Internet Overview: roadmap

1. Internet Overview: roadmap 1.5 Protocol layers, service models 1.6 Internet for Wireless 1.7 Internet under attack: security overview Lecture 3

2. Networks are complex! Millions of components: hosts routers Access networks Question: How to organize such complex structure? Protocol “Layers” • Millions of operations and conflicts among them: • What if multiple computers transmit at the same time? • What if packets get lost? • How to retransmit packets? • Retransmission: How many times? • What about the other packets? • How to find routes in the Internet? • What if I am browsing web or I am watching live broadcasting? • How to distinguish among computers (addressing)? • Just a few mentioned here… Lecture 3

3. ticket ticket (purchase) baggage (check) gates (load) runway (takeoff) airplane routing ticket (complain) baggage (claim gates (unload) runway (land) airplane routing baggage gate airplane routing airplane routing takeoff/landing airplane routing departure airport intermediate air-traffic control centers arrival airport An analogy: Organization of airline functionality • a series of steps • Layers: each layer implements a service • via its own internal-layer actions • relying on services provided by layer above/below • Another example: Postal Service! Lecture 3

4. What are the adv. of layering? • Reduce the design complexity • Ease of updating the system • change of implementation of layer’s service transparent to rest of system • e.g., Postal service (overnight flight or overnight ground) • Network is a huge complex system • Why not take help of layering architecture? Lecture 3

5. application support host/network applications Email, FTP, HTTP (HTML) transport process-process data transfer TCP, UDP network routing of datagrams from src. to destn. IP address, routing protocols link data transfer between neighboring network elements Ethernet, PPP physical bits “on the wire” application transport network link physical Internet protocol stack (Compare with the Postal System!) Lecture 3

6. presentation: allow applications to interpret meaning of data, e.g., encryption, compression, machine-specific conventions session: synchronization, checkpointing, recovery of data exchange The 5-layer protocol stack is more famous application presentation session transport network link physical ISO/OSI reference model(Open Systems Interconnection model) Lecture 3

7. Protocol Stack View • While hosts (computers) view it as 5-layer protocol stack, it is slightly different for routers/data forwarders… • Data forwarders view it as 1-layer, 2-layer or 3-layer protocol stack depending on the functionality! • Data forwarder classifications (based on complexity) • Hub (simplest) • Switch (medium complexity) • Router (most complex) Lecture 3

8. Hubs • Hubs: unsophisticated devices for connecting multiple devices together, low cost • Example: Ethernet Hub • Hubs work at the physical layer (1-layer protocol stack view only) • Any packet received in any port is broadcast out in all other ports • If multiple computers connected to a hub transmit packet at the same time, packets will collide with each other • Hub detects this collisions and signal the computers to transmit again Lecture 3 Image courtesy: Google

9. Switch • Switch: sophisticated devices for connecting multiple devices together, medium cost • Example: Ethernet Switch • Nearly identical to hubs but contain more intelligence • Switches may work at multiple layers (typically 2 layer view) • Switches have multiple buffers for incoming packets in multiple ports • Avoid packet collision Lecture 3 Image courtesy: Google

10. Router • Router: most sophisticated device, expensive • Routers work at multiple layers (typically 3 layer view) • Routers have multiple network interfaces and are more intelligent than switches • Decide routes for packets based on destination IP addresses, network load, delay etc. Lecture 3

11. network link physical link physical M M M Ht M Hn Hn Hn Hn Ht Ht Ht Ht M M M M Hn Ht Ht Hl Hl Hl Hn Hn Hn Ht Ht Ht M M M A complete view: Messages, Segments, Datagrams and Frames source message application transport network link physical segment datagram frame Encapsulation switch destination message application transport network link physical router Lecture 3

12. How about wireless connection?

13. Why Wireless? • Advantages • Mobility (on the go) • Flexibility (any place, any time, temporary, permanent) • No problems with wiring (e.g. historical buildings, fire protection, esthetics), also cost reducing • Robust against disasters like earthquake, fire; in emergency situations • It has really been a wireless revolution decade…with more to come • Wireless is no longer a luxury but a necessity Lecture 3

14. Wireless Technology is everywhere • Driven by technology and vision • Wireless technologies • Device miniaturization • Mobile computing platforms Lecture 3 Image courtesy: Google

15. Today, Variety of Wireless-Capable Devices Lecture 3 Image courtesy: Google

16. IEEE Wireless Standards RAN IEEE 802.22 WAN IEEE 802.20 IEEE 802.16e MAN IEEE 802.16d WiMAX LAN IEEE 802.11 Wi-Fi PAN IEEE 802.15 Bluetooth Lecture 3 Image courtesy: Google

17. Wireless LANs: WiFi/802.11 • Based on the IEEE 802.11a/b/g/n family of standards • Designed to provide in-building or campusbroadband coverage. • IEEE 802.11b peak physical layer data rate of 11 Mbps • IEEE 802.11a/g peak physical layer data rate of 54 Mbps and indoor coverage over a distance of 100 feet. • Operates over a bandwidth of 20 MHz • Disadvantages • WiFi users share “air” medium - inefficient for large numbers of users • Wi-Fi systems are not designed to support high-speed mobility Lecture 3

18. WPAN (Wireless Personal Area Network) • Cable replacement RF technology (low cost) • Short range {10m (1mW), 100m (100 mW)} • Lower power than WiFi • Widely supported by telecommunications, PC, and consumer electronics companies. • Hands free phone (ear set) for cars, internet chat/VoIP • Intra-car networking announced by some car manufacturers in Europe • IEEE 802.15 includes seven task groups… • Numbered from 1 – 7 with each of them having own responsibility Lecture 3 Image courtesy: Google

