An Integrated Experimental Environment for Distributed Systems and Networks- A Summary

An Integrated Experimental Environmentfor Distributed Systems and NetworksNetbed integrates the features of all three preexisting network experiment environments Emulators, simulators and Live networksIt brings the control and ease of use usually associated with simulation to emulation and live network experimentation without sacricing realismProvides a time and space shared platform for network researchAn experiment in the Netbed can be compared to a UNIX process.This implementation provides efficiency through time and space sharing

Resources used by the NetbedLocal Area Resources : Local PCs maintained in a cluster.Emulated Resources : Widearea links emulated using Dummynets and VLAN with capabilities of queue and bandwidth limitationsDistributed Resources : Nodes present at different sites throughout the worldSimulated Resources : Nodes, links and traffic whicha re simulated using NSE(NS Emulator)There are many more planned extensions to the testbed in the future. Eg WAN emulator based on Intel IXP1200 processorExperiment Life cycleIt is the central operational entity of NetbedUsers access netbed through the web interface which is easy to use.

Improving Network ExperimentationAutomated mapping of virtual topology improves the process of network experimentation by improving the time required to create the topology otherwiseEfficient use of scarce and expensive hardware by using fewer nodes and using effective time sharing techniques guarantees proper usage of the whole testbed.Virtualization of nodes also makes sure that the nodes can be used interchangeably.

Key Services and EvaluationExperiment Creation : Parallelism improves the whole creation process Mapping Local Resources : Simulated annealing to map virtual nodes and links to local nodes and VLANMapping Distributed resources : Maps virtual nodes to physical evaluating the best match in parameters like latency packet loss and band width.Disk Reloading : Most time consuming aspect. Uses disk Image loading rather than synching with a reference image.

Validation and TestingWAN emulator validating : Generate streams of UDP round trip traffic. The results were found to be matching with live networks.NSE validation : Similar to the above validation, but is tested on nse. The results had a larger relative error compared to WAN emulation.Validation against WAN : Compares the results against a live wide area network.Wide area DB replication: Matched results against CAIRN wan.Testing : Since the test bed contains physical artifacts, cannot be exhaustively tested.ConclusionNetbed provides an efficient, robust and easy to use method to create and experiment on networks.Automatic generation of topologies helps in providing a reliable test environment for a wide variety of network experiments.There have been many similar efforts also like ModelNet, N/w simulators, Cluster management etc.

QuizWhich are the different stages in the experiment life cycle?Accessing Netbed, Specification, Parsing, Global Resource Allocation, Node self configuration, Experiment control, preemption and scheduling.How are the uncontrollable elements in the connection with the distributed resources mapped?Virtual nodes are mapped to the closest matching physical network which has similar latency and bandwidth values.Which time constitutes the major portion in the initial experiment setup time?Booting time for the nodes(especially BIOS) constitute the major portion of initial time.Which are the different methods for disk reloading?Disk image direct loading and Synchronising with a a reference image.