1 Computer Networks and Communications [Δίκτυα Υπολογιστών και Επικοινωνίες] Lecture 1: Introduction Univ. of the Aegean Financial and Management Engineering Dpt Petros KAVASSALIS

2 What you will learn in this course A set of fundamental concepts for understanding Data Networks and the Internet A set of fundamental concepts for understanding Data Networks and the Internet  What is the Internet?  Internet architecture and layers  Internet applications and services  New concepts in the evolution of the Internet  The Internet goes Wireless… Familiarization with the structure and organization of Digital Networks Familiarization with the structure and organization of Digital Networks  Business and Social Networks  Electronic Markets and Online Feedback Mechanisms

3 Who am I? PhD in Economics and Management (Univ. Paris Dauphine & Ecole polytechnique) PhD in Economics and Management (Univ. Paris Dauphine & Ecole polytechnique) Research experience Research experience  Ecole polytechnique, Paris  MIT Center of Technology Policy and Industrial Development, MIT CTPID (MIT Internet Telecommunications Convergence Consortium) Current positions Current positions  Univ. of the Aegean (FME): Assoc. Professor  RACTI: Director of ATLANTIS Group

4 Communication tools pkavassalis [at] atlantis-group.gr pkavassalis [at] atlantis-group.gr Course web site: see fme website Course web site: see fme website

5 Course Textbook [ z64SJRBAC&dq=tanenbaum+networks&printsec=frontcover&source=bn&hl=el&ei=ml- dSfH9L4S2jAeJ5L3ZBQ&sa=X&oi=book_result&resnum=4&ct=result]

Supplementary Texts & References William Stallings, Computer Networking with Internet Protocols, Prentice Hall, 2004 William Stallings, Computer Networking with Internet Protocols, Prentice Hall, 2004 William Stallings, Computer Networking with Internet Protocols, Prentice Hall, 2004 William Stallings, Computer Networking with Internet Protocols, Prentice Hall, 2004 James F. Kurose and Keith W. Ross, Computer Networking: A Top-Down Approach, Addison-Wesley, 2008 James F. Kurose and Keith W. Ross, Computer Networking: A Top-Down Approach, Addison-Wesley, 2008 James F. Kurose and Keith W. Ross, Computer Networking: A Top-Down Approach, Addison-Wesley, 2008 James F. Kurose and Keith W. Ross, Computer Networking: A Top-Down Approach, Addison-Wesley,

7 Students evaluation Class Participation (20%) Class Participation (20%)+ Assignments (20%) Assignments (20%)+ Final Exam (60%) Final Exam (60%)

What is a network? A hardware and software communications system formed by the interconnection of three or more devices A hardware and software communications system formed by the interconnection of three or more devices Devices may include: Devices may include:  Telephones  PCs  Routers  Other communications devices (please give examples) 8

Why use a network? Allow multiple devices to communicate concurrently Allow multiple devices to communicate concurrently Allow communications to proceed at the highest achievable speed Allow communications to proceed at the highest achievable speed Reduce cost associated with the interconnections! Reduce cost associated with the interconnections!  Look at that      k = n (n-1) / 2 9

Network: The organization of a communication network… Assumes the use of some interconnection equipment in the middle Assumes the use of some interconnection equipment in the middle  That was, in the early days of communications, a Central Office (CO)  That is, today, a Router (please find a router picture from the Web: what is the functionality it provides?) 10

Like that! 11 Wireless Access Point Mobile Client Router Outside World (The Internet) Server Computer Client Computer Switch 1 Switch 2 Switch 3 Switch 4 Message (Frame) Access Line Trunk Line Server ApplicationClient Application Access Lines Connect Computers to Switches Access Lines Connect Computers to Switches Trunk Lines Connect Switches to Switches and Switches to Routers Trunk Lines Connect Switches to Switches and Switches to Routers

Note 1: the Ethernet 12 A1-44-D5-1F-AA-4CB2-CD-13-5B-E4-65 Switch D C4-B6-F9 C3-2D-55-3B-A9-4F Port 15 Switching Table PortHost 10A1-44-D5-1F-AA-4C 13B2-CD-13-5B-E C3-2D-55-3B-A9-4F 16 D C4-B6-F9 Switching Table PortHost 10A1-44-D5-1F-AA-4C 13B2-CD-13-5B-E C3-2D-55-3B-A9-4F 16 D C4-B6-F9 15C3-2D-55-3B-A9-4F C3- is out Port

Note 2: … and Internet 13 Host B Host A Network X Network Y Network Z R1 R2 Route A-B

Network+: Functions grouped in layers 14

The geography of the Internet 15

Internet in a nutshell Protocols control sending, receiving of msgs Protocols control sending, receiving of msgs  e.g., TCP, IP, HTTP, IM, Ethernet Composition: “network of networks” Composition: “network of networks”  loosely hierarchical  public Internet versus private intranet Standards Standards  RFC: Request for comments  IETF: Internet Engineering Task Force 16 Home network Institutional network Mobile network Global ISP Regional ISP

Infrastructures and applications… Communication infrastructure enables various distributed applications Communication infrastructure enables various distributed applications  , Web browsing, Skypying, file sharing, online games Communication applications are supported by Communication applications are supported by  reliable data delivery from source to destination  “best effort” (unreliable) data delivery 17 Home network Institutional network Mobile network Global ISP Regional ISP

… “separated” in two blocks IP (spanning-layer) separates information bitways from applications IP (spanning-layer) separates information bitways from applications Applications may work over multiple substrates (network techs) and these substrates do not pre- specify the development of new applications Applications may work over multiple substrates (network techs) and these substrates do not pre- specify the development of new applications [I will come back!] [I will come back!] 18