Slow connection from on-permise to Azure

Arkadiusz Kowalski 96 Reputation points
2021-09-09T09:26:46.127+00:00

We plan to migrate from on-premise to Azure. After deployment of a test virtual machine in Azure tenant we reported a slow connection (download and upload speed) mesured by using iperf:

[ ID] Interval Transfer Bandwidth
[ 4] 0.00-10.00 sec 19.6 MBytes 16.5 Mbits/sec sender
[ 4] 0.00-10.00 sec 19.6 MBytes 16.4 Mbits/sec receiver

Via VPN tunnel the connection is even sload:

[ ID] Interval Transfer Bandwidth
[ 4] 0.00-10.01 sec 18.6 MBytes 15.6 Mbits/sec sender
[ 4] 0.00-10.01 sec 18.5 MBytes 15.5 Mbits/sec receiver

The test virtual machine is not under heavy load, no applications are installed. No other vms are deployed in the virtual network. Someone knows what is causing this issue? We would be very grateful for any tips.

Azure Virtual Network
Azure Virtual Network
An Azure networking service that is used to provision private networks and optionally to connect to on-premises datacenters.
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Accepted answer
  1. Arkadiusz Kowalski 96 Reputation points
    2021-09-09T10:30:55.123+00:00

    VM Size: Standard D2s_v4 (2 vcpus, 8 GiB memory)
    Sorage type: Standard HDD LRS
    Storage Size: 127GB
    Storage Max IOPS: 500
    Storage Max throughput (MBps): 60
    Storage Encryption: SSE with PMK

    We tested network performance also by using other Azure tenants with different virtual network topology, different vms size and operating systems, etc in all cases we got about 20Mb / 20Mb (download/upload). We are located in northwest Poland .

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  1. Arkadiusz Kowalski 96 Reputation points
    2021-09-13T06:06:04.043+00:00

    Probably this issues results from bad interpretation of bandwidth measurement. I was conducting bandwidth tests using iperf. Then I used AzureCT - the Azure Connectivity Toolkit. In general, AzureCT is based on iperf, but it performs more complex tests. In the first case (iperf) I got the result for one tcp session (16 Mbit/sec), in the second case (AzureCT) for 32 simultaneous tcp sessions (489 Mbits/sec), as shown below:

    1 Session 16.0 Mbits/sec 0% loss 31.185ms
    32 Sessions 489 Mbits/sec 0% loss 31.225ms

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