1. Copyright © 2002 John Wiley & Sons, Inc.
Chapter 9. The Internet
Business Data Communications and Networking Fitzgerald and Dennis, 7th Edition
Copyright © 2002 John Wiley & Sons, Inc.

2. Chapter 9. Learning Objectives
Understand the overall design of the Internet
Be familiar with DSL, cable modem and Wireless Application Protocol
Be familiar with Internet 2

3. Chapter 9. Outline Introduction How the Internet Works
Basic Architecture, Connecting to an ISP, The Internet Today
Internet Access Technologies
Digital Subscriber Line, Cable Modems, Fixed Wireless, Mobile Wireless, Future Technologies
Internet Governance
Internet 2

4. Introduction

5. Introduction
The Internet is not one network but a network of networks made up of thousands of networks of national and state government agencies, non-profit organizations and for-profit companies.
It exists only to the extent that these networks agree to use Internet protocols and to exchange data packets among one another.
All networks on the Internet must conform to the TCP/IP standards for the transport and network layers, without which data communications over the Internet would not be possible.

6. How The Internet Works

7. Basic Architecture: NAPs and national ISPs
The Internet has a hierarchical structure.
At the highest level are large national Internet Service Providers that interconnect through Network Access Points (NAPs).
There are about a dozen NAPs in the U.S., run by common carriers such as Sprint and Ameritech (Figure 9-1), and many more around the world.
Regional ISPs interconnect with national ISPs and provide services to their customers and sell access to local ISPs who, in turn, sell access to individuals.

8. Basic Architecture: MAEs and local ISPs
As the number of ISPs has grown, a new type of network access point, called a metropolitan area exchange (MAE) has arisen.
There are about 50 such MAE around the U.S. today.
Sometimes large regional and local ISPs also have access directly to NAPs.
Indiana University, for example, which provides services to about 40,000 individuals, connects directly to the Chicago NAP.

9. Figure 9-1 Basic Internet Architecture

10. Internet Packet Exchange Charges
ISP at the same level usually do not charge each other for exchanging messages.
This is called peering.
Higher level ISPs, however, charge lower level ones (national ISPs charge regional ISPs which in turn charge local ISPs) for carrying Internet traffic.
Local ISPs, of course, charge individuals and corporate users for access.

11. Connecting to an ISP
ISPs provide access to the Internet through a Point of Presence (POP).
Individual users access the POP through a dial-up line using the PPP protocol.
The call connects the user to the ISP’s modem pool, after which a remote access server (RAS) checks the userid and password.
Once logged in, the user can send TCP/IP/[PPP] packets over the telephone line which are then sent out over the Internet through the ISP’s POP.
Corporate users might access the POP using a T-1, T-3 or ATM OC-3 connections provided by a common carrier.
Figure 9-2 shows an example of a POP using a collapsed backbone with a layer 2 switch.

12. Figure 9-2 Inside an ISP Point of Presence
Individual
Dial-up Customers
ISP POP
ISP Point-of Presence
Modem Pool
ISP POP
Corporate
T1 Customer
T1 CSU/DSU
Layer-2
Switch
ATM
Switch
Corporate
T3 Customer
ISP POP
T3 CSU/DSU
Remote
Access
Server
Corporate
OC-3 Customer
ATM Switch
NAP/MAE
Figure 9-2 Inside an ISP Point of Presence

13. Figure 9-2 Inside an ISP Point of Presence
(See page 270, Figure 9-2)
Figure 9-2 Inside an ISP Point of Presence

14. From the ISP to the NAP/MAE
Each ISP acts as an autonomous system, with is own interior and exterior routing protocols.
Messages destined for locations within the same ISP are routed through the ISP’s own network.
Since most messages are destined for other networks, they are sent to the nearest MAE or NAP where they get routed to the appropriate “next hop” network.
Figure 9-3 shows the connection from the local ISP to the NAP. From there packets are routed to the next higher level of ISP.
Actual connections can be complex and packets sometimes travel long distances. Each local ISP might connect a different regional ISP, causing packets to flow between cities, even though their destination is to another local ISP within the same city.

15. Figure 9-3 Inside an Internet Network Access Point
ISP A
ISP D
Router
Router
ATM
Switch
ISP B
ISP E
Router
ATM Switch
ISP C
Route
Server
ISP F
Router
ATM Switch
Figure 9-3 Inside an Internet Network Access Point

16. The Internet in 2001
Figure 9-4 illustrates the backbone networks of three national ISPs: Compuserve and CAIS in the US and iSTAR in Canada.
Compuserve mostly uses T-3 lines for its backbone, CAIS uses a mix of T-3 and ATM OC-12 lines, while iSTAR uses T-1 lines.
Compuserve and CAIS meet and peer at the Chicago NAP, while CAIS and iSTAR peer at the NAP in London, Ontario.

