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Use Packet Priority tools in VXbuilder to configure a differentiated service (DiffServ). Differentiated services is a method for guaranteeing quality of service (QoS) within an enterprise. A key characteristic of DiffServ is that flows are aggregated in the network so that core routers only need to distinguish a comparably small number of aggregated flows, even if those flows contain thousands of individual flows.

Packet Priority configuration accomplishes the following objectives:

  • Specifies the Packet Priority levels to be available for new packets originating from VX. The DiffServ value field alone is used for this.
  • Matches the DiffServ value of incoming packets for determination of the transmit priority to use (0-5) when forwarding the packets. The DiffServ mask is applied to the incoming packet's DiffServ field, then compared against the Transmit DiffServ Match. The first match found while scanning the Packet Priority Table from top to bottom, determines the priority by the Queuing Transmit Packet Priority value.

The Packet Priority mapping screen displays eight predefined levels, including Best Effort, Assured Forwarding (AF) levels, and Expedited Forwarding. You can use these designations to assign various levels of priority to traffic traversing the network, up to a maximum of 8 priority levels. The highest priority traffic (Expedited Forwarding) is more likely to be passed through with lower latency and lower jitter than the low priority traffic.

In most cases, the predefined Packet Priority levels can be used to provide QoS traffic guarantees. The predefined Packet Priority level allocate traffic into the six VX traffic queues. VX does priority queueing with the highest packets sent first. When an end device supports additional Packet Priority capabilities.

Use tools and procedures in this section to set parameters for Dial-up or Serial WAN adapters.

View Packet Priority (DiffServ) Settings

Select the Networking > Packet Priority subdirectory for the VX node and view contents at the Packet Priority screen.

Add Packet Priority (DiffServ) Entries

Insert a new line in the Packet Priority screen, then double-click the line to present the Edit Packet Priority Mapping dialog box.

Modify Packet Priority (DiffServ) Settings

Double-click on table line in the Packet Priority screen, to present the Packet Priority dialog box.

Edit Packet Priority Dialog




Optional description field in which to provide a statement about the Packet Priority setting.

IP DiffServ (binary)

The DiffServ value to be used on the wire. This value is the binary representation of value for the IP header DiffServ field.

802.1p Priority (0-7)

The 802.1p priority level for VLAN tag

This setting is only applicable for interfaces with VLAN tagging enabled.

Priority queue

The VX queue in which to place the different level packets
5 is the highest priority. 0 is the lowest priority. VX does priority queuing with the highest packets sent first.

Low priority queues can be starved if there are too many high priority packets.

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