CHAPTER 1
The Internet and Its Uses
Objectives
After completing this chapter, you should be able to answer the following questions:
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How is the Internet evolving? How do businesses and individuals use the Internet? What is the importance of standards in the continuing growth of the Internet? What is the role of an Internet service provider (ISP)? How does the hierarchical structure of the Internet allow the efficient movement of information?
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What are a point of presence (POP) and an Internet Exchange Point (IXP)? What types of devices do ISPs use to provide services? What is scalability, and why is it important in the ISP network? What support teams work at an ISP, and what is their purpose?
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Key Terms
This chapter uses the following key terms. You can find the definitions in the glossary. Internet page 2 page 2 Network Access Point (NAP) Tier 1 ISP Tier 2 ISP Tier 3 ISP page 9 page 9 page 9 page 9 page 7
electronic commerce (e-commerce) Request for Comments (RFC) Internet service provider (ISP) bandwidth page 4
page 3 page 4
Internet Control Message Protocol (ICMP) page 5 transport network page 12 DSL access multiplexer (DSLAM) page 7 page 7 cable modem termination system (CMTS) page 13 scalable network page 14 page 13
digital subscriber line (DSL) Metro Ethernet page 7
point of presence (POP)
Internet Exchange Point (IXP)
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The globalization of the Internet has occurred faster than anyone could have imagined. The manner in which social, commercial, political, and personal interactions occur is rapidly changing to keep pace with the evolution of the Internet. This expansion has created a wider audience and a larger consumer base for whatever message, product, or service can be delivered. Today millions of individuals are connected to this global network, and the number is growing. This chapter discusses the importance of standards in maintaining this rapid growth and provides an overview of the hierarchical structure of the Internet and the role of the ISP. Part II of this book includes the corresponding labs for this chapter.
What Is the Internet?
The Internet is a worldwide, publicly accessible network of networks. Through interconnected computer networks, the Internet enables individuals and businesses to share information, resources, and services. Because no single individual or group of individuals controls the Internet, it is imperative that certain rules and guidelines are adhered to so that it can function efficiently.
The Internet and Standards
In the beginning, the Internet was used strictly for scientific, educational, and military research. In 1991, regulations changed to allow businesses and consumers to connect as well. Since that time, the Internet has grown rapidly and now covers the globe. New technologies are continuously being developed that make the Internet easier and more attractive to use. Online applications are available to the Internet user, including e-mail, web browsing, streaming music and video, online gaming, and instant messaging. The way people interact, share information, and even do business is changing to keep up with the continuous evolution of this global network. The Internet is creating a wider audience and consumer base for whatever message, product, or service can be delivered. For many businesses, having Internet access has become critical, not only for communication, but also for day-to-day operation. This includes e-commerce, communications, and collaboration and training, as shown in Figure 1-1 and described in the next sections.
E-Commerce
Electronic commerce (e-commerce) is any business activity that can be conducted over the web. This includes using web space for advertisements, brochures, and catalogs, as well as ordering and distribution services. Companies can sell products and services over the Internet from their own websites, through auction sites, or through affiliated websites.
Communications
Communications refers to any electronic method of communication, such as the use of e-mail, instant messaging, and online chat. In addition, many businesses use internal phone systems that operate over the Internet using IP phones and voice over IP (VoIP) technology to reduce phone costs.
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Figure 1-1
Common Uses for the Internet
Internet
E-Commerce Employees
Communications
Collaboration and Training
Intranet
Customers
Business
Home Office
Collaboration and Training
The Internet enables the sharing of documents, presentations, and spreadsheets among users around the world. It allows teams of people to work together virtually from remote locations for business and training purposes. Examples include videoconferencing, virtual meeting places, virtual classrooms, online learning, online bulletin boards, FTP sites, and password-protected databases and applications. With the increasing number of new devices and technologies coming online, it is important that all users and technologies adhere to a set of rules or guidelines. This allows services such as e-mail to be reliably delivered to all users. These rules and guidelines are known as Internet standards. A standard is a set of rules for how something must be done. Networking and Internet standards ensure that all devices connecting to the network use the same set of rules. By having standards, different types of devices can send information to each other over the Internet. For example, an e-mail message is formatted, forwarded, and received by all devices in a standardized manner. If someone sends an e-mail via a PC, someone else can use a mobile phone to receive and read the e-mail as long as the mobile phone uses the same standards. An Internet standard is the end result of a comprehensive cycle of discussion, problem solving, and testing. When a new standard is proposed, each stage of the development and approval process is recorded in a numbered Request for Comments (RFC) document so that the evolution of the standard is tracked.
