“Intra-Network Routing Scheme using Mobile Agents”

1. “Intra-Network Routing Scheme using Mobile Agents” by Ajay L. Thakur

2. Outline • Objectives • OSPF Overview • Mobile Agents • Related Works • Proposed Best-Effort Routing Scheme • Proposed QoS Routing Scheme • Simulation Results • Conclusion

3. Objectives • Develop a Routing Scheme using Mobile agents • Given a source (s) and destination (d) find a path • Given a source (s) and destination (d) find a path which satisfies QoS constraints like required Bandwidth ( Breq) and delay

4. Open Shortest Path First (OSPF) • Overview • Uses link state routing algorithm • To reduce the routing overhead it divides the full Autonomous System (AS) into number of areas • Each router maintains link state database for routing domain • Area Border Router (ABR) keeps separate database for each area • Routers periodically send Link State Advertisement (LSA) into the network • ABR routers send summary LSA to backbone area and to the internal routers

5. OSPF Contd… Area 1 7 0 15 6 16 Area 2 2 4 8 3 14 Area 0 12 5 10 11 13 9 Area 3 ABR router Internal Router

6. OSPF issues • Memory Overhead • OSPF uses a link state database to keep track of all routers and networks within each attached area. With a complex topology, this database can be much larger and may limit the maximum size of an area. • Processor Overhead • During steady state operation the OSPF CPU usage is low, mainly due to the traffic between routers. However, when a topology change is detected, there is a large amount of processing required to support flooding of changes, and re-calculation of the routing table. In the existing implementations, the shortest path tree has to be computed from scratch after each link state change.

7. OSPF issues contd… • Synchronization of Database • Database at all routers within area should be synchronized. After changes in network it takes time to notify the change to all the routers within area. In between database is not synchronized and it may cause looping of packets.

8. Mobile Agents • Client Server Communication • Connection is maintained for full duration • If connection breaks due to link/node failure, connection has to be established once again which consumes network bandwidth Request Server Client Response

9. Mobile Agents • Mobile Agent Communication • Mobile agent is a program that can be dispatched from one computer and delivered to a remote computer for execution. After execution mobile agent comes back with the result MA Server Client Result

10. Some of the advantages of Mobile Agents • Less traffic in the network • Good for unreliable networks MA Server Link goes down Client Result Link comes up

11. Related Works • Mobile Agents Based Routing • Mobile agents collect the resource status at each node and accordingly the forwarding table is updated at each router • Mobile agent based QoS routing • Flooding of mobile agents to find a path • It strictly uses call admission control • Topology aggregation approach • Divide the topology in groups, and each node knows the information of resources at the routers within the group

12. Proposed Work

13. RIMA (Routing Intelligent Mobile agent) • What are RIMA nodes? • RIMA nodes are the subset of nodes such that, each non-RIMA node should be connected to at least one RIMA node within two hops • RIMA neighborhood • RIMA node and its neighbors within 1 hop or 2 hop distance forms neighborhood • RIMA Database • RIMA nodes are capable of managing and collecting information of all the nodes within its neighborhood e.g. link capacity, reliability of nodes, delay on the path, congestion at the nodes and color of the links • It also collects the information of the nodes which are on the path to neighbor RIMA nodes

14. 6 15 16 1 7 0 14 2 4 8 3 12 10 5 13 11 9 Example • In figure nodes 2, 6 and 10 are RIMA nodes • Neighborhood of RIMA node 2 • Nodes 0, 1, 3, 4, 5 and 7 • Neighborhood of RIMA node 6 • Nodes 1, 3, 4, 5, 7, 8, 9, 12, 13, 14, 15 and 16

15. RIMA Placement Algorithm • RIMA nodes are more responsible for routing of packets and it collects the database which is used for routing • RIMA placement algorithm takes into consideration some of the desirable properties • Processing power • Average normalized link capacity • Reliability • Connectivity

16. RIMA Placement Algorithm contd… • Send node information packet to neighbors • Receive information packet from neighbors • Calculate weight factor • Send weight factor to neighbors Weight of node > Weight of all neighbors Yes No Start timer and wait for RIMA announcement message Announce itself as RIMA node RIMA announcement Message received ? Yes No Announce itself as RIMA node

17. Finding path between RIMAs • RIMA node sends mobile agents to find path(s) to neighbor RIMA nodes • While traveling mobile agent also collect the path information like BW available on links • When mobile agent reaches at RIMA node it gives all the information to the RIMA node • Mobile agent comes back to source RIMA node and gives information to source RIMA node • RIMA nodes estimate the path delay by using time stamp in mobile agent

18. 4 7 1 8 3 6 2 5 Finding paths between RIMAs Table at node 2 Table at node 4

19. Communication Among RIMAs • RIMA node periodically sends reachability information to neighbor RIMA nodes • PATH vector protocol is implemented among RIMA nodes • Using the information obtained from neighbor RIMA nodes, RIMA node decides the next hop RIMA node for each destination e.g. tables at RIMA node 2 are,

