Mrinalini Sawhney CS-710 Presentation 2006/09/12 A Novel Queue Management Mechanism for Improving Performance of Multihop Flows in IEEE 802.11s based Mesh Networks Nagesh S. Nandiraju et al. , 2006 IEEE IPCCC Mrinalini Sawhney CS-710 Presentation 2006/09/12

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 QMMN

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 QMMN

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 QMMN

Problem Definition - Proof Mobile Stations forward UDP packets to internet gateway node (AP0) Communicating using 802.11s based interface A huge unfairness in the throughput achieved by different flows QMMN

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 QMMN

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 QMMN

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 QMMN

Queue Management in Multihop Networks (QMMN)[3/6] AP 1 AP 0 QMMN

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 QMMN

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 QMMN

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 QMMN

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) QMMN

Performance Analysis with UDP flow 1 2 3 QMMN

Performance Analysis with TCP flow 1 2 3 TCP UDP QMMN

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 QMMN

Thank you!! QMMN