Seminar on Advanced Internet applications and Systems

1. Seminar on Advanced Internet applications and Systems Hanoch Levy (hanoch at cs.tau.ac.il) Some slides adopted from Y. Mansour, Y. Afek H. Levy Advanced Net Seminar

2. Course Information Lectures: Tuesday 13-15 Kaplun324 Web site: http://www.cs.tau.ac.il/~hanoch/Courses/Seminar-2009/seminar-page.htm Resources: A list of articles (web site + class) Supporting Books: • An Engineering Approach to Computer Networking / Keshav • Computer Networks / Tanenbaum • Data Networks / Bertsekas and Gallager H. Levy Advanced Net Seminar

3. Course Objective • Get exposed to the advanced material in Computer Networks • Learn how to: • Read professional articles • Give Professional presentations • Exposition to what required of at Master Thesis. H. Levy Advanced Net Seminar

4. Structure + Grades • Structure: • Every week one lecture by a student. • Lecturer is encouraged to encourage students to participate. • Students are encouragedto participate. • Grade: • Based on material understanding + quality of presentation • Bonus for active participation H. Levy Advanced Net Seminar

5. Motivation • Last 10-15 years: communications revolution • Internet + Computer communications • Is a key factor of the Information revolution • Implications • A drastic change of some aspects of life • Revolution is affected by life • Technology drives applications • Applications drive technology H. Levy Advanced Net Seminar

6. Motivation (cont) • Applications / technology / research  rapidly change over time • If want to stay in frontier: • => Research material very dynamic • => Course material very dynamic H. Levy Advanced Net Seminar

7. Objectives • Computer Networking course: Internet infra-structure • 1 Introduction and Layering • 2 Physical Layer, Data Link Layer, MAC Protocols • 3 Hubs, Bridges, SwitchesData Link Layer • 4 Switching UnitsSTP, Switching Fabric • 5 Scheduling: Buffer Management Scheduling, WFQ example • 6 Network Layer: RoutingRouting • 7 Reliable Data TransferIP • 8 End to End ProtocolsARQ • 10 Flow Control, Congestion ControlTCP flow & congestion control • 11 Network SecurityNetwork Sniffing (no slides) • 12 DNS, HTTPTCP (state chart) • 13 DDoS • ALL – operations of network of networks. H. Levy Advanced Net Seminar

8. Objectives (2) • Advanced Material – network development following technology • Peer to Peer (P2P): Bittorent, Skype • Songs /movies / video-on-demand/video online • Wireless  AdHoc + delay tolerant networks • Social networks • Security / DDoS H. Levy Advanced Net Seminar

9. Internet Physical Infrastructure Residential access Cable Fiber DSL Wireless ISP Backbone ISP ISP • The Internet is a network of networks • Each individually administrated network is called an Autonomous System (AS) Campus access, e.g., • Ethernet • Wireless H. Levy Advanced Net Seminar 9

10. Data Networks • Set of interconnected nodes exchange information • sharing of the transmission circuits= "switching". • many links allow more than one path between every 2 nodes. • network must select an appropriate path for each required connection. H. Levy Advanced Net Seminar

11. Real Network H. Levy Advanced Net Seminar

12. Layers: Person delivery of parcel Post office counter handling Ground transfer: loading on trucks Airport transfer: loading on airplane Airplane routing from source to destination Peer entities each layer implements a service • via its own internal-layer actions • relying on services provided by layer below H. Levy Advanced Net Seminar

13. The seven Layers Application Application Presentation Presentation Session Session Transport Transport Network Network Network Data Link Data Link Data Link Physical Physical Physical There are only 5 !! Application Intermediate system End system End system H. Levy Advanced Net Seminar

14. The seven Layers - protocol stack data Application Application AH data Presentation Presentation PH data Session Session SH data Transport Transport Network Network NH data Data Link Data Link Physical Physical TH data Network Data Link DH+data+DT Physical bits • Session and presentation layers are not so important, and are often ignored H. Levy Advanced Net Seminar

15. עיקרון השכבות בשכבה X מתקבלת הודעה זהה להודעה ששכבה X מסרה בצד המקור Destination Source Application Application Identical message Transport Transport Identical message Network Network Identical message Data-Link Data-Link Network H. Levy Advanced Net Seminar