17. Figure 9-4 Three national ISPs in North America

18. Internet Backbones in 2001
As of mid-2001, most backbone circuits for national ISPs in the US are 622 Mbps ATM OC-12 lines.
The largest national ISPs are planning to convert to OC-192 (10 Gbps) by the end of 2001.
A few are now experimenting with OC-768 (40 Gbps) and some are planning to use OC-3072 (160 Gbps).
Aggregate Internet traffic reached 2.5 Terabits per second (Tbps) by mid It is expected to reach 35 Tbps by 2005.

19. Internet Access Technologies

20. Internet Access Technologies
Most people today are still using 56K dial-up lines to access the Internet, but a number of new access technologies are now being offered.
The main new access technologies are:
Digital Subscriber Line
Cable Modems
Fixed Wireless (including satellite access)
Mobile Wireless (WAP)

21. Digital Subscriber Line
Digital Subscriber Line (DSL) is one of the most promising technologies now being implemented to significantly increase the data rates over traditional telephone lines.
Historically, voice telephone circuits have had only a limited capacity for data communications because they were constrained by the 4 kHz bandwidth voice channel.
Most local loop telephone lines actually have a much higher bandwidth and can therefore carry data at much higher rates.

22. Digital Subscriber Line
DSL services are quite new and not all common carriers offer them.
Two general categories of DSL services have emerged in the marketplace.
Symmetric DSL (SDSL) provides the same transmission rates (up to 128 Kbps) in both directions on the circuits.
Asymmetric DSL (ADSL) provides different data rates to (up to 640 Kbps) and from (up to Mbps) the carrier’s end office. It also includes an analog channel for voice transmissions.

23. Figure 9-5 DSL Architecture
Customer Premises
Local Carrier End Office
DSL Modem
Line Splitter
Main
Distribution
Frame
Voice
Telephone
Network
Local Loop
Hub
Telephone
ISP POP
ATM Switch
Computer
DSL Access
Multiplexer
Computer
ISP POP
Customer
Premises
ISP POP
ISP POP
Customer
Premises
Figure 9-5 DSL Architecture

24. Figure 9-6 ADSL data rates
Type
Maximum Length
of Local Loop
Maximum
Downstream Rate
Maximum Upstream Rate T1
18,000 feet
1.5 Mbps
384 Kbps
E1*
16,000 feet
2.0 Mbps T2
12,000 feet
6.1 Mbps
E2*
9,000 feet
8.4 Mbps
640 Kbps
 * E1 and E2 are the European standard services similar to T1 and T2 services in North America
Figure 9-6 ADSL data rates

25. Very High Rate Digital Subscriber Line (VDSL)
VDSL is a high-speed member of the DSL family, designed for local loops of 1000 feet or less. Its three FDM channels are:
4 KHz analog voice channel
Upstream digital 1.6 Mbps channel
Downstream digital 52 Mbps channel

26. Figure 9-7 Anticipated VDSL data rates
Type
Maximum Length
of Local Loop
Maximum
Downstream Rate
Maximum Upstream Rate
1/4 OC-1
4,500 feet
12.96 Mbps
1.6 Mbps
1/2 OC-1
3,000 feet
25.92 Mbps
2.3 Mbps
OC-1
1,000 feet
51.84 Mbps
Figure 9-7 Anticipated VDSL data rates

27. Cable Modems
One potential competitor to DSL is the “cable modem” a digital service offered by cable television companies which offers an upstream rate of Mbps and a downstream rate of 2-30 Mbps.
A few cable companies offer downstream services only, with upstream communications using regular telephone lines.

28. Figure 9-8 Cable Modem Architecture
Customer Premises
Cable Company
Fiber Node
Cable Company Distribution Hub
TV Video
Network
Cable Modem
Cable Splitter
Downstream
Combiner
Optical/Electrical
Converter
Upstream
Hub TV
Router
Shared
Coax
Cable
System
Cable
Company
Fiber Node
Cable Modem
Termination
System
Computer
Computer
ISP POP
Customer
Premises
Customer
Premises
Figure 9-8 Cable Modem Architecture

29. Fixed Wireless
Fixed Wireless is another “dish-based” microwave transmission technology.
It requires “line of sight” access between transmitters.
Both point-to-point and point-multipoint forms are available.
Multipoint forms allow access by a limited number of stations.
Data access speeds range from 1.5 to 11 Mbps depending on the vendor.

30. Fixed Wireless (Figure 9-9)
Fig. 9-9 is an example of fixed wireless technology.
Transmissions travel between transceivers at the customer premises and ISP’s wireless access office.
Incoming signals at the customer site are first demultiplexed and then sent to the MDF where the signal is combined with voice transmissions.
This combined signal is then distributed to individual customer premises where a line splitter separates out the voice communications.
The data transmission is then sent to a DSL modem which is connected to a hub on the customer’s LAN.
The transceiver at the wireless access office is connected to a router which then sends outgoing packets over the Internet.

