Brocade Multi-Service IronWare QoS and Traffic Management Configuration Guide (Supporting R05.6.00) - Manual (Page 55)

Multi-Service IronWare QoS and Traffic Management Configuration Guide 41
53-1003037-02
Chapter
3
Configuring Quality of Service (QoS) for the Brocade NetIron
CES and Brocade NetIron CER Series
Quality of Service (QoS)
The Quality of Service (QoS) features offer many options for the Brocade NetIron CES and Brocade
NetIron CER devices.
Quality of Service (QoS) provides preferential treatment to specific traffic, possibly at the expense
of other traffic. Without QoS, the Brocade NetIron CES or Brocade NetIron CER device offers
best-effort service to each packet and transmits packets without any assurance of reliability, delay
bounds, or throughput. Implementing QoS in a network makes performance more predictable and
bandwidth utilization more effective.
QoS implementation in the Brocade NetIron CES or Brocade NetIron CER device complies with the
IETF-DiffServ and IEEE 802.1p standards. A typical QoS model deployment is based on the
following elements:
• At the network edge, the packet is assigned to a QoS service. The service is assigned based on
the packet header information (i.e., packet is trusted) or on the ingress interface configuration
(packet is not trusted).
• The QoS service defines the packet’s internal QoS handling (e.g., traffic class and drop
precedence) and optionally the packet’s external QoS marking, through either the IEEE 802.1p
User Priority or the IP header DSCP field.
• Subsequent Brocade NetIron CES and Brocade NetIron CER devices within the network core
provide consistent QoS treatment to traffic, based on the packet’s IEEE 802.1p, or DSCP
marking. As a result, an end-to-end QoS behavior is provided.
• A Brocade NetIron CES or Brocade NetIron CER device may modify the assigned service if a
packet stream exceeds the configured profile. In this case, the packet may be dropped or
reassigned to a lower QoS service.
• The Brocade NetIron CES and Brocade NetIron CER devices incorporate the required QoS
features to implement network-edge as well as network-core devices.
• The Brocade NetIron CES and Brocade NetIron CER devices provide flexible mechanisms to
classify packets into different service levels.
• The packet header may have its User Priority fields set to reflect the QoS assignment.
• Service application mechanism is based on eight egress priority queues per port (including the
CPU port), on which congestion-avoidance and congestion-resolution policies are applied.
• QoS encode policies are not supported on the NetIron CES and NetIron CER devices due to
Hardware limitations.
QoS model
This chapter describes how QoS is implemented and configured in the Brocade NetIron CES and
Brocade NetIron CER devices. The chapter contains the following sections.