NT1210 Introduction to Networking
Unit 9:
Chapter 9, The Internet
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.
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.
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The Internet as a Network of Networks
Figure 9-1Internet Access Links from TCP/IP Networks, Large and Small4
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
Figure 9-2The Internet Core, with Multiple Service Providers5
The Internet as a Network of Networks
Connecting enterprises
Figure 9-3Typical Organizations Whose TCP/IP Networks Connect to the Internet6
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
Figure 9-6An Example Case of Using an Enterprise Firewall and IPS7
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)
Figure 9-8Four Main Options for Individual Internet Access8
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
Figure 9-9ISP Point-of-Presence (PoP) Concept with Customer Access9
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
Figure 9-12Creating the Internet Core: Connections Between Large ISPs10
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
Figure 9-14Other Service Providers Connected to the Internet11
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
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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
Figure 9-18DSL Using Multiple Frequencies over a Single Local Loop13
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
Figure 9-22Cable Internet Using Multiple Frequencies over a Single Circuit on Co-axial Cable
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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
Figure 9-26Wireless WAN Examples15
Short Break
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Take 10
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
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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
Table 9-4Regional Internet Registries (RIRs)18
Name Locations ServedAfriNIC Africa
APNIC Asia Pacific
ARIN North America
LACNIC Latin America, Caribbean
RIPE NCC Europe, Middle East, Central Asia
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
Figure 9-29IANA Assigned Classful IP Network Numbers19
Network Layer Concepts Before Scarce IP Addresses
IANA IP network assignments followed these general rules:1. Only assign network IDs not yet
assigned to any other enterprise
2. 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
Figure 9-30Enterprises Subnet their One Classful IP Network20
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
Figure 9-32BGP: Choosing Routes (Indirectly) Based on Business Rules 21
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
Figure 9-34Internet Routing: IP Routes to Each Classful IP Network22
Network Layer Concepts Before Scarce IP Addresses
Routers receive packets and then send them to next router
Figure 9-35IP Forwarding (Routing) on Several ISP Routers 23
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
Figure 9-41Format and Examples Using Domain Names 24
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 entitycan use it
Figure 9-42IANA/Others Approve Subdomain Registrations 25
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
Figure 9-43IANA/Others Approve Subdomain Registrations 26
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
Figure 9-45Finding the Right DNS Server for a Domain Name in Another Company 27
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
Table 9-4Number and Sizes of Classful IP Networks28
ClassNumber 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)
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
Figure 9-48Approximate Number of Hosts Connected to the Internet, 1984 - 199229
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)
Figure 9-49IANA Assigns to ISP; ISP Assigns Smaller CIDR Block to Customer30
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
Figure 9-50CIDR Address Assignment Creates Larger Routing Tables31
Network Layer Concepts with Scarce IPv4 Addresses
Network Address Translation (NAT): Way to translate multiple PRIVATE addresses to single PUBLIC address for Internet access
Figure 9-52Hosts with Public IP Addresses Connected to Servers in the Internet32
Network Layer Concepts with Scarce IPv4 Addresses
Three different connections from one host Server maps IP address for each connection
Figure 9-53One Client Host with Three Application Connections33
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)
Figure 9-54NAT Function on a Router34
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
Figure 9-55Three Enterprises Networks, Each Using Private Network 10.0.0.035
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.
Table 9-5Private IP Networks36
ClassNumber 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)
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
Figure 9-59Various Roles of Consumer “Router”37
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.
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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.
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Questions? Comments?
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Unit 9 Assignment
1. Complete chapter 9 multiple-choice
questions.
2. Complete the Define Key Terms table.
3. Reading Assignment. Read Chapter 10
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.