Quality of Servise


Published on

its all about quality of services of network

Published in: Technology, Business
  • Be the first to comment

  • Be the first to like this

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Quality of Servise

  1. 2. Quality of Service Presented By: S.M Raza Sajjad
  2. 3. Quality of Service <ul><li>QoS refer to both CoS( Class of Service) and ToS (Type of Service). </li></ul><ul><li>The basic goal of CoS & ToS is to achieve the bandwidth and latency needed for a particular application. </li></ul><ul><li>The CoS enables a network administrator to group different packet flows each having distinct latency and bandwidth requirement. </li></ul>
  3. 4. QoS <ul><li>VoIP comes with its own set of problems (Delay, Jitter). </li></ul><ul><li>QoS can help to solve some of these problems like Packet Losses, Jitter and Handling delay. </li></ul><ul><li>Some of the Problems can’t solve by QoS are Propagation Delay, digitization delay, Sampling delay, Codec Delay. </li></ul>
  4. 5. QoS Network Tool kit <ul><li>Compressed Real-Time Transport Protocol(CRTP). </li></ul><ul><li>Queuing </li></ul><ul><ul><li>Weighted Fair Queuing (WFQ) </li></ul></ul><ul><ul><li>Custom Queuing(CQ) </li></ul></ul><ul><ul><li>Priority Queuing (PQ) </li></ul></ul><ul><ul><li>Class-Based Weighted Fair Queuing(CB-WFQ) </li></ul></ul><ul><li>Packet Classification </li></ul><ul><ul><li>IP Precedence </li></ul></ul><ul><ul><li>Policy Routing </li></ul></ul><ul><ul><li>Resource Reservation Protocol </li></ul></ul><ul><li>Fragmentation </li></ul>
  5. 6. CRTP <ul><li>To reduce the large percentage of bandwidth consumed by a G.729 voice call you can use cRTP. </li></ul><ul><li>CRTP enables you to compress the 40-byte IP/RTP/UDP header to 2 to 4 bytes most of the time. </li></ul><ul><li>With CRTP amount of traffic per VoIP call is reduced from 24kbps to 11.2 kbps. </li></ul><ul><li>This is major improvement for low bandwidth links. </li></ul><ul><li>For Example a 56 kbps link carry four G.729 VoIP Calls at 11.kbps each, without CRTP it can carry only two VoIP Calls. </li></ul>
  6. 8. CRTP <ul><li>Should not use CRTP on high speed interfaces. </li></ul><ul><li>As with any compression, the CPU incurs extra processing duties to compress the packet. </li></ul><ul><li>It should first analyzed that the advantage of lower bandwidth against higher CPU utilization. </li></ul>
  7. 9. Queuing <ul><li>Queuing in and of itself is a fairly simple concept. </li></ul><ul><li>The easiest way to think about queue is to think about highway system. </li></ul><ul><li>In Queue the concept of FIFO System is used. </li></ul><ul><li>Today’s network with their variety of applications, protocols and users, require a way to classify different traffic. </li></ul>
  8. 10. Queuing <ul><li>Out of different Queuing techniques the most popular technique is WFQ. </li></ul><ul><li>It is the default for any router interface less than 2mbps of bandwidth. </li></ul>
  9. 11. Weighted Fair Queuing <ul><li>WFQ on the other hand uses multiple queues to separate flows and gives equal amounts of bandwidth to each flow. </li></ul><ul><li>WFQ ensures that queues do not starve for bandwidth and that traffic gets predictable service. </li></ul>
  10. 12. Weighted Fair Queuing <ul><li>WFQ is superior to TDM, simply because when a stream is no longer present, WFQ dynamically adjusts to use the free bandwidth for the flows that are still transmitting. </li></ul><ul><li>The algorithm enables bandwidth to be shared fairly. </li></ul>
  11. 13. Custom Queuing <ul><li>Custom Queuing enables users to specify a percentage of available bandwidth to a particular protocol. </li></ul><ul><li>Each queue is served sequentially in a round robin fashion. </li></ul><ul><li>Transmitting a percentage of traffic on each queue before moving the next queue. </li></ul>
  12. 14. Priority Queuing <ul><li>PQ enables a NE to configure four Traffic Policies </li></ul><ul><ul><li>High </li></ul></ul><ul><ul><li>Normal </li></ul></ul><ul><ul><li>Medium </li></ul></ul><ul><ul><li>Low </li></ul></ul><ul><li>Inbound traffic is assigned to one of the four output queues. </li></ul><ul><li>Traffic in high priority queue is served until the queue is empty </li></ul><ul><li>Then packets of next priority queue is transmitted . </li></ul>
