["Peter Huber" <peterhuberpeter@xxxxxxx>]

Dear list,

this is a newbee question. We tried everything we came up with, but need help now.

We are running upstream data transfer over a high latency connection (170ms RTT, Internet2). 

In order to test the possible data rates we can get, we use 

   sudo tc qdisc add dev eth0 root netem delay 170ms

on a machine connected (1Gbit) to our local network. We experimented with different window sizes sending/receiving between 3 and 30Mbytes.

In the test environment but identically also in the real data upstream case to the remote location, we see in the wireshark IO statistics at 0.01 sec Tick interval that the data transfer only happens in short spikes (see attached plot). And indeed there are many large (nearly-constant over the transfer) delays between some packets, e.g. between packet 23822 and 23823

   23823 25.537234   0.155031

Is this normal? Is there anything we could do to improve the situation? Why does the window size not grow although we do not have packet loss?

Any help would be greatly appreciated.

All the very best,

Peter

  No.   Time        Delta Time  Source         Destination    Protocol    Info 
  23800 25.380762   0.000109    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85134728 Win=2304000 Len=0
  23801 25.380812   0.000050    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85143416 Win=2304000 Len=0
  23802 25.380942   0.000130    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85149208 Win=2304000 Len=0
  23803 25.380955   0.000013    YYY.YYY.YY.YY  XXX.XXX.XX.XX  HTTP     Continuation or non-HTTP traffic[Packet size limited during capture] 6912
  23804 25.380964   0.000009    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85153552 Win=2304000 Len=0
  23805 25.381068   0.000104    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85162240 Win=2304000 Len=0
  23806 25.381203   0.000135    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85175272 Win=2304000 Len=0
  23807 25.381303   0.000100    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85186856 Win=2304000 Len=0
  23808 25.381390   0.000087    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85195544 Win=2304000 Len=0
  23809 25.381445   0.000055    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85201336 Win=2304000 Len=0
  23810 25.381599   0.000154    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85207128 Win=2304000 Len=0
  23811 25.381660   0.000061    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85215816 Win=2304000 Len=0
  23812 25.381673   0.000013    YYY.YYY.YY.YY  XXX.XXX.XX.XX  HTTP     Continuation or non-HTTP traffic[Packet size limited during capture] 6912
  23813 25.381688   0.000015    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85220160 Win=2304000 Len=0
  23814 25.381791   0.000103    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85224504 Win=2304000 Len=0
  23815 25.381812   0.000021    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85233192 Win=2304000 Len=0
  23816 25.381832   0.000020    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85241880 Win=2304000 Len=0
  23817 25.382139   0.000307    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85253464 Win=2304000 Len=0
  23818 25.382148   0.000009    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85250568 Win=2304000 Len=0
  23819 25.382151   0.000003    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85259256 Win=2302656 Len=0
  23820 25.382165   0.000014    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85256360 Win=2304000 Len=0
  23821 25.382194   0.000029    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85267944 Win=2304000 Len=0
  23822 25.382203   0.000009    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85270840 Win=2304000 Len=0

  23823 25.537234   0.155031    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85273736 Win=2304000 Len=0

  23824 25.537545   0.000311    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85283872 Win=2304000 Len=0
  23825 25.537556   0.000011    YYY.YYY.YY.YY  XXX.XXX.XX.XX  HTTP     Continuation or non-HTTP traffic[Packet size limited during capture] 6912
  23826 25.537571   0.000015    XXX.XXX.XX.XX  YYY.YYY.YY.YY  TCP  46561 > http [ACK] Seq=153 Ack=85295456 Win=2304000 Len=0

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