19. 802.16e 802.16e WiMAX: worldwide interoperability of microwave access 802.16-2004 WiFi WiFi WiFi Urban DSL/T1 Replacement WiFi WiFi 802.16-2004 WiFi 802.16-2004 WiFi Rural Rural Rural Broadband Rural Lecture 3 Image courtesy: Google

20. WiMAX Fixed 802.16d or 802.16-2004 Usage: Backhaul, Wireless DSL Devices: outdoor and indoor installed CPE Frequencies: 2.5GHz, 3.5GHz and 5.8GHz (Licensed and LE) Description: wireless connections to homes, businesses, and other WiMAX or cellular network towers WiMAX Mobile 802.16e Usage: Long-distance mobile wireless broadband Devices: PC Cards, Notebooks and future handsets Frequencies: 2.5GHz Description: Wireless connections to laptops, PDAs and handsets when outside of Wi-Fi hotspot coverage WiMAX Fixed and Mobile Lecture 3 Image courtesy: Google

21. Wide Area: Satellite Systems • Cover very large areas • Different orbit heights • Low Earth Orbit (LEO): ~1000 miles • Mid Earth Orbit (MEO): ~6000 miles • Geosynchronous Orbit (GEO): ~22,300 miles • Optimized for one-way transmission location positioning, GPS systems, Satellite Radio • Most two-way systems struggling or bankrupt Lecture 3 Image courtesy: Google

22. Ad hoc Networks • All the wireless networks mentioned so far are known as infrastructure network • Require initial setup • Radios mostly follow master/slave concept • Base stations act as master while user devices are controlled by BS • Infrastructure networks are not appropriate in • emergency situations like natural disasters or • military conflicts or • in areas where access is difficult • Ad hoc networks are particularly suitable in such scenarios • Decentralized • Peer-to-peer • Does not depend on a central entity • Minimal configuration and quick deployment Lecture 3

23. Ad-Hoc/Mesh Networks • Wireless Ad hoc networks • Mobile ad hoc networks • Wireless mesh networks • Wireless sensor networks Wireless mesh network Mobile ad hoc network Lecture 3 Image courtesy: Google

24. Wireless Sensor Networks • Particularly useful for sensing and Event detection • Battlefield surveillance • Security surveillance • Sensor Nodes • Low power, Small size Lecture 3 Image courtesy: Google

25. Wireless Sensor Network Classification • Infrastructured • In buildings • Secured places • Infrastructure-less • No human intervention • Not replaceable • One time deployment • Finite energy available with sensor nodes Lecture 3 Image courtesy: Google

26. Despite its popularity, Wireless has many Technical Challenges Lecture 3

27. Challenge 1: Unreliable and Unpredictable Wireless Coverage • Wireless channel “feels” very different from a wired channel. • Wireless links are not reliable: they may vary over time and space • Noise adds on to the signal • Signal strength falls off rapidly with distance • Signal strength may weaken due to obstacles • Medium “air” shared among many users • Results: • Variable capacity • Unreliable channel: errors, outages • Variable delays Lecture 3

28. Challenge 2: “Open” Wireless Medium • Hidden terminal problem S1 R1 S2 Lecture 3

29. Challenge 3: Mobility • Mobility causes poor-quality wireless links • Mobility causes intermittent connection • under intermittent connected networks, traditional routing, TCP, applications all break • Mobility changes context, e.g., location Lecture 3

30. Challenge 4: Portability: Energy-Constrained Nodes • Limited battery power • Limited processing, display and storage • Transmission energy minimized to maximize life • Introduces a delay versus energy tradeoff for each bit Lecture 3

31. Internet Overview: roadmap 1.7 Internet under attack: security Lecture 3

32. Network Security • The field of network security is about: • how bad guys can attack computer networks • how we can defend networks against attacks • Internet not originally designed with (much) security in mind • original vision: “a group of mutually trusting users attached to a transparent network” • Internet protocol designers playing “catch-up” Lecture 3

33. Malware virus Worm trojan horse Spyware malware can record keystrokes, web sites visited, upload info to collection site. Infected host can be enrolled in a botnet, used for spam and DDoS attacks. Malware is often self-replicating: from an infected host, seeks entry into other hosts Bad guys can put malware into hosts via Internet Lecture 3

34. Trojan horse Hidden part of some otherwise useful software Today often on a Web page (Active-X, plugin) Virus infection by receiving object (e.g., e-mail attachment), actively executing self-replicating: propagate itself to other hosts, users Quick Malware Overview • Worm: • infection by passively receiving object that gets itself executed • self- replicating: propagates to other hosts, users Lecture 3

35. target Bad guys can attack servers and network infrastructure • Denial of service (DoS): attackers make resources (server, bandwidth) unavailable to legitimate traffic by overwhelming resource with bogus traffic select target break into hosts around the network (see botnet) send packets toward target from compromised hosts Lecture 3

36. src:B dest:A payload Packet Sniffing Packet sniffing: • broadcast media (shared Ethernet, wireless) • promiscuous network interface reads/records all packets (e.g., including passwords!) passing by C A B Lecture 3

37. src:B dest:A payload The bad guys can use false source addresses • IP spoofing: send packet with false source address C A B • This was just an overview of challenges… Lecture 3

38. We now covered Internet overview what’s a protocol? network edge, core, access network packet-switching versus circuit-switching Internet structure performance: loss, delay, throughput layering, service models Wireless Security Next Up: Application layer protocols Summary Lecture 3