Chapter 42 Configuring PFC QoS

PFC QoS Glossary

PFC QoS Glossary

This section defines some of the QoS terminology used in this chapter:

•Buffers—A storage area used for handling data in transit. Buffers are used in internetworking to compensate for differences in processing speed between network devices. Bursts of data can be stored in buffers until they can be handled by slower processing devices. Sometimes referred to as a packet buffer.

•Class of Service (CoS) is a Layer 2 QoS label carried in three bits of either an ISL, 802.1Q, or 802.1p header. CoS values range between zero and seven.

Layer 2 ISL frame

ISL header

 

Encapsulated frame 1...

 

 

 

FCS

 

 

(26 bytes)

 

 

(24.5 KB)

 

 

(4 bytes)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3 bits used for CoS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Layer 2 802.1Q and 802.1p frame

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Preamble

 

Start frame

DA

SA

Tag

 

PT

Data

FCS

 

 

delimiter

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3 bits used for CoS (user priority)

 

 

 

 

 

 

 

 

144803

•Classification is the process used for selecting traffic to be marked for QoS.

•Congestion avoidance is the process by which PFC QoS reserves ingress and egress LAN port capacity for Layer 2 frames with high-priority Layer 2 CoS values. PFC QoS implements congestion avoidance with Layer 2 CoS value-based drop thresholds. A drop threshold is the percentage of queue buffer utilization above which frames with a specified Layer 2 CoS value is dropped, leaving the buffer available for frames with higher-priority Layer 2 CoS values.

•Differentiated Services Code Point (DSCP) is a Layer 3 QoS label carried in the six most-significant bits of the ToS byte in the IP header. DSCP ranges between 0 and 63.

Layer 3 IPv4 packet

Version

ToS

Len ID Offset TTL Proto FCS IP-SA IP-DA Data

length

(1 byte)

 

3 bits for IP precedence

144804

•Frames carry traffic at Layer 2. Layer 2 frames carry Layer 3 packets.

•IP Precedence is a Layer 3 QoS label carried in the three most-significant bits of the ToS byte in the IP header. IP precedence ranges between zero and seven.

Layer 3 IPv4 packet

Version

ToS

Len ID Offset TTL Proto FCS IP-SA IP-DA Data

length

(1 byte)

 

3 bits for IP precedence

144804

•Labels—SeeQoS labels.

 

Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX

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OL-4266-08

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Cisco Systems OL-4266-08 manual PFC QoS Glossary, 42-122
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OL-4266-08 specifications

Cisco Systems OL-4266-08 is a robust and versatile certification that focuses on the essentials of implementing and troubleshooting Cisco collaborations solutions. As enterprises increasingly rely on unified communications, having professionals who are knowledgeable in the latest Cisco technologies becomes a necessity. This certification is part of the Cisco Certified Network Associate (CCNA) program, which serves as a foundational stepping stone for individuals aspiring to build a career in networking and collaboration technologies.

One of the main features of OL-4266-08 is its emphasis on collaboration foundations, which includes an understanding of voice, video, messaging, and conferencing technologies. Professionals who obtain this certification demonstrate proficiency in deploying, configuring, and troubleshooting Cisco collaboration solutions like Cisco Unified Communications Manager and Cisco Webex. This knowledge is critical as businesses seek to enhance communication and productivity through integrated systems.

Technologically, OL-4266-08 covers a wide array of essential concepts, including IP telephony, voicemail, and collaborative tools. Candidates learn about the architecture of unified collaboration systems, involving integration with routing and switching networks. Additionally, it delves into security protocols to ensure secure transmissions of voice and video data, thereby protecting sensitive corporate communication.

In terms of characteristics, OL-4266-08 is designed to be both comprehensive and practical. The certification emphasizes hands-on experience, which is essential for understanding real-world applications of Cisco technologies. The coursework provides extensive exposure to simulations and labs that mimic actual network environments. This hands-on approach enables candidates to troubleshoot issues effectively using Cisco's troubleshooting tools and methodologies.

Moreover, the certification aligns with industry standards, ensuring that individuals gain relevant and in-demand skills. Given the evolving landscape of network technologies, OL-4266-08 prepares individuals for future growth and specialization in various areas, including cloud collaboration and Internet of Things (IoT) communications.

In conclusion, Cisco Systems OL-4266-08 equips networking professionals with the necessary skills to implement and support Cisco collaboration solutions. The focus on hands-on experience, along with in-depth coverage of technology and security protocols, makes it a valuable certification in the fast-paced world of network communications. With the rise of remote work and digital collaboration, this certification is pivotal for anyone looking to enhance their career in networking and technology.
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