Congestion Management
Configuring QoS
page 25-10
OmniSwitch AOS Release 7 Network Configuration Guide
June 2013
Congestion Management
Queuing mechanisms are used to manage congestion on egress ports. When congestion occurs, packets are
prioritized and placed into queues based on the CoS markings assigned to the packets during classifica-
tion. If there is no congestion on the egress port, packets are sent out as soon as they are received.
On both the OmniSwitch 10K and OmniSwitch 6900, eight egress queues are allocated for each port.
•
The OmniSwitch 10K egress queues are virtual output queues (VOQ) that are located and managed on
the ingress. See
“OmniSwitch 10K Queue Management” on page 25-18
,
•
The OmniSwitch 6900 egress queues are located and managed on the egress.
Although the egress queue management architecture is different, the OmniSwitch 10K and OmniSwitch
6900 both incorporate the use of Queue Set Profiles (QSPs) or Data Center Bridging (DCB) profiles to
provide traffic management and QoS scheduling for the egress queues. For more information, see
and
.
Queue Sets
The queue management and related QoS functions are implemented using a framework based on Queue
Sets (QSets). A QSet is a set of eight aggregate VOQs (OmniSwitch 10K) or a set of eight egress port
queues (OmniSwitch 6900) that are associated with each switch port.
The QSET framework involves the following elements:
•
QSet instance (QSI)
—A QSI is a logical entity that refers to a set of eight queues. Each port in the
switch is automatically associated with a QSI. On the OmniSwitch 10K, the QSI represents all the
ingress Traffic Manager (TM) physical VOQs (pVOQs) associated with the port to which the QSI is
attached (see
“OmniSwitch 10K Queue Management” on page 25-18
).
•
QSet profile (QSP) or Data Center Bridging profile (DCP)
—a profile associated with each QSI that
defines the output scheduling behavior for the queues associated with the QSet instance.
>
There are four pre-defined QSPs, with QSP 1 serving as the default profile that is automatically
assigned to each QSI. See
.
>
There are ten pre-defined DCPs, with DCP 8 serving as the default profile that is automatically
assigned to each QSI. Note that only DCB profiles are applied when the switch is using the
OmniSwitch Data Center license. See
Chapter 2, “Configuring Data Center Bridging,”
in the
OmniSwitch AOS Release 7 Network Configuration Guide.
Note.
QSet profiles and DCB profiles are mutually exclusive. If the OmniSwitch Data Center software
license is installed, then DCB profiles are used. If this license is not installed, then QSet profiles are used.
•
Weighted Random Early Detection (WRED) profile
—a WRED profile (WRP) is associated with
each QSet profile to provide admission control for each QSet. One WRP is supported on the
OmniSwitch 6900 (WRP 1), which is the default profile automatically assigned to each QSP. Note that
WRED is not supported on the OmniSwitch 10K. See
.