Cisco: QoS


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Cisco: QoS

  1. 2. Convenio Marco de Cooperación y Asistencia Técnica
  2. 3. ..PresentacionSLSarra.jpg Fundación Proydesa y la filial Argentina de SLS LATAM Tienen el agrado de comunicar la formalización de un Convenio Marco de Cooperación y Asistencia Técnica con el objeto de investigar, desarrollar y promover la formación en y con tecnología, ingresando decididamente como actores protagónicos en la Educación del Siglo XXI y acompañando en forma coordinada el esfuerzo que diariamente realiza Cisco Systems por cambiar la forma en que nos comunicamos y educamos
  3. 4. Using the Medium
  4. 5. Introducing QoS Understanding the Need for QoS
  5. 6. QoS Defined
  6. 7. Before Converged Networks <ul><li>Traditional data traffic characteristics: </li></ul><ul><ul><li>Bursty data flow </li></ul></ul><ul><ul><li>First-come, first-served access </li></ul></ul><ul><ul><li>Mostly not time-sensitive – delays OK </li></ul></ul><ul><ul><li>Brief outages are survivable </li></ul></ul>
  7. 8. After Converged Networks <ul><li>Converged traffic characteristics: </li></ul><ul><ul><li>Constant small-packet voice flow competes with bursty data flow </li></ul></ul><ul><ul><li>Critical traffic must get priority </li></ul></ul><ul><ul><li>Voice and video are time-sensitive </li></ul></ul><ul><ul><li>Brief outages not acceptable </li></ul></ul>
  8. 9. Converged Networks: Quality Issues <ul><ul><li>Telephone Call: “I cannot understand you; your voice is breaking up.” </li></ul></ul><ul><ul><li>Teleconferencing: “The picture is very jerky. Voice not synchronized.” </li></ul></ul><ul><ul><li>Brokerage House: “I needed that information two hours ago. Where is it?” </li></ul></ul><ul><ul><li>Call Center: “Please hold while my screen refreshes.” </li></ul></ul>
  9. 10. QoS Traffic Requirements: Data <ul><ul><li>Different applications have different traffic characteristics. </li></ul></ul><ul><ul><li>Different versions of the same application can have different traffic characteristics. </li></ul></ul><ul><ul><li>Classify data into relative-priority model with no more than four to five classes: </li></ul></ul><ul><ul><ul><li>Mission-Critical Apps: Locally defined critical applications </li></ul></ul></ul><ul><ul><ul><li>Transactional: Interactive traffic, preferred data service </li></ul></ul></ul><ul><ul><ul><li>Best-Effort: Internet, e-mail, unspecified traffic </li></ul></ul></ul><ul><ul><ul><li>Less-Than-Best-Effort (Scavenger): Napster, Kazaa, peer-to-peer applications </li></ul></ul></ul>
  10. 11. QoS Traffic Requirements: Voice <ul><ul><li>Latency < 150 ms* </li></ul></ul><ul><ul><li>Jitter < 30 ms* </li></ul></ul><ul><ul><li>Loss < 1%* </li></ul></ul><ul><ul><li>17-106 kbps guaranteed priority bandwidth per call </li></ul></ul><ul><ul><li>150 bps (+ Layer 2 overhead) guaranteed bandwidth for voice-control traffic per call </li></ul></ul><ul><li>*one-way requirements </li></ul>– QoS Traffic Requirements: Voice
  11. 12. QoS Requirements: Videoconferencing <ul><ul><li>Latency ≤ 150 ms* </li></ul></ul><ul><ul><li>Jitter ≤ 30 ms* </li></ul></ul><ul><ul><li>Loss ≤ 1%* </li></ul></ul><ul><ul><li>Minimum priority bandwidth guarantee required is: </li></ul></ul><ul><ul><ul><li>Video stream + 20% </li></ul></ul></ul><ul><ul><ul><li>For example, a 384 kbps stream would require 460 kbps of priority bandwidth </li></ul></ul></ul><ul><li>*one-way requirements </li></ul>
