Repetition inför tentan. Kommunikation. Infrastruktur. ÖP Inga hjälpmedel. v v v

Transcription

1 Repetition inför tentan v v v ÖP Inga hjälpmedel Kommunikation Infrastruktur 1

2 Skalbarhet När det inte går bra Organisation 2

3 Illvilja Repetition inför tentan Tentan hur kommer den att bli? Inga hjälpmedel Avspegla kursens andemening att förstå hur det fungerar, vilka utmaningar som finns och hur man hanterar detta i internet. Det kommer också komma detaljfrågor på centrala saker där man ska visa att man verkligen har förstått hur något fungerar. RDT, eller en Distance Vector, Fragmentering Det kommer att komma vissa begreppsfrågor Vad är Mac-adress? Förklara kortfattat. Jämför protokoll X med Y likheter och skillnader. Vad händer? Förklara hur det verkligen fungerar när man trycker på en länk i en webbrowser. Nätverket består av ett antal ihop kopplade Ehternet. Antag att på maskin A finns en användare som kör en browser (webb-klient) och att i maskin B finns en webb-server. Noderna G1 G4 är routrar,där G1 är default för A noden. När tryckning på länken sker är all arp-cachar tomma hos alla noder. Hur hittar det första paketet rätt väg mellan A och B? Förklara vad om händer i varje protokoll i respektive nod längs vägen, samt i vilken ordning saker sker.! Introduction 1-9 3

4 Synthesis: a day in the life of a web request journey down protocol stack complete! application, transport, network, link putting-it-all-together: synthesis! goal: identify, review, understand protocols (at all layers) involved in seemingly simple scenario: requesting www page scenario: student attaches laptop to campus network, requests/receives Link Layer 5-10 A day in the life: scenario browser Comcast network /13 server school network /24 web page web server Google s network /19 Link Layer 5-11 A day in the life connecting to the Internet (runs ) connecting laptop needs to get its own address, addr of first-hop, addr of server: use request encapsulated in, encapsulated in, encapsulated in ernet ernet frame broadcast (dest: FFFFFFFFFFFF) on LAN, received at running server ernet demuxed to demuxed, demuxed to Link Layer

5 A day in the life connecting to the Internet (runs ) server formulates ACK containing client s address, address of first-hop for client, name & address of server encapsulation at server, frame forwarded (switch learning) through LAN, demultiplexing at client client receives ACK reply Client now has address, knows name & addr of server, address of its first-hop Link Layer 5-13 A day in the life ARP (before, before ) ARP query ARP ARP reply ARP (runs ) before sending request, need address of query created, encapsulated in, encapsulated in, encapsulated in. To send frame to, need MAC address of interface: ARP ARP query broadcast, received by, which replies with ARP reply giving MAC address of interface client now knows MAC address of first hop, so can now send frame containing query Link Layer 5-14 A day in the life using Comcast network /13 server (runs ) datagram containing query forwarded via LAN switch from client to 1 st hop datagram forwarded from campus network into comcast network, routed (tables created by R, OSPF, IS-IS and/or BGP routing protocols) to server demux ed to server server replies to client with address of Link Layer

6 A day in the life TCP connection carrying TCP TCP web server (runs ) to send request, client first opens TCP socket to web server TCP SYN segment (step 1 in 3- way handshake) inter-domain routed to web server web server responds with TCP (step 2 in 3-way handshake) TCP connection established! Link Layer 5-16 A day in the life request/reply TCP web page finally (!!!) displayed TCP web server (runs ) request sent into TCP socket datagram containing request routed to web server responds with reply (containing web page) datagram containing reply routed back to client Link Layer 5-17 Chapter 1 Introduction A note on the use of these ppt slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations; and can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following: If you use these slides (e.g., in a class) that you mention their source (after all, we d like people to use our book!) If you post any slides on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this material. Thanks and enjoy! JFK/KWR Computer Networking: A Top Down Approach 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 All material copyright J.F Kurose and K.W. Ross, All Rights Reserved Introduction

7 Chapter 1: introduction our goal: get feel and terminology more depth, detail later in course approach: use Internet as example overview: what s the Internet? what s a protocol? network edge; hosts, access net, physical media network core: packet/circuit switching, Internet structure performance: loss, delay, throughput security protocol layers, service models history Introduction 1-19 Chapter 1: roadmap 1.1 what is the Internet? 1.2 network edge end systems, access networks, links 1.3 network core packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks 1.5 protocol layers, service models 1.6 networks under attack: security 1.7 history Introduction 1-20 Chapter 2: application layer our goals: conceptual, implementation aspects of network application protocols transport-layer service models client-server paradigm peer-to-peer paradigm learn about protocols by examining popular application-level protocols FTP SMTP Application Layer

8 Chapter 2: 2.1 principles of network applications 2.2 Web and 2.3 FTP 2.4 electronic mail SMTP, POP3, IMAP 2.5 Application Layer 2-22 Chapter 3: Transport Layer our goals: understand principles behind transport layer services: multiplexing, demultiplexing reliable data transfer flow control congestion control learn about Internet transport layer protocols: : connectionless transport TCP: connection-oriented reliable transport TCP congestion control Transport Layer 3-23 Chapter transport-layer services 3.4 principles of reliable data transfer 3.5 connection-oriented transport: TCP segment structure reliable data transfer flow control connection management 3.7 TCP congestion control Transport Layer

9 Chapter 4: network layer chapter goals: understand principles behind network layer services: network layer service models forwarding versus routing how a works routing (path selection) broadcast, multicast instantiation, implementation in the Internet Network Layer 4-25 Chapter 4: outline 4.1 introduction 4.2 virtual circuit and datagram networks 4.4 : Internet Protocol datagram format v4 addressing ICMP v6 4.5 routing algorithms link state distance vector hierarchical routin Network Layer 4-26 Chapter 5: Link layer our goals: understand principles behind link layer services: error detection, correction sharing a broadcast channel: multiple access link layer addressing local area networks: ernet instantiation, implementation of various link layer technologies Link Layer

10 Link layer, LANs: outline 5.1 introduction, services 5.2 error detection, correction 5.3 multiple access protocols 5.4 LANs addressing, ARP ernet switches 5.7 a day in the life of a web request Link Layer 5-28 Ch. 6: Wireless and Mobile Networks Background: # wireless (mobile) phone subscribers now exceeds # wired phone subscribers (5-to-1)! # wireless Internet-connected devices equals # wireline Internet-connected devices laptops, Internet-enabled phones promise anytime untethered Internet access two important (but different) challenges wireless: communication over wireless link mobility: handling the mobile user who changes point of attachment to network Wireless, Mobile Networks 6-29 Chapter 6 outline 6.1 Introduction Wireless 6.2 Wireless links, characteristics CDMA 6.3 IEEE wireless LANs ( Wi-Fi ) 6.4 Cellular Internet Access architecture standards (e.g., GSM) Mobility 6.5 Principles: addressing and routing to mobile users 6.6 Mobile 6.7 Handling mobility in cellular networks Wireless, Mobile Networks

11 Chapter 8: Network Security Chapter goals: understand principles of network security: cryptography and its many uses beyond confidentiality authentication message integrity security in practice: firewalls and intrusion detection systems security in application, transport, network, link layers Network Security Chapter 8 roadmap 8.1 What is network security? 8.2 Principles of cryptography Network Security 11