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Thousands of Internet standards help define the rules for how devices communicate on networks. These different standards are developed, published, and maintained by a variety of organizations. These include the International Organization for Standardization (ISO), Institute of Electrical and Electronics Engineers (IEEE), Internet Corporation for Assigned Names and Numbers (ICANN), Internet Assigned Numbers Authority (IANA), and Internet Engineering Task Force (IETF). Because these organizations create and maintain standards, millions of individuals can connect to the Internet using a variety of devices, including PCs, cellular phones, handheld personal digital assistants (PDA), MP3 players, and even televisions.
ISPs and ISP Services
Regardless of the type of device an individual or business uses to connect to the Internet, the device must connect through an Internet service provider (ISP). An ISP is a company or organization through which a subscriber obtains Internet access. A subscriber can be a business, a private consumer, a government body, or even another ISP. Users connect to the ISP through a Point of Presence (POP) using a variety of access technologies. In addition to offering connection to the Internet, an ISP can offer a variety of other services:
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FTP hosting: The ISP provides the server and application software for a business FTP site. Applications and media hosting: The ISP provides the server and software to allow a business to provide streaming media such as music, video, or applications such as online databases. Technical support: Many businesses do not have the in-house technical expertise to manage large internal networks. Some ISPs provide technical support and consulting services for an additional fee. Voice over IP: A business can save on long-distance telephone charges, especially for internal calls between geographically distant offices, by using VoIP. Equipment co-location: A business may opt to have some or all internal network equipment physically located on the ISP premises. Web hosting: The ISP provides the server and application software for storing web pages and web content for the business website.
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Interactive Activity 1-1: Which ISP Is Best? (1.1.2)
In this activity, you determine the best ISP for a given scenario. Use file d2ia-112 on the CD-ROM that accompanies this book to perform this interactive activity.
Internet Service Providers
Although ISPs offer their clients many different services, their main role is to provide a connection to the Internet. The actual type of connection varies according to the region. Not all connection types are available in all areas. Some connection options provide continuous connection, and others provide connection only when required. Bandwidth, both upstream and downstream, varies between the different options and must match the requirements of the individual or business. Bandwidth is measured in bits per second (bps), kilobits per second (kbps), megabits per second (Mbps), or gigabits per second (Gbps).
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Delivering Internet Services to End Users
ISPs offer various connection options for home and business users. The main connection methods used by home and small business users include dialup, DSL, cable, and satellite connections. These are shown in Figure 1-2.
Figure 1-2 Internet Connection Technology for Home and Small Business
56 kbps Telephone Line POP Dialup Dialup Modem 512 kbps Telephone Line DSL Modem DSL 512 kbps Coaxial Cable POP Cable Modem Cable ISP B (Cable Service Provider) POP ISP A (Telephone Company)
POP Satellite Satellite Modem
ISP C (Satellite Service Provider)
This section describes these connection methods as well as dedicated bandwidth options and the role of a point of presence (POP).
Dialup Access
Dialup access is an inexpensive option that uses a phone line and a modem. To connect to the ISP, a user calls the ISP access phone number. With connection speeds of about 56 kbps, dialup is the slowest connection option. At this speed it would take approximately 12 minutes to download a 5-MB file. Dialup is typically used by mobile workers and in areas where higher-speed connection options are not available.
DSL
Digital subscriber line (DSL) is more expensive than dialup but provides a faster connection. DSL also uses telephone lines, but unlike dialup access, DSL provides a continuous connection to the Internet. This connection option uses a special high-speed modem that separates the DSL signal from the telephone signal and provides an Ethernet connection to a host computer or local-area network (LAN). Speeds of 512 kbps and higher are common with DSL services. At this speed, a 5-MB file would take approximately one minute to download. Upload and download speeds vary based on geography, distance from the ISP, and the type of service offered by the ISP.
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DSL comes in several flavors. Typically, a home user uses an asymmetric digital subscriber line (ADSL), in which the download speed is faster than the upload speed. Because most home users download significantly more than they upload, this type of connection is sufficient. In a business environment, the amount of data uploaded may be equal to or even greater than the amount of data downloaded. For these users, an ADSL line is insufficient; a symmetric digital subscriber line (SDSL) service is more appropriate. SDSL offers the same upload and download speeds.
