Enhancements

Releases M.08.90 and M.08.91 Enhancements

The “legacy-path-cost” CLI command does not affect or replace functionality of the “spanning- tree force-version” command. The “spanning-tree force-version” controls whether MSTP will send and process 802.1w RSTP, or 802.1D STP BPDUs. Regardless of what the “legacy-path-cost” parameter is set to, MSTP will interoperate with legacy STP bridges (send/receive Config and TCN BPDUs).

spanning-treelegacy-mode- A “macro” that is the equivalent of executing the “spanning-tree legacy- path-cost” and “spanning-treeforce-versionstp-compatible” commands.

no spanning-treelegacy-mode- A “macro” that is the equivalent of executing the “no spanning-treelegacy-path-cost” and “spanning-treeforce-versionmstp-compatible” commands.

When either legacy-mode or legacy-path-cost control is toggled, all default path costs will be recalculated to correspond to the new setting, and spanning tree is recalculated if needed.

QoS Pass-Through Mode

Release M.08.91 introduced a new command that allows the configuration of the Quality of Service (QoS) queues to be selected. By better matching the configuration of the QoS queues to the amount of prioritized and non-prioritized traffic being transferred, performance can be improved and packet loss due to over-subscription can be minimized.

In previous software versions, the 3400cl and the 6400cl switches had four QoS queues of equal size. Depending on the mix of prioritized and non-prioritized traffic, this configuration might not always optimize performance and could result in dropped packets when resources were over-subscribed. Starting with this software version, four QoS Pass-Through modes are available for use. The number of queues and the size of the memory buffer used by each queue differs in each mode. Table 2 below summarizes the QoS queue configuration of each mode

Table 2. QoS Pass-Through Modes

QoS Pass-Through Mode

Number of

QoS Queue Memory Buffer

Description

 

Queues

Configuration

 

 

 

 

 

typical (default)

4

One large queue for Priority 0

 

 

and 3 traffic and three other

 

 

queues for the remaining traffic.

A mix of prioritized and non- prioritized traffic. This is the default mode, used when QoS Pass-Through is disabled.

balanced

4

All queues are the same size.

Equal amounts of prioritized and

 

 

 

non-prioritized traffic. This is the

 

 

 

same mode used in pre-M.08.78

 

 

 

software versions.

 

 

 

 

one-queue

1

One large queue.1

No traffic is prioritized.

optimized

2

One small queue for Priority 6

Most traffic is not prioritized.

 

 

and 7 traffic; one large queue for

 

 

 

all other traffic.

 

1This mode has a small queue used exclusively for Priority 7 management and control traffic.

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