1. Data Communications and the Cloud
Chapter 6
Data Communications and the Cloud

2. Study Questions
Q1: What is a computer network? Q2: What are the components of a LAN? Q3: What are the fundamental concepts you should know about the Internet? Q4: What processing occurs on a typical Web server? Q5: Why is the cloud the future for most organizations? Q6: How does this chapter help you?
This chapter defines essential data communications terms and explains basic concepts. It begins with a discussion of LANs, Internet fundamentals, Web servers and purpose of basic Web technologies. Next, a discussion of why the cloud is the future for most organizations and how it can be used.

3. Q1: What Is a Computer Network?
Collection of computers that communicate with one another over wired and wireless transmission media.
Major types of network topologies
MAN: A computer network that usually spans a city or a large campus. A MAN usually interconnects a number of local area networks (LANs) using a high-capacity backbone technology, such as fiber-optical links, and provides up-link services to the Internet. Some technologies used for this purpose are Asynchronous Transfer Mode (ATM), FDDI, and SMDS. These technologies are in the process of being displaced by Ethernet-based connections (e.g., Metro Ethernet) in most areas. MAN links between local area networks have been built without cables using either microwave, radio, or infra-red laser links. Most companies rent or lease circuits from common carriers
WiMAX is now popular protocol for constructing a wireless MAN (IEEE802.16). WiMax antennas beam high-speed Internet connections to rooftop antennas of homes and businesses miles away. Good for rural areas lack of other means.
CAN: Campus (or, Corporate) Area Network. HAN: Home Area Network. SAN: Storage Area Network.
Others include PAN, HAN, MAN, SAN, CAN, etc.

4. Q2: What Are the Components of a LAN?
Types of computer networks: PAN (personal), HAN (home), SAN (Storage), CAN (campus), MAN, etc.
LAN: Switched Ethernet, most popular. LAN IEEE (10 MB/s ~ 40 GB/s) is the Ethernet broadband protocol/standard family.
Router, cable modem, DSL modem needed for the Internet access. Each computer must have a network interface card.
Computers and printers in a typical SOHO communicate via a mixture of wired and wireless connections. Computers 1, 3 and Printer 1 use wired connections, while Computers 2, 4, 5 and Printer 2 use wireless connections.
Most LAN connections use unshielded twisted pair (UTP) cable. If connection carries a lot of traffic, UTP cable may be replaced by optical fiber cables.
Wireless computers and printers have a wireless NIC (WNIC) instead of a NIC.

5. WANs
Connects computers across metropolitan, state, regional, national areas
Uses communication networks from vendors
Licensed by government

6. Wired Connectivity Switch Gateway Network interface card (NIC)
Special purpose computer that receives and transmits messages
Gateway
Network interface card (NIC)
UTP (unshielded twisted pair)
Optical fiber cable
Difference between a Gateway and a router: share information by communicating between protocols on a computer or between dissimilar computers.
UTP: most common for computer networking, TV cabling and telephone systems.
Ocean cable: costly to build and repair, terabits/s, while satellites typically offer only megabits per second and display higher latency, measure of time delay experienced in a system.

7. LAN Protocol IEEE 802.3 Protocol IEEE 802.11 Protocol Wireless LAN
Wired LAN
10/100/1000 Mbps Ethernet*
Protocol specifies hardware characteristics, cables, and how messages are packaged and processed
Wireless LAN
Most popular g (2010)
Bluetooth
Common wireless protocol for transmitting data over short distances—wireless mice and keyboards, cell phones
IEEE protocol is used for wired LAN connections. Ethernet specifies hardware characteristics, such as which wire carries which signals. It describes how messages are packaged and processed for wired transmission over the LAN. NICs in most personal computers support 10/100/1000 Ethernet.
Wireless LAN connections use the IEEE protocol. Several versions of exist. IEEE n allows speeds of up to 600 Mbps.
Bluetooth is common wireless protocol designed for transmitting data wirelessly over short distances.
*: Gigabit Ethernet, 10 gigabit Ethernet between network switches for WAN

8. Three Common Alternatives for Connecting a SOHO to the Internet

9. What Are the Alternatives for a WAN?
Use routers and public communications links between sites
Cable connections made through licensed public telecommunications companies
Internet service provider (ISP)
A company that provides customers access to the Internet
Provides legitimate Internet address
Serves as gateway to Internet
You pay for Internet access

10. DSL and Cable Internet Access
Modem: transfer digital signals to analog signals to travel on the telephone network or cable network.

