Exam JN0-648 topic 1 question 28 discussion

multifield classifiers are used to classify packets based on multiple packet fields. It is common to use multifield classifiers to classify traffic at the ingress of a network, rewrite the packet headers , then use the more efficient BA classification for transversing the network.

I think A,C is the correct answer. Classification on MF is usually done on (client) access level and since one should not trust client's classification you should reclassify based on MF

BA classifiers are based on fixed-length fields in the packet header, which makes them computationally more efficient than MF classifiers. Therefore core devices that handle high traffic volumes are normally configured to perform BA classification. The BA classifier maps packets to a forwarding class and a loss priority. The forwarding class determines the output queue for a packet. The loss priority is used by a scheduler to control packet discard during periods of congestion. MF classification is normally performed at the network edge because of the general lack of support for DSCP or IP precedence classifiers in end-user applications. On an edge switch, an MF classifier provides the filtering functionality that scans through a variety of packet fields to determine the forwarding class for a packet. Typically, any classifier performs matching operations on the selected fields against a configured value. https://www.juniper.net/documentation/us/en/software/junos/cos-ex/topics/concept/cos-ex-series-classifiers-understanding.html

Correct answer is AD. Classification is done always at the ingress interface ( it does not matter whether it is BA or Multifield)