y, rather than the fundamental requirement that a class must be defined before it is referenced.","examTip":null,"technicalDeepDive":"Under the hood, NETCONF validates the configuration against the YANG data model before applying it. The YANG model enforces that any class referenced in a policy-map must already exist in the device's running configuration or be defined in the same NETCONF payload. This prevents orphaned class references and ensures the policy-map structure is complete. In real-world scenarios, engineers often batch multiple NETCONF operations and must order them so that class-maps are created before policy-maps that reference them.","keyConcepts":[],"faqs":[],"eliminationLogic":null,"exhibitText":"\n \n \n \n QOS-POLICY\n \n VOICE\n \n 1\n \n \n 64000\n 8000\n \n \n \n \n \n \n \n \n \n \n \n","exhibitUrl":null,"hasExhibit":false,"isExhibitQuestion":false,"questionPairs":null,"hasMatchingPairs":false,"isMatchingQuestion":false,"relatedQuestions":[],"breadcrumbItems":null,"nextQuestionUrl":null,"previousQuestionUrl":null,"domainPracticeUrl":null,"certificationUrl":null,"domainUrl":null,"hasAnswerOptions":true,"updatedAt":"2026-06-25T03:54:17.251+00:00","questionType":"multiple_choice"},{"id":"56fc1a4c-23ad-425f-b81e-5f34d664e0dc","slug":"which-two-statements-correctly-describe-the-diffserv-model-djiuc","certificationSlug":"cisco-ccnp-service-provider","examCode":"350-501","examName":"Cisco SPCOR / CCNP Service Provider Core 350-501","questionText":"Which TWO statements correctly describe the DiffServ model? (Choose two.)","difficulty":"medium","domain":"Automation and Quality of Services","domainSlug":"spcor-automation-qos","topic":"","questionNumber":0,"totalQuestions":0,"options":[{"key":"A","isCorrect":false,"text":"AF classes use DSCP values 0-7","explanation":"Incorrect; AF uses values 8-63.","masteryContext":""},{"key":"B","isCorrect":true,"text":"DSCP uses 6 bits, providing 64 possible values","explanation":"Correct; DSCP is 6 bits.","masteryContext":""},{"key":"C","isCorrect":false,"text":"Best Effort is marked with DSCP 46","explanation":"Incorrect; BE is DSCP 0.","masteryContext":""},{"key":"D","isCorrect":true,"text":"Expedited Forwarding (EF) is defined as DSCP 46","explanation":"Correct; EF is DSCP 46.","masteryContext":""},{"key":"E","isCorrect":false,"text":"DiffServ uses a 3-bit field for QoS marking","explanation":"Incorrect; that is for IP precedence.","masteryContext":""}],"correctOptionKey":"B,D","correctOptions":["B","D"],"correctAnswerText":"","isMultiSelect":true,"mainExplanation":"The DiffServ model uses the 6-bit Differentiated Services Code Point (DSCP) field in the IP header to mark packets, providing 2^6 = 64 possible values (0-63). This allows for up to 64 distinct per-hop behaviors (PHBs), enabling scalable QoS classification beyond the limited 8 classes of the older IP Precedence model.","examTrap":"Cisco often tests the distinction between DSCP (6-bit) and IP Precedence (3-bit), and the specific DSCP value for EF (46) versus Best Effort (0), to catch candidates who confuse the bit length or default markings.","examTip":null,"technicalDeepDive":"The DSCP field occupies the first 6 bits of the original IPv4 ToS byte, while the remaining 2 bits are used for Explicit Congestion Notification (ECN). Expedited Forwarding (EF) is defined in RFC 3246 with DSCP 46 (binary 101110) to provide low-loss, low-latency, and low-jitter service, often used for voice traffic. In real-world deployments, misconfiguration of DSCP values (e.g