Qos Quality of services
- 1. HELLO! I am Hayder Thary M.Sc. QoS Presentation 1
- 3. “ -refers to the capability of a network to provide better service to selected network traffic over various technologies, including Frame Relay, Asynchronous Transfer Mode (ATM), Ethernet and 802.1 networks, SONET, and IP-routed networks that may use any or all of these underlying technologies. - is particularly important for the transport of traffic with special requirements. In particular, developers have introduced voice over IP technology to allow computer networks to become as useful as telephone networks for audio conversations. 3
- 4. QoS What's Goal ! to provide priority including dedicated bandwidth, controlled jitter and latency (required by some real-time and interactive traffic), and improved loss characteristics. Also important is making sure that providing priority for one or more flows does not make other flows fail.
- 5. 5 Additionally, use QoS to achieve outcomes such as the following: ▪ Prioritize network and application traffic, guaranteeing high priority to important traffic or limiting non-essential traffic. ▪ Achieve equal bandwidth sharing among different subnets, classes, or users in a network. ▪ Allocate bandwidth externally or internally or both, applying QoS to both upload and download traffic or to only upload or download traffic. ▪ Ensure low latency for customer and revenue-generating traffic in an enterprise environment. ▪ Perform traffic profiling of applications to ensure bandwidth usage.
- 7. A flow can be defined in a number of ways. One common way refers to a combination of source and destination addresses, source and destination socket numbers, and the session identifier. It can also be defined more broadly as any packet from a certain application or from an incoming interface. 7
- 8. Flow Characteristics 8 Flow Characteristics Reliability Delay Jitter Bandwidth
- 9. Flow Characteristics 9 ▪ Reliability : Lack of Reliability means losing a packet or ack. ▪ Delay: Different applications can tolerate delay in different degrees. ▪ Jitter : jitter is the variation in packets belonging to same flow. ▪ Bandwidth: different application need different B/W.
- 10. Techniques to improve the quality of service. 10 Scheduling FIFO QUEUING PRIORITY QUEUING WEIGHTED FAIR QUEUING Traffic Shaping LEAKY BUCKET TOKEN BUCKET Resource Reservation Admission Control
- 11. Scheduling 11 o Packets from different flow arrive at switch or router for processing . o A good scheduling technique treats the different flow in a fair and appropriate manner.
- 12. FIFO QUEUING 12 Packets wait in a buffer (queue) until the node is ready to process them. If avg. arrival rate>avg. processing rate =>new packets will be discarded.
- 13. Priority Queuing 13 oPackets are assigned to a priority class oEach class has its own queue. oHigher class packets are processed first. oProblem : Starvation
- 14. Weighted Fair Queuing 14 o Packets are still assigned to different classes and admitted to different queues • The queues are weighted based on the priority o Higher priority means higher weight o If weight are 3,2,1 then 3 packets are processed from q1,2 from q2,and 1 from q1 in a round robin fashion
- 15. Traffic Shaping Is the mechanism to control the amount and the rate of the traffic sent to the network 15 Leaky Bucket
- 16. The rate at which water leaks from a bucket does not depend on the rate at which the water is input to the bucket . 16 The input rate varies but the o/p remains constant ,similarly ,network can smooth out bursty traffic.
- 17. Token Bucket 17
- 18. Leaky bucket does not taken into a/c idle host , if a host is not sending for a while , its bucket becomes empty. If the host has bursty data ,leaky bucket allows only avg. rate. Token bucket takes into a/c the idle time , with each clock tick the tokens are added to bucket ,when the data needs to be send ,it collects token from bucket and then send the data packet consisting of data=no of tokens 18 Resource Reservation o A flow of data needs resources such as buffer, bandwidth, CPU time, and so on . o QoS can be improved if these resources are reserved beforehand.
- 19. Admission Control 19 -Routers or switches puts restrictions on the admission of packets from host. -Before a router accepts the flow , it checks the flow for specifications in terms of bandwidth , buffer size ,cpu speed etc.
- 20. Application ▪ Mobile communication ▪ Real-time video and sound ▪ transmission ▪ Interactive applications on network ▪ Routing for traffic with performance guarantees ▪ QoS-aware ATM application 20
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- 22. 22 Reference's I. COMPUTER NETWORKING A Top-Down Approach 6th edition II. https://www.rfc-editor.org/ III. http://www.rfc- editor.org/search/rfc_search_detail.php?rfc=2474&title=qu ality+of+s IV. http://www.cs.columbia.edu/~coms6181/slides/13/quality- of-service.ppt V. https://www.paloaltonetworks.com/documentation/71/pan- os/pan-os/quality-of-service/configure-qos VI. https://www.paloaltonetworks.com/documentation/71/pan- os/pan-os/quality-of-service/qos-overview