Controlling bandwidth usage with virtual links from the command line

FASP® transfers attempt to transfer at the maximum transfer rate available. However, too many simultaneous transfers can overwhelm your storage or leave little bandwidth available for other network activity. To set a bandwidth cap on the total bandwidth that is used by incoming or outgoing transfer sessions that are initiated by all users, set up a virtual link (Vlink).

About this task

Vlinks are virtual bandwidth caps, in that they are not assigned to a specific transfer session, but to all sessions assigned to the same Vlink. The total bandwidth that is used by all incoming or outgoing transfer sessions that are initiated by users who are assigned to the same Vlink does not exceed the Vlink capacity.

For example, if you want to limit all incoming FASP transfers to 100 Mbps, you can create a Vlink with a 100 Mbps capacity and assign it globally to all incoming transfers. If a user attempts an upload at 50 Mbps but other incoming transfers are already using 75 Mbps, then the transfer rates adjust (based on transfer policy) so that the total does not exceed 100 Mbps.

Procedure

Create a Vlink.

To create a Vlink, run the following command as administrator:

# asconfigurator -x "set_trunk_data;id,vlink_id;trunk_capacity,bandwidth;trunk_on,true"

You can also specify a multicast port and time-to-live, among other settings. To see a complete list of parameters with their corresponding asconfigurator commands, run the following command:

# /opt/aspera/bin/asuserdata -+

The following table describes several parameters that are frequently used:

Tag	Description	Values	Default
Vlink ID	The Vlink ID. Sessions assigned with the same trunk ID share the same bandwidth cap.	Positive integer in the range 1 - 255.	N/A
Vlink Name	The Vlink name. This value has no impact on actual bandwidth cap.	Text string.	Blank
Capacity	The value reflects the virtual bandwidth cap in Kbps. When applying the Vlink to a transfer, the transfer's bandwidth is restricted by this value. For example, default outgoing.	Positive integer in Kbps.	50000
On	Set to `true` to activate the Vlink. Set to `false` to deactivate the Vlink.	True or false.	False
Multicast Port	Sets the UDP port through which virtual link sends and receives multicast communication messages. Sessions that share the same virtual bandwidth cap needs to have the same port number. To avoid port conflicts, use the default UDP port 55001. Do NOT set the port number to the same one used by FASP data transfer (33001). Important: If you have a local firewall on your server, you need to allow the Vlink UDP port (55001, by default) for multicast traffic. For example, Windows^TM `firewall`, Linux® `iptables`, or Mac `ipfw`	Positive integer in the range 1 - 65535.	55001
Multicast TTL	Sets the time-to-live (TTL) field in the IP header for Vlink multicast packets.	Positive integer in the range 1 - 255.	Blank

For example, to create a Vlink with an ID of 108, named 50Mbps cap, with a capacity of 50 Mbps (50000 kbps), run the following command:

# asconfigurator -x "set_trunk_data;id,108;trunk_name,50Mbps cap;trunk_capacity,50000;trunk_on,true"

This creates the following text in aspera.conf:

<CONF version="2">
  ...
  <trunks>
    <trunk>
      <id>108</id>                                   <!-- Vlink ID -->
      <name>50Mbps cap</name>                        <!-- Vlink Name -->
      <capacity>
        <schedule format="ranges">50000</schedule>   <!-- Capacity -->
      </capacity>
      <on>true</on>                                  <!-- On -->  
    </trunk>
  </trunks>
</CONF>

The capacity of the Vlink is set within a <schedule> tag because the capacity can be scheduled as one value during a specified time period, and a default value at all other times. For more information on this configuration, see the knowledge base article Specifying a time varying schedule for a Vlink at Specifying a time varying schedule for a Vlink.

To edit aspera.conf manually, rather than running asconfigurator commands, open the file with write permissions from the following location:

/opt/aspera/etc/aspera.conf

Validate the aspera.conf file by using the asuserdata utility:

# /opt/aspera/bin/asuserdata -v

Apply the Vlink.

Assign a Vlink to global settings for transfers in or out. Use the following syntax, updating the direction (in or out) depending on your needs:

# asconfigurator -x "set_node_data;transfer_in_bandwidth_aggregate_trunk_id,id"

For example, to set Vlink 108 as the default for transfers out, run the following command:

# asconfigurator -x "set_node_data;transfer_out_bandwidth_aggregate_trunk_id,108"

These commands add the following lines to aspera.conf:

<CONF version="2">
  ...
  <default>
    <transfer>
      <out>
        <bandwidth><aggregate>
          <trunk_id>108</trunk_id> <!-- Vlink #108 for the default outgoing sessions. -->
        </aggregate></bandwidth>
      </out>
      <in>
       ...
      </in>
    </transfer>
  </default>
</CONF>