The Internet. Charging for Internet. What does 1000M and 200M mean? Dr. Hayden Kwok-Hay So

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1 The Internet CCST9015 Feb 6, 2013 What does 1000M and 200M mean? Dr. Hayden Kwok-Hay So Department of Electrical and Electronic Engineering 2 Charging for Internet One is charging for speed (How fast the apples are delivered to you, but you can eat as many as you want) Another one is charging for amount of data (Number of apples you can eat per month) What does 1GB mean? Are they charging for the same Internet? Which way is more realistic Which way is more fair 3 4

2 Conceptual Picture of the Internet n Each computer thinks it is directly connected to another one through a magic cloud. 5 6 Back in time n Before the Internet, each University and military unit has their own n Different standards n Some of them work only when the computers are ly close to each other Simple point-to-point connections n Networking was a niche Src: DEC s PDP-10 ARPANET n Advanced Research Projects Agency Network n Project active during early 70s n Commonly referred as the predecessor of the Internet n A large-scale research effort involved multiple Universities to construct a communication n First operational packet-switch 7 8

3 Design goals of the Internet n Enable communication among different private s and computers from different vendors with different standard and performance ly located at different locations to communicate n Fault tolerant Allows the overall to operate despite failures in some parts n Scalable Allows to grow very large Internet in Internet Basics n The Internet is a that connects millions of of computing devices throughout the world. n The Internet is formed by connecting many different s. Inter -Net Distributed management n Defines layers of services Connections between computers Security Application services (e.g. world wide web, , gopher, usenet) 10 Internet structure: of s Tier 3 Tier 1 Tier-2 Tier-2 Tier 1 Tier-2 NAP Tier 1 Tier-2 Tier

4 Same Internet? Internet of Things Modern mobile phones, especially smartphones, are examples of advance embedded systems Earlier question: Is the computer and the mobile phone connected to the same Internet? As powerful as a desktop computer 10 years ago For example, both smartphone and a laptop can connect to the Internet using WiFi Answer: (Mostly) Yes Except if you have an older phone with WAP access Researchers predicts the future will be an age of Internet of Things Everything will be connected to the Internet Even TV, refrigerator, microwave oven, light bulb 13 Who owns the Internet? 14 Discussion Billions of computers are connected to the Internet Q: Are they all part of the Internet? A: Technically all computers connected to the Internet is part of the Internet The Internet is made up of millions of computers. When you pay for the Internet, what are you exactly paying for? A. B. C. D. E. Each computer can be configured to perform certain core task of the Internet As a result, the Internet is a distributed effort, with distributed ownership service The world wide web The electricity charge of the servers A right to access to the Internet The software that connects to the Internet More next time 15 16

5 Internet-in-a-Box n Circa 1994, by Spry n Contains all software to connect to the Internet Mosaic browser Dial-up access Whole Internet Guide Photo source: computerhistory.org Administrivia n Homework 1 will be posted by end of today Due 23:55, Feb 26, 2013 n Quiz In-class quiz during next lecture Feb 20, minutes quiz towards the beginning of lecture time Multiple choice questions Close book, close notes no calculator, no computer, no mobile phone, no smart phone, no tablet, no PDA, no mp3 (= no electronics) n 4 quizzes in this semester What are you really paying for? n When you pay your Internet service provider () or your mobile phone company, you are paying for your access to the Internet. n But what kind of service are you really getting in return? 19 20

6 3 Big Ideas about Internet n The end-to-end design principle The core is dumb n Layering Modular design Division of labor n Packet switching Data are transmitted as packets Compared to circuit switching s Circuit Switch vs Packet Switch n Two important ways of communication: n Circuit switching dedicated circuit per connection e.g. telephone (PSTN Public Switched Telephone Network) n Packet switching Data sent through the in discrete packets e.g. Internet Circuit Switching End-to-end resources reserved for exclusive use by each connection n Network resources (e.g., bandwidth) divided into pieces n Pieces allocated to each connection n Guaranteed performance n Resource piece idle if not used by owning call (no sharing) 23 24

