Device Manager Online Help

Setting priority

A Passport routing switch can operate in either of two modes of traffic priority: Best Effort mode or Priority mode. The factory default setting is Best Effort mode. The following differences exist between these modes:

• In Best Effort mode, all traffic is treated with the same priority.
• In Priority mode, high-priority traffic flows through the switch fabric using a high-priority data path. Output buffers are reserved for high-priority traffic.

Enable high-priority traffic on a per-port, per-MAC, per-VLAN, or per-flow basis as follows:

• When a port is set to High Priority mode, all traffic received on this port is assigned a high priority.
• When a MAC address is set to High Priority mode, all traffic from the MAC address is assigned a high priority.
• When a VLAN is set to High Priority mode, frames received on any of the active ports of the VLAN and classified as belonging to that VLAN are assigned a high priority.
• An IP flow record can be used to assign high switching priority to an IP packet based on its source and destination IP addresses, protocol type source port number, and destination port number.
• When a high-priority frame is sent out a tagged port, the 3-bit User Priority field in the IEEE VLAN tag is set to 7. A normal priority frame has a User Priority of 0. Any received tagged frames with a User Priority greater than 0 are treated as high priority.

There are four ways to prioritize traffic. The following sections describe assigning priority to traffic in these areas:

• By port

In Device Manager, you can specify that any traffic that originates or emanates from a particular port be treated as high priority. For example, you might give a port that supports a video server a higher priority than other ports from which data traffic originates.

• By MAC address

You can set the priority to high or low for either a learned or a static entry.

• By VLAN

You can set the priority to high on a new VLAN or existing VLAN. When you set the priority to high on a VLAN (for example, a video VLAN), any traffic through this VLAN is placed in the high-priority queue.

• By flow

You can use IP flows to identify a particular stream of traffic at the IP layer and at the TCP/UDP layer. Setting IP flows as a priority method uses the following addresses and ports:

­	Source IP address

­	Destination IP address

­	Source IP port

­	Destination IP port

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Protocol

Two additional options are available by using IP filters:

• By setting the IEEE 802.1p priority bits in the IeeeVlanPriority text box

These bits can be set when creating a filter and have a range of 0 to 7. If a tagged frame is received with bits set and the IeeeVlanPriority is greater than 0, the priority is high. If the IeeeVlanPriority is set to 0, the frame's priority is normal.

• By setting the filter to HighPriority

When using IP filters, matching frames have high priority. Refer to the chapter on IP filters in Reference for Passport Management Software Switching Operations, Release 2.1 for information about how to use filters to set priority.