Top Down Approach Computer Networking Ppt

[Priamo Gregory]

This textbook is for a first course on computer networking. It has been used in computer science and electrical engineering departments, information systems and informatics departments, in business schools, and elsewhere - at both the undergraduate and graduate levels. It should also be of interest to practitioners in industry as well. Find out more about the textbook here.

Computer Networking: A Top-Down Approach is a classic textbook in the field of computer networking. The two authors, Jim Kurose and Keith Ross, have carefully crafted a course website to support the textbook, with lecture recordings, interactive online questions, and WireShark labs for network packet analysis. The only pity is that this course doesn't have hardcore programming assignments, and Stanford's CS144 makes up for that.

Network design is a beast of a topic. Even if you are well-versed in the basics of networking, creating a new network from scratch can be a daunting project. It involves the meticulous planning of hardware and infrastructure, exploring business requirements and budgets, and a bit of luck.

With most projects, certain key decisions must be made early on. These are foundational and will drive many smaller decisions and most of the work to come. If made well, these decisions set a solid foundation for the work to come. If made poorly, they can create headaches and delays, blow out budgets, or drive projects straight into the ground.

One foundational decision in any network design project is whether to adopt a bottom-up or top-down design. We'll explore these two methods of network design, their merits and drawbacks, and why to choose one over the other for your network design project.

With either a bottom-up or top-down approach, we're talking about where on the OSI model to start. A bottoms-up design begins at the bottom of the model, the physical layer, and works its way up through the layers. However, it's not as literal as running all the cabling, then moving up to OSI layer 2 and installing all the switches, etc.

A bottoms-up design is about establishing a functional network first, focusing on decisions around the hardware, bandwidth, security, etc. Then you move on to higher layers like applications and the decisions that affect those.

The bottom-up approach emphasizes building infrastructure to support whatever application and business goals are to come. It's a rapid and robust deployment, with the idea that change can (and will) happen later as needs shift.

To meet future needs for change, the network is overbuilt, with plenty of power and buffers for room to grow. Ultimately, the immediate needs for networking are more than met without sweating too many of the details.

While the network can be built quickly, critical considerations must still be made towards hardware selection. Some baseline of performance needs must be established, otherwise, lower-quality gear will immediately show its shortcomings. Since bandwidth needs will always increase, starting with room to grow is a necessity, even if you aren't calculating requirements down to the megabit.

After bandwidth, other hardware considerations like compatibility, integration, and long-term support must be considered to keep the network humming long well into the future as hardware ages and is replaced.

Security also must be carefully considered when choosing hardware. Decisions around next-generation firewalls, intrusion detection systems, and traffic inspection must be made to cast a wide security net, given how the bottoms-up design can't inform specific needs. Again, get more capacity than you think you need to leave room for growth.

Despite its advantages, the urgency to get a network off the ground that comes with the bottoms-up model can create problems. The emphasis on speed over business needs can overshadow decisions that should be more strategic. Scalability and capacity are always expensive though; without a more tailored plan, the bottoms-up design can call for spending way more budget than might be required to meet the actual needs to come.

Without business needs and strategic objectives first identified and analyzed, the bottoms-up design can create more problems that overshadow its advantages. Time can be more important and worth the spend, but any project that rushes implementation over planning is more likely to have overruns, be late, or fully fail.

The top-down design does the obvious: plan the network from the top of the OSI layer. It requires considering first not only the application layer but also the organization's business goals and how the technology must align with them. Long-term planning for specific needs is the name of the game here, requiring meticulous and time-consuming planning of goals, service-level agreements, personnel, and budgets.

The most significant advantage of the top-down approach is a tack-sharp alignment with organizational goals. Instead of building a one-size-fits-all, bottom-up network, starting at the top ensures the technical solutions you choose are tailored to meet specific and well-defined business objectives, while still providing room for long-term growth.

Foundationally, the top-down approach requires thorough analysis and collaboration across the business to identify organizational needs and requirements. Only after these items are defined and captured can the tech be chosen.

To meet goals, service-level agreements (SLAs) must be established so measurable metrics can be aligned with these goals. These metrics become the objective standards to measure success and effective service deliverability.

