Network Layer Routing Issues (I)

1. Network LayerRouting Issues (I)

2. Infrastructure vs. multi-hop • Infrastructure networks: • One or several Access-Points(AP) connected to the wired network • Mobile nodes communicate through the AP • Multi-hop network (Infrastructureless): • Mobile nodes communicate directly with each other • Multi-hop networks: all nodes can also act as routers

3. Adaptivity and Cooperation • Multi-hop networks require more cooperation between layers: • Channel variation • network topology changes affect the application • Routing in a multi-hop considerably affects the medium access control (MAC) performance • Collisions and channel fading affect both the physical layer and the MAC

4. Problems in Multi-Hop Networks • Routing • How to keep up-to-dateinformation on the network topology? • How to determine number of hops • How to cope with network topology changes • Higher Delay • Resource Limitations • Security Issues (Unreliability) • Complex and Large Structures (Routing tables) • Hard-to-Control

5. Routing Protocols Routing Classification • Unicast Routing (one-to-one connection) • Multicast routing (one-to-many connection) • Broadcasting (one-to-all connection)

6. Routing Protocols Routing (unicasting) Protocols • Proactive Routing • Reactive Routing • Hybrid Routing • Geometric Routing

7. Routing Protocols Proactive Routing (table-driven) • Keep routing information current at all times • Route maintenance • Good for static networks • High overhead and low delay • Route invalidity • Examples: (DSDV) Destination-Sequenced Distance Vector

8. Routing Protocols Reactive Routing (on-demand routing) • Finds a route to the destination only after a request comes in • Good for more dynamic networks • Low overhead and high delay • Higher delay • examples: AODV(Ad hoc On-Demand Distance Vector), dynamic source routing (DSR)

9. Routing Protocols Hybrid Schemes • Combines the advantages of reactive and proactive • Performs better both under dynamic and static conditions • Reasonable delay compared to reactive • Reasonable overhead compared to proactive • example: Zone Routing Protocol (ZRP)

10. Routing Protocols Geometric routing: • Assume location-awareness • Locating nodes by Global Positioning System (GPS) • Forwarding the packets toward the node location • Take advantage of the geometry of plane • Example: Geographic-based routing protocols

11. Proactive vs Reactive Routing 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

12. Proactive vs Reactive Routing 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

13. Flooding for Data Delivery Network-wide Broadcasting • Sender S broadcasts data packet P to all its neighbors • Each node receiving P forwards P to its neighbors for the first time • Packet P reaches destination D provided that D is reachable from sender S • Node D does not forward the packet

14. Flooding for Data Delivery Communication link Represents that the nodes are within each other’s transmission range Y S E Z F B C M L J A G H D K I N

15. Flooding for Data Delivery Broadcast transmission Y S Z E F B C M L J A G H D K I N Represents a node that receives packet P for the first time Represents transmission of packet P

16. Flooding for Data Delivery Y S Z E F B C M L J A G H D K I N

17. Flooding for Data Delivery Y S E Z F B C M L J A G H D K I N • Node C receives packet P from G and H, but does not forward it again, because node C hasalready forwarded packet Ponce

18. Flooding for Data Delivery Y S Z E F B C M L J A G H D K I N

19. Flooding for Data Delivery Y S Z E F B C M L J A G H D K I N • Node Ddoes not forwardpacket P, because node D • is theintended destination of packet P

20. Flooding for Data Delivery Y S Z E F B C M L J A G H D K I N • Flooding completed • Nodesunreachablefrom S do not receive packet P (e.g., node Z) • Nodes for which all paths from S go through the destination D • also do not receive packet P (example: node N)

21. Flooding for Data Delivery Y S Z E F B C M L J A G H D K I N • Broadcast Storm Problem • Flooding may deliver packets to too many nodes (intheworstcase, all nodes reachable from sender may receive the packet)

22. Flooding: Advantages • Simplicity (no complex control mechanism) • More efficient than other protocols • In small networks • Under light load traffic conditions • Highly dynamic networks • Potentially higher reliability of data delivery • Because packets may be delivered to the destination on multiple paths

23. Flooding: Disadvantages • Very high overhead • Data packets may be delivered to too many nodes who do not need to receive them • Energy consuming • Bandwidth consuming • Congestion

24. Flooding of Control Packets • Many protocols perform flooding of control packets, instead of data packets • The control packets are used to discover routes • Discovered routes are subsequently used to send data packet(s)

25. Flooding Overhead reduction • Virtual Backbone Formation (VBF) • Connected Dominating Set (CDS) • Maximal Independent Set (MIS) • Forwarding Group (FG) • Network Clustering

26. Flooding Scoped Flooding Scope Limited Flooding ?

27. Routing Protocols • Link-state Routing Protocols • Routes are constructed based on the selection of the communication links • Routes are optimized based on the link characteristics • Shortest Path Problem • Spanning Tree (Steiner Tree)

28. Routing Protocols • Node-state Routing Protocols • Routes are constructed based on the selection of the nodes • Routes are optimized based on the node characteristics • Connected dominating set (CDS)

29. Routing Protocols • Link-state Routing Protocols • Relative mobility • Link duration • Link Bandwidth, … • Node-state Routing Protocols • Node Failure Rate • Node Mobility • Node Energy • Nodal capacity