An engineer is designing a data center that uses FCIP. How is QoS configured in this environment?

FCIP encapsulates Fibre Channel frames into IP packets for transport over an IP network. To maintain link integrity and manage data flow, FCIP establishes two distinct TCP connections between endpoints: a control connection for link management and a data connection for user data. To provide effective QoS over the IP WAN, different priorities must be assigned to these connections. This is achieved by configuring a unique Differentiated Services Code Point (DSCP) value for each TCP connection, allowing network devices to prioritize the critical control traffic over the bulk data traffic.

A. Control Plane Policing (CoPP) is used to protect the switch's control plane from DoS attacks, not for QoS on FCIP data plane traffic.
B. Applying a single DSCP value for all FCIP traffic within a VSAN fails to differentiate between critical control traffic and data traffic, which is essential for link stability.
C. While priority queuing might be used in the underlying IP network, the key configuration on the MDS switch is differentiating traffic types using separate DSCP values.

1. Cisco, "Cisco MDS 9000 Series FCIP Configuration Guide, Release 8.x," Chapter: FCIP QoS, Section: Information About FCIP QoS. This section explicitly states, "FCIP uses two TCP connections... You can configure a different Differentiated Services Code Point (DSCP) value for the control and data TCP connections."

2. IETF, "RFC 3821 - Fibre Channel Over TCP/IP (FCIP)," Section 4. TCP Connections. This RFC defines the standard, specifying the use of separate TCP connections for FCIP link control and data.