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Is an Office Without Wires Feasible?

Is an Office Without Wires Feasible?. Sharad Agarwal Jakob Eriksson, Victor Bahl, Jitu Padhye. All-Wireless Office. No wires No switches No APs. 2. All-Wireless Office. Not large corporation Small offices 10-100 PCs Rapid deployment Short-term office Low-cost solution

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Is an Office Without Wires Feasible?

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  1. Is an Office Without Wires Feasible? Sharad Agarwal Jakob Eriksson, Victor Bahl, Jitu Padhye

  2. All-Wireless Office No wires No switches No APs 2

  3. All-Wireless Office Not large corporation Small offices 10-100 PCs Rapid deployment Short-term office Low-cost solution Not replacement for wire • Looking for good performance • how long a user waits for a transaction • small additional delay 3

  4. All-Wireless Office • Office PCs • Two 802.11 interfaces • simultaneous xmit & rcv on non-interfering channels • frequency diversity; range-rate tradeoff • Office servers • mail, domain controllers, code repositories • proxies with wires • Mesh routing • A lot of prior work • Routing protocols • Link quality metrics

  5. Questions • What additional delay penalty will a mesh network impose • In typical office configurations • With typical office traffic • How should an administrator pick : • Wireless hardware • IEEE 802.11 band • Routing metric • User-server placement • Spatial reuse, hidden terminal 5

  6. Don’t We Already Know? Typical evaluation Select sender, receiver at random; 1 TCP flow, 2 mins Repeat 100 times, calculate median 6

  7. Methodology • Capture traffic from 11 office users • Packet level capture insufficient • TCP effects in wireless, multihop very different • Socket level is best: open, send, receive, close • Replay on mesh testbed among office users • MCL by Draves, Padhye, Zill @ MSR (2004) • DSR-like routing with virtual link layer optimizations • Link metrics: hop, RTT, PKTPAIR, ETX, WCETT • Assign users, application servers to testbed • Examine several design choices • Not disrupt actual users 7

  8. Captured Traffic • Very diverse traffic types, sizes, concurrency • Map each type to 1-2 mesh machines for replay • Non-winsock traffic not captured • Get user RPC; miss SMB, NBT (almost all IDS for us) 8

  9. Replay Model • Concurrent sessions • Session • connect to disconnect • multiple transactions; not concurrent • Transaction • 1 send, 0+ receives • Response time • start of send • end of last receive of the transaction 9

  10. Mesh Testbed 10

  11. Light Load, Central Placement 11

  12. Heavy Load, Distant Placement 12

  13. Summary of Results • Results are unusual • Captured traffic is very different than synthetic • Prior work’s throughput results not very helpful • Many configurations – median delay <20ms • 802.11 hardware had upto 2.5x difference • 802.11 band had upto 2x difference • Server placement had upto 3x difference • No benefit of spatial reuse, hidden node avoidance • 2 routing metrics bad, 3 good & very similar • "Feasibility Study of Mesh Networks for All-Wireless Offices", in ACM Mobisys, June 2006 13

  14. Open Issues / Limitations • 1 testbed, 1 set of user traces • but many configurations, different time periods • Performance can be improved further • cross interference detection & adaptation • gateway balancing • Skipped some real world issues • fairness • security / DoS • