© 2004 Cisco Systems, Inc. All rights reserved. IPTX v2.06-1 Introducing IP Quality of Service IP QoS Mechanisms. - презентация

1 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Introducing IP Quality of Service IP QoS Mechanisms

2 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Outline Overview QoS Mechanisms Classification Marking Trust Boundaries Congestion Management Traffic Shaping Compression Link Fragmentation and Interleaving Summary

3 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v QoS Mechanisms Classification: Each class-oriented QoS mechanism has to support some type of classification Marking: Used to mark packets based on classification and/or metering Congestion Management: Each interface must have a queuing mechanism to prioritize transmission of packets Traffic Shaping: Used to enforce a rate limit based on the metering by delaying excess traffic Compression: Reduces serialization delay and bandwidth required to transmit data by reducing the size of packet headers or payloads Link Efficiency: Used to improve bandwidth efficiency through compression and link fragmentation and interleaving

4 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Classification Classification is the identifying and splitting of traffic into different classes Traffic can be classed by various means including the DSCP Modular QoS CLI allows classification to be implemented separately from policy

5 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Classification Classification is the identifying and splitting of traffic into different classes Traffic can be classed by various means including the DSCP Modular QoS CLI allows classification to be implemented separately from policy

6 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Classification Classification is the identifying and splitting of traffic into different classes Traffic can be classed by various means including the DSCP Modular QoS CLI allows classification to be implemented separately from policy

7 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Marking Marking, which is also known as coloring, marks each packet as a member of a network class so that the packets class can be quickly recognized throughout the rest of the network

8 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Marking Marking, which is also known as coloring, marks each packet as a member of a network class so that the packets class can be quickly recognized throughout the rest of the network

9 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Marking Marking, which is also known as coloring, marks each packet as a member of a network class so that the packets class can be quickly recognized throughout the rest of the network

10 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Trust Boundaries Classify Where? Ciscos QoS model assumes that the CoS carried in a frame may or may not be trusted by the network device For scalability, classification should be done as close to the edge as possible End hosts can mostly not be trusted to tag a packets priority correctly The outermost trusted devices represent the trust boundary 1 and 2 are optimal, 3 is acceptable (if access switch cannot perform classification) 123

11 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Trust Boundaries Mark Where? For scalability, marking should be done as close to the source as possible

12 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v QoS Trust Boundary in the LAN Classify and Mark Where? Ciscos QoS model assumes that the CoS carried in a frame may or may not be trusted by the network device Classification should be done as close to the edge as possible End hosts like user PCs can mostly not be trusted to tag a packets priority correctly

13 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Connecting the IP Phone 802.1Q trunking between the switch and IP phone for multiple VLAN support (separation of voice/data traffic) is preferred The 802.1Q header contains the VLAN information and the CoS 3-bit field, which determines the priority of the packet For most Cisco IP phone configurations, traffic sent from the IP phone to the switch is trusted to ensure that voice traffic is properly prioritized over other types of traffic in the network The trusted boundary feature uses CDP to detect an IP phone and otherwise disables the trusted setting on the switch port to prevent misuse of a high- priority queue

14 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Congestion Management Congestion management uses the marking on each packet to determine which queue to place packets in Congestion management utilizes sophisticated queuing technologies such as Weighted Fair Queuing (WFQ) and Low Latency Queuing (LLQ) to ensure that time-sensitive packets like voice are transmitted first

15 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Shaping Shaping queues packets when a pre-defined limit is reached

16 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Shaping Shaping queues packets when a pre-defined limit is reached

17 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Shaping Shaping queues packets when a pre-defined limit is reached

18 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Shaping Shaping queues packets when a pre-defined limit is reached

19 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Shaping Shaping queues packets when a pre-defined limit is reached

20 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Compression Header compression can dramatically reduce the overhead associated with voice transport

21 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Compression Header compression can dramatically reduce the overhead associated with voice transport

22 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Link Fragmentation and Interleaving Without Link Fragmentation and Interleaving, time-sensitive voice traffic can be delayed behind long, non-time-sensitive data packets Link Fragmentation breaks long data packets apart and interleaves time-sensitive packets so that they are not delayed

23 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Link Fragmentation and Interleaving Without Link Fragmentation and Interleaving, time-sensitive voice traffic can be delayed behind long, non-time-sensitive data packets Link Fragmentation breaks long data packets apart and interleaves time-sensitive packets so that they are not delayed

24 © 2004 Cisco Systems, Inc. All rights reserved. IPTX v Summary Different mechanisms can be used to implement QoS in a network: classification, marking, congestion management, shaping, compression, and link efficiency. First step is always to identify classes of traffic so that the appropriate QoS treatment can be applied to different traffic types. Traffic conditioners such as shapers are used to limit the maximum rate of traffic sent or received on an interface. Compression is a technique that is used to reduce the amount of bandwidth required to transmit data by compressing packet headers or payloads. Bandwidth efficiency can be improved through link efficiency mechanisms such as compression and fragmentation and interleaving.

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