Cable Modem
A cable modem is a connection option offered by cable television service providers. It offers faster connection speeds than that generally provided by DSL. Cable Internet connections offer speeds of 5 Mbps to 10 Mbps. At these speeds a 5-MB file would take only seconds to download. The Internet signal is carried on the same coaxial cable that delivers cable television to homes and businesses. A special cable modem separates the Internet signal from the other signals carried on the cable and provides an Ethernet connection to a host computer or LAN. Unlike DSL, the distance from the ISP does not affect the performance of the cable connection. Cable is a shared-bandwidth service, so as more customers in an area connect and use the Internet, the speed is negatively affected.
Satellite
Satellite connection is an option offered by satellite service providers. The user’s computer connects through Ethernet to a satellite modem that transmits radio signals to the nearest POP within the satellite network. Satellite Internet access speeds range from 128 Kbps to 512 Kbps, depending on the subscriber plan. Satellite connection may be the only available technology in many regions of the world.
Dedicated Bandwidth Options
Business customers often require dedicated, high-bandwidth connections to the Internet. Figure 1-3 shows the three main types of dedicated, high-bandwidth connection options that are used by businesses: T1/E1, T3/E3, and Metro Ethernet.
Figure 1-3 High-Speed, Dedicated-Bandwidth Internet Connections
Medium-Sized Business
T1/E1 1.544/2.048 Mbps
POP
Large Business
T3/E3 44.736/34.368 Mbps Branch Office (Main Street) POP
ISP
Large Business with Branch Offices in Same City Head Office (Downtown)
Ethernet Switch Metro Ethernet 10 Gbps
Branch Office (Industrial Park)
Branch Office (Suburb)
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T1/E1 Connections
T1 connections transmit data at rates of up to 1.544 Mbps. They are symmetrical, meaning that the upload bandwidth is the same as the download bandwidth. A medium-sized business may need only one T1 connection for all its connectivity requirements. T1 connections are common in North America and some other parts of the world. E1 is a European standard that transmits data at 2.048 Mbps.
T3/E3 Connections
T3 connections allow data to be transmitted at rates of up to 45 Mbps. Although T3 is considerably more expensive than a T1 connection, a larger business may need a T3 connection to accommodate all its employees or business volume. Large businesses with multiple locations might use a combination of T1 and T3 lines. Quite often the main office or data center has a T3 line, and each branch office has a T1 connection. E3 is a European standard that transmits data at 34.368 Mbps.
Metro Ethernet
Metro Ethernet offers a wide range of high-bandwidth options, including Gbps links. Large companies with many branches in the same city, such as banks, often use Metro Ethernet. Metro Ethernet connects the main office location and all the branches using switched technology. It allows the transfer of large amounts of data faster and less expensively than other high-bandwidth connection options.
Point of Presence
After the type of connection is established, it is necessary to connect to the ISP to get access to the Internet. Individual computers and business networks connect to the ISP at a point of presence (POP). POPs are located at the edge of the ISP’s network and serve a particular geographic region. They provide a local point of connection and authentication (password control) for multiple end users. An ISP may have many POPs, depending on the size of the area it services. Within the ISP network, high-speed routers and switches move data between the various POPs. Multiple links interconnect the POPs to provide alternative routes in case one of the links becomes overloaded with traffic or fails.
Internet Hierarchy
The Internet has a hierarchical structure. At the top of this hierarchy are the ISP organizations. The ISP POPs connect to an Internet Exchange Point (IXP). In some countries, this is called a Network Access Point (NAP). An IXP or NAP is where multiple ISPs are joined to gain access to each others’ networks and exchange information, as shown in Figure 1-4. Currently more than 100 major exchange points exist worldwide.
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Figure 1-4
Internet Hierarchy
IXP Seattle IXP New York IXP IXP Tokyo Hong Kong
IXP Internet Backbone ISP 1 POP POP POP POP
IXP
POP ISP 2 POP POP POP
I am sending an e-mail to Mr. Chu in Hong Kong. Company A Intranet Company B Intranet
Hong Kong
New York
The Internet backbone consists of this group of networks owned by various organizations and interconnected through IXPs and private peering connections. The Internet backbone is like an information superhighway that provides high-speed data links to interconnect the POPs and IXPs in major metropolitan areas around the world. The primary medium that connects the Internet backbone is fiber-optic cable. This cable typically is installed underground to connect cities within continents. Fiber-optic cables also run under the sea to connect cities between continents. ISPs are classified into different tiers according to how they access the Internet backbone. Three tiers of ISPs are identified.
