Voice Over IP
Birla Institute Of Technology,India
14th
MAY 2008
Pramod Jindal BE266/04
Gaurav Kumar BE222/04
Akansha Nag B...
Today’s Plan:
 VOIP
 Current state of internet
 Differentiated service
 Simulations of existing algorithms
 Limitatio...
How does VOIP work?
• Analogue speech is first converted into 1s and 0s.
• Digital signal is then broken up into packets.
...
Pictorially VOIP
Internet/
Private IP Network
) ) )) ) )
10101010000101010101000010
10010101010101001010101010
10010101010...
Current State of Internet
 Uses best-effort service model
 No guarantee of timeliness or delivery
 No service discrimin...
VOIP QOS Requirements
 VoIP is a time-critical, loss-critical application
 Delay
150 ms max end-to-end delay
 Loss
Slig...
Differentiated service
 Packets entering a router, are first classified based on their e.g.
source address/port, destinat...
IP Header
Scheduling Algorithms
 FIFO (First in First out)
 PQ (Priority queue)
 WFQ (Weighted fair Queueing)
 Proposed Algorith...
Scheduling Requirements
 Isolation and sharing:
 Allow sharing of common resources in a controlled way
 In circuit swit...
Packet Scheduling Algorithm
 First In First Out (FIFO) :The first packet that arrives at a router is the first
packet to ...
Packet Scheduling Algorithm(cont)
 Weighted Fair Queuing (WFQ) : Separate queue for each flow is
maintained by the router...
Simulation Using OPNET
Simulation Snapshot
 Three Scenarios FIFO,PQ,WFQ each with
three traffic classes!
Simulation Results
Simulation Results cont….
Simulation Results cont….
Simulation Results
Simulation Results
 We have implemented and evaluated existing Packet Schedulers
(FIFO, WFQ, PQ) at router level. Through...
Current Limitations and
Motivation
 Undoubtedly WFQ and at times PQ scores well among the existing
algorithms for schedul...
Results Continued…
 With these promising results we wish to model a packet scheduler using PQ
for real time traffic and W...
Algorithm Model
 Since real time traffic is de-queued using PQ instead of WFQ,optimum
performance is reached for services...
Queuing Delay for TCL1 < 8msec, for TCL2 < 20msec, TCL3 < 50msec and
for TCL4 < 80 msec
Simulation Results cont….
Simulation Results cont….
Simulation Results cont….
Simulation Results cont….
Conclusion
 Proposed Algorithm is able to implement differentiated service giving a fair
pie of resources to different tr...
Future Work
• Our simulation results verify the design and correctness of proposed
algorithm
• However still better result...
References
1)http://www.cisco.com/en/US/tech/tk652/tk698/technologies_co
nfiguration_09186a00800a954d.shtml
2)OPNET, http:...
THANK YOU!!
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Research on VOIP