  12. 13. Converged Networks: Quality Issues (Cont.) <ul><ul><li>Lack of bandwidth: Multiple flows compete for a limited amount of bandwidth. </li></ul></ul><ul><ul><li>End-to-end delay (fixed and variable): Packets have to traverse many network devices and links that add up to the overall delay. </li></ul></ul><ul><ul><li>Variation of delay (jitter): Sometimes there is a lot of other traffic, which results in more delay. </li></ul></ul><ul><ul><li>Packet loss: Packets may have to be dropped when a link is congested. </li></ul></ul>
  13. 14. <ul><ul><li>Best-Effort: No QoS is applied to packets. </li></ul></ul><ul><ul><li>IntServ: Applications signal to the network that they require special QoS. </li></ul></ul><ul><ul><li>DiffServ: The network recognizes classes that require special QoS. </li></ul></ul>
  14. 15. Best-Effort Model It will get there when it gets there. <ul><ul><li>Internet initially based on a best-effort packet delivery service </li></ul></ul><ul><ul><li>The default mode for all traffic </li></ul></ul><ul><ul><li>No differentiation between types of traffic </li></ul></ul><ul><ul><li>Like using standard mail </li></ul></ul>
  15. 16. Best-Effort Model (Cont.) <ul><ul><li>Benefits: </li></ul></ul><ul><ul><ul><li>Highly scalable </li></ul></ul></ul><ul><ul><ul><li>No special mechanisms required </li></ul></ul></ul><ul><ul><li>Drawbacks: </li></ul></ul><ul><ul><ul><li>No service guarantees </li></ul></ul></ul><ul><ul><ul><li>No service differentiation </li></ul></ul></ul>
  16. 17. IntServ Model <ul><ul><li>Some applications have special bandwidth or delay requirements or both </li></ul></ul><ul><ul><li>IntServ introduced to guarantee a predictable behavior of the network for these applications </li></ul></ul><ul><ul><li>Guaranteed delivery: no other traffic can use reserved bandwidth </li></ul></ul><ul><ul><li>Like having your own private courier plane </li></ul></ul>It will be there by 10:30 a.m.
  17. 18. IntServ Model (Cont.) <ul><ul><li>Provides multiple service levels </li></ul></ul><ul><ul><li>Requests specific kind of service from the network before sending data </li></ul></ul><ul><ul><li>Uses RSVP to reserve network resources </li></ul></ul><ul><ul><li>Uses intelligent queuing mechanisms </li></ul></ul><ul><ul><li>End to end </li></ul></ul>
  18. 19. <ul><ul><li>RSVP QoS services </li></ul></ul><ul><ul><ul><li>Guaranteed-rate service </li></ul></ul></ul><ul><ul><ul><li>Controlled-load service </li></ul></ul></ul><ul><ul><li>RSVP provides policy to QoS mechanisms </li></ul></ul>IntServ Model (Cont.)
  19. 20. IntServ Model (Cont.) <ul><ul><li>Benefits: </li></ul></ul><ul><ul><ul><li>Explicit resource admission control (end to end) </li></ul></ul></ul><ul><ul><ul><li>Per-request policy admission control (authorization object, policy object) </li></ul></ul></ul><ul><ul><ul><li>Signaling of dynamic port numbers (for example, H.323) </li></ul></ul></ul><ul><ul><li>Drawbacks: </li></ul></ul><ul><ul><ul><li>Continuous signaling because of stateful architecture </li></ul></ul></ul><ul><ul><ul><li>Flow-based approach not scalable to large implementations such as the public Internet (can be made more scalable when combined with elements of the DiffServ model) </li></ul></ul></ul>
  20. 21. DiffServ Model <ul><ul><li>Network traffic identified by class </li></ul></ul><ul><ul><li>Network QoS policy enforces differentiated treatment of traffic classes </li></ul></ul><ul><ul><li>You choose level of service for each traffic class </li></ul></ul><ul><ul><li>Like using a package delivery service </li></ul></ul>Do you want overnight delivery? Do you want two-day air delivery? Do you want three- to seven-day ground delivery?