7 Packet Switching A B 10 Mbs Ethernet queue of packets waiting for output statistical multiplexing 1.5 Mbs n Each end-end data stream divided into packets n Different users share the same resource as needed n Excessive queuing might cause packet drop D E C Packet Routing n Getting packets from one computer to another n Each data packet must be marked with the destination Just like the address on a postcard n The header of a packet stores all the information about the content of the packet The payload contains the actual data n The machine that decides how to route a packet in the is called a router. 25 Internet Routers n Surprisingly, the Internet routing protocol is relatively simple. n Each stop between router is called a hop. n Each router only knows the general direction on where to route a packet A hierarchal routing idea n Example: Send a packet form the USA to Rm 516, Dept of EEE, HKU, HK 1. Send to HK 2. Postman (router) at HK sends to HKU 3. Router at HKU sends to EEE 4. Router at EEE sends to Rm Internet structure: of s a packet passes through many s! Tier 3 Tier 1 Tier-2 Tier-2 Tier 1 Tier-2 NAP Tier 1 Tier-2 Tier-2 28

8 Visualizing Internet Routes n Traceroute A standard tool to look for all the intermediate routers to a remote site n Interesting website that provides visualization of routes Is packet switch always better? n Great for bursty data e.g. Web browsing resource sharing n Excessive congestion: packet delay and loss n Q: How to provide circuit-like behavior? bandwidth guarantees needed for audio/video apps still an unsolved problem Internet traffic going out of New York (2008) Unlimited Access? n Most Internet service providers offer unlimited access in Hong Kong n Recall the notion of free : Since you can transfer unlimited amount of data with a fixed price, each packet of data transfer is essentially free IF each packet of data transfer is free, and the performance is not guaranteed, then what are you paying the for? 2nd semester, 2012 CCST Dr. H. So 31 32

9 Layered Architecture (1) n Divides the task of data communication into layers of smaller modules n Each layer has a well defined sub-task n Each module has restricted interaction with each other n Each layer provides services to the layer(s) above utilizes services from the layer(s) below Uses services of Uses services of Layer 2 Layer 1 Layer 0 Provides services to Provides services to 33 Layered Architecture (2) n The module in a particular layer only communicates with its counterpart on the other side of the at the same layer. n Any module can be replaced with another module at the same layer as long as it provides the exact same interface. This is the reason, e.g., your web browser works identically regardless of whether you are using WiFi or a wired, or 3G mobile 34 Internet protocol stack n : supporting s FTP, SMTP, HTTP n : host-host data transfer TCP, UDP n : routing of datagrams from source to destination IP, routing protocols n : data transfer between neighboring elements PPP, Ethernet n : bits on the wire How Layering Works? n Each layer hides the layers above from any detail about lower layers. Each layer focuses on its core functions, assuming other layers will handle the rest. data data e.g. A logical connection at layer ack data 35 36

10 Layering: communication data data 37 Summary: layering abstracts details n Each computer thinks it is directly connected to another one through a magic cloud. 38 End-to-End Design Principle In laymen s term: n What happens at the end host is what really matters Slightly more technical: n Some information are only known to the end hosts, so there should be a distinction in responsibility on what the end hosts should perform and what the should perform. Jump to conclusion: The core should be dumb

11 Example: Reliable File Transfer n While you are uploading your photo to Facebook on your mobile phone, you entered into an elevator and lost your mobile phone connection. n Q: which of the following makes more sense? 1. The is smart, so that when the connection comes back (after you exit the elevator), it should retry the upload of the photo. 2. The is dumb, and terminates the connection to Facebook without uploading the picture. File Upload (cont d) n According to E2E principle, the Internet design picks (2) as the answer. n Reason: the mobile phone should not retry the upload because it does not, and should not understand the high-level requirement of the user. n e.g. You may decide to redo the upload if it has failed, and if the photo upload was really that important. n Or, you may just give up and upload another photo n If the (think your mobile phone carrier) retries the upload, AND you perform another upload at the same time, you will end up with two different versions of photo uploaded Summary n Internet is a collection of global s n End-to-End architecture allows the core of the be constantly changing without affecting the end nodes n Packet-switch architecture allows many more nodes to share the same resource than circuit switch n Standardized protocols allow different computers to communicate n Protocol stacks provide layer abstractions 43