Advance Topics in Networking

1. Lecture 4 Advance Topics in Networking

2. Lecture Overview • Presenting a Research Topic • Sample Thesis Topics • More Thesis Topics • Ad hoc Networking • Reviewers Guidelines • Paper Review Guidelines • First Papers: For this week

3. Presenting a Research Topic Typical steps of thesis research • accumulate background • network track courses • independent studies, research group meetings • define problem, search literature, and develop solution • implement a prototype (in JAVA or C/C++) • measure and analyze performance of prototype • summarize results in one technical paper / thesis

4. Sample Thesis Topics • Programming of CISCO Routers • How to deploy new services without modifying IOS? • Policy-based Networking • How to efficiently detect conflicts among policy rules specified • Smart Routing and Rerouting Algorithms • How to reduce call blocking probability and data loss rate? • Study of Distributed Denial of Service attacks • How to identify sources of attacks? • How to filter out malicious traffic early?

5. More Thesis Topics • Security Protocols for Wireless LANs • How to strengthen WEP? • How to detect intrusions? • Extreme (Ad hoc) Networking • How to mitigate effect of large propagation delays? • How to guarantee performance to selected traffic?

6. More Thesis Topics • Mobile Agents and Survivable Networking • How to make a service ubiquitous, i.e., available while moving around the network and regenerating if necessary • Software Architecture for Dynamically Reconfigurable Systems • How to reduce programming complexity of these systems?

7. 802.11a/b/g Networks Some slides taken from UIUC Wireless Networking Group

8. 802.11a/b/g • Operates in 2 different modes: • Infrastructure mode • Associates with an access point • All communication goes through the access point • Used for wireless access at a company or campus • Peer-to-Peer Ad Hoc Mode • If two nodes are within range of each other they can communicate directly with no access point • A few users in a room could quickly exchange files with no access point required

9. Infrastructure Access • Access Points: • Provide infrastructure access to mobile users • Cover a fixed area • Wired into LAN

10. Peer to Peer Ad Hoc Mode

11. Infrastructure Access

12. Infrastructure Access

13. 802.11a/b/g are multi-rate devices 1 Mbps 2 Mbps 5.5 Mbps 11 Mbps

14. MAC Layer Fairness Models • Per Packet Fairness: If two adjacent senders continuously are attempting to send packets, they should each send the same number of packets. • Temporal Fairness: If two adjacent senders are continuously attempting to send packets, they should each be able to send for the same amount of medium time. • In single rate networks these are the SAME!

15. Temporal Fairness Example Per Packet Fairness 11 Mbps 1 Mbps Temporal Fairness 11 Mbps 1 Mbps

16. 802.11b Channels • 11 available channels (in US) • Only 3 are non-overlapping!

17. 802.11b Channel Usage Channel 1 Channel 6 Channel 11

18. 802.11b Channel Reuse

19. Problems • Access Point placement depends on wired network availability • Obstructions make it difficult to provide total coverage of an area • Site surveys are performed to determine coverage areas • Security Concerns: rogue access points in companies etc.. • Each Access Point has limited range

20. Peer to Peer Ad Hoc Mode

21. Peer to Peer Ad Hoc Mode X X X

22. Problems • Communication is only possible between nodes which are directly in range of each other

23. Problems for both Infrastructure and Ad hoc Mode • If nodes move out of range of the access point (Infrastructure Mode) OR • nodes are not in direct range of each other (Ad Hoc Mode) • Then communication is not possible!!

24. What if ?? Multi-hop Infrastructure Access Multi-hop Ad Hoc Network OR

25. Multi-hop Infrastructure Access • Nodes might be out of range of the access point, BUT in range of other nodes. • The nodes in range of the access point could relay packets to allow out of range nodes to communicate. • NOT part of 802.11

26. Multi-hop Ad Hoc Network • If communication is required between two nodes which are out of range of each other, intermediary nodes can forward the packets. • NOT part of 802.11 Destination Source

27. How can this be done? -< ROUTING!! • Wired Networks: • Hierarchical Routing • Network is divided into subnets • Nodes look at network address and determine if the address is directly reachable. If not, just forward to the default gateway. • Different protocols for different levels of the hierarchy • RIP, OSPF, BGP

28. Wireless Routing • Flat routing • You can’t assume that since a node is in your subnet that it is directly accessible • Node must maintain or discover routes to the destination • All nodes are routers

