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Ecommerce Technology (20-751)


Readings for the intellectually stimulated

S.M. Das, MSEC Mini 1, 2002


Welcome to the unofficial page for 20-751 (I did stick to the official color guide though). This page has links to lots of interesting articles and papers related to each lecture you do in the class. Though this stuff will not be tested, knowing it should make everything else easier.



q       Check out the nitty gritty in using XML for EDI

q       Nice though a little outdated tutorial on UDDI

q       This is a nice discussion of ASN.1 in the context of the OSI model




q       Check out this e-payments primer

q       Look at this comprehensive list of payment mechanisms and take ur pick

q       You will know the rest in your class next fall!




q       This here is a nice intro to public key crypto.

q       Read on about the histories and controversies behind public key cryptography

q       This is a nice tutorial on signing ur docs digitally

q       Look at a paper describing how PKC can be used for complicated authentication schemes

q       Is it possible to decide whether a cryptographic protocol is secure or not ?



q       You have learnt stuff on wireless networks and now on security. Why not look at wireless security which is the next big thing nowadays? Click here for a comprehensive list of articles on the topic

q       To get the whole big picture from the guys in control read the security handbook from NIST

q       I like this article on firewall forensics. Check it out





q       The importance of a Web page is an inherently subjective matter, which depends on the readers¡¯ interests, knowledge and attitudes. But there is still much that can be said objectively about the relative importance of Web pages. Read this to learn more about a scientific way to go about it.

q       Read this paper to get an understanding g of how GOOGLE works. This paper will give you insight into the core of this major search engine. *S. Brin and L. Page, The Anatomy of a Large-Scale Hypertextual Web Search Engine, Seventh International World Wide Web Conference / Computer Networks 30(1-7): 107-117. 1998. (ps, pdf )

q       This is an interesting article on how to use your robots.txt file The ROBOTS.TXT file is used to prevent web robots from indexing some or all of a web site. This is useful to exclude anything which is felt does not need to be included in search engines.

q       Learn what a bot is from¡­¡­the botspot. Where else?






q       Large internet websites can improve their performance by increasing the number of Web servers. This involves an attempt to distribute the traffic onto a cluster of back-end Web servers. Aside from the technical hurdles, this is an interesting approach, because the back-end servers don't need to be large-scale machines -- medium-scale hardware works just fine. Look at various techniques to do this here. Also read about the hardware that gets this done such as a load balancing switch. Nowadays all in one devices such as the Cisco Catalyst 6500 exist which do load balancing, QoS and security for your system.

q       Read this article to get an idea of how SANs came about.

q       If you want to get into EJBs this is a great place to start

q       Or if you prefer JSPs this is a nice tutorial






q       If you want to know the core of CDMA technology (not just the spreading/despreading) but all about modulation, encoding , RAKE receivers etc explained very simply go here. If you want a more involved discussion of CDMA go here.

q       Also have a look at this UMTS guide.

q       Look at the handoffs in general and the soft handoffs in CDMA here

q       This article gives some insight into WAP

q       and this one into Bluetooth

q       This is the granddaddy of all the tutorials on cellular networks


So you learnt wireless today! It seems to be real rage with the industry and public at large right! But wireless is really being rediscovered. It has been there for such a long time. Read The History of Wireless for a great account of how wireless developed. 

Many of you may have heard of CDMA (Code Division Multiple Access). Developed by Viterbi (Qualcomm) , it is based on spread spectrum which makes our very own Wireless LAN work.

Look at the picture to the right. Looks like a classic flick playing 40 years ago right!

Wrong! The two people hold the patent on Spread Spectrum. Two individuals who left Germany to come to the United States invented something that would change the way we communicate. One was the American music composer, George Antheil. The other was the actress Hedy LaMarr, who was considered, at the time, the "most beautiful woman in the world."


Today, cellular telephones are owned by more than 50 million Americans and new technological breakthroughs have seen a migration from analog to digital architectures along with the recent introduction of "Personal Communications Services (PCS)" as a competitor to the cellular market. You may have heard of impending legislations to ban or reduce cellphone use while driving. Read this article for more.

