CS 352 Internet Technology

Transcription

1 CS 352 Internet Technology Badri Nath Dept. of Computer Science Rutgers University 1

2 About us: Management Professor: Badri Nath Office hours: Monday 12 noon-2 PM or by appt Core 320 Class: Mon, Thu 8:40 to 10 AM PH-115 TAs 1. Alireza, Naghizadeh 2. Gale Abraham Course info 2

3 Class etiquette Cell phones in off position No FB status updates, texting, selfies in class If you need to surf while in class ( I prefer you do not), do not disturb your neighbors Stop me anytime to ask questions Try to learn as much as you can in class 3

4 What is a Network? Carrier of information between 2 or more entities Interconnection may be any medium capable of communicating information: copper wire Lasers (optic fibre) Microwave Cable (coax) satellite link Wireless link (cellular, , bluetooth) Examples: Ethernet, (WIFI), cable modem, cellular 4

5 A single link network Send bits of data in packets or frames Need to worry about errors, how to convert bits into signals and vice versa 5

6 A single link multiple access network Send bits of data in packets or frames Need to worry about errors, how to convert bits into signals and vice versa In addition, how to differentiate among many receivers Every host as a link layer address MAC address Packets or frames will have destination address Cant have every computer in the world on the same link! 6

7 A network Router Router Connect multiple links via routers Router Need to figure out how to route packets from one host to another host 7

8 Components of a network Links Communication links for transmission Host Computer running applications of end user Router Computer for routing packets from input line to another output line Gateway A device directly connected to two or more possibly different networks (serves as an access point), provides access Network A group of hosts, links, routers capable of sending packets among the members of the network 8

9 Why Networks? Availability of Resources Resources become available regardless of the user s physical location Load Sharing Jobs processed on least loaded machine High Reliability Alternative source of supply (multiple copies) Human-to-Human Communication e.g., Telephone (Voice-over IP), messaging 9

10 What is Internet Technology? What is an internet? Network of networks What is the Internet? A global internet based on the IP protocol Network to network adopt a common language To what does Internet technology refer? Architecture, protocols and services 10

11 Architecture-wise Network : Collection of interconnected machines 11

12 Internet Growth Mobile Phones: in M, now 5 B 12

13 Evolution of Internet Applications 2010-now ftp web chat Games IM Yahoo! news Blog Search Music itunes Games search Wikipedia Craiglist Youtube 13

14 Web evolution Web 1.0 Read-only web Content Users Yahoo, google, daily targum Web 2.0 Read-write web Content Users and Users Content Blog, wikipedia, facebook, twitter, youtube Web 3.0 Contextual web Personalized, location dependent Craiglist on your phone changes as you drive around!! Apps on your phone get organized, Google NOW Web 4.0 Inanimate objects or devices will be connected as first class objects -- refrigerator, car, fitbit smart phone,. Thermostat Prediction-Machine learning 14

15 400 Hrs Content is exploding 2018 HD quality video: 2G to 4G / hour Source: Mary Meeker Internet trends Presentation 15

16 1.8 B youtube users 16

17 Transforming entire economy Mobile payment Venmo, square, paytm Shared resource platforms Uber, Airbnn, weworks 17

18 Just dancing and listening to video, tweets, selfies, share Source: Mary Meeker Internet trends Presentation 18

19 Scale of Web apps 2.23 B active users > 1 B iphones 300 M ipads 3.5 B searches/day 19

20 Impact of the Net on People Access to remote information HW assignments from my server Stock quotes from financial web site News, wikipedia, google Person to person and group communication , whatsapp, blogs,fb,twitter, instagram, snapchat Interactive entertainment youtube (video clips), netflix (movies) music (itunes), spotify, pandora (radio) Online commerce Priceline, Amazon, Ebay, 20

21 Impact of the Net on Society The good Access to information (i-commerce), e- commerce, incredible productivity tool The bad gossip, too much information, chat room, net addicts, The ugly Fraud, pornography, phishing, threatening (bullying) But, it is just a mirror of society 21

