.
2. Complete the Define Key Terms table.
3. Reading Assignment. Read Chapter 10

42. Unit 9 Lab Complete all Labs in Chapter 9 of the lab book.
Lab should be completed in class.
Uncompleted Lab must be submitted in the next class.