1. Mrinalini Sawhney CS-710 Presentation 2006/09/12
A Novel Queue Management Mechanism for Improving Performance of Multihop Flows in IEEE s based Mesh Networks
Nagesh S. Nandiraju et al. ,
2006 IEEE IPCCC
Mrinalini Sawhney
CS-710 Presentation
2006/09/12

2. Contents Introduction Problem Definition Related works
Queue Management in Multihop Networks (QMMN)
Data structures
The QMMN algorithm
Performance Analysis
Performance with UDP flows
Performance with one TCP flow with interfering UDP traffic
Conclusion
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3. Introduction #. of hops bandwidth Wireless Mesh Networks Issues QMMN
Forward traffic in a hop-by-hop fashion
Idea is similar to multi-hop ad hoc networks
Intermediate nodes act as router by forwarding data
Advantage
Extension in the network coverage area without any additional infrastructure
Issues
Bandwidth decreases with an increase in the # of hops
Spatial based throughput performance
Flows spanning multiple hops Vs flow traversing fewer hops
No considertion to # of hops in current queueing mechanisms
#. of hops bandwidth
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4. Problem Definition QMMN The unfairness problem in multi-hop networks
A packet needs to be forwarded by mesh points
Is a fair treatment provided to all flows ? 2 1 3
Internet
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5. Problem Definition - Proof
Mobile Stations forward UDP packets to internet gateway node (AP0)
Communicating using s
based interface
A huge unfairness in the throughput achieved by different flows
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6. Recent Works
Most existing QM scheme -> congestion in the Internet router
RED
Maintains 2 thresholds viz. minth maxth
No flow level differentiation
FRED
No consideration for various issues inherent to multihop wireless networks
Jun & Sichitui [7]
Suggest maintaining a separate queue for each individual source at all relaying nodes
Others
Do not consider link layer buffer management
This paper
Exposes the role of buffer management in the dismal performance of multihop flows - QMMN
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7. Queue Management in Multihop Networks (QMMN)[1/6]
A novel link layer queue management scheme
Guarantees fair buffer share at each intermediate mesh point
Irrespective of the hop length
Depends on -> source node’s granted buffer quota
Data Structures
Each mesh point maintains a fairness table
Field in the table
Source Address
Max_Share
Fair_Share
Occupied_Share
Arrival_rate
Maintains a global variable
residual_share = max_share – fair_share
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8. Queue Management in Multihop Networks (QMMN)[2/6]
max_share – fair_share
AP 1
AP 0
Total buffer space
# of sources in the table
= Max Share
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9. Queue Management in Multihop Networks (QMMN)[3/6]
AP 1
AP 0
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10. Queue Management in Multihop Networks (QMMN)[4/6]
Estimate the average arrival rate of traffic from each source using moving averages
new_fair_share for a source is calculated as,
Finally, fair_share & residual_share are given by
α = 0.3, a good estimate for calculations
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11. Queue Management in Multihop Networks (QMMN)[5/6]
This condition
Makes the residual share is not monopolized by any single source
Limits usage of the residual buffer space by a node
As the MAC layer dequeues packets from the buffer -> update the occupied_share of the corresponding source
At any time, if there is a residual space
A mesh point can buffer more packets than its estimated fair_share
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12. Queue Management in Multihop Networks (QMMN)[6/6]
Main idea
Drop packets from aggressive sources
Limits usage of the residual buffer space by a node
Which packet to drop ?
Packets traversing several hops and
consuming considerable network resources Vs
near by sources
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13. Performance Analysis Simulation Scenario QMMN
QMMN algorithm Vs default link layer drop tail queue
Simulation time ->100sec
Static routing
Constant packet size of 1024 bytes
Packets get forwarded towards the Internet gateway (AP0)
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14. Performance Analysis with UDP flow1 2 3
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15. Performance Analysis with TCP flow1 2 3
TCP
UDP
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16. Conclusions
Buffer management at the intermediate nodes degrades the performance of multihop networks
The role of buffer management in the dismal performance of multihop flows
Controlling the throughput of short hop length flows
QMMN algorithm improves the performance of multihops without changing the MAC-layer
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17. Thank you!!
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