31. Wireless Architecture
Customer Premises
Individual Premise
Main
Distribution
Frame
Voice
Telephone
Network
DSL Modem
Line Splitter
Hub
Individual
Premise
Telephone
Wireless
Transceiver
DSL Access
Multiplexer
Individual
Premise
Computer
Computer
Wireless Access Office
Customer
Premises
Wireless
Transceiver
Router
Customer
Premises
ISP POP
Fig. 9-9 Fixed
Wireless Architecture

32. Mobile Wireless
Mobile wireless is the next step in cell phone technology, allowing users to access the Internet from any location.
Access speeds are currently slow compared to fixed wired access such as DSL or cable modem.
Mobile wireless uses the wireless application protocol (WAP) used by the wireless application environment (WAE).
WAP uses WAE and WML instead of HTTP and HTML, which essentially streamlines the latter for use in the very limited low speed and small screen wireless mobile networking environment.

33. Basic WAP Architecture (Figure 9-10)
WAP clients (e.g., cell phone or palm computer) run a WAP program called a WAE user agent that generates WAE requests and sends them to the WAP gateway.
The WAP gateway transceiver next passes the requests to a wireless telephony application (WTA) server.
The server sends WAE responses back to the WAP client.
If the client has requested a Web page, the WAE request is sent to a WAP proxy which translates both outgoing requests from WAE to HTTP and incoming HTTP responses back into WAE
The WAE responses are then sent back to the WTA server which, in turn, sends them back to the WAP client.

34. Figure 9-10 Mobile Wireless Architecture for WAP applications
WAP Client
WAP Gateway
Web Site
WAE
User
Agent
Web Server
WAE
Requests
Wireless
Transceiver
Wireless Telephony
Application Server
WAE
Requests
WAE
Responses
(plus WML, etc.)
WAE
Responses
(plus WML, etc.)
WAE
Responses
(plus WML, etc.)
WAE
Requests
HTTP Requests
WAP Proxy
HTTP Responses
(plus HTML, jpeg, etc.)
Figure 9-10 Mobile Wireless
Architecture for WAP applications

35. Future Access Technologies
Two potentially important technologies for Internet access in the near future are:
Passive Optical Networking (PON)
PON, also called Fiber to the Home will unleash the potential of optical fiber communications to end users.
With WDM hundreds or thousand of channels are possible. Passive optical doesn’t require electricity, lowering cost, but limiting its maximum distance.
Ethernet to the Home
Gives home users 10BaseT or 100BaseT connections.
Yipes.com is now doing this in several large US cities.
The common carrier installs TCP/IP routers connected to an Ethernet MAN.

36. Internet Governance

37. ISOC and Internet Governance
The Internet Society (ISOC) is the closest thing to an “owning” organization that exists for the Internet.
ISOC is an open society whose members include 175 organizational and 8,000 professional members worldwide.
ISOC works in three areas:
In public policy by participating in national and international debates on issues such as censorship, copyrights, privacy and universal access.
In education, ISOC provides training and education programs aimed at improving Internet infrastructure in developing nations.
In standards, ISOC works through four inter-related standards bodies: IETF, IESG, IAB and IRTF.

38. 4 ISOC-related Standards Bodies
Internet Engineering Taskforce (IETF) includes network designers, vendors, and researchers who develop new Internet architecture. IETF sends out requests for comment (RFCs) which form the basis of new Internet standards.
Internet Engineering Steering Group (IESG) is responsible for technical management of IETF activities and standards and is governed by rules ratified by ISOC trustees. Each IETF group is chaired by an IESG member.
Internet Architecture Board (IAB) provides strategic direction by promoting which actions the IETF and IESG should take. The IAB also elects the IETF chair and all IESG members out of the IETF nominating committee’s list.
Internet Research Taskforce (IRTF) works through small research groups focused on specific research topics. IETF generally works on short-term issues, IRTF works on long-term ones related to Internet protocols, applications, architecture, and technology.

39. Internet 2

40. Internet 2 (Figure 9-11)
New networks are being developed to develop future Internet technologies including:
The very high performance Backbone Network Service (vBNS) run by Worldcom. 34 universities participate.
The Abilene network (also called Internet 2) is being developed by the University Corporation for Advanced Internet Development (UCAID).
CA*Net3 is the Canadian government initiative.
Access is through Gigapops, similar to NAPs, but which operate at very high speeds (622 Mbps to 2.4 Gbps) using SONET, ATM and IPv6 protocols.
Protocol development focuses on issues like Quality of Service and multicasting.
New applications include tele-immersion and videoconferencing.

41. Figure 9-11 Gigapops and high speed backbones
Abilene
vBNS
CA*Net 3
Figure 9-11 Gigapops and high speed backbones
of Internet 2/Abilene, vBNS, and CA*Net 3

42. Figure 9-12 Inside the Pacific/Northwest Gigapop
Sprint
Abilene
UUNet
CA*Net 3
Verio
DREN
WSU
Boeing
Router
Router
Router
Microsoft
U Idaho
Switch
Switch
Router
Router
Montana State U
HSCC
High-speed
Router
High-speed
Router
Router
U Montana
AT&T
Router
Switch
Switch
SCCD
Router
Sprint
U Alaska
U Wash
OC-48
OC-12
T-3
Portland POP
Figure 9-12 Inside the Pacific/Northwest Gigapop

43. End of Chapter 9