Using the NCTUns 2.0 Network Simulator/Emulator to Facilitate Network Researches

Transcription

1 Using the NCTUns 2.0 Network Simulator/Emulator to Facilitate Network Researches Prof. Shie-Yuan Wang Department of Computer Science National Chiao Tung University Network and System Laboratory

2 Introduction Architecture Simulation methodology Design and implementation Result validation Simulation performance Product status Concluding remarks Outline

3 Introduction

4 Introduction The NCTUns network simulator is developed at NCTU, Taiwan. Its predecessor is the Harvard network simulator (1999). By using a novel simulation methodology, it can do several tasks that traditional network simulators cannot easily do. After more than five years developments, it has become a useful tool. More and more people are using it. (Use the Google to search it for yourself.)

5 The IEEE Network Magazine reports this tool in its July 2003 issue.

6 Selected as a Research Demo by ACM MobiCom 02

7 Again selected by MobiCom 2003 Ranked #1 of the 12 selected

8 First local workshop on 12/05/2002

9 Second local workshop on 12/12/2003

10 A Tutorial Made at IEEE Vehicular Technology Society, Taipei Chapter 09/22/2004

11 Selected as a tutorial by IEEE MASCOT 2004

12 Selected as a Demo by IEEE INFOCOM 2005

13 Society for modeling and simulation, International. Philadelphia, PA, USA

14 Main Unique Features The real-world TCP/IP protocol stack is directly used to generate accurate simulation results. Real-world application programs can be directly run on a simulated network to generate realistic traffic. Using a distributed architecture to support remote and concurrent simulations. Providing a very easy-to-use and fullyintegrated GUI environment

15 Main Features (2) Using an open-system (source) architecture to allow a researcher to easily add his (her) own protocol modules into the simulator Simulation methodology is endorsed by three journal papers (Computer Networks 2002, Computer Networks 2003, Wiley s Wireless Communication and Mobile Computing 2005) and one conference paper (IEEE INFOCOM 99).

16 Network Simulation Capabilities Can simulate fixed IP networks, (b) wireless LANs, mobile ad hoc networks (sensor networks), GPRS phone networks, optical networks (circuit-switched and optical burst-switched), Diffserv QoS networks, wireless mesh networks, military strategic mobile ad hoc networks, IEEE (e) QoS networks, etc. Can function as an emulator, too

17 Useful for Many Purposes Network research Network planning Network education Performance evaluation of real-world distributed applications (e.g., Internet online games or distributed database)

18 Useful for Various Researchers EE and communication people Eg., Study the effect of channel modeling or modulation technique on the performance of higher layer protocols or applications. CS and network people E.g., Study how a new MAC or routing protocol would affect various performances of a mobile ad hoc network. IT and information management people E.g., Study how various network conditions and parameters would affect the performance of a distributed application.

19 Architectures

20 Eight Components GUI Client Applications Daemons Coordinator Job Dispatcher Protocol Modules + Simulation Engine Kernel Patches (Fedora 2.0 Linux 2.6.X) Simulation Server

21 Distributed Architecture Simulation Server Dispatcher Paris GUI Client Tokyo NCTU, Taiwan Boston Simulation Service Center

22 Open-System Architecture Protocol modules Module API Simulation Engine User-level Simulator

23 Main GUI Components Topology editor Draw a network topology Node editor Specify a node s protocol stack Performance monitor Plot performance curves Packet animation player Playback packet transfer animation

24 Topology Editor

25 Node Editor

26 Performance Monitor

27 Packet Animation Player

28 Simulation Methodology

29 Novel Simulation Methodology Use a kernel re-entering technique (invented by Prof. Wang in 1999) to provide two advantages: Use real-life protocol stacks to simulate networks simulation results are more accurate. All existing real-life application programs can directly run on a simulated network can test the performance of any real-life application program. These advantages cannot be easily achieved by traditional network simulators such as OPNET modeler and ns-2.

30 Inspiration from lo0 Interface Suppose that we want to simulate the following network: stcp rtcp Host 1 Host 2

31 Stcp and rtcp Actually Can Run on the Same Machine stcp rtcp User level Kernel level Host lo0

32 (a) TCP_sender Link 1 TCP_receiver Link 2 Host 1 Host 2 (b) Virtual Link 1 Simulation engine TCP sender Read Virtual Link 2 user-level Write TCP receiver TCP/IP stack Kernel TCP/IP stack 1999 version Tunnel interface 1 Tunnel interface 2 Using tunnel interfaces to replace lo0 interface

33 (a) A network to be simulated. TCP Sender Link 1 TCP Receiver Host 1 Host 2 Current version (b) Using the simulation server to simulate the network depicted in (a). Simulation Engine TCP sender ARP ARP PSBM PSBM PHY PHY User-level TCP receiver Various protocol modules now can be flexibly added to the simulation engine. TCP/IP stack Kernel TCP/IP stack Tunnel interface 1 Tunnel interface 2 (a) A network to be simulated. (b) Using the simulation server to simulate the network depicted in (a).

