ndt-users list created

[Sotiris Tsimbonis <>]

Hello everyone,

I have a strange problem with the results of ndt-3.3.12 compared to 
ndt-3.1.13..
The "upload" speed reported by ndt-3.3.12 is always higher than the real 
one..

I have setup two identical linux boxes,
athdslt02:~# uname -a
Linux athdslt02 2.6.17.6-web100 #1 PREEMPT Thu Jul 20 10:50:50 EEST 2006 
i686 GNU/Linux
athdslt02:~# java -version
java version "1.4.2_12"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_12-b03)
Java HotSpot(TM) Client VM (build 1.4.2_12-b03, mixed mode)

The results below are from an aDSL 512/128 kbit line using IE 6; SP1 
with Sun Java plugin 1.5.0_07, and other people with IE/firefox have 
same results ..

ndt-3.3.12 always reports upload speeds above 160kb/s which is an order 
higher than what ndt-3.1.13 correctly reports..
The boxes are publically available, so you can try it out as well..

Any ideas/suggestions about this situation?
Best regards,
Sotiris.


http://athdslt02.forthnet.gr/ runs ndt-3.3.12, reports upload incorrectly
-------------------------------------------------------------------------------------
TCP/Web100 Network Diagnostic Tool v5.4.8
click START to begin
Checking for Middleboxes . . . . . . . . . . . . . . . . . .  Done
checking for firewalls . . . . . . . . . . . . . . . . . . .  Done
running 10s outbound test (client-to-server [C2S]) . . . . . 160.0kb/s
running 10s inbound test (server-to-client [S2C]) . . . . . . 414.93kb/s
Your PC is connected to a Cable/DSL modem
Information: Other network traffic is congesting the link
 [S2C]: Excessive packet queuing detected

click START to re-test

WEB100 Enabled Statistics:
Checking for Middleboxes . . . . . . . . . . . . . . . . . .  Done
checking for firewalls . . . . . . . . . . . . . . . . . . .  Done
running 10s outbound test (client-to-server [C2S]) . . . . . 160.0kb/s
running 10s inbound test (server-to-client [S2C]) . . . . . . 414.93kb/s

        ------  Client System Details  ------
OS data: Name = Windows 2000, Architecture = x86, Version = 5.0
Java data: Vendor = Sun Microsystems Inc., Version = 1.5.0_07

        ------  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 = 189.64 msec; the Packet size = 1432 
Bytes; and
There were 24 packets retransmitted, 148 duplicate acks received, and 
163 SACK blocks received
The connection was idle 0 seconds (0%) of the time
S2C throughput test: Excessive packet queuing detected: 97.52%
This connection is network limited 99.53% 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: OFF
RFC 1323 Window Scaling: ON

Server 'athdslt02' 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 [212.251.121.42] but Client says [10.0.0.3]

