1. Confluent vs. Splittable Flows
Niranjan Mysore, Radhika
Woo, Dong Hyuk

2. Problem Definition and Motivation
Todays Internet – Confluent Flow Model - routing protocols are responsible for constructing paths to the destination
Static Routing – Manually configure next hop.
Dynamic Routing – Optimal path - metrics :
Hop Count
Bandwidth of link
Communication cost
So although multiple paths may exist – current Internet utilises only the optimal path to the destination
Some sophisticated routing protocols support multiple paths to the same destination. Unlike single-path algorithms, these multipath algorithms permit traffic multiplexing over multiple lines. The advantages of multipath algorithms are obvious: They can provide substantially better throughput and reliability. This is generally called load sharing.
ECE Advanced Internetworking

3. Problem Definition and Motivation
Load balancing – Different flows are routed through different paths to the destination – so as to utilize network capacity.
If congestion aware load balancing is done, better bandwidth availability for the flows is ensured – by avoiding the congested paths.
ECE Advanced Internetworking

4. Problem Definition and Motivation
Flow Splittability - Each flow takes more than one path to reach the destination.
If sequencing and other factors are managed for the flow, and decisions are taken based on bandwidth available along each path, it is possible to make good use of the network capacity.
ECE Advanced Internetworking

5. Need for Flow Splittability / Load Balancing
Fault tolerance
Bandwidth aggregation (FS only)
Utilizing multiple low bandwidth links in an under provisioned network to the best of its capacity
Increasing Internet Capacity utilization, and thus indirectly improving underlying service
ECE Advanced Internetworking

6. Problem Definition and Motivation
We want to compare an approach to Load Balancing to Flow Splittability and try to find which is better
ECE Advanced Internetworking

7. ECE4605 - Advanced Internetworking
Background Reading
Enabling the lowest-cost multiservice networks - Marconi White Paper
Flow Splitting Approach for Path Provisioning and Path Protection Problems - Rauf Izmailov et al.
A Transport Layer Approach for Achieving Aggregate Bandwidths on Multi-homed Mobile Hosts - R. Sivakumar et al
pTCP: An End-to-End Transport Layer Protocol for Striped Connections - R. Sivakumar et al
On Achieving Weighted Service Differentiation: An End-to-End Perspective -R. Sivakumar et al
ECE Advanced Internetworking

8. ECE4605 - Advanced Internetworking
Work done
Custom Simulator – to model graph theoretic problem
Chose set of nodes and define bandwidth of links between them
Introduce flows into the network between any pairs of nodes
In load balancing – find the widest path between source and destination for flow. Subtract the flow bw requirement from the path (to account for flow)
In flow splittability – split the flow in the ratio of the bandwidths along all paths to the destination. Subtract the bw along each path by flow requirement
ECE Advanced Internetworking

9. Simulation on custom simulator
Random load generation
Random source / destination selection
Inter-arrival time between each flow
Uniformly distributed between [0, 4]
Lifetime
Uniformly distributed between [150, 249]
Required bandwidth
Uniformly distributed between [0, bw]
Used admission control
ECE Advanced Internetworking

10. ECE4605 - Advanced Internetworking
Planet Lab
An overlay network supported by a consortium of educational and corporate institutions for research
Chose from available nodes. Built a client server application which could send and receive TCP flows between source and destination – employing tunneling in intermediate nodes.
Use same Load balancing and Flow Splittability policies as before.
Measurements are real time – involve real delays (queuing and transmission), drops
ECE Advanced Internetworking

11. 2.93
0.50
3.25
4.75
1.01
3.77
2.87
4.12

12. Simulation on PlanetLab
Simulation architecture
Scenario generation
Scheduling based on policy
Execution by ordering Agent
Agent
Client
Server
Tunnel
Main controller
Agent
Client
Server
Tunnel
Agent
Client
Server
Tunnel
Agent
Client
Server
Tunnel
Measure throughput using
Tcpdump and ethereal
ECE Advanced Internetworking

13. Simulation on custom simulator (cont’d)
ECE Advanced Internetworking

14. Simulation on custom simulator (cont’d)
ECE Advanced Internetworking

15. Simulation on PlanetLab (cont’d)
Problem with the Internet simulation
Need to measure in-flight available bandwidth
We cannot know the congestion size of TCP on Planetlab
Just used simple policy in the following results
LB: alternating link
FS: splitting traffic evenly
Demo
ECE Advanced Internetworking

16. Simulation on PlanetLab (cont’d)
ECE Advanced Internetworking

17. Simulation on PlanetLab (cont’d)
LB (UT)
ECE Advanced Internetworking

18. Simulation on PlanetLab (cont’d)
FS1 (UT)
ECE Advanced Internetworking

19. Simulation on PlanetLab (cont’d)
FS2 (UT)
ECE Advanced Internetworking

20. ECE4605 - Advanced Internetworking
Summary
FS performed better than LB when we used large loads and admission control – and assumed no underlying rate control
LB performed equal or better than FS in certain situations when we used different light load and underlying rate control – with simple policies
FS performs better as the number of reflection points increases.
ECE Advanced Internetworking