ONL At A Glance

Contents

• General Comments
• The RLI
• Filters, Queues And Bandwidth
• Using Plugins

The description below assumes that you will be using the NPRs. Most of the description also applies to the older NSPs. See the The NSP Tutorial for the details.

• The NPR Tutorial describes most of the features of the ONL Testbed and the Remote Laboratory Interface (RLI). The earlier tutorial The NSP Tutorial describes the Network Services Platform, the first-generation experimental router and the RLI. Both tutorials can be accessed from the sidebar of the main ONL web page http://www.onl.wustl.edu.
• Some users find the examples in the NPR Tutorial useful. These can be accessed by clicking The NPR Tutorial => Examples or through the NPR Tutorial link in the sidebar of the ONL website www.onl.wustl.edu.

More information can be found in the tutorial page NPR Tutorial => The Remote Laboratory Interface.

• In the beginning, use NPRs, hosts and links. Later, try GigE switches. You can try NSPs, but their plugins can not run at line speed. NetFPGAs will be available soon.
• Route Tables: Both NPR and NSP routers initially have an empty forwarding (route) table. So, you have to define some forwarding mechanism. Topology => Generate Default Routes will setup default route tables at each of the input ports.
• Reservations: The only way to reserve resources is through the RLI. And the only way to change that reservation is to delete it and add a new reservation. So, the typical user sequence is:
  • Use the RLI to define the maximal network.
  • Save the configuration periodically (File => Save As ... or File => Save).
  • Make a reservation (File => Make Reservation).
• File => Commit:
  • You can monitor the progress of your File => Commit using the Testbed Status link in the sidebar of the ONL website.
  • The My Reservations link gives you a page showing your reservations.
  • The Resource Availability link gives you a page showing you what resources are available.
• Monitoring Charts:
  • Metrics such as bandwidth and queue length are obtained by daemons that read counters at some specified polling period (default 1 second) and in the case of bandwidth, computing the rate over the polling period.
  • On an existing chart, you can see the source of the data by clicking on the line label in the legend which will open a dialogue box which contains the properties of the line (e.g. units, rate or absolute value).
  • The Y-axis label can be changed to something more meaningful by selecting View => Change Y-Axis Label in the monitoring window and choosing more appropriate units (e.g., Mb/s for bandwidth charts).
  • Use Monitoring => Add Parameter to add a parameter to a chart. For example, to add an output port bandwidth:
    • Main Window: Select Monitoring => Add Parameter.
    • Main Window: Select the port.
    • Port Window: Select Monitoring => TXBYTE
    • Dialogue Box: Enter the polling rate; check the rate box; and select Enter.
    • No Commit is needed.

More information can be found in the tutorial page NPR Tutorial => Filters, Queues and Bandwidth.

• Packet Forwarding:
  • Packets are forwarded to (packet scheduling) queues associated with each output port. The queues are identified by non-negative integers (i.e., QIDs). The forwarding is based on route tables and filter tables at each input port.
  • These tables can be configured by selecting the port in the router icon and then selecting Configuration => Route Table or Configuration => Filters.
  • The entry used for forwarding is the highest priority (smallest priority number) matching entry. Route tables are matched using a Longest Prefix Matching algorithm.
  • Packets forwarded by a routing table match are hashed into one of 64 datagram queues (i.e., stochastic queueing).
• Packet Dropping and Duplication
  Filters can also be used to drop packets (drop checkbox) or duplicate packets (aux checkbox for auxilliary filter).
• Output Port Rate (Capacity)
  The actual output port rate after configuration has completed is the largest integer multiple of 64 Kb/s that is no greater than the value entered in the port rate box. This means that if you ask for 300 Mb/s, you will actually get something slightly less than 300 Mb/s.
• Packet Queues
  • Packet queues are scheduled using a Weighted Deficit Round Robin (WDRR) scheduling algorithm. The weight is controlled by the quantum value of the queue. The ratio of quantum values determines the relative rate. e.g., if the port capacity is 12 Mb/s and two queues have quantum values of 1500 and 3000, the long-term backlogged service rates will be 4 Mb/s and 8 Mb/s. The absolute quantum values can be thought of as the number of bytes to add to a token counter. The packet at the head of a queue is transmitted when the queue's turn arrives and its token counter is atleast equal to the size of the packet.
  • The default size (drop threshold) of packet queues is 32,000 bytes.
  • The datagram queues are numbered from 0-63. The reserved flow queues are numbered from 64-8191.
  • A route table entry hashes to one of the datagram queues (0-63). A filter table entry is configured to forward to a specific queue in the range 0-8191 or a plugin microengine. If a queue is chosen, it is typically a reserved queue (64-8191).

More information can be found in the tutorial page NPR Tutorial => Router Plugins.

• Plugins
  Plugins allow you to do custom packet processing. Each NPR has five IXP microengines (MEs) that can be loaded with plugins. One of the most useful provided plugins is the delay plugin that allows you to delay packets as they move from an input port to a packet queue at an output port.
• Using A Plugin
  To use a plugin, you need to install the plugin and a filter to direct packets to the plugin. Note: You can not install a plugin until after a File => Commit has finished.
• Installing A Plugin
  To install the delay plugin (after File => Commit has finished):
  • RLI Window: Click the center of the NPR icon, and select Configuration => Plugin Table.
  • Plugin Table: Select Edit => Add Plugin => delay
  • Plugin Dialogue Box: Enter an integer from 0 to 4 to indicate the plugin microengine (ME) number where you want the plugin to be loaded. Note: Only one plugin can be loaded into each ME.
  This loads a plugin with a default delay of 50 msec.
• Installing A Filter
  The previous section Filters, Queues And Bandwidth explained how to install a filter to direct packets to a scheduling queue. To install a filter to direct packets to a plugin involves two changes:
  • Select plugin only from the port/plugin selection menu, and
  • Enter the microengine number (0-4) of the plugin in the output plugins field.
• Sending A Message To A Plugin
  • Plugins respond to a small set of messages. For example, the delay plugin responds to five messages including:
    • =counts:
      Return three counter values: (ninq) the number of packets seen by the plugin, (maxinq) the maximum number of packets in its delay queue, and (ndrops) the number of packets dropped because of a full delay queue.
    • reset:
      Reset the counters.
    • delay= X: (the space after the '=' is important)
      Set the delay to X milliseconds.
  • To change the delay in a delay plugin that has been installed in ME 2 to 10 msec:
    • Plugin Window: Select Edit => Send Command to Plugin.
    • Send Command Window:
      Enter 2 in the microengine box;
      Enter delay= 10 in the message box (Note the space after the '='character.).
• The section NPR Tutorial => Writing A Plugin explains how you can write your own plugin.