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Re: the indeterminate link type


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  • From: Maurice Volaski <>
  • To: Richard Carlson <>
  • Cc:
  • Subject: Re: the indeterminate link type
  • Date: Wed, 17 Sep 2008 13:44:43 -0400

The NDT server puts the interface into promiscuous mode and measures the arrival time of packet-pairs. The "unknown link type" message indicates that this task is failing. The typical reason for this is because there are multiple NIC's installed and you are not using the 1st interface in the list.

Run the '/sbin/ifconfig' command and determine the name of the interface you are using (eth0 is the 1st interface).
Then start the web100srv process with the '-iethx' option (where x is the interface number). If you are using the ndt start script from the conf directory, then edit this file and add this option to the

Thanks, that fixes the unknown problem, but it still doesn't quite report ordinary gigabit, but "2.4 Gbps OC-48" instead. In the statistics, the result is more complex, the client report OC-48, the server and client "acks" report OC-12 and the server "acks" report 10 Gig.


WEB100 Enabled Statistics:
Checking for Middleboxes . . . . . . . . . . . . . . . . . . Done
checking for firewalls . . . . . . . . . . . . . . . . . . . Done
running 10s outbound test (client-to-server [C2S]) . . . . . 373.36Mb/s
running 10s inbound test (server-to-client [S2C]) . . . . . . 419.60Mb/s

------ Client System Details ------
OS data: Name = Mac OS X, Architecture = i386, Version = 10.4.11
Java data: Vendor = Apple Computer, Inc., Version = 1.5.0_13

------ Web100 Detailed Analysis ------
2.4 Gbps OC-48 link found.
Link set to Full Duplex mode
No network congestion discovered.
Good network cable(s) found
Normal duplex operation found.

Web100 reports the Round trip time = 0.87 msec; the Packet size = 1448 Bytes; and
No packet loss - but packets arrived out-of-order 4.34% of the time
S2C throughput test: Packet queuing detected: 0.10%
This connection is receiver limited 4.32% of the time.
Increasing the the client's receive buffer (63.0 KB) will improve
performance
This connection is sender limited 94.21% of the time.
This connection is network limited 1.47% 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: OFF

Server 'theradargun.aecom.yu.edu' 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
Client IP addresses are preserved End-to-End
-----------

WEB100 Kernel Variables:
Client: localhost/127.0.0.1
CurMSS: 1448
X_Rcvbuf: 33554432
X_Sndbuf: 33554432
AckPktsIn: 74954
AckPktsOut: 0
BytesRetrans: 0
CongAvoid: 0
CongestionOverCount: 0
CongestionSignals: 0
CountRTT: 68278
CurCwnd: 99912
CurRTO: 204
CurRwinRcvd: 65535
CurRwinSent: 6144
CurSsthresh: 2147483647
DSACKDups: 0
DataBytesIn: 0
DataBytesOut: 526888512
DataPktsIn: 0
DataPktsOut: 365616
DupAcksIn: 3255
ECNEnabled: 0
FastRetran: 0
MaxCwnd: 99912
MaxMSS: 1448
MaxRTO: 216
MaxRTT: 92
MaxRwinRcvd: 65535
MaxRwinSent: 6144
MaxSsthresh: 0
MinMSS: 1448
MinRTO: 204
MinRTT: 0
MinRwinRcvd: 8648
MinRwinSent: 5792
NagleEnabled: 1
OtherReductions: 0
PktsIn: 74954
PktsOut: 365616
PktsRetrans: 0
RcvWinScale: 9
SACKEnabled: 3
SACKsRcvd: 0
SendStall: 0
SlowStart: 67
SampleRTT: 0
SmoothedRTT: 4
SndWinScale: 0
SndLimTimeRwin: 432412
SndLimTimeCwnd: 147750
SndLimTimeSender: 9440825
SndLimTransRwin: 8813
SndLimTransCwnd: 11
SndLimTransSender: 8825
SndLimBytesRwin: 215916064
SndLimBytesCwnd: 272960
SndLimBytesSender: 310699488
SubsequentTimeouts: 0
SumRTT: 59448
Timeouts: 0
TimestampsEnabled: 1
WinScaleRcvd: 0
WinScaleSent: 9
DupAcksOut: 0
StartTimeUsec: 114657
Duration: 10028744
c2sData: 8
c2sAck: 6
s2cData: 6
s2cAck: 9
half_duplex: 0
link: 100
congestion: 0
bad_cable: 0
mismatch: 0
spd: 420.63
bw: 1268826.32
loss: 0.000000000
avgrtt: 0.87
waitsec: 0.00
timesec: 10.00
order: 0.0434
rwintime: 0.0432
sendtime: 0.9421
cwndtime: 0.0147
rwin: 0.5000
swin: 256.0000
cwin: 0.7623
rttsec: 0.000871
Sndbuf: 33554432
aspd: 0.00000
CWND-Limited: 171.84
minCWNDpeak: -1
maxCWNDpeak: -1
CWNDpeaks: -1

The theoretical network limit is 1268826.32 Mbps
The NDT server has a 16384.0 KByte buffer which limits the throughput to 293915.04 Mbps
Your PC/Workstation has a 63.0 KByte buffer which limits the throughput to 574.05 Mbps
The network based flow control limits the throughput to 875.20 Mbps

Client Data reports link is 'OC-48', Client Acks report link is 'OC-12'
Server Data reports link is 'OC-12', Server Acks report link is '10 Gig'

--

Maurice Volaski,

Computing Support, Rose F. Kennedy Center
Albert Einstein College of Medicine of Yeshiva University



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