 Chapter 1.5. ~ 1.6.

2 KNSS  Students ’ feedback  Had difficulties due to: Lack of knowledge in networking English No microphone for audience  Picked up new terms/ideas ad-hoc networking incentives, coupons QoS  Overall, it was a good experience

3 Chapter 1. Foundation  Requirements of applications and people  Network architecture  Key elements of computer networks  Key performance metrics

4 What do we do with the Internet?  Run Applications  WWW, , soribada, bugsmusic, daum cafes, MP3 file sharing, MSN messengers, etc.  Type of data vs Application  text/video/audio vs  video/audio vs eDonkey/KaZaa

5 How do these applications differ?

6 Requirements in Network Design  Different from one ’ s perspective  Application programmer e.g. needs reliable delivery guarantee  Network designer cost-effective in that resources are efficiently utilized and fairly allocated  Network provider easy to administer, manage, isolate faults, and account for usage  Ordinary user?

7 Basic Requirements  Connectivity  Cost-effective resource sharing  Support for common services

8 Basic Requirements: Connectivity

9

10 Basic Requirements: Connectivity source destination Address? Routing?

11 Basic Requirements: Cost-effective resource sharing Full Mesh

12  Resource sharing  Synchronous time division multiplexing each user takes a turn in transmission user idles when one has nothing to send  Frequency division multiplexing e.g. different TV stations on a physical TV cable link  Statistical multiplexing physical link is shared over time transmission on demand Basic Requirements: Cost-effective resource sharing

13 STDM vs Statistical Multiplexing user1 user2 STDM Statistical Multiplexing

14  How to share?  Whose packet to serve first? First-In First-Out (FIFO) Round Robin  Whose packet to drop? in congestion  How to guarantee or allow special treatment? Quality of service (QoS) guarantee Basic Requirements: Cost-effective resource sharing

15 Basic Requirements: Support for common services  Identify common communication patterns  request/reply  message stream  Reliability against  bit/burst error  packet loss  node/link failure

16 Network Architecture  What is it?  Blueprint that guides design and implementation of networks  Core ideas: layering and protocols  Layering  Abstraction of functions  It provides manageability and modularity  Protocols  abstract objects that make up layers  service interface vs peer interface  protocol specification vs protocol implementation

17 OSI Architecture Application Presentation Session Transport Network Data link Physical Application Presentation Session Transport Network Data link Physical Network Data link Physical Network Data link Physical

18 Internet Architecture UDPTCP IP Network Application

19 The Internet Hourglass IP TCP, UDP,... SMTP, HTTP, RTP,... , WWW, phone,... ethernet, PPP,... CSMA, Sonet,... Copper, fiber, radio,...