Exam 350-401 topic 1 question 574 discussion

It is tricky and actually stupid (Cisco style I guess...) as classification and marking go together and one is useless without another. The traffic needs to be classified first so it could ba marked. The IPP bits are actually used to mark something which is in line with Cisco's Cert Guide official flashcard: "ToS: An 8 bit field where only the first 3 bits, referred to as IP Precedence (IPP), are used for marking, and the rest of the bits are unused."

My thought on this: The question asks the feature that "Uses" the bits, so we could say it uses the bits to mark the packets and it will have different priority levels. At the same time, we could use the bits (already marked) and classify them into different priority levels. My point is - I hope you don't have this question on your exam.

D: it's classification! Traffic Descriptor for classification are COS/DSCP (TOS) etc. Using classification you can partition network traffic in different priority level

Traffic marking sets the priority levels for the traffic by manipulating the IP precedence field. The IP Precedence field allows you to set priority levels from 0 to 7: 0: Routine 1: Priority 2: Immediate 3: Flash 4: Flash Override 5: Critical 6: Internetwork Control 7: Network Control Each value corresponds to a different priority level, with 7 being the highest priority.

classification is by using access-list or NBAR

the first thing came to my mind is A so I will stick with A

Marking uses the IP Precedence bits to set the priority level of the traffic, thereby partitioning it into different priority levels. Classification, while essential, identifies the traffic type and typically leads to the marking process.

I got to go with Marking on this one. Classification is more how it's treated based on it's characteristics/markings Marking is a way to implement those treatment decisions, by modifying packet headers to desired priority level

Speaking strictly from the OCG, both classification and marking use those bits: - classification to identify and categorize the packets - marking changes those bits based on classification, in order for other QoS mechanisms to be applied based on those changed bits, or for other network devices to classify the packets. Classification is applied before any other mechanism. The question is bullshit because classification and marking go hand in hand. You can't have one without the other. However, I believe the answer is A because, indeed classification may be done based on IPP, however, the question asks 'to partition traffic into different priority levels'. And the actual 'separation' of traffic based on priority is done by marking it.

This is more how you interpret the question. You can go with the reflex response answer of Marking or you could go with, the packet is already marked and the feature to partition the marking packets is Classification. I'm a bit on the fence but slightly leaning towards Classification.

Marker—Set the DSCP field based on the traffic profile.

The ToS field is an 8-bit field where only the first 3 bits of the ToS field, referred to as IP Precedence (IPP), ARE USED FOR MARING, and the rest of the bits are unused. IPP values, which range from 0 to 7, ALLOW THE TRAFFIC TO BE PARTITIONED IN UP TO SIX USABLE CLASSES OF SERVICES; IPP 6 and 7 are reserved for internal network use. OCG Page 371

Marking is the answer according to Cisco Official Cert Guide page 371 where it shows in Figure 14-3 ToS field containing IP Precedence and DiffServ fields.

group traffic - Classification Identify - Marking A

I think it's D. In the question the action is a discrimination of the already marked packet. This discrimination is the process of classification.

Correct Answer is A. Marking means that we set the TOS (Type of Service) byte with an IP Precedence value or DSCP value. https://networklessons.com/quality-of-service/qos-marking-cisco-ios-router While classification is how we look at the traffic that is running through our router and identify (classify) it so we know to which application it belongs. That’s what classification is about. https://networklessons.com/quality-of-service/qos-classification-cisco-ios-router

Correct Answer is A. Marking means that we set the TOS (Type of Service) byte with an IP Precedence value or DSCP value. https://networklessons.com/quality-of-service/qos-marking-cisco-ios-router