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Advance Topics in Networking

This lecture covers topics such as presenting a research topic, sample thesis topics, ad hoc networking, reviewer guidelines, and paper review guidelines. It also provides an overview of the steps involved in thesis research and offers sample thesis topics for further exploration.

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Advance Topics in Networking

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  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

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