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![8
Internet[work]
Internet[work]
• A collection of
interconnected
networks
• Host: network
endpoints (computer,
PDA, light switch, …)
• Router: node that
connects networks
• Internet vs. internet](https://image.slidesharecdn.com/lesson1-introductiontocomputernetworks-250822223608-9c67d041/75/LESSON-1-INTRODUCTION-TO-COMPUTER-NETWORKS-ppt-8-2048.jpg)
![29
Next Lecture: Design Considerations
• How to determine split of functionality
• Across protocol layers
• Across network nodes
• Assigned Reading
• [SRC84] End-to-end Arguments in System
Design
• [Cla88] Design Philosophy of the DARPA
Internet Protocols
• Optional Reading
• [Cla02] Tussle in Cyberspace: Defining
Tomorrow’s Internet](https://image.slidesharecdn.com/lesson1-introductiontocomputernetworks-250822223608-9c67d041/75/LESSON-1-INTRODUCTION-TO-COMPUTER-NETWORKS-ppt-27-2048.jpg)
![8
Internet[work]
Internet[work]
• A collection of
interconnected
networks
• Host: network
endpoints (computer,
PDA, light switch, …)
• Router: node that
connects networks
• Internet vs. internet](https://crownmelresort.com/image.slidesharecdn.com/lesson1-introductiontocomputernetworks-250822223608-9c67d041/75/LESSON-1-INTRODUCTION-TO-COMPUTER-NETWORKS-ppt-8-2048.jpg)
![29
Next Lecture: Design Considerations
• How to determine split of functionality
• Across protocol layers
• Across network nodes
• Assigned Reading
• [SRC84] End-to-end Arguments in System
Design
• [Cla88] Design Philosophy of the DARPA
Internet Protocols
• Optional Reading
• [Cla02] Tussle in Cyberspace: Defining
Tomorrow’s Internet](https://crownmelresort.com/image.slidesharecdn.com/lesson1-introductiontocomputernetworks-250822223608-9c67d041/75/LESSON-1-INTRODUCTION-TO-COMPUTER-NETWORKS-ppt-27-2048.jpg)
LESSON 1-INTRODUCTION TO COMPUTER NETWORKS.ppt
- 1. 1 Class Coverage • Littlecoverage of physical and data link layer • Little coverage of undergraduate material • Students expected to know this • Focus on network to application layer • We will deal with: • Protocol rules and algorithms • Investigate protocol trade-offs • Why this way and not another?
- 2. 2 Lecture Topics • Layering •Internet architecture • Routing (IP) • Transport (TCP) • Queue management (FQ, RED) • Naming (DNS)
- 3. 3 What is theObjective of Networking? • Communication between applications on different computers • Must understand application needs/demands • Traffic data rate • Traffic pattern (bursty or constant bit rate) • Traffic target (multipoint or single destination, mobile or fixed) • Delay sensitivity • Loss sensitivity
- 4. 4 Back in theOld Days…
- 5.
- 6. 6 Packet Switching • Interleavepackets from different sources • Efficient: resources used on demand • Statistical multiplexing • General • Multiple types of applications • Accommodates bursty traffic • Addition of queues
- 7. 7 Characteristics of PacketSwitching • Store and forward • Packets are self contained units • Can use alternate paths – reordering • Contention • Congestion • Delay
- 8. 8 Internet[work] Internet[work] • A collectionof interconnected networks • Host: network endpoints (computer, PDA, light switch, …) • Router: node that connects networks • Internet vs. internet
- 9. 9 Challenge • Many differencesbetween networks • Address formats • Performance – bandwidth/latency • Packet size • Loss rate/pattern/handling • Routing • How to translate between various network technologies?
- 10. 10 How To FindNodes? Internet Computer 1 Computer 2 Need naming and routing
- 11. 11 Naming What’s the IPaddress for www.cmu.edu? It is 128.2.11.43 Translates human readable names to logical endpoints Local DNS Server Computer 1
- 12.
- 13. 13 Meeting Application Demands •Reliability • Corruption • Lost packets • Flow and congestion control • Fragmentation • In-order delivery • Etc…
- 14. 14 What if theData gets Corrupted? Internet GET windex.html GET index.html Solution: Add a checksum Problem: Data Corruption 0,9 9 6,7,8 21 4,5 7 1,2,3 6 X
- 15. 15 What if Networkis Overloaded? Problem: Network Overload • Short bursts: buffer • What if buffer overflows? • Packets dropped • Sender adjusts rate until load = resources “congestion control” Solution: Buffering and Congestion Control
- 16. 16 What if theData gets Lost? Internet GET index.html Problem: Lost Data Internet GET index.html Solution: Timeout and Retransmit GET index.html GET index.html
- 17. 17 Problem: Packet size Solution:Fragment data across packets What if the Data Doesn’t Fit? • On Ethernet, max IP packet is 1.5kbytes • Typical web page is 10kbytes GET inde x.ht ml GET index.html
- 18. 18 Solution: Add SequenceNumbers Problem: Out of Order What if the Data is Out of Order? GET x.ht inde ml GET x.htindeml GET index.html ml 4 inde 2 x.ht 3 GET 1
- 19. 19 Lots of FunctionsNeeded • Link • Multiplexing • Routing • Addressing/naming (locating peers) • Reliability • Flow control • Fragmentation • Etc….
- 20. 20 What is Layering? •Modular approach to network functionality • Example: Link hardware Host-to-host connectivity Application-to-application channels Application
- 21. 21 Protocols • Module inlayered structure • Set of rules governing communication between network elements (applications, hosts, routers) • Protocols define: • Interface to higher layers (API) • Interface to peer • Format and order of messages • Actions taken on receipt of a message
- 22. 22 Layering Characteristics • Eachlayer relies on services from layer below and exports services to layer above • Interface defines interaction • Hides implementation - layers can change without disturbing other layers (black box)
- 23. 23 Layering Host Host Application Transport Network Link User AUser B Layering: technique to simplify complex systems
- 24. 24 E.g.: OSI Model:7 Protocol Layers • Physical: how to transmit bits • Data link: how to transmit frames • Network: how to route packets • Transport: how to send packets end2end • Session: how to tie flows together • Presentation: byte ordering, security • Application: everything else
- 25. 25 OSI Layers andLocations Switch Router Host Host Application Transport Network Data Link Presentation Session Physical
- 26. 28 Is Layering Harmful? •Sometimes.. • Layer N may duplicate lower level functionality (e.g., error recovery) • Layers may need same info (timestamp, MTU) • Strict adherence to layering may hurt performance
- 27. 29 Next Lecture: DesignConsiderations • How to determine split of functionality • Across protocol layers • Across network nodes • Assigned Reading • [SRC84] End-to-end Arguments in System Design • [Cla88] Design Philosophy of the DARPA Internet Protocols • Optional Reading • [Cla02] Tussle in Cyberspace: Defining Tomorrow’s Internet