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Tier 1 ISPs
Tier 1 ISPs are at the top of the hierarchy. Tier 1 ISPs are huge organizations that connect directly with each other through private peering, physically joining their individual network backbones to create the global Internet backbone. Within their own networks, the Tier 1 ISPs own the routers, high-speed data links, and other pieces of equipment that join them to other Tier 1 ISP networks. This includes the undersea cables that connect the continents.
Tier 2 ISPs
Tier 2 ISPs are the next tier in terms of backbone access. Tier 2 ISPs can also be very large, even extending across several countries, but very few have networks that span entire continents or between continents. To provide their customers with global Internet access, some Tier 2 ISPs pay Tier 1 ISPs to carry their traffic to other parts of the world. Some Tier 2 ISPs exchange global traffic with other ISPs less expensively through public peering at IXPs. A large IXP may bring together hundreds of ISPs in a central physical location for access to multiple networks over a shared connection.
Tier 3 ISPs
Tier 3 ISPs are the farthest from the backbone. Tier 3 ISPs generally are found in major cities and give customers local access to the Internet. Tier 3 ISPs pay Tier 1 and 2 ISPs for access to the global Internet and Internet services.
Identifying the Structure of the Internet
Network utilities can be used to create a map of the Internet to visualize how ISP networks interconnect. These utilities also illustrate the speed at which each connecting point can be reached. The ping command tests the accessibility of a specific IP address. This command sends an Internet Control Message Protocol (ICMP) echo request packet to the destination address and then waits for an echo reply packet to return from that host, as shown in Figure 1-5. It measures the time that elapses between when the request packet is sent and the response packet is received.
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Figure 1-5
ping Utility
Is H2 reachable? ping 192.168.30.1
H1 ICMP Echo Request 192.168.10.1
H2 192.168.30.1
Yes, I am here. ICMP Echo Reply H1 192.168.10.1 H2 192.168.30.1
The ping command output indicates whether the reply was received successfully and displays the round-trip time for the transmissions. Example 1-1 shows the syntax and result of a successful ping command from a Windows-based host. Note that either the IP address or the domain name may be used. If the Domain Name System (DNS) is not functioning properly, the IP address should be used.
Example 1-1 Sample Output from the ping Command
C:\> ping cisco.netacad.net
Pinging cisco.netacad.net [128.107.229.50] with 32 bytes of data:
Reply from 128.107.229.50: bytes=32 time=560ms TTL=115 Reply from 128.107.229.50: bytes=32 time=636ms TTL=115 Reply from 128.107.229.50: bytes=32 time=460ms TTL=115 Reply from 128.107.229.50: bytes=32 time=645ms TTL=115
Ping statistics for 128.107.229.50:
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Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 460ms, Maximum = 645ms, Average = 575ms
C:\> ping 128.107.229.50
Pinging 128.107.229.50 with 32 bytes of data:
Reply from 128.107.229.50: bytes=32 time=118ms TTL=115 Reply from 128.107.229.50: bytes=32 time=376ms TTL=115 Reply from 128.107.229.50: bytes=32 time=577ms TTL=115 Reply from 128.107.229.50: bytes=32 time=120ms TTL=115
Ping statistics for 128.107.229.50: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 118ms, Maximum = 577ms, Average = 297ms
If a packet does not reach the destination, or if delays are encountered along the way, you can use the traceroute utility to display information about where the packet encountered problems. The traceroute utility displays the path that a packet takes from the source to the destination host. Each router that the packet passes through is called a hop. The traceroute utility displays each hop along the way. It also calculates the time between when the packet is sent and when a reply is received from the router at each hop. If a problem occurs, use the output of the traceroute command to help determine where a packet was lost or delayed. The output shows the various ISPs that the packet must pass through during its journey from source to destination. The Windows tracert utility works the same way. Also, a number of visual traceroute programs provide a graphical display of the route a packet takes. Example 1-2 shows an example of tracert command output.
Example 1-2 Sample Output from the tracert Command
C:\> tracert cisco.netacad.net
Tracing route to cisco.netacad.net [128.107.229.50] over a maximum of 30 hops:
1 2 3 4 5 6 7 8 9 10 11 12 13
1 ms 8 ms 7 ms 6 ms 7 ms 16 ms 17 ms 18 ms 68 ms 69 ms 68 ms 68 ms 70 ms 