Describe the difference between Class of Service (CoS) and Differentiated Services Code Point (DSCP).

Describe the difference between Class of Service (CoS) and Differentiated Services Code Point (DSCP).
A . CoS is only used to determine CLASS of traffic DSCP is only used to differentiate between different Classes.
B . CoS is only contained in VLAN Tag fields DSCP is in the IP Header and preserved throughout the IP packet flow
C . They are similar and can be used interchangeably.
D . CoS has much finer granularity than DSCP

View Answer

Answer: B

Explanation:

CoS and DSCP are both methods of marking packets for quality of service (QoS) purposes. QoS is a mechanism that allows network devices to prioritize and differentiate traffic based on certain criteria, such as application type, source, destination, etc. CoS stands for Class of Service and is a 3-bit field in the 802.1Q VLAN tag header. CoS can only be used on Ethernet frames that have a VLAN tag, and it can only be preserved within a single VLAN domain. DSCP stands for Differentiated Services Code Point and is a 6-bit field in the IP header. DSCP can be used on any IP packet, regardless of the underlying layer 2 technology, and it can be preserved throughout the IP packet flow, unless it is modified by intermediate devices.

References:

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos/configuration/15-mt/qos-15-mt-book/qos-overview.html

https://www.cisco.com/c/en/us/support/docs/lan-switching/8021q/17056-741-4.html

https://www.cisco.com/c/en/us/support/docs/quality-of-service-qos/qos-packet-marking/10103-dscpvalues.html