SLIDE 1 BBBBBBBBBBBBBBBB Network Layer Support for Gigabit TCP Flows in Wireless Mesh Networks
This work is collaborated with
- Prof. Ramanathan, Univ. of Wisconsin Madison
Chin-ya Huang
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Outline
– Dynamic change of network environment – Related works
- Spare Bandwidth Rate Adaptive Network Coding (SRNC) Scheme
– Digraph diversity – Inter-flow network coding – Spare bandwidth exploitation – Buffer management
- Evaluation
- Conclusions and Discussions
– Summary of SRNC – Extended research of SRNC
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Motivation
- Growing need of real-time streaming applications :
– HDTV – Video conferencing – Movie on demands
- Characteristics of these applications [Goel et al, TOMCCAP 2008] :
– Long-lived – High data rate for each application (>1Gbps in the future)
- Seamless deliver these applications require
– High physical layer data rate (>1Gbps) – New techniques and protocols at higher layers
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Problems of Mesh Networks
- Mesh networks are able to provide high data link rate
– Gigamesh network provides gigabit physical layer data rate in mesh networks – When data rate exceeds Gbps, packet loss, handoff delays, re-routing,
- etc. would have more severe impact on network throughput
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Impact of different link bandwidth
- TCP throughput drops while the link bandwidth fluctuates.
– When the link bandwidth exceeds 1Gpb, TCP throughput < 50% of the maxflow.
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0.75 0.59 0.31 0.21 0.21 0.74 0.63 0.46 0.42 0.27 0.99 0.99 0.99 0.99 0.99 0.2 0.4 0.6 0.8 1 1.2 10M 100M 500M 800M 1G Normalized TCP Throughput Bottleneck link bandwidth (bps) NewReno CTCP CBR
H I 10 TCP flows 10 TCP flows Cross traffic G C B A
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Spare Bandwidth Rate Adaptive Network Coding (SRNC)
[Huang et al, TMC 2014]
Goal: To develop strategies for improving end-to-end throughput – TCP based
Develop and integrate the following four ideas: – Digraph diversity (direct acyclic graph diversity) – Inter-flow network coding – Spare bandwidth exploitation – Buffer management
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multiple routes [Wang et al,
CoRoNet 2009]
Pro: + More tolerant congestion + Load balance Con:
expensive
Related Work: multipath routing A B C E F G H
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Related Work: forward error correction (FEC)
bandwidth by sending redundant packets to recover packet loss [Medard
et al, INFOCOM 2009]
+ Loss tolerance
network condition
schemes to adaptively exploit available bandwidth
losses due to buffer
1 1 3 3 1 2 1 2 1 A B C E F H G 2 2 3 2 2 1 2
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Motivation of SRNC
- SRNC: Adapt the idea of network coding into unicast transmission
along with previous ideas
- Network coding: linear combination of packets in the queue
- Network coding is first proposed for multicasting aimed to increase
datarate in 2000 [Ahlswede et al, TIT 2000].
- Packets are encoded from the same flow [Medard et al, INFOCOM 2009].
- Specifically, we network encode packets from multiple flows.
We will show that: + Adapts to the changes in available bandwidth in a distributed fashion + Needs much less re-routing
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Outline
– Dynamic change of network environment – Related works
- Spare Bandwidth Rate Adaptive Network Coding (SRNC) Scheme
– Digraph diversity – Inter-flow network coding – Spare bandwidth exploitation – Buffer management
- Evaluation
- Conclusions and Discussions
– Summary of SRNC – Extended research of SRNC
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- Gateway node (A) finds the direct graph in the network for multipath routing
based on the destination (D1, D2).
SRNC: digraph diversity
2 2 1 1 3 3 2 2 1 D2 S1 S2 D1
A B C D E F G
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SRNC: inter-flow network coding
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A B C D E F G
- Packets are encoded from multiple flows.
- All mesh nodes network encode packets before forwarding them.
- Loss of one packet may result in loss of all coded packets.
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SRNC: exploit available bandwidth
- Assume all traffic from A to G without cross traffic
- Each mesh node conditionally sends as many as possible to next hop
– Send additional packets to outgoing links in a distributed fashion 2 2 2 2 3 3 2 2 1 D2 S1 S2 D1
A B C D E F G
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SRNC: buffer management
- Gateway marks appropriate number of packets as high priority
- Each mesh node adaptively manages packets in the queue.
– High priority packets are sent first – Forward high priority packets no more than received – Drop low priority from buffer if necessary H H H L L
a) More bandwidth on outgoing links
H H H L L
b) Buffer overflow occurs
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SRNC: example
Packets are received successfully!
- Although packet loss occurs, packets are still decodable because
SRNC fully and distribultedly utilize the available bandwidth for transmission aimed to recover the packet loss during transmission.
