Evolution of Computer Networks: From Mainframes to Peer-to-Peer

1. Overview CS 332 – Computer Networks CS332 - Computer Networks

2. How did we get here? • 1950 - 1968 The golden age of the mainframe/data center • 1968 Initial ARPAnet deployment • 1970 First 16-bit minicomputer • 1976 Ethernet introduced • 1979 Initial USENET news deployment • 1980 IBM PC introduced 4.0BSD Unix with integrated (inter)networking • 1980-present Popularization of "workstations" • 1990s Explosion of the Internet/Web Peer to Peer networking etc. CS332 - Computer Networks

3. Trends Mainframe - Terminal Isolated PC - SneakerNet Client/Server Networked PCs Hosted Apps/Web Apps Trending toward applications on central servers with relatively "dumb" PCs? Difference between web-app paradigm and old mainframe/terminal? CS332 - Computer Networks

4. Sun/Oracle "Network Computer" • Late 1990's, small footprint, no disk, ran Java apps hosted on an application server. • Image found on the GlobalNerdy blog by Joey DeVilla CS332 - Computer Networks

5. Applications • SSH, E-mail, file transfer • Business: electronic funds transfer, electronic data interchange (EDI), point-of-sale, e-commerce, reservation systems, telepresence • Control: factory floor, HVAC, automotive, avionics • Entertainment: Web, DVR, streaming media • Science: I2, deep space communication CS332 - Computer Networks

6. Example: Mars Rover • Rover can communicate directly with earth or with orbiters • Direct-to-earth data rate: 3.5 – 12 kilobits per second, for 3 hours per day (power and thermal limitations) – max 130 Megabits per day (CD – 700 megabytes) CS332 - Computer Networks

7. Spirit's West Valley Panorama – original size, 5.8 MB – roughly 1 hour transmission time • Engineering challenges: • Compression • Error correction • Lag time CS332 - Computer Networks

8. How do we connect computers? • 2 computers is pretty easy CS332 - Computer Networks

9. How do we connect computers? • Where does # 3 connect? ? CS332 - Computer Networks

10. How do we connect computers? • Where does # 3 connect? ? CS332 - Computer Networks

11. How do we connect computers? • Where does # 3 connect? ? ? CS332 - Computer Networks

12. Interconnection strategies • Point-to-point: Internet, phone network CS332 - Computer Networks

13. … Interconnection strategies • Multipoint – shared channel. • Example – original Ethernet CS332 - Computer Networks

14. Interconnection stragegies • Ring: examples – FDDI, SONET CS332 - Computer Networks

15. Interconnection strategies • Star or switched hub – examples: various Ethernet versions CS332 - Computer Networks

16. Datacom Evolution • Early data networks used a technique called circuit switching • Large, widely separated computers establish an end-to-end connection through a point-to-point switching network for each conversation • The connection reserves bandwidth for communication between the two computers Referred to as Wide Area Network (WAN) CS332 - Computer Networks

17. Data conversations are bursty. • During quiet periods, reserved bandwidth is wasted. • Connection setup and teardown take time • Utilization of bandwidth can be quite poor How can we do better? CS332 - Computer Networks

18. Data Comm Evolution: Packet Switching • Bundle data that needs to be transmitted into a "packet" with all the information needed to route it to its destination • No connection setup/teardown • Channel can be shared more efficiently by many bursty data sources • Routing info in each packet is overhead CS332 - Computer Networks

19. Data Comm Evolution: PCs • Companies with many PCs wanted to network them • WAN solutions were too complex to be used on simpler, less capable machines • Large scale networking technologies are optimized for situations that don't hold on small networks CS332 - Computer Networks

20. Data Comm Evolution: Local Area Networks • Use shared communication medium to reduce cost • Simplify addressing • Boost speed • Use packet switching for efficient sharing of communication channel CS332 - Computer Networks

21. Evolution: Migration of services As Packet Switching technology matured, former circuit-switched applications migrated to packet-switched networks • Voice-over-IP • Audio/Video broadcast CS332 - Computer Networks

22. Evolution: mobility • Unplug a laptop from the internet in one location and plug back in somewhere else • Communication without wires • Communication while on the move - cellular CS332 - Computer Networks

23. Transmission media: Copper wire • Good conductor of electricity • Signals attenuate as they propagate • Susceptible to electromagnetic interference unless carefully shielded • Good conductor of (harmful) electricity such as power spikes or lightning strikes CS332 - Computer Networks

24. Medium: Copper • Coaxial cable (Cable TV, old Ethernet) • Unshielded Twisted Pair (UTP) - phone wire • Shielded Twisted Pair • 10 - 3000 Megabit/sec data rate CS332 - Computer Networks

25. Medium: Unguided Broadcast • No wire to pull • Allows portability • Attenuation is worse than copper, so range is limited • Walls block and reflect signals • Some varieties require unobstructed line of sight CS332 - Computer Networks

26. Medium: Unguided Broadcast • Radio (UH Alohanet, PRnet, Cellular communication) • Microwave • Satellite • Infrared • Laser • 300 Megabit/sec maximum data rate (802.11N with channel bonding. 130 Mbps is more common.) CS332 - Computer Networks

27. Medium: Optical Fiber • Very high bandwidth • Low attenuation • Impervious to electromagnetic interference • Inexpensive compared to copper • Driver hardware is more expensive than corresponding electronic equipment • Difficult to “tap,” so topologies are limited CS332 - Computer Networks

28. Medium: Optical Fiber • Multimode • Graded Index Multimode • Single Mode • Typical data rates range from 45 Mbps to 40 Gigabits/sec. per channel, up to 80 multiplexed channels per fiber (3.2 Tbps) • Data rate record: 155 multiplexed 100 Gbps connections over 7000 km (Bell Labs in Villarceaux, France) CS332 - Computer Networks

29. Protocols A protocol is a set of rules which allows the transfer of information between two or more entities. Examples: Two-way radio communication Human communication CS332 - Computer Networks

30. Evolution of Protocols • Proprietary networks • ARPAnet • Ethernet • Unix and the Open Systems movement • Network standardization • The Internet CS332 - Computer Networks

31. Layered Protocol Stacks • The accepted general architecture for the design of complex network protocols calls for a series of software layers. Characteristics of this approach: • Sets of related objectives are isolated into a single layer of the network software. • A given layer only needs to know how to interact with the layers directly above and below it, simplifying each layer. • The interface between layers is well defined, improving interoperability of differing implementations. • The layer interface is designed to hide the details of how the services offered by the layer are actually carried out (abstraction). • As long as the specified interfaces between layers are preserved, lower layers can be changed without affecting higher layers. CS332 - Computer Networks