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Quality of Service

Quality of Service. Classification and marking. What is QoS?. It’s a CCIE topic – but that doesn’t mean you can’t learn! Understand traffic flows. TCP. A. B. UDP. A. B. SYN. SRC & DST IPs and Ports. SYN, ACK. ACK. ESTABLISHED. Categories of QoS. Classification and Marking

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Quality of Service

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  1. Quality of Service Classification and marking

  2. What is QoS? • It’s a CCIE topic – but that doesn’t mean you can’t learn! • Understand traffic flows TCP A B UDP A B SYN SRC & DST IPs and Ports SYN, ACK ACK ESTABLISHED

  3. Categories of QoS • Classification and Marking • Congestion Management and Avoidance Packet (EF)Packet Hardware Queue (AF21)Data Packet (EF)Voice Packet

  4. Categories of QoS • Classification and Marking • Congestion Management and Avoidance • Shaping, Policing, and Link Fragmentation • Rate limiting • Shaping buffers offending packets while policing is a little more rough and by default drops offending packets. Packet (EF)Packet Hardware Queue Soft Priority Queue (AF21)Data Packet (EF)Voice Packet Soft Queue

  5. QoS Fields • IP ToS Byte • CoS (802.1q and ISL) • WAN

  6. QoS Fields • IP ToS Byte

  7. QoS Fields • CoS and WAN fields • CoS has 3 bits to work with on the 802.1q header and ISL header • WAN markings aren’t’ much • MPLS has 3 bits to work with, Frame-Relay and ATM both have 1 bit • IP header maintains it’s markings, but not much good over L2 and L2.5 WAN networks

  8. QoS Fields Continued…

  9. Per Hop Behaviors (PHB)

  10. Assured Forwarding PHB and DSCP Values • Expedited Forwarding PHB and DSCP Values • Two PHBs • Quick scheduling low latency queuing • Police to ensure EF packets do not hog all the bandwidth and/or starve the other queues. • Decimal 46 – Binary 101110

  11. Assured Forwarding PHB and DSCP Values Continued… • AF11 / 10 / 001010 • AF1 | 1 = 001 | 01 | 0 • 001010 = 10 • AF43 / 38 / 100110 • AF4 | 3 = 100 | 11 | 0 • 100110 = 38

  12. Modular Quality of Service CLI • Class map • Used to Classify your traffic • Policy Map • Used to Mark your traffic (and choose what to do with marked traffic) this is also where you set Congestion Management and Policing. Normally we want to keep marking as close to the source as possible, but best practices aren’t always possible… • Service Policy • Same thing as a policy-map, but you use the service-policy command on an interface to apply the policy map

  13. Network Based Application Recognition (NBAR) • NBAR is also known as Deep Packet Inspection • NBAR has the ability to look past TCP and UDP ports such as the URL, MIME type in HTTP requests allowing recognition of application information • Ability to use regular expressions to isolate the domain or another portion • Use the match protocol command under a class map to use NBAR to match traffic

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