ndt-users list created

["Nathan C. Broome" <>]

Teresa,

This might help:

http://www.psc.edu/networking/projects/tcptune/

About 3/4 of the way into the document they talk about how to tune the 
TCP/IP stack in Linux.  I changed mine to the settings they recommended 
in this document, and it seems to be fine.


Here's my info if it helps:

ndt:/proc/sys/net/core # cat rmem_max
2500000

ndt:/proc/sys/net/core # cat wmem_max
2500000

ndt:/proc/sys/net/ipv4 # cat tcp_wmem
4096    65536   5000000

ndt:/proc/sys/net/ipv4 # cat tcp_rmem
4096    5000000 5000000


Nathan Broome
Oberlin College














Teresa Beamer wrote:

> I've finally gotten some time to review the statistics we've been gathering 
> via
> NDT and I am consistently seeing a low kb/s for NDT server to Client with a
> high kb/s from Client to NDT server.  I'm beginning to think I need to adjust
> some parameters on the NDT server, but am not quite sure where to make the
> changes (I'm fairly new to linux).  I've included sample below of a run from 
> my
> machine.  I did notice this time a line that says: "The NDT server has a 214.0
> KByte buffer which limits the throughput to 208.98 Mbps."
>
> Should I make changes to the buffers on the server?  And if so where do I go 
> to
> make those changes.  A pointer to documentation that describes this 
> information
> would be great.
>
> Thanks for any help you can provide.
>
> Teresa Beamer
> Computing Services
> Denison University
>
> TCP/Web100 Network Diagnostic Tool v5.3.3e
> click START to begin
> Checking for Middleboxes . . . . . . . . . . . . . . . . . .  Done
> running 10s outbound test (client to server) . . . . . 863.86Kb/s
> running 10s inbound test (server to client) . . . . . . 237.58kb/s
> The slowest link in the end-to-end path is a 100 Mbps Full duplex Fast 
> Ethernet
> subnet
>
> WEB100 Enabled Statistics:
> Checking for Middleboxes . . . . . . . . . . . . . . . . . .  Done
> running 10s outbound test (client to server) . . . . . 863.86Kb/s
> running 10s inbound test (server to client) . . . . . . 237.58kb/s
>
>         ------  Client System Details  ------
> OS data: Name = Windows XP, Architecture = x86, Version = 5.1
> Java data: Vendor = Sun Microsystems Inc., Version = 1.4.2_03
>
>         ------  Web100 Detailed Analysis  ------
> 100 Mbps FastEthernet 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 = 8.0 msec; the Packet size = 1460 Bytes; 
> and
> There were 201 packets retransmitted, 2 duplicate acks received, and 5 SACK
> blocks received
> The connection stalled 1 times due to packet loss
> The connection was idle 0.21 seconds (1.5%) of the time
> This connection is network limited 99.87% of the time.
> Excessive packet loss is impacting your performance, check the auto-negotiate
> function on your local PC and network switch
>
> 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: 82
> AckPktsOut: 0
> BytesRetrans: 292165
> CongAvoid: 67
> CongestionOverCount: 0
> CongestionSignals: 7
> CountRTT: 1
> CurCwnd: 7300
> CurMSS: 1460
> CurRTO: 208
> CurRwinRcvd: 0
> CurRwinSent: 5840