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Research on VOIP

  1. 1. Voice Over IP Birla Institute Of Technology,India 14th MAY 2008 Pramod Jindal BE266/04 Gaurav Kumar BE222/04 Akansha Nag BE17/03 Dr R K LAL Final Project
  2. 2. Today’s Plan:  VOIP  Current state of internet  Differentiated service  Simulations of existing algorithms  Limitations and motivation  Design and simulation of proposed algorithm with OPNET
  3. 3. How does VOIP work? • Analogue speech is first converted into 1s and 0s. • Digital signal is then broken up into packets. • Packets are sent over the Internet and re-assembled at destination and converted back into audio.
  4. 4. Pictorially VOIP Internet/ Private IP Network ) ) )) ) ) 10101010000101010101000010 10010101010101001010101010 10010101010101001010101010 01010100010010101010001001 IP PacketIP Packet 10101010000101010101000010 10010101010101001010101010 10010101010101001010101010 01010100010010101010001001 IP PacketIP Packet 10101010000101010101000010 10010101010101001010101010 10010101010101001010101010 01010100010010101010001001 10101010000101010101000010 10010101010101001010101010 10010101010101001010101010 01010100010010101010001001 ( ( (( ( (
  5. 5. Current State of Internet  Uses best-effort service model  No guarantee of timeliness or delivery  No service discrimination  Bandwidth and network congestion problems
  6. 6. VOIP QOS Requirements  VoIP is a time-critical, loss-critical application  Delay 150 ms max end-to-end delay  Loss Slight loss (lesser than 1%) is tolerable but leads to deterioration of voice quality. Steps need to be taken for correction  However , delay requirement is more critical because a lost packet is better than a late packet
  7. 7. Differentiated service  Packets entering a router, are first classified based on their e.g. source address/port, destination address/port. After that, they are forwarded to the output interface of the router, where they experience a predefined scheduling mechanism.  The packet scheduler is responsible for the order in which the packets of the various queues are dequeued and transmitted in the network.
  8. 8. IP Header
  9. 9. Scheduling Algorithms  FIFO (First in First out)  PQ (Priority queue)  WFQ (Weighted fair Queueing)  Proposed Algorithm :  PQ :real time  WFQ : other traffic with dynamically assigned weights
  10. 10. Scheduling Requirements  Isolation and sharing:  Allow sharing of common resources in a controlled way  In circuit switched network full isolation, no sharing  Under-utilization of resources  Delay Bounds  Either deterministic (guaranteed service) or statistical  Deterministic bounds give the best isolation  Statistical delay bound allow more efficient sharing, less isolation  Bandwidth allocation  When there is a contention for resources, BW must be allocated fairly to all competing flows.
  11. 11. Packet Scheduling Algorithm  First In First Out (FIFO) :The first packet that arrives at a router is the first packet to be transmitted . If a packet arrives and the queue (buffer space) is full, then the router discards (drops) that packet. FIFO offers high cost-efficiency and no versatility.  Priority Queuing (PQ) : Each packet is given a Priority , in the IP Type of Service (ToS) field. Multiple FIFO queues implemented, one for each priority class, still managed in a FIFO manner. Packet are dequeued on basis of priority Drawback: May lead to STARVATION. If a source sends too much traffic with highest priority, may occupy up to 100% of the bandwidth.
  12. 12. Packet Scheduling Algorithm(cont)  Weighted Fair Queuing (WFQ) : Separate queue for each flow is maintained by the router. The router then services these queues in a round robin manner. It compares the weight for each sub-queue with the bandwidth share Advantage : No starvation Fair Bandwidth Bounded Delay
  13. 13. Simulation Using OPNET
  14. 14. Simulation Snapshot  Three Scenarios FIFO,PQ,WFQ each with three traffic classes!
  15. 15. Simulation Results
  16. 16. Simulation Results cont….
  17. 17. Simulation Results cont….
  18. 18. Simulation Results
  19. 19. Simulation Results  We have implemented and evaluated existing Packet Schedulers (FIFO, WFQ, PQ) at router level. Through these Simulations we have shown the relative advantages of FIFO , PQ ,WFQ algorithms • Packet Dropped • FIFO has busty nature and drops significant number of packets. It may work for Best efford traffic but not for real time • WFQ gives near optimum performance • Delay • FIFO: No bounded delay ,PQ : starvation In Packet Networks a dropped packet is better than a late packet. Through these promising results , we wish to model an algorithm that has all the best features of these .We use PQ for real time traffic and WFQ for other types of traffic along with dynamically assigned weights.
  20. 20. Current Limitations and Motivation  Undoubtedly WFQ and at times PQ scores well among the existing algorithms for scheduling however WFQ scheduling has some limitations.  In WFQ schemes, every new packet arrival is stamped with a tag and packets are transmitted in an increasing order of tags. The complexity of WFQ arises from the following sources, of which the second is present in all WFQ schemes. a) Tracking the System State: For the computation of tags to be stamped on new arrivals, all WFQ schemes have to track (with time) the state of the system (called “virtual time” or “system potential”). Each of these events invoke moderate amount of processing. b) Tag Sorting: In all WFQ schemes, before scheduling any packet transmission, it is required to determine which session among has the packet with the smallest tag. Such a tag sorting requirement may become a bottleneck at high transmission speeds. Complexity for the same can be O(n)
  21. 21. Results Continued…  With these promising results we wish to model a packet scheduler using PQ for real time traffic and WFQ for other traffic types along with dynamically assigned weights  A model of our proposed algorithm is something like this, serving different classes of traffic  TCL1-Highly Interactive Traffic  TCL2-Lesser Interactive Traffic  TCL3-Non real time traffic  TCL4-Best Effort Traffic
  22. 22. Algorithm Model  Since real time traffic is de-queued using PQ instead of WFQ,optimum performance is reached for services like voice. Also limitations of WFQ have been eliminated on VOICE traffic  While other services should not starve they are served by WFQ, whose weights are assigned dynamically depending on traffic pattern , which is given near fair bandwidth  It must provide Bounded Delay Fair Bandwidth share Low Latency lesser sorting overhead
  23. 23. Queuing Delay for TCL1 < 8msec, for TCL2 < 20msec, TCL3 < 50msec and for TCL4 < 80 msec Simulation Results cont….
  24. 24. Simulation Results cont….
  25. 25. Simulation Results cont….
  26. 26. Simulation Results cont….
  27. 27. Conclusion  Proposed Algorithm is able to implement differentiated service giving a fair pie of resources to different traffic types  Instead of using a single packet scheduler ,proposed algorithm uses two types of scheduler treating each traffic class separately  Since real time Voice traffic is scheduled by PQ instead of WFQ, the sorting overhead for voice packets for WFQ has been avoided  The delay encountered by each traffic class in our simulations falls pretty much in the tolerable limits as per ITU-T recommended QOS requirements  Advantage is taken of the fact that VOIP is insensitive to dropped packets ( upto 1%) to make a tradeoff between bounded delay and packet loss!
  28. 28. Future Work • Our simulation results verify the design and correctness of proposed algorithm • However still better results can be obtained if we could really vary the weights of WFQ packets depending on traffic pattern • We faced problems in JIT allocations of weights which would not only provide bounded end to end delay but also fair bandwidth share at times when traffic pattern goes unexpectedly bursty! • There is still enough of scope in the betterment of Router Design
  29. 29. References 1)http://www.cisco.com/en/US/tech/tk652/tk698/technologies_co nfiguration_09186a00800a954d.shtml 2)OPNET, http://www.opnet.com/ 3)Lee Breslau, et al., “Advances in Network Simulation, IEEE Computer, Vol. 33, No. 5, pp.59-67, May 2000. 4)Uyless black, Voice over IP, Prentice Hall PTR, 1999. 5)P.J. Kuhn, C.D. Pack and R.A. Skoog, “Common Channel Signaling Networks: Past, Present, Future,” IEEE Journal on Selected Areas in Communications, pp. 381-393, April 1994. 6)Sheldon M. Ross, Introduction to Probability Models, 7th ed., Academic Press, Feb. 2000.
  30. 30. THANK YOU!!

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