DRAG DROP
Select and Place:
Correct Answer:
Explanation/Reference:
Classification is the process of partitioning traffic into multiple priority levels or classes of service. Information in the frame or packet header is inspected, and the frame’s priority is determined. Marking is the process of changing the priority or class of service (CoS) setting within a frame or packet to indicate its classification. Classification is usually performed with access control lists (ACL), QoS class maps, or route maps, using various match criteria.
Congestion-avoidance techniques monitor network traffic loads so that congestion can be anticipated and avoided before it becomes problematic. Congestionavoidance techniques allow packets from streams identified as being eligible for early discard (those with lower priority) to be dropped when the queue is getting full. Congestion avoidance techniques provide preferential treatment for high priority traffic under congestion situations while maximizing network throughput and capacity utilization and minimizing packet loss and delay.
Weighted random early detection (WRED) is the Cisco implementation of the random early detection (RED) mechanism. WRED extends RED by using the IP
Precedence bits in the IP packet header to determine which traffic should be dropped; the drop-selection process is weighted by the IP precedence.
Traffic conditioner consists of policing and shaping. Policing either discards the packet or modifies some aspect of it, such as its IP Precedence or CoS bits, when the policing agent determines that the packet meets a given criterion. In comparison, traffic shaping attempts to adjust the transmission rate of packets that match a certain criterion. Shaper typically delays excess traffic by using a buffer or queuing mechanism to hold packets and shape the flow when the source’s data rate is higher than expected. For example, generic traffic shaping uses a weighted fair queue to delay packets to shape the flow. Traffic conditioner is also referred to as Committed Access Rate (CAR).
Congestion management includes two separate processes: queuing, which separates traffic into various queues or buffers, and scheduling, which decides from which queue traffic is to be sent next. There are two types of queues: the hardware queue (also called the transmit queue or TxQ) and software queues. Software queues schedule packets into the hardware queue based on the QoS requirements and include the following types: weighted fair queuing (WFQ), priority queuing (PQ), custom queuing (CQ), class-based WFQ (CBWFQ), and low latency queuing (LLQ).
LLQ is also known as Priority Queuing-Class-Based Weighted Fair Queuing (PQ-CBWFQ). LLQ provides a single priority but it’s preferred for VoIP networks because it can also configure guaranteed bandwidth for different classes of traffic queue. For example, all voice call traffic would be assigned to the priority queue, VoIP signaling and video would be assigned to a traffic class, FTP traffic would be assigned to a low-priority traffic class, and all other traffic would be assigned to a regular class.
Link efficiency techniques, including link fragmentation and interleaving (LFI) and compression. LFI prevents small voice packets from being queued behind large data packets, which could lead to unacceptable delays on low-speed links. With LFI, the voice gateway fragments large packets into smaller equal-sized frames and interleaves them with small voice packets so that a voice packet does not have to wait until the entire large data packet is sent. LFI reduces and ensures a more predictable voice delay.
(Reference: Cisco Press Designing for Cisco Internetwork Solutions)
Explanation/Reference:
Classification is the process of partitioning traffic into multiple priority levels or classes of service. Information in the frame or packet header is inspected, and the frame’s priority is determined. Marking is the process of changing the priority or class of service (CoS) setting within a frame or packet to indicate its classification. Classification is usually performed with access control lists (ACL), QoS class maps, or route maps, using various match criteria.
Congestion-avoidance techniques monitor network traffic loads so that congestion can be anticipated and avoided before it becomes problematic. Congestionavoidance techniques allow packets from streams identified as being eligible for early discard (those with lower priority) to be dropped when the queue is getting full. Congestion avoidance techniques provide preferential treatment for high priority traffic under congestion situations while maximizing network throughput and capacity utilization and minimizing packet loss and delay.
Weighted random early detection (WRED) is the Cisco implementation of the random early detection (RED) mechanism. WRED extends RED by using the IP
Precedence bits in the IP packet header to determine which traffic should be dropped; the drop-selection process is weighted by the IP precedence.
Traffic conditioner consists of policing and shaping. Policing either discards the packet or modifies some aspect of it, such as its IP Precedence or CoS bits, when the policing agent determines that the packet meets a given criterion. In comparison, traffic shaping attempts to adjust the transmission rate of packets that match a certain criterion. Shaper typically delays excess traffic by using a buffer or queuing mechanism to hold packets and shape the flow when the source’s data rate is higher than expected. For example, generic traffic shaping uses a weighted fair queue to delay packets to shape the flow. Traffic conditioner is also referred to as Committed Access Rate (CAR).
Congestion management includes two separate processes: queuing, which separates traffic into various queues or buffers, and scheduling, which decides from which queue traffic is to be sent next. There are two types of queues: the hardware queue (also called the transmit queue or TxQ) and software queues. Software queues schedule packets into the hardware queue based on the QoS requirements and include the following types: weighted fair queuing (WFQ), priority queuing (PQ), custom queuing (CQ), class-based WFQ (CBWFQ), and low latency queuing (LLQ).
LLQ is also known as Priority Queuing-Class-Based Weighted Fair Queuing (PQ-CBWFQ). LLQ provides a single priority but it’s preferred for VoIP networks because it can also configure guaranteed bandwidth for different classes of traffic queue. For example, all voice call traffic would be assigned to the priority queue, VoIP signaling and video would be assigned to a traffic class, FTP traffic would be assigned to a low-priority traffic class, and all other traffic would be assigned to a regular class.
Link efficiency techniques, including link fragmentation and interleaving (LFI) and compression. LFI prevents small voice packets from being queued behind large data packets, which could lead to unacceptable delays on low-speed links. With LFI, the voice gateway fragments large packets into smaller equal-sized frames and interleaves them with small voice packets so that a voice packet does not have to wait until the entire large data packet is sent. LFI reduces and ensures a more predictable voice delay.
(Reference: Cisco Press Designing for Cisco Internetwork Solutions)