Home » Cisco » 350-080 » What is the benefit of the Priority-Based Flow control feature in Data Center Bridging?
What is the benefit of the Priority-Based Flow control feature in Data Center Bridging?
A. provides the capability to manage a bursty, single traffic source on a multiprotocol link
B. enables bandwidth management between traffic types for multiprotocol links
C. addresses the problem of sustained congestion by moving corrective action to the network edge
D. allows autoexchange of Ethernet parameters between switches and endpoints
Correct Answer: A
Explanation/Reference:
Explanation:
Link sharing is critical to I/O consolidation. For link sharing to succeed, large bursts from one traffic type must not affect other traffic types, large queues of traffic from one traffic type must not starve other traffic types’ resources, and optimization for one traffic type must not create high latency for small messages of other traffic types. The Ethernet pause mechanism can be used to control the effects of one traffic type on another. PFC is an enhancement to the pause mechanism. PFC enables pause based on user priorities or classes of service. A physical link divided into eight virtual links (Figure 1) with PFC provides the capability to use pause on a single virtual link without affecting traffic on the other virtual links. Enabling pause based on user priority allows administrators to create lossless links for traffic requiring no-drop service, such as Fibre Channel over Ethernet (FCoE), while retaining packet-drop congestion management for IP traffic.
The current Ethernet pause option stops all traffic on a link; essentially, it is a link pause for the entire link. However, PFC creates eight separate virtual links on the physical link and allows any of these links to be paused and restarted independently. This approach enables the network to create a no-drop class of service for an individual virtual link that can\ coexist with other traffic types on the same interface. PFC allows differentiated quality-of-service (QoS) policies for the eight unique virtual links. PFC also plays a primary role when used with an arbiter for intraswitch fabrics, linking ingress ports to egress port resources.
Reference: http://www.cisco.com/c/dam/en/us/solutions/collateral/data-center-virtualization/ieee-802-1-data-center-bridging/at_a_glance_c45-460907.pdf (see table 1, first row)
