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Measure time differences from when traffic reaches a physical interface to a virtual interface.
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Measure virtual networking performance with varying traffic patterns and underlying configurations.

Overhead explained


  • Paramiko pip install paramiko
  • XenServer 5.6 or greater; easily extended to other hypervisors by overriding determine_vif_number()
  • Key based root SSH to destination hypervisor
  • Specific root SSH key in authorized_keys on source VM

Getting Started

Example usage:

-n instance-<uuid> \
--hv <hv_ip> \
-s <source_ip> \
-i <host interface|default: eth0> \
--num <vif num|default: 0> \
-d <destination_ip> \
-k <keyfile>
Spawning packet captures...
Captures finished, waiting for files to flush.
Transferring files...
{'average': 21.174698795180724, 'minimum': 0, 'maximum': 514, 'stdev': 50.798123981202764}

Most options are self explanatory. --num refers to x in vif1.x… most single nic VMs will only have a vif1.0, each additional vif gets that 0 incremented.

The numbers output are in microseconds.


source_command runs in all source VMs. It should be a command that generates a specific traffic pattern that has an end. For example:

source_command = 'hping3 -c 10000 -S -L 0 -Q --fast %s' % (destination_ip)

While source_command runs, two other commands will run on the destination VM's hypervisor to analyze the physical interface and vif traffic. The difference in the timestamps on the vif and the physical device is the overhead by various components.

destination_pif_cmd and destination_vif_cmd. These commands should have the same duration as source_command and be extremely verbose in their timestamp reporting. For example:

destination_pif_cmd = 'tcpdump -tttt -nnni %s -w /tmp/destination_uuid_pif -c10000 %s src host %s and dst host %s' % (host_interface, source_ip, destination_ip, output)

destination_vif_cmd = 'tcpdump -tttt -nnni %s -w /tmp/destination_uuid_vif -c10000 %s src host %s and dst host %s' % (vif, source_ip, destination_ip, output)

You also need to know what sort of packet your source_command produces. The source_command in the example produces this:

2013-05-21 20:53:56.421831 IP > S 36550021:36550021(0) win 512

The call to analyze() requires the following parameters:

  • seq_no_col : packet sequence number column (starting from 0 -(#7 in the example packet)
  • timestamp_col : timestamp column (starting from 0 - #1 in the example packet)
  • seq_no_split_by : split sequence number by (':' in the example packet)
  • seq_no_split_index : sequence number split index (starting from 0 - 0 in the example packet)

The result is that weaver will say packet #36550021 came into eth0 at 20:53:56.421831. It then measures the amount of time it took for packet #36550021 to arrive on the vif.

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