22 Internet Players Users, people who use the applications Everyone (mom and pop, kids) get something done (hopefully useful) Designers You: protocol design and implementation performance, cost and scale Service Providers Administrators and ISPs ( Management, revenue, deployment Market/business models for the Internet Consumer to consumer (ebay), Business to consumer (amazon, orbitz, netflix), Business to business (alibaba, importers.com,21food.com), Consumer to business (hotjobs, monster), Govt to C, Govt to B etc 22

23 Internet service providers (ISPs) Local ISPs- Tier 3 (cablevision) Regional ISPs Tier2 (internap) Global ISPs (verizon, Sprint, ATT, level 3, century link, Deutsche Telekom, NTT) provide access to entire internet; connect ISP to other ISPs Peering ISPs Have a mutual relationship about forwarding traffic of each others customers (no $ involved) Transit ISPs Provides access to all reachable customers ($$ involved) 23

24 Core Networks: ISP Tiers Local and tier- 3 ISPs are customers of higher tier ISPs connecting them to rest of Internet local ISP local ISP Tier 3 ISP Tier-2 ISP Tier 1 ISP Tier-2 ISP local ISP local ISP Tier 1 ISP local ISP Tier-2 ISP NAP Tier 1 ISP Tier-2 ISP local ISP local ISP Tier-2 ISP local ISP 24

25 ISPs connected via Exchanges Flatter Internet Business models among, content provider, transit providers, and customers Net Neutrality 25 Internet Inter-domain traffic By Labovitz et.al, SIGCOMM 2010

26 Types of Networks in an Internet Local area networks Privately owned, within building High speed, broadcast, Ethernet 2 to 100 Mbps Wide area networks Spans a large area Point-to-point, high speed fiber or trunk lines Long delays but very high speed links Several Gbps 26

27 Types of Networks (cont d) Wireless networks Hosts connected by infrared or radio links Local area and wide area Satellite networks 27

28 GOOGLE WAN 28

29 Microsoft WAN 29

30 Historical perspective Late 1960 s: ARPAnet (4 nodes) Early 1970 s: Aloha net, ethernet, multiple access problem Mid-to-late 1970 s: TCP/IP, 4.2BSD 1980 s to early 1990 s: early internet growth, & file transfer dominant, NSFNET Mid 1990s: NSFnet handed over to commercial service providers, WWW explodes Late 90s, business models using the internet; dot-com boom and bust Early to mid 2000s, WEB 2.0, Facebook, google, wikipedia Future: Embedded networks, 5 to 10 billion devices waiting to be networked, media convergence. RFID tags 30

31 Course Goals Understand the basic principles of computer networks Understand the Internet and its protocols Understand the key design principles used to build the Internet 31

32 Course Work Written Homeworks (5%) 4 or 5 2 Mid-terms (15% each) No electronic devices or notes allowed. No cheat sheets allowed Final (35%) You must send the instructor at least 2 weeks before the final if you need to take the makeup! Project (30%) Part 1 (10%) Part 2 (10%) Part 3 (10%) 32

33 Programming assignments Single long project Broken into three parts Can work in a group of 2 Both program and write-up required Background needed to get started: C or Python (211, 214 level) Comfortable using data structures(stacks, trees, vector) Unix (login, handin, permissions, gcc) W1L2 33

34 Programming Assignment Each phase of the code feeds into the next phas Make improvements for next phase of the assignment. No late handin Handin via sakai Failure to meet the deadline will result in a zero for all team members. No exceptions! 34

35 Academic integrity No cheating on projects and exams Run code similarity detectors on the projects & code review Scrutinize exams for copying Department academic integrity policy rity/ Acknowledge your awareness of this policy by the end of September to continue to access department computing facilities 35

36 Some Definitions Network: Collection of interconnected machines Host: Machine running user application Subnet: Subset of the network, responsible for carrying messages between hosts Channel: Logical line of communication Topology: Network configuration Router: Process packets and routes packets towards the destination Protocol: Rules of communication 36

37 With 1 s and 0 s 1. How Do Computers Communicate? Computers only deal with 1 s and 0 s So do networks How do we transmit 1 s and 0 s in a network? 37

