End-to-end QoS deployment techniques for Cisco Catalyst series switches
Examine various QoS components, including congestion management, congestion
avoidance, shaping, policing/admission control, signaling, link efficiency mechanisms, and classification and marking
Map specified class of service (CoS) values to various queues and maintain CoS values through the use of 802.1q tagging on the Cisco Catalyst 2900XL, 3500XL and Catalyst 4000 and 2948G/2980G CatOS Family of Switches
Learn about classification and rewrite capabilities and queue scheduling on the Cisco Catalyst 5000
Implement ACLs, ACPs, ACEs, and low-latency queuing on the Cisco Catalyst 2950 and 3550 Family of Switches
Understand classification, policying, and scheduling capabilities of the Catalyst 4000 and 4500 IOS Family of Switches
Configure QoS in both Hybrid and Native mode on the Catalyst 6500 Family of Switches Utilize Layer 3 QoS to classify varying levels of service with the Catalyst 6500 MSFC and Flexwan
Understand how to apply QoS in campus network designs by examining end-to-end case studies
Quality of service (QoS) is the set of techniques designed to manage network resources. QoS refers to the capability of a network to provide better service to selected network traffic over various LAN and WAN technologies. The primary goal of QoS is to provide flow priority, including dedicated bandwidth, controlled jitter and latency (required by some interactive and delay-sensitive traffic), and improved loss characteristics.
While QoS has become an essential technology for those organizations rolling out a new
Token Bucket Mechanism
A token bucket is a formal definition of a rate of transfer. For this discussion, assume the token bucket starts full. This implies the maximum amount of tokens is available to sustain incoming traffic. Assume a bucket, which is being filled with tokens at a rate of x tokens per refresh interval. Each token represents 1 bit of data. To successfully transmit a packet, there must be a one-to-one match between bits and tokens. As a result, when a packet or frame arrives at the port or interface, and enough tokens exist in the bucket to accommodate the entire unit of data, the packet conforms to the contract, and therefore is forwarded. When the packet is successfully transmitted, the number of tokens equal to the size of the transmitted packet is removed from the bucket. Figure 2-1 illustrates the token bucket mechanism.
Figure 2-1. Token Bucket Mechanism
• Table of Contents
• Index
Cisco Catalyst QoS: Quality of Service in Campus Networks By Mike Flannagan CCIE® No. 7651, Richard Froom CCIE No. 5102, Kevin Turek CCIE No. 7284
Publisher: Cisco Press Pub Date: June 06, 2003
ISBN: 1-58705-120-6 Pages: 432
End-to-end QoS deployment techniques for Cisco Catalyst series switches
Examine various QoS components, including congestion management, congestion
avoidance, shaping, policing/admission control, signaling, link efficiency mechanisms, and classification and marking
Map specified class of service (CoS) values to various queues and maintain CoS values through the use of 802.1q tagging on the Cisco Catalyst 2900XL, 3500XL and Catalyst 4000 and 2948G/2980G CatOS Family of Switches
Learn about classification and rewrite capabilities and queue scheduling on the Cisco Catalyst 5000
Implement ACLs, ACPs, ACEs, and low-latency queuing on the Cisco Catalyst 2950 and 3550 Family of Switches
Understand classification, policying, and scheduling capabilities of the Catalyst 4000 and 4500 IOS Family of Switches
Configure QoS in both Hybrid and Native mode on the Catalyst 6500 Family of Switches Utilize Layer 3 QoS to classify varying levels of service with the Catalyst 6500 MSFC and Flexwan
Understand how to apply QoS in campus network designs by examining end-to-end case studies
Quality of service (QoS) is the set of techniques designed to manage network resources. QoS refers to the capability of a network to provide better service to selected network traffic over various LAN and WAN technologies. The primary goal of QoS is to provide flow priority, including dedicated bandwidth, controlled jitter and latency (required by some interactive and delay-sensitive traffic), and improved loss characteristics.
While QoS has become an essential technology for those organizations rolling out a new
If the actual ingress traffic rate exceeds the configured rate, and there are insufficient tokens in the token bucket to accommodate the arriving traffic, the excess data is considered out-of-profile and can be dealt with in one of two ways:
Re-assign QoS values to appropriate header Drop packet
If the decision is to mark down the nonconforming traffic, the DSCP value is derived from the mapping tables.
The token bucket mechanism has three components: a burst size, a mean rate, and a time interval (Tc). Although the mean rate is generally represented as bits per second, any two values may be derived from the third by the relation shown as follows:
Mean rate = burst size / time interval Here are some definitions of these terms:
Mean rate— Also called the committed information rate (CIR), it specifies how much data can be sent or forwarded per unit time on average.
Burst size— Also called the committed burst (Bc) size, it specifies in bits (or bytes) per burst how much traffic can be sent within a given unit of time to not create scheduling concerns. (For a shaper, such as generic traffic shaping (GTS), it specifies bits per burst;
for a policer, such as committed access rate (CAR), it specifies bytes per burst.)
Time interval— Also called the measurement interval, it specifies the time quantum in seconds per burst.
By definition, over any integral multiple of the interval, the bit rate of the interface will not exceed the mean rate. The bit rate, however, may be arbitrarily fast within the interval.
