ipqos

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Which Applications Have Which QoS Requirements?
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Why IP QoS?
Application X is slow. Video broadcast occasionally stalls. Phone calls over IP are no better than over satellite. Phone calls can have very bad voice quality. ATMs (the money-dispensing type) are nonresponsive.
Priority Queuing (PQ) Custom Queuing (CQ) Strict Priority MDRR IP RTP Prioritization Class-Based Low-Latency Queuing (CBLLQ)
Compress the Payload
Compressed Packet
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Processing, Queuing, and Propagation Delay
Forwarding
Bandwidth andwidth Propagation Delay
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IP
IP
IP
IP
Processing Delay
IP Quality of Service
Objectives
Upon completing this module, you will be able to:
Describe the need for IP QoS Describe the Integrated Services model Describe the Differentiated Services model Describe the building blocks of IP QoS mechanisms (classification, marking, metering, policing, shaping, dropping, forwarding, queuing)
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How to Reduce Delay?
TCP Header Compression RTP Header Compression cRTP Data
Compress the Headers IP UDP RTP Data
FIFO Queuing Fancy queuing
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Available Bandwidth
IP
IP
IP
IP
512 kbps 256 kbps 10 Mbps 100 Mbps
BWmax = min(10M, 256k, 512k, 100M)=256 kbps BWavail = BWmax /Flows
Propagation Delay (P3) Processing and Queuing Delay (Q3)
Propagation Delay (P4)
Delay = P1 + Q1 + P2 + Q2 + P3 + Q3 + P4 = X ms End-to-end delay equals a sum of all propagation, processing, and queuing delays in the path. Propagation delay is fixed; processing and queuing delays are unpredictable in best-effort networks.
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How to Prevent Packet Loss?
Weighted Random Early Detection (WRED)
IP
Data
Dropper
Fancy queuing FIFO Queuing
Custom Queuing (CQ) Modified Deficit Round Robin (MDRR) Class-Based Weighted Fair Queuing (CBWFQ)
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Packet Loss
Forwarding
IP
IP
IP
IP
IP
Tail-drop
Tail-drops occur when the output queue is full. These are the most common drops which happen when a link is congested. There are also many other types of drops (input queue drop, ignore, overrun, no buffer, etc), which are not as common and which may require a hardware upgrade. These drops are usually a result of router congestion.
Maximum available bandwidth equals the bandwidth of the weakest link. Multiple flows are competing for the same bandwidth, resulting in much less bandwidth being available to one single application.
Upgrade the link—the best solution but also the most expensive.
• Guarantee enough bandwidth to sensitive packets. • Prevent congestion by randomly dropping less important packets before congestion occurs.
Stacker Predictor
Upgrade the link—the best solution but also the most expensive.
• Forward the important packets first. • Compress the payload of Layer-2 frames (it takes time). • Compress the header of IP packets.
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What Causes ...
Lack of bandwidth?: Multiple flows are contesting for a limited amount of bandwidth. Too much delay?: Packets have to traverse many network devices and links. Variable delay?: Sometimes there is a lot of other traffic, which results in more delay. Drops?: Packets have to be dropped when a link is congested.
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End-to-End Delay
IP
IP
IP
IP
Propagation Delay (P1) Processing and Queuing Delay (Q1)
Propagation Delay (P2) Processing and Queuing Delay (Q2)
FIFO Queuing Fancy queuing
Compressed Packet
Stacker Predictor
Upgrade the link—the best solution but also the most expensive.
• Take some bandwidth from less important applications. • Compress the payload of Layer 2 frames. • Compress the header of IP packets.
Inner Mongolia University
Introduction
Objectives
Upon completing this lesson, you will be able to:
Describe different types of applications and services that have special resource requirements List the network components that affect the throughput, delay, and jitter in IP networks List the benefits of deploying QoS mechanisms in IP networks Describe typical enterprise and service provider networks and their QoS-related requirements