The top-down approach is very time-consuming on the front end, obviously. The planning required will definitely push out deploying hardware, leading to what some might perceive as delays in establishing a functional network. Meticulous planning, while avoiding overspending and overscaling at the front end of the project, might limit flexibility as circumstances change or unforeseen problems arise (as they always do.)

Hopefully, it's clear by now that the network design you choose at the beginning of the project can have substantial effects on how the project goes. This initial decision is critical to your project, possibly making or breaking your success.

A bottom-up design can be implemented quickly, be super adaptable and scale to meet any needs that arise. A top-down design, however, is often more cost-effective and has a higher likelihood of long-term success, as long as the planning is done well.

The choice is a critical one that will shape the trajectory of your network project. There's no one-size-fits-all solution; different designs will fit different needs. Whether you go with the agile bottoms-up design or a strategically planned tops-down design, your success can hinge on how well a network is planned and executed.

CS-UY 4793 Computer Networking3 Credits This course takes a top-down approach to computer networking. After an overview of computer networks and the Internet, the course covers the application layer, transport layer, network layer and link layers. Topics at the application layer include client-server architectures, P2P architectures, DNS and HTTP and Web applications. Topics at the transport layer include multiplexing, connectionless transport and UDP, principles or reliable data transfer, connection-oriented transport and TCP and TCP congestion control. Topics at the network layer include forwarding, router architecture, the IP protocol and routing protocols including OSPF and BGP. Topics at the link layer include multiple-access protocols, ALOHA, CSMA/CD, Ethernet, CSMA/CA, wireless 802.11 networks and link-layer switches. The course includes simple quantitative delay and throughput modeling, socket programming and network application development and Ethereal labs.

Prerequisite(s): Prerequisite for Brooklyn Students: (CS-UY 2134 or CS-UY 1134 ) and (CS-UY 2124 or CS-UY 1124 ) (C- or better) Prerequisite for Abu Dhabi Students: ENGR-UH 3510 or CS-UH 1050 (C- or better) Prerequisite for Shanghai Students: CSCI-SHU 210 (C- or better)
Also listed under: CS-GY 6843
Weekly Lecture Hours: 3 Weekly Lab Hours: 0 Weekly Recitation Hours: 0

Unique among computer networking texts, the Seventh Edition of the popular Computer Networking: A Top Down Approach builds on the author's long tradition of teaching this complex subject through a layered approach in a "top-down manner." The text works its way from the application layer down toward the physical layer, motivating readers by exposing them to important concepts early in their study of networking. Focusing on the Internet and the fundamentally important issues of networking, this text provides an excellent foundation for readers interested in computer science and electrical engineering, without requiring extensive knowledge of programming or mathematics. The Seventh Edition has been updated to reflect the most important and exciting recent advances in networking.

Jim Kurose is a Distinguished University Professor of Computer Science at the University of Massachusetts, Amherst. He is currently on leave from the University of Massachusetts, serving as an Assistant Director at the US National Science Foundation, where he leads the Directorate of Computer and Information Science and Engineering. Dr. Kurose has received a number of recognitions for his educational activities including Outstanding Teacher Awards from the National Technological University (eight times), the University of Massachusetts, and the Northeast Association of Graduate Schools. He received the IEEE Taylor Booth Education Medal and was recognized for his leadership of Massachusetts' Commonwealth Information Technology Initiative. He has been the recipient of a GE Fellowship, an IBM Faculty Development Award, and a Lilly Teaching Fellowship.

Dr. Kurose is a former Editor-in-Chief of IEEE Transactions on Communications and of IEEE/ACM Transactions on Networking. He has been active in the program committees for IEEE Infocom, ACM SIGCOMM, ACM Internet Measurement Conference, and ACM SIGMETRICS for a number of years and has served as Technical Program Co-Chair for those conferences. He is a Fellow of the IEEE and the ACM. His research interests include network protocols and architecture, network measurement, sensor networks, multimedia communication, and modeling and performance evaluation. He holds a PhD in Computer Science from Columbia University.

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