ndt-users list created

[Rich Carlson <>]

Christian;

The reported throughput values are not calculated or derived from the 
web100 data.  These values are calculated using the measured test data. 
 The server keeps a counter with the number of bytes sent/received and 
it also calculates the time it spend sending/receiving data from the 
client. The throughput values are then calculated as bytes/time.

Rich

On 10/7/2010 5:17 PM, Christian Reimsbach wrote:
> Hi,
>
> I am trying to understand how outbound and inbound throughput are being
> calculated based on the WEB100 kernel variables.
>
> I read Rich's answer to Lize saying that:
>
> "The speeds reported in the Test Results section are the measured speed
> achieved during this test. The values reported in the More Details
> section are calculations of the maximum possible speed based on the
> buffer size and RTT. [...] The NDT report calculates the max possible
> speed by dividing the appropriate max buffer value (sender, receiver,
> congestion control) by the average RTT. The theoretical limit is
> calculated using the Mathis et.al. formula where speed is a function of
> packet size, RTT, and packet loss."
>
> I am still confused where in my case the 23.21Mb/s and 927kb/s (see
> below) come from. Or does Rich's answer mean that the "speeds reported
> in the Test Results section" cannot be derived out of the WEB100 variable?
>
> Thanks!
>
> Christian
>
>
>
> WEB100 Enabled Statistics:
> Checking for Middleboxes . . . . . . . . . . . . . . . . . . Done.
> Checking for firewalls . . . . . . . . . . . . . . . . . . . Done.
> running 10s outbound test (client-to-server [C2S]) . . . . . 927.0kb/s
> running 10s inbound test (server-to-client [S2C]) . . . . . . 23.21Mb/s
>
> ------ Client System Details------
> OS data: Name = Linux, Architecture = amd64, Version = 2.6.32-25-generic
> Java data: Vendor = Sun Microsystems Inc., Version = 1.6.0_20
>
> ------ Web100 Detailed Analysis ------
> Cable modem/DSL/T1 link found.
> Link set to Full Duplex mode
> Information: throughput is limited by other network traffic.
> Good network cable(s) found
> Normal duplex operation found.
>
> Web100 reports the Round trip time = 21.57 ms; the Packet size = 1448
> Bytes; and
> 69 packets retransmitted, 369 duplicate acks received, and 373 SACK
> blocks received
> The connection stalled 1 times due to packet loss
> The connection was idle 0.23 seconds (2.3% of the time)
> S2C throughput test: Packet queuing detected: 1.73%
> This connection is network limited 99.6% of the time.
>
> Web100 reports TCP negotiated the optional Performance Settings to:
> RFC 2018 Selective Acknowledgment: ON
> RFC 896 Nagle Algorithm: ON
> RFC 3168 Explicit Congestion Notification: OFF
> RFC 1323 Time Stamping: ON
> RFC 1323 Window Scaling: ON; Scaling Factors - Server=7, Client=7
>
> Server 'ndt.iupui.donar.measurement-lab.org' is not behind a firewall.
> [Connection to the ephemeral port was successful]
> Client is probably behind a firewall. [Connection to the ephemeral port
> failed]
> Information: Network Middlebox is modifying MSS variable
> Server IP addresses are preserved End-to-End
> Information: Network Address Translation (NAT) box is modifying the
> Client's IP address
> Server says [85.168.247.43], but Client says [192.168.0.10]
>
> WEB100 Kernel Variables:
> Client: localhost/127.0.0.1
> CurMSS: 1448
> X_Rcvbuf: 87380
> X_Sndbuf: 926744
> AckPktsIn: 1854
> AckPktsOut: 0
> BytesRetrans: 99912
> CongAvoid: 1074
> CongestionOverCount: 0
> CongestionSignals: 6
> CountRTT: 1486
> CurCwnd: 33304
> CurRTO: 232
> CurRwinRcvd: 776192
> CurRwinSent: 5888
> CurSsthresh: 17376
> DSACKDups: 2
> DataBytesIn: 0
> DataBytesOut: 30157608
> DataPktsIn: 0
> DataPktsOut: 20384
> DupAcksIn: 369
> ECNEnabled: 0
> FastRetran: 5
> MaxCwnd: 403992
> MaxMSS: 1448
> MaxRTO: 1263
> MaxRTT: 485
> MaxRwinRcvd: 776192
> MaxRwinSent: 5888
> MaxSsthresh: 201272
> MinMSS: 1448
> MinRTO: 209
> MinRTT: 4
> MinRwinRcvd: 5888
> MinRwinSent: 5792
> NagleEnabled: 1
> OtherReductions: 10
> PktsIn: 1854
> PktsOut: 20384
> PktsRetrans: 69
> RcvWinScale: 7
> SACKEnabled: 3
> SACKsRcvd: 373
> SendStall: 0
> SlowStart: 391
> SampleRTT: 26
> SmoothedRTT: 29
> SndWinScale: 7
> SndLimTimeRwin: 0
> SndLimTimeCwnd: 10087802
> SndLimTimeSender: 40308
> SndLimTransRwin: 0
> SndLimTransCwnd: 29
> SndLimTransSender: 29
> SndLimBytesRwin: 0
> SndLimBytesCwnd: 29560040
> SndLimBytesSender: 597568
> SubsequentTimeouts: 0
> SumRTT: 32048
> Timeouts: 1
> TimestampsEnabled: 1
> WinScaleRcvd: 7
> WinScaleSent: 7
> DupAcksOut: 0
> StartTimeUsec: 694357
> Duration: 10132874
> c2sData: 2
> c2sAck: 2
> s2cData: 8
> s2cAck: 4
> half_duplex: 0
> link: 100
> congestion: 1
> bad_cable: 0
> mismatch: 0
> spd: 23.82
> bw: 29.86
> loss: 0.000294349
> avgrtt: 21.57
> waitsec: 0.23
> timesec: 10.00
> order: 0.1990
> rwintime: 0.0000
> sendtime: 0.0040
> cwndtime: 0.9960
> rwin: 5.9219
> swin: 7.0705
> cwin: 3.0822
> rttsec: 0.021567
> Sndbuf: 926744
> aspd: 0.00000
> CWND-Limited: 769.73
> minCWNDpeak: 1448
> maxCWNDpeak: 403992
> CWNDpeaks: 6
>
> The theoretical network limit is 29.86 Mbps
> The NDT server has a 452.0 KByte buffer which limits the throughput to
> 327.83 Mbps
> Your PC/Workstation has a 758.0 KByte buffer which limits the throughput
> to 274.58 Mbps
> The network based flow control limits the throughput to 142.91 Mbps
>
> Client Data reports link is 'T1', Client Acks report link is 'T1'
> Server Data reports link is 'OC-48', Server Acks report link is 'T3'