Videoconferencing: Network Tools & Troubleshooting Dave Devereaux-Weber University of Wisconsin-Madison Internet2 Commons Site Coordinator Training September 27, 2004 Austin, Texas

2 Duplex Mismatch – Detection  Show port statistics on the Ethernet switch. When mismatched, the full-duplex end will report a high level of CRC or alignment errors; the half-duplex end will report a high number of late collisions.  PortAlignFCSXmitRcvUnderSize  ErrErrErrErr  2/   Port Single-Multi-Late-Excess-CarriSenRuntsGiants  CollCollCollColl  2/

3 Ping  Test for availability, loss, and roundtrip time  ICMP Echo Request Plus optional dummy payload – only in the direction of the ping, i.e., source to destination

4 Sample Ping from Windows  C:\WINDOWS>ping  Pinging with 32 bytes of data:  Reply from : bytes=32 time=88ms TTL=112  Reply from : bytes=32 time=72ms TTL=112  Reply from : bytes=32 time=69ms TTL=112  Ping statistics for :  Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),  Approximate round trip times in milli-seconds:  Minimum = 69ms, Maximum = 88ms, Average = 74ms  C:\WINDOWS>

5 Sample Ping from Windows  C:\WINDOWS>ping -l  Pinging with bytes of data:  Reply from : bytes=40000 time=2412ms TTL=112  Reply from : bytes=40000 time=2721ms TTL=112  Reply from : bytes=40000 time=2761ms TTL=112  Reply from : bytes=40000 time=2714ms TTL=112  Ping statistics for :  Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),  Approximate round trip times in milli-seconds:  Minimum = 2412ms, Maximum = 2761ms, Average = 2652ms  C:\WINDOWS>

6 Ping Big and Fast on Linux  ping -c2000 -i.03 -s1470 -q [destination] Count of 2000 packets Interval of.03 seconds between packet starts Packet size of 1470 bytes (2000)(.03) = 60 second long test (1/(.03 sec/packet))(1470 bytes/packet)(8 bits/byte) = 392 Kbps

7 Ping Big and Fast on Linux  $ ping -c2000 -i.03 -s1470 -q [hostname]  PING [hostname] ([hostaddr]) from [hostaddr2] : 1470(1498) bytes of data.  --- [hostname] ping statistics ---  2000 packets transmitted, 2000 packets received, 0% packet loss  round-trip min/avg/max = 4.8/5.1/13.2 ms

8 Traceroute  Used to discover the layer-3 network path (routers) between the two endpoints  Doesn’t identify layer-2 devices (switches)  Take baselines – know what your path should be in advance of trouble

9 Traceroute  Microsoft Windows tracert uses ICMP  Unix traceroute uses UDP  If Microsoft Windows tracert appears to show continuous timeouts, the router may be filtering ICMP traffic – try a Unix/Linux traceroute.

10 Traceroute; Sample Output  dodpears]$ traceroute  traceroute to ( ), 30 hops max, 38 byte packets  1 wcc-sub5-hp1 ( ) ms ms ms  2 iub-gw ( ) ms ms ms  ( ) ms ms ms  4 abilene-iupui.abilene.ucaid.edu ( ) ms ms ms  5 clev-ipls.abilene.ucaid.edu ( ) ms ms ms  6 nycm-clev.abilene.ucaid.edu ( ) ms ms ms  7 border-abilene-oc3.advanced.org ( ) ms ms ms  8 ( ) ms ms ms

11 Traceroute  8 ( ) ms ms ms  Hop  Router/host name  Router/host address  Round-trip times of each of three probes

12 Traceroute – Example Uses  Identify the path, and then perform pings along the path segments to isolate troublesome segments.  Insure that Internet2 is being used for a connection, rather than commercial Internet.

13 Looking Glass  These network tools work from your vantage point out; what if you want to measure from some other vantage point back in? You want a looking glass:  See traceroute.org

14 Ping Plotter  Shareware tool; $15  Performs a visual traceroute and ping tests along the entire path  Permits identification of bottlenecks along a path

15 Ping Plotter

16 MRTG.ORG  Multi Router Traffic Grapher  Open Source  Collect and graph scalar, time-based data, e.g., router and link performance data.

17 MRTG Example MRTG graph showing traffic from SLAC to a physics lab at University of Wisconsin

18 Iperf  Client/server application that Measures maximum TCP bandwidth Facilitates tuning of TCP and UDP parameters Reports bandwidth, jitter, and packet loss 

19 Iperf Example on Intercampus DS3  At server, invoke:  iperf -fk -i30 -u -s (f)ormat reports in kbps (i)nterval for reporting = 30 seconds (u)dp (s)erver mode

20 Gnuplotping  Pings multiple hosts in parallel with graphical display (gnuplot) of the delay distribution.  Runs on Unix/X-Windows

21 Gnuplotping

22 Network Traffic Analyzer  Reveals the traffic on a LAN  Protocol analysis  Reports such as utilization, protocols, conversations, nodes, etc.

23 Network Traffic Analyzer: Software  Ethereal  EtherPeek

24 Network Traffic Analyzer: Commercial Hardware  Fluke Networks NetTool This is a technician-oriented tool to perform diagnostics and testing.  Fluke has an excellent white paper on auto-negotiation problems. Highly recommended.  Network Associates Sniffer This is an engineer-oriented tool to analyze packets and traffic- often needs interpretation.

25 Internet2 Detective  I2 Detective is a small application.  Very easy to use  Detects Internet2 connection.  Measures connection bandwidth (using Iperf).  Detects multicast connection.

26 ANL Web100 based Network Diagnostic Tester (NDT)  Highly recommended  Located at Argonne National Laboratory; 100 Mbps FastEthernet network connection This java applet was developed to test the reliability and operational status of your desktop computer and network connection. It does this by sending data between your computer and this remote NDT server. These tests will determine: The slowest link in the end-to-end path (Dial-up modem to 10 Gbps Ethernet/OC-192) The Ethernet duplex setting (full or half); If congestion is limiting end-to-end throughput. It can also identify 2 serious error conditions: Duplex Mismatch Excessive packet loss due to faulty cables.

27 H.323 Beacon  Open Source Software  Used to measure, monitor and qualify the performance of an H.323 Videoconference session.  Provides H.323-protocol specific evidence and other information necessary to troubleshoot H.323 application performance problems in the network and at the host (end-to-end)

28 Other Tools  CAIDA Internet Measurement Tool Taxonomy

29 ViDe Videoconferencing Cookbook 

30 The Network Information on these slides courtesy of Doug Pearson Indiana University And David Devereaux-Weber University of Wisconsin-Madison