Seminar on Advanced Internet applications and Systems Hanoch Levy (hanoch at cs.tau.ac.il) Some slides adopted from Y. Mansour, Y. Afek 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar Course Information Lectures: Wed 10-12 Kaplun324 Web site: http://www.cs.tau.ac.il/~hanoch/ 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 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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. 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar Structure + Grades Structure: Every week one lecture by a student. Lecturer is encouraged to encourage students to participate. Students are encouraged to participate. Grade: Based on material understanding + quality of presentation Bonus for active participation 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar Motivation (cont) Applications / technology / research  rapidly change over time If want to stay in frontier: => Research material very dynamic => Course material very dynamic 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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. 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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 21.11.2018 H. Levy Advanced Net Seminar

Internet Physical Infrastructure Residential access Cable Fiber DSL Wireless 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 21.11.2018 H. Levy Advanced Net Seminar 9

H. Levy Advanced Net Seminar 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. 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar Real Network 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar The seven Layers There are only 5 !! Application Presentation Application Session Transport Network Data Link Physical Presentation Application Session Transport Network Data Link Physical Network Data Link Physical Intermediate system End system End system 21.11.2018 H. Levy Advanced Net Seminar

The seven Layers - protocol stack data AH PH SH Presentation Application Session Transport Network Data Link Physical Presentation Application Session Transport Network Data Link Physical TH data Network data NH Data Link DH+data+DT Physical bits Session and presentation layers are not so important, and are often ignored 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar עיקרון השכבות בשכבה X מתקבלת הודעה זהה להודעה ששכבה X מסרה בצד המקור Source Destination Application Application Identical message Transport Transport Identical message Network Network Identical message Data-Link Data-Link Network 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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” 21.11.2018 H. Levy Advanced Net Seminar

Protocol layering and data source destination application transport network Link physical M H t n l message M H t n l application transport network Link physical segment datagram frame 2nd break ?! 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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. 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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 21.11.2018 H. Levy Advanced Net Seminar

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. 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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 21.11.2018 H. Levy Advanced Net Seminar

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 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar Session layer Not common Provides full-duplex service, expedited data delivery, and session synchronization Internet doesn’t have a standard session layer 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar Application layer The set of applications that use the network Doesn’t provide services to any other layer 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar עיקרון השכבות Source Destination אפליק 3 אפליק 2 אפליק 1 Application UDP TCP Transport Network (IPv4) Network Modem Ethernet WiFi Data-Link Network 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar עיקרון השכבות Source Destination אפליק 3 UDP Network (IPv4) Ethernet אפליק 2 אפליק 1 TCP WiFi Modem אפליק 3 אפליק 2 אפליק 1 UDP TCP Network (IPv4) Modem Ethernet WiFi Network 21.11.2018 H. Levy Advanced Net Seminar

Advanced Topics – this course Peer to Peer systems (files, video on demand, streaming) Wireless Networks Mobility Delay tolerant networks Social network Denial of service (network security) – network maliciousness ?? 21.11.2018 H. Levy Advanced Net Seminar

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 21.11.2018 H. Levy Advanced Net Seminar

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 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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) 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar Peer to Peer A (source) sends to K. K (client) may become now a server. K sends to C (another client). 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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) 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar Wireless Networks Cellular net: base stations tx to mobiles 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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? 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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) 21.11.2018 H. Levy Advanced Net Seminar

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) 21.11.2018 H. Levy Advanced Net Seminar

H. Levy Advanced Net Seminar 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? 21.11.2018 H. Levy Advanced Net Seminar