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