Brocade Multi-Service IronWare QoS and Traffic Management Configuration Guide (Supporting R05.6.00) - Manual (Page 186)

172 Multi-Service IronWare QoS and Traffic Management Configuration Guide
53-1003037-02
Hierarchical QoS (HQoS) for 8x10G modules
5
Hierarchical QoS (HQoS) for 8x10G modules
NOTE
HQoS is supported on the egress of 10G ports of the NI-MLX-10GX8-M and BR-MLX-10GX8-X
modules.
HQoS is not supported on the NI-MLX-10GX8-D module.
Hierarchical QoS (HQoS) allows a carrier to consolidate different services on the same physical
device running on the same physical infrastructure.
HQoS is a valuable tool, especially for networks that support multiple business customers who are
running multiple applications with different prioritization and scheduling requirements over the
same infrastructure.
HQoS uses an advanced scheduling mechanism, with multiple levels and multiple instances of
scheduling and traffic shaping for the different services over a same connection. HQoS allows
lower priority traffic to fully utilize the available bandwidth on a port, while ensuring high levels of
QoS, e.g., low latency and guaranteed bandwidth, to higher priority traffic classes on that port. In
summary, HQoS allows providers to offer improved customer SLAs and optimizes use of network
resources.
How HQoS works
Hierarchical Quality of Service (HQoS) organizes a scheduler policy into a hierarchical tree that
consists of a root node, branches nodes, and leaf nodes, where:
• The root node is the convergence point for all traffic and corresponds to a scheduler followed
by a traffic shaper. The root node schedules and shapes the aggregated egress traffic of a
physical port.
• A branch node is located in the middle of the hierarchy and corresponds to a scheduler
followed by a traffic shaper.
• A leaf node corresponds to a scheduling queue.
HQoS scheduling levels do not support packet field matching capabilities. Packets are inspected
once before being queued. Once packets go into a queue, everything beyond that point is a
sequence of rate shapers and schedulers as defined by the hierarchical scheduling tree for that
egress port.
HQoS supports a number of scheduling and shaping levels. Each level performs scheduling and
shaping functions. By careful configuration, the different HQoS levels can map directly to a desired
hierarchical traffic management model. For example, a hierarchy can be configured where an
HQoS level represents the aggregated traffic of individual Customers, another level the individual
VLANs of each customer, and another level the traffic following a Logical port downstream.