Service Assignment

The Service Assignment tab allows you to configure how the optimizer handles different types of traffic and traffic to or from particular sites. It is your primary tool for exercising fine-grained control over the traffic that flows through the optimizer. This control is achieved using quality-of-service (QoS) queues.

Please see Section 3.4.4, “Quality of Service” for an overview of the QoS subsystem. The Service Assignment tab is essentially an editor for QoS queues.

Before making QoS changes, we recommend that you first configure all of your network's links and sites, and that you test them thoroughly. Once you have a working network, it is much easier to implement and troubleshoot traffic shaping.

The following screen shot shows the Service Assignment tab populated with the links and sites from Example 4.1.

The QoS queues on this tab are arranged according to the links and sites that were initially configured in the device with the Networks tab. From here you can create new top-level queues or child queues, and edit or delete any queue.

The tab is divided in two sections. The main part is a table containing all the QoS queues on the device.

The lower part is a firewall rule editor you use to associate traffic with a particular queue. When you select a leaf queue in the upper table, the queue's associated firewall rules appear in the rule editor. The firewall rule editor is described in the Traffic Assignment tab section.

Only bottom-most (leaf) queues have associated firewall rules.

Select a QoS queue by clicking on its name in the blue Queue Name column on the left. The selected queue is highlighted in red. If a queue has child queues, you can view (or hide) the children by first selecting the parent queue, then clicking on the parent queue's name a second time.

When you select a queue, a context menu button appears to the left of the queue's name. Click on this button to open a context menu for the selected queue.

The queue context menu has the following options:

• Edit queue: Edit the queue's properties. You can also edit a queue by clicking on one of its values in the white columns. This places the queue's properties into editable controls:

• Add child queue: Creates a new queue as a child of the selected queue.

• Clone queue: Creates a new queue as a sibling of the selected queue, and copies the selected queue's properties into its new sibling.

• Delete queue: Removes the selected queue (and its associated firewall rules) from the system.

• Add filter rule: Adds a new firewall rule associated with the selected queue.

4.5.3.1. Queue Properties

Remember that queue properties apply to traffic transmitted from the optimizer over the Wireless interface.

Queue Name: The name of the QoS queue. Normally queue names correspond to links and sites in your network, but you can use any names you like.

Max TX: The maximum speed at which the optimizer will transmit traffic in this queue.

Gtd TX: The guaranteed transmission speed that the optimizer will use for this queue when the link is congested.

Pri TX: The priority transmission speed that the optimizer will both guarantee and prioritize to service real-time protocols. Use this in conjunction with the maximum queue delay (Max Q Dly) value to ensure sufficient response rates for traffic such as voice, streaming media or gaming. The optimizer will still make priority bandwidth available to other traffic if this queue does not need it. The priority speeds of a queue's children can not together exceed 80% of the queue's maximum speed.

RTT: The round trip time, in milliseconds. This value is only used in top-level queues (which usually represent network links).

Max RX: The expected maximum rate for traffic received in this queue. This value controls how many buffers the optimizer allocates to receive the queue's traffic. For optimum performance, the value here should match the corresponding Max TX value on the device sending traffic in this queue to this optimizer (or the sum of those values if more than one device is sending such traffic).

Setting Max RX too low can reduce the rate at which the queue will receive traffic.

Max Q Dly: The queue's maximum packet latency, in milliseconds. Packets will not be held in this queue for longer than this time. Always use Auto here for TCP traffic.

Enc Budgt: The encapsulation budget for packets in this queue. If you are using an external system that adds a per-packet overhead, enter the number of bytes that system adds to each packet here. Note that the optimizer automatically takes into account the encapsulation overhead of its own features (like XipLink's own Lightweight tunnelling), so you do not need to account for those here.

Sess Rate: The maximum transmission speed for TCP sessions associated with this queue.

Per-class TCP Optimizations: Leaf queues associated with TCP traffic can override various system-wide TCP optimization settings. This allows you to apply different optimizations to different links in your network.

To configure class-specific TCP optimizations, select the TCP class in the Service Assignment table then click the context menu button on the right. The TCP optimizations you can override are:

• The transport control algorithm.

• The use of SCPS.

• Slow-reader detection.

• Acknowledgement frequency reduction (AFR).