WEB100 Kernel Variables:
Client: localhost/127.0.0.1
CurMSS: 1432
X_Rcvbuf: 33554432
X_Sndbuf: 33554432
AckPktsIn: 382
AckPktsOut: 0
BytesRetrans: 34368
CongAvoid: 0
CongestionOverCount: 0
CongestionSignals: 6
CountRTT: 217
CurCwnd: 11456
CurRTO: 360
CurRwinRcvd: 75256
CurRwinSent: 6144
CurSsthresh: 8592
DSACKDups: 0
DataBytesIn: 0
DataBytesOut: 913308
DataPktsIn: 0
DataPktsOut: 629
DupAcksIn: 148
ECNEnabled: 0
FastRetran: 6
MaxCwnd: 31504
MaxMSS: 1432
MaxRTO: 536
MaxRTT: 296
MaxRwinRcvd: 133968
MaxRwinSent: 6144
MaxSsthresh: 143200
MinMSS: 1432
MinRTO: 272
MinRTT: 36
MinRwinRcvd: 75256
MinRwinSent: 5840
NagleEnabled: 1
OtherReductions: 0
PktsIn: 382
PktsOut: 629
PktsRetrans: 24
RcvWinScale: 10
SACKEnabled: 3
SACKsRcvd: 163
SendStall: 0
SlowStart: 0
SampleRTT: 136
SmoothedRTT: 148
SndWinScale: 2
SndLimTimeRwin: 0
SndLimTimeCwnd: 10999950
SndLimTimeSender: 50684
SndLimTransRwin: 0
SndLimTransCwnd: 1
SndLimTransSender: 1
SndLimBytesRwin: 0
SndLimBytesCwnd: 913308
SndLimBytesSender: 0
SubsequentTimeouts: 0
SumRTT: 41152
Timeouts: 0
TimestampsEnabled: 0
WinScaleRcvd: 2
WinScaleSent: 10
DupAcksOut: 0
StartTimeUsec: 586942
Duration: 11051383
c2sData: 2
c2sAck: 2
s2cData: 2
s2cAck: 2
half_duplex: 0
link: 0
congestion: 1
bad_cable: 0
mismatch: 0
spd: 0.66
bw: 0.59
loss: 0.009538951
avgrtt: 189.64
waitsec: 0.00
timesec: 11.00
order: 0.3874
rwintime: 0.0000
sendtime: 0.0046
cwndtime: 0.9954
rwin: 1.0221
swin: 256.0000
cwin: 0.2404
rttsec: 0.189641
Sndbuf: 33554432
aspd: 0.00000
CWND-Limited: 282.94

The theoretical network limit is 0.59 Mbps
The NDT server has a 16384.0 KByte buffer which limits the throughput to 
1349.91 Mbps
Your PC/Workstation has a 130.0 KByte buffer which limits the throughput 
to 5.38 Mbps
The network based flow control limits the throughput to 1.26 Mbps

Client Data reports link is 'T1', Client Acks report link is 'T1'
Server Data reports link is 'T1', Server Acks report link is 'T1'

-------------------------------------------------------------------------------------


http://athdslt03.forthnet.gr/ runs ndt-3.1.13, reports upload correctly
-------------------------------------------------------------------------------------
TCP/Web100 Network Diagnostic Tool v5.3.5a
click START to begin
Checking for Middleboxes . . . . . . . . . . . . . . . . . .  Done
running 10s outbound test (client to server) . . . . . 115.79Kb/s
running 10s inbound test (server to client) . . . . . . 426.99kb/s
Your PC is connected to a Cable/DSL modem
Information: Other network traffic is congesting the link

click START to re-test

WEB100 Enabled Statistics:
Checking for Middleboxes . . . . . . . . . . . . . . . . . .  Done
running 10s outbound test (client to server) . . . . . 115.79Kb/s
running 10s inbound test (server to client) . . . . . . 426.99kb/s

        ------  Client System Details  ------
OS data: Name = Windows 2000, Architecture = x86, Version = 5.0
Java data: Vendor = Sun Microsystems Inc., Version = 1.5.0_07