11. DSL Modems 256 kbps to 40 Mbps Digital Subscriber Line (DSL)
Operates over telephone lines
Data signals do not interfere with voice telephone service
Faster data transmission than dial--up
256 kbps to 40 Mbps
DSL modems use their own protocols
Download and upload speeds differ
Asymmetric digital subscriber lines (ADSL)
Symmetrical digital subscriber lines (SDSL)
ADSL: speed up to 40 Mb/s for down links. SDSL: a separate high speed line that does not support analog signals.
VHDSL (Very high bit-rate DSL) is capable of more than 50 mbit/s download speed; 2nd generation, VDSL2, is capable of over 100 mbit/s both ways.
DSL Router = Modem + Router

12. Cable Modems (IEEE 802.14) Provide high-speed data transmission
Use cable television lines
High-capacity optical fiber cable to neighborhood
Optical fiber cable connects to regular cable-television cables run to subscribers home or business. Does not interfere with television transmission.
Up to 500 users share facility
Performance varies based on number of people connected
Download speed up to 50 Mbps, upload up to 512 kbps
Cable Modem Flap: The connection by the modem to the head-end has been dropped (gone offline) and then comes back online.
Cable Modem Flap: Connection problems.

13. WAN Wireless Connection (WWAN)
Amazon’s Kindle uses a Sprint wireless network to provide wireless data connections
Variety of WAN wireless protocols exist. Sprint and Verizon use EVDO (based on CDMA2000); AT&T supports iPhone and T-Mobile use HSDPA (3G+); WiMax (802.16e, 4G) by Clearwire
WAN wireless provides average performance of 500 kbps, with peaks of up to 1.7 Mbps, as opposed to the typical 50 Mbps for LAN wireless
American standard for broadband data transmission – 4mbps for downloading and 1mbps uploading (2010). WiMax is used for a number of applications including broadband connections, cellular backhaul, hotspots, etc. similar to Wi-Fi, but it can enable usage at much greater distances.
Narrowband lines transmission speed <= 56 kbps vs. <=4mbps
Broadband lines speeds in excess of 256 kbps by OECD
EVDO: Evolution-Data Optimized
WiMax: Worldwide Interoperability for Microwave Access

14. Using the Internet for a Hotel Reservation
Q3: What Are the Fundamental Concepts You Should Know About the Internet?
Using the Internet for a Hotel Reservation
Assume you send a message to a server in New Zealand hotel. The message is too big to travel in one piece, so it’s broken into packets and each packet passes along from WAN to WAN until it reaches its destination. Once all packets arrive, message is reconstructed and delivered to server for processing. All of this is accomplished by computers and data communications devices that most likely have not interacted before.
Gateway: including protocol translators, rate convertors, and signal translators to insure system interoperability

15. Key Digital Networking Technologies
Client/server computing
Packet Switching
TCP/IP connectivity

16. Packed-Switched Networks and Packet Communications

17. TCP/IP Architecture (Model)
Protocols used on the Internet are arranged according to an international standardized structure known as TCP/IP Protocol architecture. TCP/IP has five protocol types arranged in layers. Data communications and software vendors write computer programs that implement the rules of a particular protocol.
“Why should I know about this?” So that you will understand the terms you will hear and the products you will use, buy, or possibly invest in that relate to each other via this architecture.
Internet Protocol Suite

18. Application Layer Protocols
Hyper Text Transfer Protocol (HTTP)
Protocol used between browsers and web servers.
Simple Mail Transfer Protocol (SMTP)
Used for transmissions.
File Transfer Protocol (FTP)
Used to move files over Internet.
Web-Internet-based network of browsers and servers that process http or https. When you use ftp or smtp, you are using Internet, not web.
HTTP is the protocol used for data communication between browsers and Web servers.
HTTPS is a secure data transmission based on http + SSL/TLS.
SMTP is the protocol for transmissions.
FTP is the protocol for transmitting files over the Internet.
How about HTTPS?