There has been lot of talk of wireless communication being insecure. Read this article to learn more.

The wireless channel is has a TIME-VARYING response and has multipath. This is what makes the medium so difficult to work with. In fact there are lots of problems caused to TCP traffic due to the nature of the wireless channel. To visualize the wireless channel imagine your voice as a radio signal for example. In a wireless channel it would reach your listener multiple times!! and each time it goes to the listener it would have a different volume. The more interesting effect is that if you shout the same thing after 5 minutes; it will sound different all over again and have a totally different response. The wireless channel is a real challenge to engineers and getting the physical layer right can do wonders for your applications. This is a difficult problem believe me. Its part of my research and is real difficult to analyze and overcome.

You must be happy with your wireless card and the LAN here. Makes things easy doesn't it. However what if your cellular company wants to give you the same service. For him the area of CMU is too small a service area. Suppose I am the Shady Wireless Company. If I give my customers wireless service I have to ensure roaming. But as you can see, if CMU has it's LAN and Pitt has it's own, you cant roam around from CMU to the Pitt library and expect your connection to work. So what does the Shady Wireless Company need, He needs Mobile IP. Read the stuff from the horse's mouth....Mobile Networking Through Mobile IP (Charles Perkins), 

I am sure you all have used net2phone, dialpad etc sometime. This VoIP technology is essentially transforming the telephony industry and causing regulatory headaches at the FCC! Read all about it in Internet Protocol/Intelligent Network Integration Tutorial (IEC), 

SO you want to keep track of the movements of you better/worse half. Use The Global Positioning System. A satellite based positioning technology. Surprisingly the use I mentioned doesnt seem to be very popular now.:) But it can be used for navigation, inventory management etc. Some companies use GPS for tracking shipments. Cool stuff.



q       Get information on what the backbone of the Internet is really made of

q       Learn how packet switching was invented

q       All possible tutorials on all possible aspects of optical networks can be found here

q       This article from ACM give a nice overview of what happens in your operating system¡¯s network stack

q       Look at what goes in to the design of something as simple as a URL

q       This is a nice paper which gives the nuts and bolts of HTTP from a stack perspective and give you an idea of how the devil is always in the details when it comes to optimizing a protocol

Get the big picture with this article from a researcher in CMU EPP. This article talks broadly about telecommunications and the services it make possible. Interesting reading. "Sirbu, M., Technology and Infrastructure, in A National Information Network: Changing Our Lives in the 21st Century, Annual Review of the Institute for Information Studies (IIS: Queenstown, Md., 1992)"

What happens when you pick up the phone and dial a call? Do you know the nitty gritty. Telephony has long been a viable (though intrusive!) medium for commerce. The current Advanced Intelligent Networks as shown in this article really show how the telephony world has become a service oriented world rather than just a phone service. For this and more read Telephony 101.

We all take the Internet for granted. It has become part of our daily lives. But do you really know it's history, the politics and the technology, the evolution of a revolution. Read this for more...Leiner, et al, A Brief History of the Internet. This article provides a concise history of the development of the internet from the 1960s to the present.

Have you ever wondered about the mechanisms that delivered this page to you? Chances are (Probability=0.99 less 0.01 for printing fanatics!) you are sitting at a computer right now, viewing this page in a browser -- so when you clicked on the link for this page, or typed in its URL (Uniform Resource Locator), what happened behind the scenes to bring this page onto your screen? If you've ever been curious about the process, or have ever wanted to know some of the specific mechanisms that allow you to surf the Internet, then How Web Servers and the Internet Work (, will be a real eye opener for you.

Client/Server computing was a paradigm shift from the traditional mainframe-dumb terminal systems that dominated in the 70s. Apart from making distributed computing a reality and removing the bottleneck at the mainframe this allowed the clients to transform from mere zombies to intelligent machines which you could run AOL Messenger on to chat and reduce productivity of your business! Read more about this here Client-Server Software Architectures (SEI)

It's tough remembering URLs sometime ....take this webpage remembering it is not a cakewalk. But what if you had to remember and different numbers for each and every site you visited. Not very easy is it. What makes it possible to use than an IP address? Read How DNS Servers Work (ZDNet) to find out more.