A token bucket is used to manage a device that regulates the data in a flow. For example, the regulator might be a traffic policer, such as CAR, or a traffic shaper, such as Frame Relay traffic shaping (FRTS) or GTS. A token bucket itself has no discard or priority policy. Rather, a token bucket discards tokens and leaves to the flow the problem of managing its transmission queue if the flow overdrives the regulator. (Neither CAR nor FRTS and GTS implement either a true token bucket or true leaky bucket.)
In the token bucket metaphor, tokens are put into the bucket at a certain rate. The bucket itself has a specified capacity. If the bucket fills to capacity, newly arriving tokens are discarded. Each token is permission for the source to send a certain number of bits into the network. To send a packet, the regulator must remove from the bucket a number of tokens equal in representation to the packet size.
If not enough tokens are in the bucket to send a packet, the packet either waits until the bucket has enough tokens (in the case of GTS) or the packet is discarded or marked down (in the case of CAR). If the bucket is already full of tokens, incoming tokens overflow and are not available to future packets. Thus, at any time, the largest burst a source can send into the network is roughly proportional to the size of the bucket.
Note that the token bucket mechanism used for traffic shaping has both a token bucket and a data buffer, or queue; if it did not have a data buffer, it would be a policer. For traffic shaping, packets that arrive that cannot be sent immediately are delayed in the data buffer.
• Table of Contents
• Index
Cisco Catalyst QoS: Quality of Service in Campus Networks By Mike Flannagan CCIE® No. 7651, Richard Froom CCIE No. 5102, Kevin Turek CCIE No. 7284
Publisher: Cisco Press Pub Date: June 06, 2003
ISBN: 1-58705-120-6 Pages: 432
End-to-end QoS deployment techniques for Cisco Catalyst series switches
Examine various QoS components, including congestion management, congestion
avoidance, shaping, policing/admission control, signaling, link efficiency mechanisms, and classification and marking
Map specified class of service (CoS) values to various queues and maintain CoS values through the use of 802.1q tagging on the Cisco Catalyst 2900XL, 3500XL and Catalyst 4000 and 2948G/2980G CatOS Family of Switches
Learn about classification and rewrite capabilities and queue scheduling on the Cisco Catalyst 5000
Implement ACLs, ACPs, ACEs, and low-latency queuing on the Cisco Catalyst 2950 and 3550 Family of Switches
Understand classification, policying, and scheduling capabilities of the Catalyst 4000 and 4500 IOS Family of Switches
Configure QoS in both Hybrid and Native mode on the Catalyst 6500 Family of Switches Utilize Layer 3 QoS to classify varying levels of service with the Catalyst 6500 MSFC and Flexwan
Understand how to apply QoS in campus network designs by examining end-to-end case studies
Quality of service (QoS) is the set of techniques designed to manage network resources. QoS refers to the capability of a network to provide better service to selected network traffic over various LAN and WAN technologies. The primary goal of QoS is to provide flow priority, including dedicated bandwidth, controlled jitter and latency (required by some interactive and delay-sensitive traffic), and improved loss characteristics.
While QoS has become an essential technology for those organizations rolling out a new For traffic shaping, a token bucket permits burstiness but bounds it. It guarantees that the burstiness is bounded so that the flow never sends faster than the capacity of the token bucket plus the time interval multiplied by the established rate at which tokens are placed in the bucket.
It also guarantees that the long-term transmission rate does not exceed the established rate at which tokens are placed in the bucket.
All Catalyst switches that support policing utilize the token bucket algorithm for bandwidth-limiting traffic flows. Chapters 6, 7, and 8 discuss the token bucket algorithm for the Catalyst 2950 and 3550, 4000 IOS, and 6500 Family of switches, respectively.
• Table of Contents
• Index
Cisco Catalyst QoS: Quality of Service in Campus Networks By Mike Flannagan CCIE® No. 7651, Richard Froom CCIE No. 5102, Kevin Turek CCIE No. 7284
Publisher: Cisco Press Pub Date: June 06, 2003
ISBN: 1-58705-120-6 Pages: 432
End-to-end QoS deployment techniques for Cisco Catalyst series switches
Examine various QoS components, including congestion management, congestion
avoidance, shaping, policing/admission control, signaling, link efficiency mechanisms, and classification and marking
Map specified class of service (CoS) values to various queues and maintain CoS values through the use of 802.1q tagging on the Cisco Catalyst 2900XL, 3500XL and Catalyst 4000 and 2948G/2980G CatOS Family of Switches
Learn about classification and rewrite capabilities and queue scheduling on the Cisco Catalyst 5000
Implement ACLs, ACPs, ACEs, and low-latency queuing on the Cisco Catalyst 2950 and 3550 Family of Switches
Understand classification, policying, and scheduling capabilities of the Catalyst 4000 and 4500 IOS Family of Switches
Configure QoS in both Hybrid and Native mode on the Catalyst 6500 Family of Switches Utilize Layer 3 QoS to classify varying levels of service with the Catalyst 6500 MSFC and Flexwan
Understand how to apply QoS in campus network designs by examining end-to-end case studies
Quality of service (QoS) is the set of techniques designed to manage network resources. QoS refers to the capability of a network to provide better service to selected network traffic over various LAN and WAN technologies. The primary goal of QoS is to provide flow priority, including dedicated bandwidth, controlled jitter and latency (required by some interactive and delay-sensitive traffic), and improved loss characteristics.
While QoS has become an essential technology for those organizations rolling out a new