> CurSsthresh: 2920
> DSACKDups: 0
> DataBytesIn: 0
> DataBytesOut: 785985
> DataPktsIn: 0
> DataPktsOut: 520
> DupAcksIn: 2
> ECNEnabled: 0
> FastRetran: 1
> MaxCwnd: 7300
> MaxMSS: 1460
> MaxRTO: 208
> MaxRTT: 8
> MaxRwinRcvd: 0
> MaxRwinSent: 5840
> MaxSsthresh: 2920
> MinMSS: 1460
> MinRTO: 208
> MinRTT: 8
> MinRwinRcvd: 2147483647
> MinRwinSent: 5840
> NagleEnabled: 1
> OtherReductions: 5
> PktsIn: 82
> PktsOut: 520
> PktsRetrans: 201
> X_Rcvbuf: 219136
> RcvWinScale: 2147483647
> SACKEnabled: 3
> SACKsRcvd: 5
> SendStall: 0
> SlowStart: 13
> SampleRTT: 8
> SmoothedRTT: 8
> X_Sndbuf: 219136
> SndWinScale: 2147483647
> SndLimTimeRwin: 0
> SndLimTimeCwnd: 14495340
> SndLimTimeSender: 19349
> SndLimTransRwin: 0
> SndLimTransCwnd: 1
> SndLimTransSender: 1
> SndLimBytesRwin: 0
> SndLimBytesCwnd: 785985
> SndLimBytesSender: 0
> SubsequentTimeouts: 5
> SumRTT: 8
> Timeouts: 1
> TimestampsEnabled: 0
> WinScaleRcvd: 2147483647
> WinScaleSent: 2147483647
> DupAcksOut: 0
> StartTimeUsec: 15742
> Duration: 14520643
> c2sData: 5
> c2sAck: 5
> s2cData: 7
> s2cAck: 4
> half_duplex: 0
> link: 100
> congestion: 0
> bad_cable: 0
> mismatch: 0
> spd: 0.00
> bw: 12.00
> loss: 0.013461538
> avgrtt: 8.00
> waitsec: 0.21
> timesec: 14.00
> order: 0.0244
> rwintime: 0.0000
> sendtime: 0.0013
> cwndtime: 0.9987
> rwin: 0.0000
> swin: 1.6719
> cwin: 0.0557
> rttsec: 0.008000
> Sndbuf: 219136
> aspd: 0.30399
>
> Checking for mismatch on uplink
>         (speed > 50 [0>50], (xmitspeed < 5) [0.86<5]
>         (rwintime > .9) [0>.9], (loss < .01) [0.01<.01]
> Checking for excessive errors condition
>         (loss/sec > .15) [9.61>.15], (cwndtime > .6) [0.99>.6],
>         (loss < .01) [0.01<.01], (MaxSsthresh > 0) [2920>0]
> Checking for 10 Mbps link
>         (speed < 9.5) [0<9.5], (speed > 3.0) [0>3.0]
>         (xmitspeed < 9.5) [0.86<9.5] (loss < .01) [0.01<.01], (mylink > 0) 
> [100.0>0]
> Checking for Wireless link
>         (sendtime = 0) [0.00=0], (speed < 5) [0<5]
>         (Estimate > 50 [12.0>50], (Rwintime > 90) [0>.90]
>          (RwinTrans/CwndTrans = 1) [0/1=1], (mylink > 0) [100.0>0]
> Checking for DSL/Cable Modem link
>         (speed < 2) [0<2], (SndLimTransSender = 0) [1=0]
>          (SendTime = 0) [0.0013=0], (mylink > 0) [100.0>0]
> Checking for half-duplex condition
>         (rwintime > .95) [0>.95], (RwinTrans/sec > 30) [0>30],
>          (SenderTrans/sec > 30) [0.07>30], OR (mylink <= 10) [100.0<=10]
> Checking for congestion
>         (cwndtime > .02) [0.99>.02], (mismatch = 0) [0=0]
>         (MaxSsthresh > 0) [2920>0]
>
> estimate = 12.0 based on packet size = 11Kbits, RTT = 8.0msec, and loss =
> 0.013461538
> The theoretical network limit is 12.0 Mbps
> The NDT server has a 214.0 KByte buffer which limits the throughput to 208.98
> Mbps
> Your PC/Workstation has a 0 KByte buffer which limits the throughput to 0 Mbps
> The network based flow control limits the throughput to 6.96 Mbps
>
> Client Data reports link is 'FastE', Client Acks report link is 'FastE'
> Server Data reports link is 'GigE', Server Acks report link is 'T3'
>