Transcript UDL Mesh Network over DVB-S
Implementation of IP Mesh Network using ULE Protocol over DVB-S Links
Ang Way Chuang ([email protected]) Wan Tat Chee ([email protected]) Network Research Group School Of Computer Sciences Universiti Sains Malaysia 11800 USM, Penang, Malaysia.
Introduction
Satellite-based Internet connectivity • Provides access to rural / underserved communities • Able to operate in areas without existing telecommunications infrastructure • Quick setup for disaster relief and recovery efforts (e.g., earthquakes, tsunami, etc.) April 12 2 (c) 2006 TC Wan
Issues
Existing satellite-link based Internet access equipment is expensive Existing technology has inefficient spectrum usage Existing hub-based network averages two hops among nodes (high latency) DVB-S is a cost-effective method used in satellite TV broadcast (e.g., Astro) However, It is unidirectional in nature Unidirectional Link Mesh Network implements bidirectional network access using DVB-S technology April 12 3 (c) 2006 TC Wan
Existing Point-to-Point Satellite Links April 12 (c) 2006 TC Wan 4
UniDirectional Link Mesh Networking Approach April 12 (c) 2006 TC Wan 5
Hardware Requirements
An ASI (Asynchronous Serial Interface) card to transmit MPEG2-TS packet (Linear Systems’ DVB Master FD).
(N – 1) DVB receiver cards where N is the number of nodes in the UDL mesh network. List of supported DVB receiver cards: http://www.linuxtv.org/wiki/index.php/DV B-S_cards .
A DVB-S modulator (Newtec NTC2177).
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Node Configuration (for 3-Node WAN network)
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Configuration for 3 Nodes Test Bed
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Bidirectional DVB-S ULE Architecture April 12 (c) 2006 TC Wan 9
Experiment and Result
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Experiment and Result (cont)
Throughput for TCP Unicast v.s. TCP Window Size
2000 1800 1600 1400 1200 1000 800 600 400 200 0 1 14 27 40 53 66 79 92 105 118 131 144 157 170 183 196
Time (s)
TCP WS 216KBytes TCP WS 180KBytes Log. (TCP WS 216KBytes) Log. (TCP WS 180KBytes) April 12 (c) 2006 TC Wan 11
Experiment and Result (cont)
Throughput Comparison for TCP Unicast on 8Mbps DVB-Mesh v.s. Benchmark on 10Mbps Wired LAN
10000 9000 8000 7000 6000 5000 4000 3000 2000 1000 0 1 15 29 43 57 71 85 99 113 127 141 155 169 183 197
Time (s)
Benchmark 10Mbps Wired LAN TCP WS 216KBytes 8Mbps UDL Mesh TCP WS 216KBytes Log.
(Benchmark 10Mbps Wired LAN TCP WS 216KBytes) Log. (8Mbps UDL-Mesh TCP WS 216KBytes) April 12 (c) 2006 TC Wan 12
Experiment and Result (cont)
Throughput for UDP Unicast v.s. Offered Load
7000 6000 5000 4000 3000 2000 1000 0 1 2 3 4 5
Time (s)
6 7 8 9 1Mbps 2Mbps 3Mbps 4Mbps 5Mbps 6Mbps 7Mbps 8Mbps April 12 (c) 2006 TC Wan 13
Experiment and Result (cont)
45% 40% 35% 30% 25% 20% 15% 10% 5% 0%
Average Packet Loss for UDP Unicast
5Mbps 16% 1Mbps 0% 2Mbps 0% 3Mbps 0% 4Mbps 0.18%
Bandwidth Type
6Mbps 29% 7Mbps 32% 8Mbps 40% April 12 (c) 2006 TC Wan 1Mbps 2Mbps 3Mbps 4Mbps 5Mbps 6Mbps 7Mbps 8Mbps 14
Experiment and Result (cont)
Throughput Comparison for TCP Unicast and UDP Unicast
4500 4000 3500 3000 2500 2000 1500 1000 500 0 1 13 25 37 49 61 73 85 97 109 121 133 145 157 169 181 193
Time (s)
TCP (Window Size 216KBytes) UDP (Bandwidth 4Mbps) Log. (UDP (Bandwidth 4Mbps)) Log. (TCP (Window Size 216KBytes)) April 12 (c) 2006 TC Wan 15
Analysis of Result
All UDL nodes are allocated 8Mbps of bandwidth for the tests.
The throughputs of TCP and UDP traffic are about 1/2 and 1/8 of allocated bandwidth respectively.
ASI card buffer queue affects the latency of packet sending. Less buffer queue decreases latency, but increases CPU usage due to more interrupts and context switches.
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Analysis of Result (cont)
Faulty ASI card firmware disables automatic null packets insertion. Thus bidirectional module need to insert null packets manually.
Consequently, real data packets have to compete with null packets for resources. Thus the performance is less than ideal.
Due to high latency, bigger TCP window size results in better throughput.
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Future Work
Reimplemention of bidirectional module as a kernel space module to cut the cost of context switches and improve performance.
Try to obtain an ASI card that properly insert null packets automatically.
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Links & Contacts
IP over DVB-S via ULE research page: http://nrg.cs.usm.my/satellite_ule.htm
Bidirectional module research page: http://nrg.cs.usm.my/ule.htm
Coordinator: [email protected]
Developers: [email protected]
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