16. Internet protocol stack application transport network link physical • application: supporting network applications • ftp, smtp, http • transport: host-host data transfer • tcp, udp • network: routing of datagrams from source to destination • ip, routing protocols • link: data transfer between neighboring network elements • ppp, ethernet • physical: bits “on the wire” H. Levy Advanced Net Seminar

17. Protocol layering and data M M H H H H H H H H H H H H t t n t n l n l t t n t M M M M application transport network Link physical M M source destination message application transport network Link physical segment datagram frame H. Levy Advanced Net Seminar

18. Physical layer L1 • Moves bits between physically connected end-systems • Standard prescribes • coding scheme to represent a bit • shapes and sizes of connectors • bit-level synchronization • Internet • technology to move bits on a wire, wireless link, satellite channel etc. H. Levy Advanced Net Seminar

19. Datalink layer L2 • (Reliable) communication over a single link. • Introduces the notion of a frame • set of bits that belong together • Idle markers tell us that a link is not carrying a frame • Begin and end markers delimit a frame • Internet • a variety of datalink layer protocols • most common is Ethernet • others are FDDI, SONET, HDLC H. Levy Advanced Net Seminar

20. Datalink layer (contd.) • Ethernet (broadcast link) • end-system must receive only bits meant for it • need datalink-layer address • also need to decide who gets to speak next • these functions are provided by Medium ACcess sublayer (MAC) • Datalink layer protocols are the first layer of software • Very dependent on underlying physical link properties • Usually bundle both physical and datalink in hardware. H. Levy Advanced Net Seminar

21. Network layer L3 • Carries data from source to destination. • Logically concatenates a set of links to form the abstraction of an end-to-end link • Allows an end-system to communicate with any other end-system by computing a route between them • Hides individual behavior of datalink layer • Provides unique network-wide addresses • Found both in end-systems and in intermediate systems H. Levy Advanced Net Seminar

22. Network layer (contd.) • Internet • network layer is provided by Internet Protocol (IP) • found in all end-systems and intermediate systems • provides abstraction of end-to-end link • segmentation and reassembly • packet-forwarding, routing, scheduling • unique IP addresses • can be layered over anything, but only best-effort service H. Levy Advanced Net Seminar

23. Network layer (contd.) • At end-systems • primarily hides details of datalink layer • segments and reassemble • detects errors • At intermediate systems • participates in routing protocol to create routing tables • responsible for forwarding packets • schedules the transmission order of packets • chooses which packets to drop H. Levy Advanced Net Seminar

24. Transport layer L4 • Reliable end-to-end communication. • creates the abstraction of an error-controlled, flow-controlled and multiplexed end-to-end link (Network layer provides only a ‘raw’ end-to-end service) • Some transport layers provide fewer services • e.g. simple error detection, no flow control, and no retransmission • Internet • TCP provides error control, flow control, multiplexing • UDP provides only multiplexing H. Levy Advanced Net Seminar

25. Transport layer (contd.) • Error control • GOAL: message will reach destination despite packet loss, corruption and duplication • ACTIONS: retransmit lost packets; detect, discard, and retransmit corrupted packets; detect and discard duplicated packets • Flow control • match transmission rate to rate currently sustainable on the path to destination, and at the destination itself • Multiplexes multiple applications to the same end-to-end connection • adds an application-specific identifier (port number) so that receiving end-system can hand in incoming packet to the correct application H. Levy Advanced Net Seminar

26. Session layer • Not common • Provides full-duplex service, expedited data delivery, and session synchronization • Internet • doesn’t have a standard session layer H. Levy Advanced Net Seminar

27. Session layer (cont.) • Duplex • if transport layer is simplex, concatenates two transport endpoints together • Expedited data delivery • allows some messages to skip ahead in end-system queues, by using a separate low-delay transport layer endpoint • Synchronization • allows users to place marks in data stream and to roll back to a prespecified mark H. Levy Advanced Net Seminar

28. Presentation layer • Usually ad hoc • Touches the application data (Unlike other layers which deal with headers) • Hides data representation differences between applications • characters (ASCII, unicode, EBCDIC.) • Can also encrypt data • Internet • no standard presentation layer • only defines network byte order for 2- and 4-byte integers H. Levy Advanced Net Seminar