20. Path finding in RIMA based routing • Consider source (s) and destination (d) • ssends a packet to connected RIMA node (R1) • At R1: if destination is in neighborhood it sends directly to d otherwise it sends the packet to next hop RIMA node R2 • Suppose at a RIMA node Rndestination is in neighborhood. In that case RIMA node directly sends packet to destination node • Path of packet can be represented as s  R1  R2  …  Rn  d

21. RIMA Based Best-Effort Routing Source=1 and Destination=11 Source=9 and Destination=14 6 15 16 1 7 0 14 2 4 8 3 12 10 5 11 13 9

22. Dynamic Network Behavior • After link/node failure corresponding node sends update message to only connected RIMA nodes and one hop neighbor nodes • RIMA node updates its neighborhood • If there is change in cost to reach some node in neighborhood • Send reachability information to neighbor RIMA nodes • If neighborhood is unchanged • No need to send messages

23. Quality of Service (QoS) • Need of QoS • Internet provides Best-Effort service • New Emerging real time applications need Guaranteed QoS; specially in case of interactive application like IP telephony, video conferencing • Metrics used in QoS routing • Bandwidth, Delay, Delay jitter, packet loss • Issues in QoS • Knowledge propagation and maintenance: When to send the link state information to other network • Periodic: Router periodically send • Threshold based: When significant change in resources • Metric and path computation • How to measure and collect network state information • How to compute routes based on the information collected

24. RIMA based QoS Routing Scheme • On-Demand Routing algorithm • QoS metrics used are bandwidth and delay • RIMA based QoS routing is same as RIMA based Best-effort routing but only difference is that each RIMA node strictly selects a path according to QoS constraints • Consider source s , destination d , requested bandwidth Breq and delay Δmax

25. RIMA based QoS Routing Scheme • Source node sends mobile agent to a connected RIMA node on the path with sufficient bandwidth and minimum delay • At RIMA node: If destination is within a neighborhood or it is on the path to other RIMA node and feasible path exist, • then RIMA node directly sends the mobile agent to destination node • otherwise RIMA node sends the mobile agent to next hop RIMA node on the path which satisfies QoS constraints • When mobile agent reaches to destination, destination node sends reservation request on the same path • When source node gets mobile agent it finds the time taken by mobile agent to setup the connection and it estimates delay to destination. If application can sustain that much delay then it sends the packet. Otherwise it releases the resources

26. QoS Routing Source=1 and Destination=11 Reservation successful 6 15 16 7 1 0 14 2 4 8 3 12 10 5 11 13 9

27. Modified RIMA based QoS Routing • In previous algorithm • Source sends request to only one RIMA node • In modified RIMA based QoS routing • Source sends the path request to all the connected RIMA nodes • Advantage • More than one mobile agent reaches at destination hence possibility of finding path increases i.e. increase in success ratio • Disadvantage • Cost per connection increases as more requests are send in the network • Destination will choose one path and sends the reservation request on that path

28. Modified QoS Routing Source=1 and Destination=11 Reservation successful 6 15 16 1 7 0 14 2 8 4 3 12 10 5 11 13 9

29. Simulation of Intranet • Different Simulation Methods • Waxman Method • P (x ,y) =a e -d/(Lβ) • Regular Method • Regular topologies are used for simulation e.g. star, mesh, ring • Hierarchical Method • Transit-Stub Method

30. Hierarchical Method • Transit-Stub model

31. Example

32. OSPF Simulation • Topology is generated using Transit-Stub model and edges are added using Waxman’s method • Total domain is divided into NA areas + backbone area. • Each area has more than one ABR ( Area Border Router) • Topology size is changed by changing Number of areas and Number of routers per area

33. Simulation • RIMA topology simulation • We consider topology as Flat topology • Generate the topology using Transit-Stub model and added edges using Waxman’s method • RIMA placement algorithm decides RIMA nodes

34. Assumption and Features of Intranet Simulation • Assumptions • Propagation delay considered to be 1 unit time • Error free transmission • Links are symmetric • No packet loss at the router due to insufficient buffer • Features • Simulated up to 800 nodes • At each router two queues one for best effort service and other for guaranteed service • Best effort traffic is background traffic • Weighted fair queue is used at each router • Processing delay, transmission delay and queuing delays are considered

35. RIMA Placement • Number of RIMAs required

36. RIMA-to-RIMA average number of paths

37. Node Convergence: Number of messages 10

38. Node Convergence Time

39. Path Convergence: Number of messages

40. Path Convergence Time

41. RIMA based QoS Routing: Path setup

42. Success ratio Vs Number of connections

43. Connections Rejected Vs Breq

44. Number of update messages generated Vs connection generated

45. Connection Blocking Probability Vs number of hops

46. Conclusion • Developed RIMA based Best-effort routing scheme • Developed RIMA based QoS routing scheme • Comparisons of the performance of proposed routing scheme and OSPF routing

47. Publications (submitted) • Ajay L. Thakur and P. Venkataram , "RIMA Based Intra-Network QoS Routing Scheme", Computer Communications Journal (Elsevier) • Ajay L. Thakur and P. Venkataram , "Intra-Network Routing Scheme using Mobile Agents”, SPCOM 2004

48. Thank You!