2 2 2 2 3 3 2 2 1 D2 S1 S2 D1
A B C D E F G
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SRNC
- Packets are routed in a routing digraph.
- Packets across different flows are linearly combined before being forwarded to
each mesh node’s outgoing links.
- Each mesh node forwards network encoded packets based on the available
bandwidth. – Number of forwarded packets is not necessary to be the same as received. – Packets are discarded conditionally when necessary.
- Access node reconstructs packets after decoding.
2 2 2 2 3 3 2 2 1 D2 S1 S2 D1 G C F H B E A
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Outline
– Dynamic change of network environment – Related works
- Spare Bandwidth Rate Adaptive Network Coding (SRNC) Scheme
– Inter-flow network coding – Diagraph routing – Forward error correction – Buffer management
- Evaluation
- Conclusions and Discussions
– Summary of SRNC – Extended research of SRNC
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Simulation Configurations
x (Mbps) : Average link bandwidth in the mesh. y (Mbps) : Link bandwidth to the users. Simulation tool: Network Simlator-2 (NS-2) Simulation topology:
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H A B C D G I J x x x x x x x x x x y y y y Internet : Mesh node : TCP sender : Wireless host
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Impact of different link bandwidth
- Maximum possible TCP Throughput = min {y, }
- x = 10 Gbps
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Large Spare Bandwidth Moderate Spare Bandwidth Tight Spare Bandwidth 100 200 300 400 500 600 700 800 900 1000 500M 800M 1G 1.2G 1.5G Average TCP Throughput (Mbps) MR PRO [JK2009] SRNC Link bandwidth between mobile hosts and
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0.5 1 1.5 2 TCP Cross-traffic Before After Ratio of SRNC over MR Throughput
Fairness between heterogeneous flow sets
- TCP Cross-traffic does not implement SRNC.
- The performance of cross-traffic is not effected by SRNC.
- The performance of TCP in SRNC is improved after bandwidth fluctuation.
– SRNC utilizes spare bandwidth to enhance the throughput.
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Effectiveness in Different Topologies
: TCP flows : TCP Cross-traffic flows
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(a) Topo 1 (b) Topo 2 (c) Topo 3 (d) Topo 4 (e) Topo 5 (f) Topo 6 (g) Topo 7
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Effectiveness in Different Topologies
(TCP,Before) (TCP,After) (Cross- traffic,Before) (Cross- traffic,After) Topo 1 0.93 1.98 1 1.05 Topo 2 0.95 5.25 1 1.04 Topo 3 0.95 2.15 1 1 Topo 4 0.9 3.61 1 1.09 Topo 5 0.93 9.11 1 1.36 Topo 6 0.93 4.23 1 1.48 Topo 7 0.93 0.72 1 1.43
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The achieved throughput for TCP and TCP cross-traffic before and after bandwidth fluctuation
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Impact of wireless loss
- Consider wireless loss occurs on each link with independent probability p.
- Approximately, the wireless loss of the mesh is 4p.
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100 200 300 400 500 600 700 2 4 6 8 10 TCP Throughput (Mbps) Overall Wireless Packet Loss Probability (%) PRO [JK2009] SRNC
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Outline
– Dynamic change of network environment – Related works
- Spare Bandwidth Rate Adaptive Network Coding (SRNC) Scheme
– Inter-flow network coding – Diagraph routing – Forward error correction – Buffer management
- Evaluation
- Conclusions and Discussions
– Summary of SRNC – Extended research of SRNC
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Summary
- Link bandwidth fluctuates due to the change of network
environments. – TCP throughput drops significantly when BDP increases. – Network needs to react to the change to sustain the performance.
- SRNC increases TCP throughput by effectively utilizing available
bandwidth in the network. – Four components are involved.
- SRNC shares bandwidth fairly with cross traffic no matter SRNC
is applied or not.
- SRNC is fully distributed and can be integrated in existing
protocol stack and deploying in real network testbed.
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Experimenting with SRNC
- To execute the network coding in a link rate
– Implement on FPGA
- Global Environment for Network Innovations (GENI) project :
– Implementing SRNC in Openflow enabled router. – Evaluating SRNC in network testbed.
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Internet Internet
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Extended research of SRNC
- One characteristic of gigabit TCP flows in the mesh is large bandwidth delay
product (BDP).
- Underwater mesh networks also have large BDP.
– The BDP between gigabits mesh and underwater mesh is similar. – Apply the idea of SRNC to improve the end-to-end throughput in the underwater mesh networks [Huang et al, JSAC, 2011].
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Other Applications of SRNC
- Cognitive radio enabled networks
- Data centers
- Priority based traffic management for real-time flows
- Non-TCP type flows
- Anything else ?
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Thank you for your attention ! Please feel free to contact me by e-mail : yaya.wisc@gmail.com if you have any thoughts regarding this work.
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