34 A Configuration Example stcp p rtcp p tun1 tun Configuration commands: ifconfig tun ifconfig tun route add interface tun1 route add interface tun2

35 A Route Conflict Problem The simulation methodology presented so far works very well for a single-hop network. However, we will encounter a route conflict problem when the network is extended to multi-hops. This is because we use only one machine to simulate all routers and store their routing entries together.

36 Problem Example tun1 tun tun3 tun route add interface tun1 route add interface tun1 route add interface tun1 route add interface tun2 route add interface tun3 Stored Together route add interface tun1 route add interface tun3 Conflict!

37 S.S.D.D IP Address Scheme We solve this problem by internally using the S.S.D.D IP address scheme for an application to send its packets to its destination node. The meaning of S.S.D.D. is SrcSubnetID. host#onsrcsubnet. DstSubnetID. host#ondstsubnet. However, a NCTUns user need not know and use this strange scheme. He (she) can still use the normal subnetid. host# address scheme. The kernel hides all the details.

38 The Same Example tun1 tun tun3 tun route add interface tun1 route add interface tun1 route add interface tun1 Stored Together route add interface tun2 route add interface tun3 route add interface tun2 route add interface tun3 route add interface tun1 route add interface tun3 route add interface tun3 No conflict Now!

39 Design and Implementation

40 Automatic TCP/UDP Port Mapping Because a single machine is used to simulate many hosts and routers, different application programs running on different nodes in a simulation cannot bind to the same TCP/UDP port. However, this is allowed in the real world. We solve this by automatically mapping the same ports to different ports in the kernel. A NCTUns user need not know the details. He can still use the same port on multiple nodes in a simulated network as usual. The kernel hides all the details.

41 Fast Discrete-Event Simulation By precisely controlling the scheduling of the simulation engine process and all traffic generator processes on a UNIX machine, the simulation engine can use the discreteevent simulation methodology to quickly advance its virtual clock. The 1999 Harvard network simulator uses a slow and polling simulation engine.

42 A Comparison Suppose that at time 0, a ping program starts to send out one packet every two seconds time Discrete-Event Polling

43 Result Validation

44 Result Validation Is Important Before trusting the results generated by a simulator, we must validate its results. We have performed extensive validation tests and confirmed the correctness of generated results. Also, its simulation methodology, design, and implementation have been endorsed several prestigious papers. If you find a protocol implementation bug in this tool, please report it to us.

45 Simulation Performance

46 Simulation Performance Test Machine IBM T30 notebook with a 2.2 GHz Pentium processor and 128 MB RAM Network topology A source and destination hosts connected by a single link. (BW:1 Gbps, delay:1 ms) Traffic CBR UDP packet stream with various packet interval time. (Data payload size: 1400 bytes) Performance Metric The ratio of simulated time to required time

47 CBR time interval (sec) CBR BW 1 Gbps Mbps Mbps 9.32 Mbps 1.86 Mbps Kbps Kbps Kbps Kbps Ratio (higher is better)

48 Performance Comparisons with ns-2: A Test Case Greedy TCP or UDP 100 Mbps and 1 ms for all links

49 Greedy UDP Traffic

50 Greedy TCP Traffic

51 Performance Discussions The main memory usages of NCTUns and ns2 are about the same. In some cases, NCTUns runs a few times slower than ns2. This is the cost that NCTUns needs to pay. This is because real-world protocol stacks and applications are directly run rather than their abstractions. The size of NCTUns trace file is a few times smaller than that of ns2 trace file. We attribute this to the denser and binary format used by NCTUns.

52 Product Status

53 Product Has Been Ready Since November 1, 2002

54 Download Web Site Is Here As of 12/1/2005, more than 4,600 people from 95 countries have registered and downloaded this tool since its release on November 1, 2002.

55 Its users are all over the world.

56 Dear NCTUns developers, I'm a university professor teaching computer networks. I've recently discovered your simulator, and I like it so much that I've discontinued my (expensive) OPNET Modeler license as I plan to use NCTUns in my network design class. Thanks a lot in advance. With my best regards, -- Cosimo Anglano ================================== Prof. Cosimo Anglano Dipartimento di Informatica Universita' del Piemonte Orientale Alessandria, Italy Many s have arrived praising NCTUns or asking how to purchase NCTUns.

57 Dear Prof. Wang, We have been very impressed by NCTUns and many of its amazing capabilities! The simulation-emulation integration capabilities are quite remarkable. We have been quite impressed with the design of the GUI interface. We are going to be demo-ing NCTUns to another network analysis software development group within our company to show them some of the exciting features of NCTUns. Zeke Weeks Consulting Services Specialist AT&T Government Solutions, Inc. Suite Gallows Road Vienna, VA

58 Distribution of the nationality of NCTUns registered users (up to 2005/11/16)

59

60 Concluding Remarks

61 Concluding Remarks The NCTUns 2.0 now is a useful network simulator and emulator with many unique advantages over traditional ones. Based on users feedback, we are still continuing to enhance and improve the quality of the NCTUns network simulator. You are very welcome to use it and we appreciate your suggestions and/or bug reports.

62 Thank you. Q & A