  13. 15. CB-WFQ <ul><li>CB-WFQ has all the benefits of WFQ, with the additional functionality of providing support for network administrator-defined classes of traffic. </li></ul><ul><li>Using CB-WFQ, you can create a specific class for voice traffic. </li></ul><ul><li>Network Administrator define these classes through Access Lists. </li></ul>
  14. 17. Packet Classification <ul><li>To achieve intended packet delivery, you must know how to properly weight WFQ. </li></ul><ul><li>Packet classification have the different weighting techniques and way you can use them in various networks to achieve the amount of QoS. </li></ul><ul><ul><li>IP Precedence </li></ul></ul><ul><ul><li>Policy Routing </li></ul></ul><ul><ul><li>RSVP </li></ul></ul>
  15. 18. IP Precedence <ul><li>IP Precedence refer to the three bits in the ToS field in the IP Header. </li></ul><ul><li>These three bits are used for eight different CoS </li></ul><ul><li>Enables a routing to group traffic flows based on the eight precedence settings. </li></ul><ul><li>There is no extra signaling involved nor does additional packet header overhead exist. </li></ul><ul><li>Due to these factors IP Precedence is the QoS mechanism that large scale networks used. </li></ul>
  16. 19. ToS (IP Precedence) IP precedence 6 & 7 are reserved for network information. This leaves 6 remaining precedence settings for normal IP traffic flows. Service Type Purpose Routine [Lowest] Set routine precedence (0) Priority Set priority precedence (1) Immediate Set immediate precedence (2) Flash Set Flash precedence (3) Flash-Override Set Flash-Override precedence (4) Critical Set Critical precedence (5) Internet* Set Internetwork control precedence (6) Network* [Highest] Set network control precedence (7)
  17. 20. Policy Routing <ul><li>Policy based routing can configure a defined policy for traffic flows and not have to rely completely on routing protocols to determine traffic forwarding and routing. </li></ul><ul><li>Policy routing also enables you to set the IP Precedence filed so that the network can utilize different classes of service. </li></ul><ul><li>Policies can base on IP Address, Port Numbers, Protocols and the size of packets. </li></ul>
  18. 21. Policy Routing <ul><li>You can used one of these descriptors to create a simple policy , or can use all of them to create a complicated policy. </li></ul><ul><li>All packets receive on an interface with policy based routing enabled are passed through enhanced packet filters known as route maps. </li></ul><ul><li>The route maps decides where to forward the packets. </li></ul>
  19. 22. RSVP <ul><li>RSVP is an out of band, end to end signaling protocol that requests a certain amount of bandwidth and latency with each network hop that supports RSVP. </li></ul><ul><li>If a network hop (Router) does not support RSVP , it moves onto the next hop. </li></ul><ul><li>A network node has the option to approve or deny the reservation based upon the load of the interface to which the service is requested. </li></ul>
  20. 23. Traffic Policing <ul><li>Use to regulate or limit the amount of traffic an application is allowed to send across various interfaces or networks. </li></ul><ul><li>CAR(Committed Access Rate) and traffic shaping tools are similar in that they both identify when traffic exceeds the thresholds set by the network administrator. </li></ul>
  21. 24. Traffic Policing <ul><li>Often, these two tools are used together . </li></ul><ul><li>Traffic shaping is used at the edge of the network(customer premises) to make sure the customer is utilizing the bandwidth for business needs. </li></ul><ul><li>CAR is often used in service networks to ensure that a subscriber does not exceed the amount of bandwidth set by contract with the service provider. </li></ul>
  22. 25. Fragmentation <ul><li>Large packets(1500-byte MTUs)take a long time to move across low-bandwidth links(768 kbps and less). </li></ul><ul><li>Fragmentation breaks larger packets into smaller packets. </li></ul>
  23. 26. Link Fragmentation and Interleaving (LFI) For links < 128kbps Voice Packet Jumbogram 64 kbps 1500 bytes  190ms
  24. 27. Link Fragmentation and Interleaving (LFI) <ul><li>Supported interfaces: </li></ul><ul><li>Multilink PPP </li></ul><ul><li>Frame Relay DLCI </li></ul><ul><li>ATM VC </li></ul>64 kbps
  25. 28. Conclusion <ul><li>QoS is not an exotic feature any more </li></ul><ul><li>QoS allows specific applications (VoIP, VC) to share network infrastructure with best-effort traffic </li></ul><ul><li>QoS in IP networks simplifies their functionality avoiding Frame Relay and ATM usage </li></ul>
  26. 29. ? Questions???