19. TCP and IP Protocols TCP or Transmission Control Protocol
Breaks traffic up into data packets and sends each packet along its way (reliable and ordered data packets)
IP (Internet Protocol)
Specifies routing of pieces of data communication through networks that comprise any Internet
Packet is a piece of a message that is handled by programs that implement IP
Router is a special purpose computer that moves packet traffic according to rules of IP protocol (i.e., IPv4, IPv6)
These protocols manage traffic as it passes across an internet (including the Internet) from one network to another. Most important protocol in transport layer is Transmission Control Protocol (TCP).

20. IP Addressing Identify a particular device on public Internet
Public IP Addresses
Identify a particular device on public Internet
Public IP Addresses must be unique, worldwide
Assignment controlled by ICANN (Internet Corporation for Assigned Names and Numbers)
Private IP Addresses
Identify a particular device on a private network, usually on a LAN
Major benefits
Public IP: All devices on LAN share a public IP address
Private IP address, need not register device with ICANN-approved agencies

21. Functions of the LAN Device
Switch processing: IEEE wired LAN traffic
Access-point processing: IEEE wireless LAN traffic
Translating between IEEE and IEEE
Converting between Analog and Digital
Assigning private IP addresses
Converting IP address between private and public IP addresses
Routing packets
And more…
Router, proxy server,

22. Use of Private IP Addresses
Source:

23. Public IP Addresses and Domain Names
IPv4 Supports (232) or 4,294,967,296 addresses
Four decimal dotted notation like
IPv6 - Supports 2128 addresses
Domain name
Unique name affiliated with public IP address
URL (Uniform Resource Locator) or ftp://
IPv4 main ranges used up in Newer enterprise servers may have adopted IPv6 address.
Affiliation of domain names with IP addresses is dynamic. Multiple domain names to same IP address. Affiliation of domain names with IP addresses is dynamic. Owner of domain name can change the affiliated IP addresses at its discretion.
Private address: for private or internal uses
Public address: for server address on the Internet
Static address: permanently by fixed configuration of its hardware or software
Dynamic Address: the computer's IP address is assigned newly each time
IPv6 Example: 2001:0DB8:AC10:FE01::
2001:0DB8:AC10:FE01:0:0:0:0
Domain Registrar Co.

24. The Domain Name System
DNS server: maintains a database containing IP addresses mapped to their corresponding domain names and converts domain names to IP addresses. This server is maintained by ICANN.

25. Q4. What processing occurs on a typical Web server?
Three-Tier Architecture
Web Farm: a cluster of servers
IIS: Microsoft windows operating system run on Microsoft web server
Apache: Web server run on Unix-like operating system
Almost all e-commerce applications use the three-tier architecture.
User tier consists of computers, phones, and other devices with browsers that request and process Web pages.
Server tier consists of computers running Web servers and application programs.
Database tier consists of computers that run a DBMS that processes SQL requests to retrieve and store data.
Commerce server — an application program that runs on a server-tier computer. It receives requests from users via Web server, takes some action, and returns a response to users. Typical commerce server functions are to obtain product data from a database, manage items in a shopping cart, and coordinate checkout process. The core system components comprise Catalog, Inventory, Orders, Profiles, and Marketing. It also comes with Data Warehouse Analytics and some sophisticated reporting functionality.

26. Sample of Commerce Server Page
Assume customer has navigated through zulily.com to find an item. To produce this page, commerce server accessed a database to obtain product picture, price, special terms, product information, and related products. Customer places items in shopping cart.
When customer checks out, commerce server program processes payment, schedules inventory processing, and arranges shipping.

27. Web Farm Servers (cluster of servers)
Programs that run on a server tier computer
Manage HTTP traffic by sending and receiving web pages to and from clients
Web servers
Application programs that run on a server tier computer
Receives requests from users via web server, takes some action, and returns a response to users via the web server
Commerce servers
Commerce server: Microsoft product for commercial website development and maintenance which retains its core systems of Catalog, Inventory, Orders, Profiles, and Marketing. Data warehouse analytics added.
Microsoft Commerce Server 2009: create e-commerce solutions and Web sites that simplify setup, management, and administration tasks.

28. Hypertext Markup Language (HTML)
Hypertext Markup Language (HTML) code defines structure and layout of Web pages.
HTML headings provide metadata about page and a body that contains content. Tag <h1> means to format indicated text as a level-one heading; <h2> means a level two heading. Tag <a href=“ defines a hyperlink.
Each attribute has a standard name. Attribute for a hyperlink is href, and its value indicates URL of Web page to display when link is clicked.
HTML has problems and limitations overcome by newer technologies. HTML5 most current version.