The World Wide Web works more like painting than it does like taking photographs. A Web server "serves up" a page over the Internet, and a Web browser program interprets it. The results may be almost as different as the two painting styles described above. This is the central, surprising truth about the World Wide Web: what you see on a Web page is described, not defined, by its HTML code. It is up to the user's browser program to render it in its final form. Many new Web developers are shocked to discover that they have so little control over the final appearance of their pages. But, for better or worse, that's how the Web works. If you want to create Web pages that can be viewed accurately by a wide range of WWW users, you're going to have to be aware of How Web Browsers and Servers work together

So you learnt what TCP/IP is and how it glues together the networking it seems all nice and pretty! But wait! there is never a free lunch! Nothing is perfect in this world. For the technically inclined this is a good overview of what is wrong with TCP and how it has to be changed for the future  TCP : A combination of Timing, Technology, Implementation and Politics (pdf)

You learnt about routing in class today. However, there are a lot of practical issues to be dealt with when configuring your network. Read (just filter out their inbuilt advertising and its a good article) and this. If you are interested in meeting an animated router click here. What happens when this animated router is part of the internet.

So we learnt that packets of data are sent from one place to the other using TCP. But who is policing this. Imagine you are in a roomful of people and everyone is talking to everyone else at their own speed and accent. The result : you leave the room or someone cries "shut-up y-all". What happens in the network is congestion and overwhelming of one host from another. So what is the way out - flow control !!! As the name suggests TCP uses sliding window flow control. The receiver defines the window, and the sender can transmit any of the data in the window. When the sender receives an acknowledgment, the window moves ahead to include new, unsent data. Click here to see how this is done. By changing the size of the window, the receiver can control the rate at which data is sent. Click here to see this in action. However, as you know the Internet is a "stupid" network (lucky for us the hosts and servers are intelligent!)....much different from the telephone network in which all the functionality is in the network. So what this means is that it loses packets. To see how to deal with this situation click here.

RFCs were mentioned as the primary method for communicating new ideas on protocols, research and standards. An archive of all RFCs is available at More interesting are some RFCs of the not-so-uptight kind, like this one on the Hyper Text Coffee Pot Control Protocol (HTCPCP/1.0) and this one on The Twelve Networking Truths

Clickstream analysis involves studying patterns in the viewing sequence and time of website content. Companies like Webtrends provide products that help website administrators do Data Mining and "Management, analysis and reporting on traffic" on their own websites.

Others like Doubleclick & MediaMetrix provide third party analysis of global clickstreams using innovative techniques. Doubleclick uses the HTTP-referer request-header field (detailed in Section 14.37 of RFC 2068) while MediaMetrix uses a client-resident software program (detailed on their website).

Rivaling these startups are companies like @plan and cyber dialogue that follow the "traditional" route of user surveys. They use telephonic surveys of large samples sizes (40,000 and 80,000 people respectively) to garner in-depth data on Internet users

Which of these two models do you think will survive ? Can both co-exist ?

I guess that enough to irritate you till Friday when I throw another barrage of incessant technology at you. Till then ciao!

Lecture 1 ¨C OVERVIEW

The professor gave you an overview of the different components that are used to build a e-commerce system. By the end of your stay in CMU you will pretty much cover all theses areas in one course or the other. What is critical for you is not to see them as a continuous stream of acronyms but understand their capabilities and applicability so that you can build the future of e-commerce systems. This course is a toolbox of information which you are supposed to use in making new innovative ideas for e-commerce systems. 

   I wont be giving you any good readings from this lecture because they will pretty much be covered in the lectures to come. The key to this lecture was really to understand how the stuff fits together in many meaningful ways to build a complete system. If you build an ecommerce system you need to make use of all these technologies to be successful and therein lies the importance of getting the fundamentals of why they are required.