Which functionality enables creating virtual links on a single physical link and independently pausing a virtual link in an FCoE environment?

Question

Exhibit

Options

• AEnhanced transmission selection
• BData center bridging exchange
• CBuffer-to-buffer credit
• DPriority-based flow control

• A
  11% (3)
• B
  4% (1)
• C
  7% (2)
• D
  79% (22)

Explanation

Priority Based Flow Control Traditional FC manages congestion through the use of a link-level, credit-based flow control that guarantees no loss of frames. Typical Ethernet, coupled with TCP/IP, uses a packet drop flow control mechanism. The packet drop flow control is not lossless. This challenge is eliminated by using an IEEE 802.3x Ethernet PAUSE control frame to create a lossless Ethernet. A receiver can send a PAUSE request to a sender when the receiver's buffer is filling up. Upon receiving a PAUSE frame, the sender stops transmitting frames, which guarantees no loss of frames. The downside of using the Ethernet PAUSE frame is that it operates on the entire link, which might be carrying multiple traffic flows. PFC provides a link level flow control mechanism. PFC creates eight separate virtual links on a single physical link and allows any of these links to be paused and restarted independently. PFC enables the pause mechanism based on user priorities or classes of service. Enabling the pause based on priority allows creating lossless links for traffic, such as FCoE traffic. This PAUSE mechanism is typically implemented for FCoE while regular TCP/IP traffic continues to drop frames. Figure in the slide illustrates how a physical Ethernet link is divided into eight virtual links and allows a PAUSE for a single virtual link without affecting the traffic for the others.

No community discussion yet for this question.