Videoconferencing: Network Tools & Troubleshooting

Videoconferencing: Network Tools & Troubleshooting

Dave Devereaux-Weber

University of Wisconsin-Madison

Internet2 Commons Site Coordinator TrainingSeptember 27, 2004Austin, 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.

Port Align FCS Xmit Rcv UnderSize Err Err Err Err 2/11 - 0 0 3077 0 Port Single- Multi- Late- Excess- CarriSen Runts Giants Coll Coll Coll Coll 2/11 32330 2588 0 0 2489 0

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 10.1.1.1 Pinging 10.1.1.1 with 32 bytes of data: Reply from 10.1.1.1: bytes=32 time=88ms TTL=112 Reply from 10.1.1.1: bytes=32 time=72ms TTL=112 Reply from 10.1.1.1: bytes=32 time=69ms TTL=112 Reply from 10.1.1.1: bytes=32 time=69ms TTL=112 Ping statistics for 10.1.1.1: 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 40000 10.1.1.1 Pinging 10.1.1.1 with 40000 bytes of data: Reply from 10.1.1.1: bytes=40000 time=2412ms

TTL=112 Reply from 10.1.1.1: bytes=40000 time=2721ms

TTL=112 Reply from 10.1.1.1: bytes=40000 time=2761ms

TTL=112 Reply from 10.1.1.1: bytes=40000 time=2714ms

TTL=112 Ping statistics for 10.1.1.1: 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@huck dodpears]$ traceroute www.internet2.edu traceroute to www.internet2.edu (209.211.239.208), 30 hops max, 38 byte

packets

1 wcc-sub5-hp1 (129.79.5.253) 11.726 ms 0.627 ms 0.571 ms 2 iub-gw (129.79.8.10) 3.133 ms 0.717 ms 0.651 ms 3 156.56.249.22 (156.56.249.22) 2.544 ms 3.138 ms 2.538 ms 4 abilene-iupui.abilene.ucaid.edu (198.32.11.13) 5.245 ms 3.402 ms

3.493 ms 5 clev-ipls.abilene.ucaid.edu (198.32.8.26) 9.381 ms 9.586 ms 9.244 ms 6 nycm-clev.abilene.ucaid.edu (198.32.8.30) 23.198 ms 21.963 ms

21.775 ms 7 border-abilene-oc3.advanced.org (209.211.237.97) 23.448 ms 23.268

ms 23.052 ms 8 www.internet2.edu (209.211.239.208) 23.559 ms 23.478 ms 23.234

ms

11

Traceroute

8 www.internet2.edu (209.211.239.208) 23.559 ms 23.478 ms 23.234 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• http://www.pingplotter.com

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

http://dast.nlanr.net/Projects/Iperf/

19

IperfExample 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 http://ethereal.com/

EtherPeek http://wildpackets.com/

24

Network Traffic Analyzer: Commercial Hardware

Fluke Networks NetTool http://www.flukenetworks.com/us/LAN/Handheld+Testers/NetTool/Overview.htm 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 http://nai.com/ 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.• http://detective.internet2.edu/

26

ANL Web100 based Network Diagnostic Tester (NDT)

Highly recommendedhttp://miranda.ctd.anl.gov:7123/

• 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) •http://www.itecohio.org/beacon/

28

Other Tools

CAIDA Internet Measurement Tool Taxonomy http://www.caida.org/tools/taxonomy/measurement/

29

ViDe Videoconferencing Cookbook

http://videnet.gatech.edu/cookbook/

30

The Network

Information on these slides courtesy of

Doug Pearson

Indiana University

And

David Devereaux-Weber

University of Wisconsin-Madison