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

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


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


Connecting enterprises

Figure 9-3Typical Organizations Whose TCP/IP Networks Connect to the Internet6


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


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


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


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


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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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


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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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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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


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


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


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


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


Routers receive packets and then send them to next router

Figure 9-35IP Forwarding (Routing) on Several ISP Routers 23


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


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


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


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)


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


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


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 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


Three different connections from one host Server maps IP address for each connection

Figure 9-53One Client Host with Three Application Connections33


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


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


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)


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.

Documents

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