29. XML, Flash, Silverlight, HTML 5
XML (eXtensible Markup Language)
Flash and Silverlight
HTML 5.0
Fixes several HTML deficiencies
Program-to-program interaction over web
Add-ons to browsers
Provides animation, movies, other advanced graphics inside a browser
New version of HTML supports animation, movies, and graphics
HTML 5.0: Latest revision of HTML and support for the latest multimedia while keeping it easily readable by humans and consistently understood by computers. New syntactic features include <video>, <audio>, <canvas>, etc. According to the development plan by W3C, 2013 is the year for review and 2014 should see formal recommendation of stable HTML5.0. HTML 5 is also a potential candidate for cross-platform mobile applications.
Adobe Flash, Microsoft Silverlight

30. How Do Organizations Benefit From Virtual Private Networks (VPNs)
Uses Internet or private network to create appearance of point-to-point connections
Uses public Internet to create appearance of private network
VPNs can connect individual users to a remote network or connect multiple networks together.

31. WAN Using VPN Remote Access: Actual Connections
Remote Client (Apparent connection)
VPN: security is provided by using tunneling protocols (encapsulation), and security procedures such as encryption.
A VPN server uses Internet to create a secure, private point-to-point connection.
Actual connections (P2P leased lines*)
*: A dedicated circuit connecting two end points for transferring and sharing data between them.

32. Remote Access Using VPN: Apparent Connection
Remote user perspective

33. WAN Using VPN
VPN client software encrypts original message; then, appends Internet address of VPN server to message and sends it over Internet to VPN server. When VPN server receives message, it strips off address, decrypts coded message, and sends plain text message to designated address on LAN.

34. Q5: Why Is the Cloud the Future for Most Organizations?
What is the Cloud?
Elastic leasing of pooled computer resources over the Internet
Elastic?
Dynamically increasing/decreasing leased resources programmatically in short time span, and only pay for resources used
Cloud resources “pooled” because many different organizations use same physical hardware and share it using virtualization.
Cloud resources accessed via Internet protocols that enable cloud-hosting vendors to provide processing capabilities in flexible, yet standardized ways.

35. Apple Data Center in Maiden, NC
Building contains computers in a server farm to support Apple’s iCloud offering.
Billion-dollar facility contains more than 500,000 square feet. IBM, Google, Amazon, Microsoft, Oracle, and others operate similar farms.

36. Why Is the Cloud Preferred to In-House Hosting?
Positives heavily tilted toward cloud-based computing. Cloud vendor, RackSpace, will lease one medium server for as low as 1.5 cents per hour. Companies can obtain and start using cloud services in a few minutes.
As long as you’re dealing with large, reputable cloud vendors, you will get the best-of-breed security and disaster recovery services.

37. Why Is the Cloud Preferred to In-House Hosting? (cont’d)
Negatives of cloud computing involve loss of control due to vendor dependency. Changes in management, policies, and prices are beyond your control. You don’t know where your data are located, how many copies there are, where they’re located, or whether security and disaster preparedness measures are actually in place.

38. Why Now?
Technology now supports construction and use of enormous data centers
Processors, data communication, data storage nearly free
Web farms providing virtual machine for about 1.5¢ per hour
Virtual Private Server (VPS)

39. When Does the Cloud Not Make Sense?
Law or industry standard practices require physical control over the data
Private cloud
In-house hosting, delivered via Web service standards
Community Cloud
It might not make sense when required by law, or by industry standard practices, to have physical control over the data. Organizations, such as a financial institution, might be forced to create and maintain their own hosting infrastructure.

40. How Can Organizations Use the Cloud?
Three Fundamental Cloud Type
SaaS provides hardware infrastructure, operating systems and application programs.
PaaS vendors provide hosted computers, an operating system, and possibly a DBMS.
IaaS is cloud hosting on barebones server or disk drive.
GearUp needs to put its Web servers and its database server in the cloud using PaaS. GearUp could use Windows Azure for Web servers and SQL Azure for database server.

41. How Does the Knowledge In This Chapter Help You?
Provides general knowledge needed by business professionals
Helps you develop project plans and budgets involving IT and data communications
Helps you be a better consumer of IT services
Helps you understand how your organization can weave cloud-based applications into its strategy