29. Ad Hoc Networking   29

30. Initial Architectures - Low power sensors networks “surveillance” web - small, relatively static, embedded ad hoc networks `“bluetooth-type” networks - Small-to-medium sized, mobile ad hoc networks “802.11-style”

31. Terminlology Mobile Ad Hoc Networking = = Mobile, Multi hop, Wireless Networking = Mobile Mesh Networking = Mobile Packet Networking

32. Ad hoc network applicability Scale Small scale Large scale Network type (few nodes) (many nodes) Commercial home/office personal mobile cellular like industrial local networks Government specific Public Safety Large-scale military network Community/urban “covert” networks local communications networks

33. Hybrid Communication Networks Satellite overlay High speed backbone network MANET No fixed infrastructure Fixed/static infrastructure

34. IETF MANET standardization • MANET - established in 1997 chartered working group within Internet Engineering Task Force (IETF) • Focussed on studying routing specification with the goal of supporting network scaling up to hundreds of routers • Unicast routing protocol • Multicast routing protocol • Work on routing for large and small scale networks • Work relies on the existing IETF standards such as mobile-IP and IP addressing • For large-scale MANET the lack of interest have put this work in question • Flooding: work on requirements had started

35. Mobile Ad Hoc Networking (MANET) • Dynamic topologies • Bandwidth-constrained • Asymmetric links with variable capacity • Energy constrained • Multiple technologies can be used simultaneously

36. Open issues • A optimisation network layer and radio layers for different systems (incl. 802.11, HiperLAN) • B QoS support • C secuirity • D mobility • B, C, D issues could be orthogonal, joint -optimization is very difficult (system design choice) • tradeoff between centralized and distributed algorithms for B,C,D

37. Relevant ETSI activities • MESA Project - ad hoc network on future Public Safety communications • BRAN - HiperLAN-2, other Standardization challenges => There is need for standard-based approach at the network layer.

38. Mobile Ad Hoc Networks • Formed by wireless hosts which may be mobile • Without (necessarily) using a pre-existing infrastructure • Routes between nodes may potentially contain multiple hops

39. Mobile Ad Hoc Networks • May need to traverse multiple links to reach a destination

40. Mobile Ad Hoc Networks (MANET) • Mobility causes route changes

41. Why Ad Hoc Networks ? • Ease of deployment • Speed of deployment • Decreased dependence on infrastructure

42. Many Applications • Personal area networking • cell phone, laptop, ear phone, wrist watch • Military environments • soldiers, tanks, planes • Civilian environments • taxi cab network • meeting rooms • sports stadiums • boats, small aircraft • Emergency operations • search-and-rescue • policing and fire fighting

43. Challenges • Limited wireless transmission range • Broadcast nature of the wireless medium • Packet losses due to transmission errors • Mobility-induced route changes • Mobility-induced packet losses • Battery constraints • Potentially frequent network partitions • Ease of snooping on wireless transmissions (security hazard)

44. Unicast RoutinginMobile Ad Hoc Networks

45. Why is Routing in MANET different ? • Host mobility • link failure/repair due to mobility may have different characteristics than those due to other causes • Rate of link failure/repair may be high when nodes move fast • New performance criteria may be used • route stability despite mobility • energy consumption

46. Unicast Routing Protocols • Many protocols have been proposed • Some have been invented specifically for MANET • Others are adapted from previously proposed protocols for wired networks • No single protocol works well in all environments • some attempts made to develop adaptive protocols

47. Routing Protocols • Proactive protocols • Determine routes independent of traffic pattern • Traditional link-state and distance-vector routing protocols are proactive • Reactive protocols • Maintain routes only if needed • Hybrid protocols

48. Trade-Offs • Latency of route discovery • Proactive protocols may have lower latency since routes are maintained at all times • Reactive protocols may have higher latency because a route from X to Y will be found only when X attempts to send to Y • Overhead of route discovery/maintenance • Reactive protocols may have lower overhead since routes are determined only if needed • Proactive protocols can (but not necessarily) result in higher overhead due to continuous route updating • Which approach achieves a better trade-off depends on the traffic and mobility patterns

49. Overview of Unicast Routing Protocols

50. Flooding for Data Delivery • Sender S broadcasts data packet P to all its neighbors • Each node receiving P forwards P to its neighbors • Sequence numbers used to avoid the possibility of forwarding the same packet more than once • Packet P reaches destination D provided that D is reachable from sender S • Node D does not forward the packet