  21. 22. Overview R1 R2
  22. 23. QoS for Converged Networks
  23. 24. Step 1: Identify Traffic and Its Requirements <ul><ul><li>Network audit </li></ul></ul><ul><ul><ul><li>Identify traffic on the network </li></ul></ul></ul><ul><ul><li>Business audit </li></ul></ul><ul><ul><ul><li>Determine how each type of traffic is important for business </li></ul></ul></ul><ul><ul><li>Service levels required </li></ul></ul><ul><ul><ul><li>Determine required response time </li></ul></ul></ul>
  24. 25. Step 2: Divide Traffic into Classes
  25. 26. Classification <ul><ul><li>Classification is the identifying and splitting of traffic into different classes. </li></ul></ul><ul><ul><li>Traffic can be classed by various means, including the DSCP. </li></ul></ul><ul><ul><li>Modular QoS CLI allows classification to be implemented separately from policy. </li></ul></ul>
  26. 27. Marking <ul><ul><li>Marking, also known as coloring, marks each packet as a member of a network class so that the packet class can be quickly recognized throughout the rest of the network. </li></ul></ul>
  27. 28. Differentiated Services Model <ul><ul><li>The Differentiated Services model describes services associated with traffic classes. </li></ul></ul><ul><ul><li>Complex traffic classification and conditioning is performed at the network edge, resulting in a per-packet DSCP . </li></ul></ul><ul><ul><li>No per-flow state in the core. </li></ul></ul><ul><ul><li>The core only performs simple “per-hop behaviors” on traffic aggregates. </li></ul></ul><ul><ul><li>The goal is scalability. </li></ul></ul>
  28. 29. DSCP Encoding <ul><ul><li>DiffServ field: The IP version 4 header ToS octet or the IPv6 traffic class octet, when interpreted in conformance with the definition given in RFC 2474 </li></ul></ul><ul><ul><li>DSCP: The first six bits of the DiffServ field, used to select a PHB (forwarding and queuing method) </li></ul></ul>
  29. 30. DiffServ Model (Cont.) <ul><ul><li>Benefits: </li></ul></ul><ul><ul><ul><li>Highly scalable </li></ul></ul></ul><ul><ul><ul><li>Many levels of quality possible </li></ul></ul></ul><ul><ul><li>Drawbacks: </li></ul></ul><ul><ul><ul><li>No absolute service guarantee </li></ul></ul></ul><ul><ul><ul><li>Complex mechanisms </li></ul></ul></ul>
  30. 31. Break - 10 mins
  31. 32. QoS for Converged Networks
  32. 33. QoS Mechanisms <ul><ul><li>Classification: Each class-oriented QoS mechanism has to support some type of classification. </li></ul></ul><ul><ul><li>Marking: Used to mark packets based on classification, metering, or both. </li></ul></ul><ul><ul><li>Congestion management: E ach interface must have a queuing mechanism to prioritize transmission of packets. </li></ul></ul><ul><ul><li>Congestion avoidance: Used to drop packets early to avoid congestion later in the network. </li></ul></ul><ul><ul><li>Policing and shaping: Used to enforce a rate limit based on the metering (excess traffic is either dropped, marked, or delayed). </li></ul></ul><ul><ul><li>Link Efficiency: Used to improve bandwidth efficiency through compression, link fragmentation, and interleaving. </li></ul></ul>
  33. 34. Classification <ul><ul><li>Classification is the identifying and splitting of traffic into different classes. </li></ul></ul><ul><ul><li>Traffic can be classed by various means, including the DSCP. </li></ul></ul><ul><ul><li>Modular QoS CLI allows classification to be implemented separately from policy. </li></ul></ul>
  34. 35. Marking <ul><ul><li>Marking, also known as coloring, marks each packet as a member of a network class so that the packet class can be quickly recognized throughout the rest of the network. </li></ul></ul>