38 Physical Transmission See Tanenbaum Fig. 2-18, pp

39 (1) Circuit Switching Switching Schemes (2) Message Switching (Store-and-Forward) (3) Packet Switching (Store-and-Forward) 39

40 Circuit Switching Provides service by setting up the total path of connected lines from the origin to the destination Example: Telephone network 40

41 Circuit Switching (cont d) 1. Control message sets up a path from origin to destination 2. Return signal informs source that data transmission may proceed 3. Data transmission begins 4. Entire path remains allocated to the transmission (whether used or not) 5. When transmission is complete, source releases the circuit 41

42 Time Circuit Switching (cont d) Call request signal Propagation Delay Transmission Delay Call accept signal Data Transmission Time Data A B C D IMPs 42

43 Message Switching Each message is addressed to a destination When the entire message is received at a router, the next step in its journey is selected; if this selected channel is busy, the message waits in a queue until the channel becomes free Thus, the message hops from node to node through a network while allocating only one channel at a time Analogy: Postal service 43

44 Time Message Switching (cont d) Header Msg Transmission Delay Msg Queueing Delay Msg A B C D IMPs 44

45 Packet Switching Messages are split into smaller pieces called packets These packets are numbered and addressed and sent through the network one at a time Pipelining 45

46 Time Packet Switching (cont d) Header Pkt 1 Pkt 2 Pkt 3 Pkt 1 Transmission Delay Pkt 2 Pkt 3 Pkt 1 Pkt 2 Pkt 3 A B C D IMPs 46

47 Comparisons (1) Header Overhead Circuit < Message < Packet (2) Transmission Delay Short Bursty Messages: Packet < Message < Circuit Long Continuous Messages: Circuit < Message < Packet 47

48 Telephone Network Internet Connection-based Admission control Intelligence is in the core network Every service provided by the telephone company Traffic carried by relatively few, wellknown communications companies Packet-based Best effort Intelligence is at the endpoints Services provided by anyone Traffic carried by many routers, operated by multitude of service providers 48

49 Protocols Building blocks of a network architecture Each protocol object has two different interfaces service interface: operations on this protocol peer-to-peer interface: messages exchanged with peer Term protocol refers to both the specification and implementation of the module 49

50 Internet Architecture Defined by Internet Engineering Task Force (IETF) Hourglass Design Application vs Application Protocol (FTP, HTTP) HTTPS FTP HTTP SIP RTSP TCP UDP IP NET 1 NET 2 NET n 50

51 Why Layering? Network communication is very complex Testing and maintenance is simplified Easy to replace a single layer with a different version 51

52 Issues at each layer Application Port# Address Transport Network End-to-end Routing Link Access 52

53 functionality at each layer Application Port# IP Address Transport Network E-2-E Routing Link Access 53

54 TCP/IP Layering Architecture Application Transport Internet/Network Host-to-Net A simplified model The network layer Hosts drop packets into this layer, layer routes towards destination- only promise- try my best The transport layer reliable byte-oriented stream 54

55 Functions: Host-to-Network layer: a) Physical Layer Transmission of a raw bit stream Forms the physical interface between devices Issues: Which modulation technique (bits to pulse)? How long will a bit last? Bit-serial or parallel transmission? Half- or Full-duplex transmission? How many pins does the network connector have? How is a connection set up or torn down? 55

56 Functions: Host-to-network layer b) Data Link Layer Provides reliable transfer of information between two adjacent nodes Creates frames, or packets, from bits and vice versa Provides frame-level error control Provides flow control In summary, the data link layer provides the network layer with what appears to be an errorfree link for packets 56

57 Functions: Network Layer Responsible for routing decisions Dynamic routing Fixed routing Performs congestion control 57

58 Functions: Transport Layer Hide the details of the network from the session layer Example: If we want replace a point-to-point link with a satellite link, this change should not affect the behavior of the upper layers Provides reliable end-to-end communication 58

59 Functions (cont d): Transport Layer (cont d) Perform end-to-end flow control Perform packet retransmission when packets are lost by the network 59

