ndt-users list created

["Mike Diehl" <>]

Hi all.

We are evaluating the NDT to see if it's going to be usefull to us in our 
efforts to optimize our network.  So far, it looks promising.

However, we've seen some test results that look.... odd.

Here is the result of a particular test:

click START to re-test
Checking for Middleboxes . . . . . . . . . . . . . . . . . .  Done
running 10s outbound test (client to server) . . . . . 925.73Mb/s
running 10s inbound test (server to client) . . . . . . 4.83Mb/s
The slowest link in the end-to-end path is a 2.4 Gbps OC-48 subnet
Alarm: Duplex mismatch condition exists: Host set to HD and Switch set
to FD

For this test, both the client and server are on the same switch, connected 
at 
Gig-E via fiber.

I understand why the bottleneck is detected at oc48; I'll try to resolve this 
in my Linux kernel.

I'm more concerned about the asymetric throughput measurement as well as the 
duplex mismatch alarm.  I know that the connection is full duplex, 
end-to-end.  I also know that there are no client firewalls active for this 
test.  What am I missing?

For completeness, I've pasted in all of the other (quite interesting) 
statistics that the tool reports:

Thanx in advance,


2.4 Gbps OC-48 link found.
Link set to Half Duplex mode
No network congestion discovered.
Good network cable(s) found
Alarm: Duplex mismatch condition found:  Host set to HD and Switch set
to FD

Web100 reports the Round trip time = 0.23 msec; the Packet size = 1460
Bytes; and 
There were 59 packets retransmitted, 92 duplicate acks received, and 66
SACK blocks received
The connection stalled 2 times due to packet loss
The connection was idle 0.40 seconds (4.07%) of the time
This connection is sender limited 2.45% of the time.
This connection is network limited 97.53% of the time.
  Contact your local network administrator to report a network problem

    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: OFF
Packet size is preserved End-to-End
Server IP addresses are preserved End-to-End
Client IP addresses are preserved End-to-End

WEB100 Kernel Variables:
Client: localhost/127.0.0.1
AckPktsIn: 2523
AckPktsOut: 0
BytesRetrans: 85268
CongAvoid: 0
CongestionOverCount: 0
CongestionSignals: 2
CountRTT: 2363
CurCwnd: 1460
CurMSS: 1460
CurRTO: 204
CurRwinRcvd: 64512
CurRwinSent: 5840
CurSsthresh: 20440
DSACKDups: 0
DataBytesIn: 0
DataBytesOut: 7427654
DataPktsIn: 0
DataPktsOut: 5215
DupAcksIn: 92
ECNEnabled: 0
FastRetran: 0
MaxCwnd: 32120
MaxMSS: 1460
MaxRTO: 204
MaxRTT: 4
MaxRwinRcvd: 64512
MaxRwinSent: 5840
MaxSsthresh: 146000
MinMSS: 1460
MinRTO: 204
MinRTT: 0
MinRwinRcvd: 0
MinRwinSent: 5840
NagleEnabled: 1
OtherReductions: 1
PktsIn: 2523
PktsOut: 5215
PktsRetrans: 59
X_Rcvbuf: 87380
SACKEnabled: 3
SACKsRcvd: 66
SendStall: 0
SlowStart: 0
SampleRTT: 0
SmoothedRTT: 4
X_Sndbuf: 64224
SndLimTimeRwin: 656
SndLimTimeCwnd: 10068888
SndLimTimeSender: 253435
SndLimTransRwin: 2
SndLimTransCwnd: 14
SndLimTransSender: 14
SndLimBytesRwin: 57532
SndLimBytesCwnd: 376114
SndLimBytesSender: 6994008
SubsequentTimeouts: 0
SumRTT: 548
Timeouts: 2
TimestampsEnabled: 0
WinScaleRcvd: 2147483647
WinScaleSent: 2147483647
DupAcksOut: 0
StartTimeUsec: 558227
Duration: 10326645
c2sData: 8
c2sAck: 8
s2cData: 7
s2cAck: 6

Checking for mismatch condition
        (cwndtime > .3) [0.97>.3], (MaxSsthresh > 0) [146000>0],
         (PktsRetrans/sec > 2) [5.90>2], (estimate > 2) [2452.66>2]
Checking for mismatch on uplink
        (speed > 50 [5.75>50], (xmitspeed < 5) [925.73<5]
        (rwintime > .9) [6.35>.9], (loss < .01) [3.83<.01]
Checking for excessive errors condition
        (loss/sec > .15) [3.83>.15], (cwndtime > .6) [0.97>.6], 
        (loss < .01) [3.83<.01], (MaxSsthresh > 0) [146000>0]
Checking for 10 Mbps link
        (speed < 9.5) [5.75<9.5], (speed > 3.0) [5.75>3.0]
        (xmitspeed < 9.5) [925.73<9.5] (loss < .01) [3.83<.01], (link >
0) [0>0]
Checking for Wireless link
        (sendtime = 0) [0.02=0], (speed < 5) [5.75<5]
        (Estimate > 50 [2452.66>50], (Rwintime > 90) [6.35>.90]
         (RwinTrans/CwndTrans = 1) [2/14=1], (link > 0) [0>0]
Checking for DSL/Cable Modem link
        (speed < 2) [5.75<2], (SndLimTransSender = 0) [14=0]
         (SendTime = 0) [0.024550568203228932=0], (link > 0) [0>0]
Checking for half-duplex condition
        (rwintime > .95) [6.35>.95], (RwinTrans/sec > 30) [0.20>30],
         (SenderTrans/sec > 30) [1.39>30], OR (link <= 10) [0<=10]
Checking for congestion
        (cwndtime > .02) [0.97>.02], (mismatch = 0) [1=0]
        (MaxSsthresh > 0) [146000>0]

bw = 2452.66 based on packet size = 11Kbits, RTT = 0.23msec, and loss =
3.835091192740947E-4
The theoretical network limit is 2452.66 Mbps
The transmit buffer (62.0 KByte) limits the application to 2112.85 Mbps
Your receive buffer (63.0 KByte) limits the application to 2122.33 Mbps
The network based flow control limits the application to 1056.69 Mbps

Client Data reports link is 'OC-48', Client Acks report link is 'OC-48'
Server Data reports link is 'GigE', Server Acks report link is 'OC-12'

-- 
Mike Diehl,
Network Management Tool Devl.
SAIC at Sandia National Laboratories.
(505) 284-3137