Hyacinth An IEEE based Multi-channel Wireless Mesh Network

Transcription

1 Hyacinth An IEEE based Multi-channel Wireless Mesh Network 1

2 Gliederung Einführung Vergleich und Problemstellung Algorithmen Evaluation 2

3 Aspects Backbone Last mile access stationary commodity equipment 3

4 Architecture Mesh HYACINTH wireless toilet control 4

5 Work done until now with MAC modifications 1 NIC multiple channels -> packet by packet Multiple NIC -> 1 fixed channel / NIC Centralized channel assignment Load unaware Improvement: no control interface 5

6 Work done until now 2 Load-balancing Number of packets Number of paths here: traffic/node + bandwidth of link on path Greedy algorithm: Node with least load Furthest node } durch Node/Interferenz Zone here: load from interfering nodes + bandwith of nodes here: Mobile Agent Paradigma + Traffic Profiling 6

7 HYACINTH Design Gateway Link: wire /16 Mobile = 1 NIC ähnlich Infrastruktur Quelle:hyacinth-infocom.pdf 7

8 Channel Assignment Problem Different to Mobile Networks: graph not connected under certain circumstances goal: keep connection, build many collision domains 2 subproblems (!) Neighbor Interface Interface Channel 1 NIC n neighbors 8

9 Channel Assignment Problem # channels/node # NIC 2 nodes communicating = 1 channel Channel Raw capacity limited in interference zone Number of channels fixed (non overlapping) graph coloring? No edge coloring No node multicoloring No constrained edge coloring 9

10 Load Balancing + Metrics Internet access Enterprise server access No network bottlenecks Maximizes network throughput 10

11 Algorithms Old: central channel assignment Knowledge: topology + traffic NP hard (multiple subset sum P channel assignment) new: distributed algorithms mobile agents 11

12 Algorithms Load Balancing 1. Routing Tree Construction - similar 802.1D (MAC Briding) - Differences: parent = dynamic, load aware channel assignment ADV 1 Internet - T a ADVERTISE packet (distance metric) X ACCEPT - gateway only down the tree JOIN ADV 2 - send JOIN packet send ACCEPT packet Y 12

13 ACCEPT Message Algorithms Load Balancing - channel(s) information + IP for forwarding X = parent of Y Y sends LEAVE packet Y sends ADV packets to +1 neighbors X ADV 1 Internet ACCEPT LEAVE Route updates: RT_ADD + RT_DEL ADV 2 JOIN Y ADV 3 13

14 Algorithms Load Balancing Routing Metric: 1. hop count (static) JOIN, ACCEPT, LEAVE reliable (top of UDP) Neighbor Discovery: HELLO packets HELLO,ADVERTISE broadcast, unreliable 2. gateway capacity (dynamic) 3. path capacity (dynamic) } Route ping pong - BGP? - REJECT, RT_ADD updates capacity 14

15 Algorithms Channel Assignment 1. Neighbor Interface - channel dependency - introduce UP-NICs + DOWN-NICs - gateway: only DOWN-NICs - lower priority on lower tree levels - more DOWN-NICs (collect bandwidth) 15

16 Algorithms Channel Assignment 2. Interface Channel - CHNL_USAGE packet - (k+1) neighbors (k = interference range) - total channel load = (aggr.) traffic + # nodes (weighted) search least used channels - higher nodes = higher prio. (higher bandwidth) fat tree architecture - T c channel load balancing time, CHNL_CHANGE packet 16

17 Packet Overview ADVERTISE, JOIN, ACCEPT, REJECT, LEAVE RT_ADD, RT_DEL CHNL_CHANGE, CHNL_USAGE HELLO much packets but low load on network Convergence time + Overhead depends on load balancing period: 20s-50ms+12Kbps ; 60s-100ms+5Kbps 17

18 Algorithmen Virtual Control Network + Failure Recovery Control NIC (common channel) or VCN New node scans for HELLO on all channels (5-10sec) 1 NIC scans, 1 NIC receives on 1 channel Remember other ADVERTISE packets JOIN to backup node FAILURE packet to children if no backup available Children might know a route 18

19 Evaluation ns-2 extension (mult. NICs per node) 12 channels (802.11a), 2 NICs Interference range: 2 Channel Load Balancing: 1 min. CHNL_USAGE, ADVERTISE: 30 sec. 10 scenarios with 60 nodes on 9x9 square Random traffice (0-3Mbps) Saturate network (until only 80% can be routed) Ns2: PACKMIME extension (REQ,RESP times random) 19

20 Evaluation Indentical CA +MR-LQSR each gateway seperate channel Results Baseline: Single-channel net Identical CA: 2x improvement Centralized CA: 6-7x gains Distributed CA: 6-7x gains Single-NIC Multi-channel: only marginal improvement 20

21 Evaluation 21

22 Evaluation 22

23 Evaluation 23

24 Evaluation 24

25 Evaluation 25

26 Evaluation 150 ms detection 450 ms route prop ms channel switching 26

27 Evaluation Real World Traffic Changes network converges after 2 load balancing periods Almost same like ns2 Windows 2/3 NICs (channel switching speed) at 1mW, external antenna 20 x 10m lab FTP traffic 27

28 ENDE 28