HP Virtual Connect 8Gb 20-port Fibre Channel Module for c-Class BladeSystem - Manual (Page 103)

Virtual Connect networks 103
Quality of Service
QoS is used to provide different priorities for designated networking traffic flows and guarantee a certain
level of performance through resource reservation. QoS is important for the following reasons:
• It provides Service Level Agreements for network traffic and to optimize network utilization.
• Different traffic types such as management, backup, and voice have different requirements for
throughput, jitter, delays and packet loss.
• IP-TV, VOIP, and Internet expansion create additional traffic and latency requirements.
• In some cases, capacity cannot be increased. Even when possible, increasing capacity may still
encounter issues if traffic needs to be re-routed because of a failure.
Traffic must be categorized and then classified. Once classified, traffic is given priorities and scheduled for
transmission. For end-to-end QoS, all hops along the way must be configured with similar QoS policies of
classification and traffic management. VC manages and guarantees its own QoS settings as one of the hops
within the networking infrastructure.
The following diagram illustrates how VC receives traffic and categorizes it into classes. Packets can be
reordered based on priority as shown for packet number 3. Packets can also be dropped during congestion
as shown for packet number 2.
Prior to the VC 4.01 release, VC QoS support was limited apart from dynamic Max rate limiting bandwidth
control. VC Ethernet modules passed Layer 2 and Layer 3 markings in VLAN tunnel mode but in some cases
removed L2 markings in mapped mode. VC would not perform any traffic classification, marking, policing,
or traffic shaping for Ethernet traffic flows. FCoE traffic is prioritized and classified in FlexFabric modules but
controls were fixed and not exposed to administrators.