QOS (Quality of Services) - Computer Networks

Quality Of Services (Qos) Computer Networks Rahul Ranjan (16010121) Indian Institute of Information Technology Manipur March 26, 2018 Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 1 / 26

Introduction to QoS Quality of service is the ability to provide different priority to different applications, users, or data flows, or to guarantee a certain level of performance to a data flow. It defines the quality of service as something a flow seeks to attain. Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 2 / 26

Flow- Characterstics There are mainly 4 types of Flow - Characterstics::– 1 Reliability 2 Delay 3 Jitter 4 Bandwidth Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 3 / 26

Flow Characterstics Reliability 1 Reliability is a characterstics that a flow needs in order to deliver the packets safe & sound to the destination. 2 Lack of Reliability means losing a packet or acknowledgement. Delay 1 Different applications can tolerate delay in different degrees. Jitter 1 Jitter is the variation in packets belonging to same flow. Bandwidth 1 Different application need different bandwidths. Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 4 / 26

Techniques to improve quality of services 1 Scheduling FIFO Queuing Priority Queuing Weighted Fair Queuing 2 Traﬃc Shaping LEAKY BUCKET TOKEN BUCKET 3 Resource Reservation 4 Admission Control Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 5 / 26

Scheduling Packets from different flow arrive at switch or router for processing. A good scheduling technique treats the different flow in a fair and appropriate manner. Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 6 / 26

FIFO Queuing 1 Packets wait in a buﬀer (queue) until the node is ready to process them. 2 If avg. arrival rate > avg. processing rate => new packets will be discarded. 3 FIFO Queuing is default scheduling in the Internet. 4 In FIFO Queuing the packets depart in order they arrive. Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 7 / 26

FIFO Queuing Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 8 / 26

Priority Queuing Each class has its own queue. Packets are assigned to a priority class. Higher class packets are processed ﬁrst. The main problem with Priority Queuing is that of starvation. Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 9 / 26

Priority Queuing Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 10 / 26

Weighted Fair Queuing Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 11 / 26

Weighted Fair Queuing Packets are still assigned to diﬀerent classes and admitted to diﬀerent queues. The queues are weighted based on the priority. Higher priority means higher weight. 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 Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 12 / 26

Traffic Shaping 1 Traffic Shaping is the mechanism to control the amount and the rate of the traffic sent to the network. 2 There are 2 techniques of traffic shaping– Leaky Bucket. Token Bucket. Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 13 / 26

Leaky Bucket Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 14 / 26

Leaky Bucket The rate at which water leaks from a bucket does not depend on the rate at which the water is input to the bucket. The input rate varies but the o/p remains constant ,similarly ,network can smooth out bursty traﬃc. Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 15 / 26

Token Bucket Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 16 / 26

Token Bucket 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 Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 17 / 26

Resource Reservation QoS can be improved if these resources are reserved beforehand. A ﬂow of data needs resources such as buﬀer, bandwidth, CPU time, and so on . Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 18 / 26

Admission Control 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. Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 19 / 26

Models deploying QoS There are mainly 2 models have been designed to provide QoS:— 1 Integrated Service Model(IntServ). 2 Diﬀerentiated Service Model(Diﬀserv) Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 20 / 26

IntServ 1 User needs to create flow, kind of virtual circuit ,from source to destination and inform all routers of requirement. The model is based on three schemes— 2 The packets are first classified according to the services they required. 3 The model uses scheduling to forward the packets according to their flow characterstics. 4 Devices like router uses Admission control to determine if the devices has the capacity before making the commitment. Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 21 / 26

RSVP: Resource Reservation Protocol Receiver based reservation : the receiver not the sender make the reservation(eg : youtube). RSVP messages: Path Messages Resv Messages Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 22 / 26

RSVP: Resource Reservation Protocol Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 23 / 26

DiffServ The router routes the packet based on the class of service defined in the packet. The main processing was moved from the core of the network to the edge of the network.This solves the Scalability problem of IntServ ,i.e., the router doesn’t have to store information about flow. The per-flow service is changed to per-class service. The router routes the packet based on the class of service defined in the packet, not the flow.This solves the service - type limitation problem. Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 24 / 26

DiffServ* ToS: Type of Service field is used to define the class of service for each packet. Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 25 / 26

Thank You!! ”Thank You for listenning me!!!” Rahul Ranjan(16010121) (Indian Institute of Information Technology Manipur)Quality Of Services (Qos) March 26, 2018 26 / 26

QOS (Quality of Services) - Computer Networks

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