        ------  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 = 185.47 msec; the Packet size = 1432 
Bytes; and
There were 20 packets retransmitted, 121 duplicate acks received, and 
130 SACK blocks received
The connection was idle 0 seconds (0%) of the time
This connection is network limited 99.65% 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: OFF
RFC 1323 Window Scaling: ON
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 [212.251.121.42] but Client says [10.0.0.3]
WEB100 Kernel Variables:
Client: localhost/127.0.0.1
CurMSS: 1432
X_Rcvbuf: 33554432
X_Sndbuf: 33554432
AckPktsIn: 340
AckPktsOut: 0
BytesRetrans: 28640
CongAvoid: 0
CongestionOverCount: 0
CongestionSignals: 5
CountRTT: 204
CurCwnd: 12888
CurRTO: 372
CurRwinRcvd: 133968
CurRwinSent: 6144
CurSsthresh: 10024
DSACKDups: 0
DataBytesIn: 0
DataBytesOut: 829112
DataPktsIn: 0
DataPktsOut: 572
DupAcksIn: 121
ECNEnabled: 0
FastRetran: 5
MaxCwnd: 28640
MaxMSS: 1432
MaxRTO: 468
MaxRTT: 260
MaxRwinRcvd: 133968
MaxRwinSent: 6144
MaxSsthresh: 143200
MinMSS: 1432
MinRTO: 272
MinRTT: 56
MinRwinRcvd: 133968
MinRwinSent: 5840
NagleEnabled: 1
OtherReductions: 0
PktsIn: 340
PktsOut: 572
PktsRetrans: 20
RcvWinScale: 10
SACKEnabled: 3
SACKsRcvd: 130
SendStall: 0
SlowStart: 0
SampleRTT: 176
SmoothedRTT: 160
SndWinScale: 2
SndLimTimeRwin: 0
SndLimTimeCwnd: 9945654
SndLimTimeSender: 34708
SndLimTransRwin: 0
SndLimTransCwnd: 1
SndLimTransSender: 1
SndLimBytesRwin: 0
SndLimBytesCwnd: 829112
SndLimBytesSender: 0
SubsequentTimeouts: 0
SumRTT: 37836
Timeouts: 0
TimestampsEnabled: 0
WinScaleRcvd: 2
WinScaleSent: 10
DupAcksOut: 0
StartTimeUsec: 105338
Duration: 9982069
c2sData: 2
c2sAck: 2
s2cData: 2
s2cAck: 2
half_duplex: 0
link: 100
congestion: 1
bad_cable: 0
mismatch: 0
spd: -0.01
bw: 0.63
loss: 0.008741259
avgrtt: 185.47
waitsec: 0.00
timesec: 9.00
order: 0.3559
rwintime: 0.0000
sendtime: 0.0035
cwndtime: 0.9965
rwin: 1.0221
swin: 256.0000
cwin: 0.2185
rttsec: 0.185471
Sndbuf: 33554432
aspd: 0.00000
CWND-Limited: 286.66

Checking for mismatch on uplink
        (speed > 50 [-0.01>50], (xmitspeed < 5) [0.11<5]
        (rwintime > .9) [0>.9], (loss < .01) [0.00<.01]
Checking for excessive errors condition
        (loss/sec > .15) [9.71>.15], (cwndtime > .6) [0.99>.6],
        (loss < .01) [0.00<.01], (MaxSsthresh > 0) [143200>0]
Checking for 10 Mbps link
        (speed < 9.5) [-0.01<9.5], (speed > 3.0) [-0.01>3.0]
        (xmitspeed < 9.5) [0.11<9.5] (loss < .01) [0.00<.01], (mylink > 0) 
[3.0>0]
Checking for Wireless link
        (sendtime = 0) [0.00=0], (speed < 5) [-0.01<5]
        (Estimate > 50 [0.63>50], (Rwintime > 90) [0>.90]
         (RwinTrans/CwndTrans = 1) [0/1=1], (mylink > 0) [3.0>0]
Checking for DSL/Cable Modem link
        (speed < 2) [-0.01<2], (SndLimTransSender = 0) [1=0]
         (SendTime = 0) [0.0035=0], (mylink > 0) [3.0>0]
Checking for half-duplex condition
        (rwintime > .95) [0>.95], (RwinTrans/sec > 30) [0>30],
         (SenderTrans/sec > 30) [0.11>30], OR (mylink <= 10) [3.0<=10]
Checking for congestion
        (cwndtime > .02) [0.99>.02], (mismatch = 0) [0=0]
        (MaxSsthresh > 0) [143200>0]

estimate = 0.63 based on packet size = 11Kbits, RTT = 185.47msec, and 
loss = 0.008741259
The theoretical network limit is 0.63 Mbps
The NDT server has a 16384.0 KByte buffer which limits the throughput to 
1380.26 Mbps
Your PC/Workstation has a 130.0 KByte buffer which limits the throughput 
to 5.51 Mbps
The network based flow control limits the throughput to 1.17 Mbps

Client Data reports link is 'T1', Client Acks report link is 'T1'
Server Data reports link is 'T1', Server Acks report link is 'T1'