29. Application layer • The set of applications that use the network • Doesn’t provide services to any other layer H. Levy Advanced Net Seminar

30. עיקרון השכבות Destination Source אפליק 3 אפליק 2 אפליק 1 Application UDP TCP Transport Network (IPv4) Network Modem Ethernet WiFi Data-Link Network H. Levy Advanced Net Seminar

31. עיקרון השכבות אפליק 3 אפליק 2 אפליק 1 UDP TCP Network (IPv4) Modem Ethernet WiFi Destination Source אפליק 3 אפליק 2 אפליק 1 UDP TCP Network (IPv4) Modem Ethernet WiFi Network H. Levy Advanced Net Seminar

32. Advanced Topics – this course • Denial of service (network security) – network maliciousness • Peer to Peer systems (files, video on demand, streaming) • Wireless Networks • Mobility • Delay tolerant networks • Social network H. Levy Advanced Net Seminar

33. Network Maliciousness – Denial of service • Network fundamental design principle: • User is polite/obey rules • User aims at maximizing his/her own performance • Today: Some users’ aim: • DEGRADE NETWORK PERFORMANCE • Many aspects of network design may collapse • Research subject: • How much damage: malicious user to innocent users • How vulnerable network mechanisms to malicious behavior H. Levy Advanced Net Seminar

34. Network Maliciousness – Cont • Anything studied in: Data structures /algorithms / Computer networks • If one user becomes malicious • How much damage can she pose • How should we pick our algorithms/design • Examples: Hash Table (open / closed) • Data structure course: Equivalent = O(1) avg per insert/delete/member • Malicious analysis (our master student) • Closed much more vulnerable • Attacker can hurt performance of innocent much more •  if you design a net  pick open closed open H. Levy Advanced Net Seminar

35. Peer to Peer • “Historical” Internet : send data from A to K. • Client-server model: • A = server = data source • K = client data consumer • If C wants too – get from A (unicast or broadcast) H. Levy Advanced Net Seminar

36. Peer to Peer • A (source) sends to K. • K (client) may become now a server. • K sends to C (another client). H. Levy Advanced Net Seminar

37. Peer to Peer – WHY?? • Legal (this is how it started…) • Broadcast is not really implemented • A is bottleneck • Resource Utilization: K is idle X% (95?)of the day • Communications (costs!!) • CPU • Issues: • BW cost? Free ride? • Files? Video on demand? Stream (video Broadcast) H. Levy Advanced Net Seminar

38. Wireless Networks • Cellular net: base stations tx to mobiles H. Levy Advanced Net Seminar

39. Wireless Networks • Multihop wireless – use wireless devices as forwarding mechanisms • Difficulty: when node x transmits the whole area must be quiet (avoid colision). • How much spatial capacity the network has? H. Levy Advanced Net Seminar

40. Wireless Networks 1 • Questions: • Difficulty (1) : when node x transmits the whole area must be quiet (avoid collision). • How much spatial capacity the network has? • Paper 2.1 • Difficulty (2): How connected is the network • Paper 2.2 X 2 H. Levy Advanced Net Seminar

41. Wireless Networks 1 • Questions: • How do you allocate resources fairly + efficiently among users? • Difficulty (3) : x can be noisy on purpose, or can request many resources  denial of service to others. • Paper 2.3 X 2 H. Levy Advanced Net Seminar

42. Wireless – Mobility • Wireless devices move around. • Movement can determine: • Density/ Load on network • Connectivity • Ability to transfer data from place to place • Need to understand the mobility patterns • Papers (3) H. Levy Advanced Net Seminar

43. Delay tolerant networks • Network of wireless mobiles • Not necessarily connected all the time • Application can afford DELAY (not real time). E.g: • Non urgent email • Copy of a song • General news • handheld mobility assist in transfering the info over the net. • Delay Tolerant Net • E.g: use the buss system over a campus • Papers (4) H. Levy Advanced Net Seminar

44. Social networks • The new (old?) hot thing on the net. • Data generated by users – for users == YouTube. • Understanding its properties = 5.1 • Social contacts can be used to transfer data • E.g – spread info in campus. • Understanding the social interaction is needed. • Paper (5.2) Spreading info in university? In conference? H. Levy Advanced Net Seminar