  35. 36. Congestion Management <ul><ul><li>Congestion management uses the marking on each packet to determine in which queue to place packets. </li></ul></ul><ul><ul><li>Congestion management uses sophisticated queuing technologies, such as WFQ and LLQ, to ensure that time-sensitive packets such as voice are transmitted first. </li></ul></ul>
  36. 37. Congestion Avoidance <ul><ul><li>Congestion avoidance may randomly drop packets from selected queues when previously defined limits are reached. </li></ul></ul><ul><ul><li>By dropping packets early, congestion avoidance helps prevent bottlenecks downstream in the network. </li></ul></ul><ul><ul><li>Congestion avoidance technologies include random early detection and weighted random early detection. </li></ul></ul>
  37. 38. Policing <ul><ul><li>Policing drops or marks packets when a predefined limit is reached. </li></ul></ul>
  38. 39. Shaping <ul><ul><li>Shaping queues packets when a predefined limit is reached. </li></ul></ul>
  39. 40. Compression <ul><ul><li>Header compression can dramatically reduce the overhead associated with voice transport. </li></ul></ul>
  40. 41. Link Fragmentation and Interleaving <ul><ul><li>Without link fragmentation and interleaving, time-sensitive voice traffic can be delayed behind long, non-time-sensitive data packets. </li></ul></ul><ul><ul><li>Link fragmentation breaks long data packets apart and interleaves time-sensitive packets so that the time-sensitive packets are not delayed. </li></ul></ul>
  41. 42. Applying QoS to Input and Output Interfaces
  42. 43. Methods for Implementing QoS Policy <ul><ul><li>CLI </li></ul></ul><ul><ul><li>MQC </li></ul></ul><ul><ul><li>AutoQoS VoIP (voice QoS) </li></ul></ul><ul><ul><li>AutoQoS Enterprise (voice, video, and data QoS) </li></ul></ul><ul><ul><li>QPM </li></ul></ul>
  43. 44. Implementing QoS with CLI interface Multilink1 ip address ip tcp header-compression iphc-format load-interval 30 custom-queue-list 1 ppp multilink ppp multilink fragment-delay 10 ppp multilink interleave multilink-group 1 ip rtp header-compression iphc-format ! <ul><ul><li>Traditional method </li></ul></ul><ul><ul><li>Nonmodular </li></ul></ul><ul><ul><li>Cannot separate traffic classification from policy definitions </li></ul></ul><ul><ul><li>Used to augment, fine-tune newer AutoQoS method </li></ul></ul>
  44. 45. Implementing QoS with MQC <ul><ul><li>A command syntax for configuring QoS policy </li></ul></ul><ul><ul><li>Reduces configuration steps and time </li></ul></ul><ul><ul><li>Configure policy, not “raw” per-interface commands </li></ul></ul><ul><ul><li>Uniform CLI across major Cisco IOS platforms </li></ul></ul><ul><ul><li>Uniform CLI structure for all QoS features </li></ul></ul><ul><ul><li>Separates classification engine from the policy </li></ul></ul>class-map VoIP-RTP match access-group 100 class-map VoIP-Control match access-group 101 ! policy-map QoS-Policy class VoIP-RTP priority 100 class VoIP-Control bandwidth 8 class class-default fair-queue ! interface serial 0/0 service-policy output QoS-Policy ! access-list 100 permit ip any any precedence 5 access-list 100 permit ip any any dscp ef access-list 101 permit tcp any host range 2000 2002 access-list 101 permit tcp any host range 11000 11999
  45. 46. Implementing QoS with AutoQoS [trust] option is used to trust DSCP marking <ul><ul><li>AutoQoS VoIP supported both in the LAN and WAN environments </li></ul></ul><ul><ul><li>AutoQoS Enterprise supported on WAN interfaces </li></ul></ul><ul><ul><li>Routers can deploy Enterprise QoS policy treatment for voice, video, and data traffic </li></ul></ul><ul><ul><li>Switches can deploy QoS policy treatments for voice by a single command </li></ul></ul>
  46. 47. Comparing Methods for Implementing QoS