Chapter 42 Configuring PFC QoS

Common QoS Scenarios

These are the three traffic classes in the sample network:

•Voice

•High-priority application traffic

•Best-effort traffic

The QoS configuration described in this section identifies and prioritizes each of these traffic classes.

Note If your network requires more service levels, PFC QoS supports up to 64 traffic classes.

These QoS scenarios describe the following three fundamental QoS configurations, which are often a general part of QoS deployment:

•Classifying traffic from PCs and IP phones in the access layer

•Accepting the traffic priority value on interswitch links between layers

•Prioritizing traffic on interswitch links between layers

 

 

These QoS scenarios assume that the network carries only IP traffic and use the IP DSCP values to assign

 

 

traffic priority. These QoS scenarios do not directly use IP type of service (ToS) or Ethernet 802.1p class

 

 

of service (CoS).

 

 

IP packets can carry a priority value, which can be set at various points within the network topology.

 

 

Best-practice design recommendations are to classify and mark traffic as close to the source of the traffic

 

 

as possible. If traffic priorities are set correctly at the edge, then intermediate hops do not have to

 

 

perform detailed traffic identification. Instead, they can administer QoS policies based on these

 

 

previously set priority values. This approach simplifies policy administration.

 

 

 

Note

• You should develop a QoS deployment strategy for assigning packet priorities to your particular

 

 

network traffic types and applications. For more information on QoS guidelines, refer to RFC 2597

 

 

and RFC 2598 as well as the various QoS design guides published by Cisco Systems, Inc.

 

 

• Do not enable PFC QoS globally and leave all other PFC QoS configuration at default values. When

 

 

you enable PFC QoS globally, it uses its default values. These are two problems that exist with the

 

 

PFC QoS default configuration:

 

 

– With PFC QoS globally enabled, the default trust state of the Ethernet ports in the system is

 

 

untrusted. The untrusted port state sets the QoS priority of all traffic flowing through the router

 

 

to the port CoS value (zero by default): all traffic will be zero-priority traffic.

 

 

– With PFC QoS globally enabled, the port buffers are allocated into CoS-based queues and only

 

 

part of the buffer is available for zero-priority traffic: zero-priority traffic has less buffer

 

 

available than when PFC QoS is disabled.

 

 

These problems with the PFC QoS default configuration can have a negative effect on network

 

 

performance.

 

 

 

Classifying Traffic from PCs and IP Phones in the Access Layer

The access layer routers have a PC daisy-chained to an IP phone on a 100 Mbps link. This section describes how to classify voice traffic from the phone and data traffic from the PC so that they have different priorities.

 

 

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

 

 

 

 

 

 

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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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