60 Application Layer Application layer protocols are application-dependent Provides session support and presentation support Session state, encryption, encoding Implements communication between two applications of the same type Examples: FTP HTTP SMTP ( ) XMPP Extensible messaging and presence protocol SIP Session Inititation Protocol 60

61 Internet Design Principles Scale Protocols should work in networks of all sizes and distances Incremental deployment New protocols need to be deployed gradually Heterogeneity Different technologies, autonomous organizations End-to-end argument Application requirements, to the extent possible should be delegated to the edges; application knows best Encryption: Should the network provide as default or let applications or end points implement encryption on a need basis? 61

62 Measuring a Network s Performance A Brief Introduction 62

63 Some Definitions Packet length: size of a packet (units = bits or bytes) Channel speed or bandwidth: How fast the channel can transmit bits (units = bits/second or Bytes/second or packets/second) Packet transmission time: amount of time to transmit an entire packet (units = seconds) Propagation delay: Delay imposed by the properties of the link. Depends on the link s distance (units = seconds) Total transfer time =propagation delay + packet transmission time 63

64 Digression: Units Bits are the units used to describe an amount of data in a network 1 kilobit (Kbit) = 1 x 10 3 bits = 1,000 bits 1 megabit (Mbit) = 1 x 10 6 bits = 1,000,000 bits 1 gigabit (Gbit) = 1 x 10 9 bits = 1,000,000,000 bits Seconds are the units used to measure time 1 millisecond (msec) = 1 x 10-3 seconds = seconds 1 microsecond (msec) = 1 x 10-6 seconds = seconds 1 nanosecond (nsec) = 1 x 10-9 seconds = seconds Bits per second are the units used to measure channel capacity/bandwidth and throughput bit per second (bps) kilobits per second (Kbps) megabits per second (Mbps) Bytes (8 bits a byte) Mega bytes, Giga bytes, Tera bytes, Peta Bytes, Exa bytes 64

65 Example 500 m A B packet length = 1500 bytes channel capacity = 10 Mbps propagation delay factor = 5 msec/km 1. How long does it take a single bit to travel on the link from A to B? 2. How long does it take A to transmit an entire packet onto the link? 65

66 Conveyor belt Time for the first box = time to travel the length of the belt Propagation delay Time for successive boxes (1/rate at which boxes are put on the belt) Transmission time = number of boxes /rate For packets the units are bits/sec, Bytes/sec or packets/sec Total transfer time= Transmission time + Propagation delay 66

67 Propagation Delay 1. How long does it take a single bit to travel on the link from A to B of length 500 m with a prop. delay factor = 5 msec/km? Another way to ask this question: If it takes a signal 5 msec to travel 1 kilometer, then how long does it take a signal to travel 500 meters? 5 msec 1000 m = 500 m t Solving for t t = 2.5 msec 67

68 Packet Transmission Time 2. How long does it take A to transmit an entire packet onto the link? Relevant information: packet length = 1500 bytes channel speed = 10 Mbps Another way to ask this question: If the link can transmit 10 million bits in a second, how many seconds does it take to transmit 1500 bytes (8x1500 bits)? 10 Mbits 1 sec = 1500 x 8 bits t Solving for t t = sec (or 1.2 msec) 68

69 Message switching vs Packet switching R1 Link speed is 1000 Bytes/sec. (ignore prop delay) Packet size is 100 Bytes, file size is 1000 Bytes Find total time to transfer the entire file under the two switching techniques Msg switching Packet switching 69

70 Message switching vs Packet switching R1 Link speed is 1000 Bps. (prop delay for each link=10 msec) Packet size is 100 bytes, file size is 1000 bytes Find total time to transfer the entire file under the two switching techniques Msg switching Packet switching 70

71 Message switching vs Packet switching L1 L2 L3 R1 R2 Link speed is 1000 Bytes per second. (ignore prop delay, ignore header overhead) Packet size is 100 Bytes, file size is 1000 Bytes Find total time to transfer the entire file under the two switching techniques 71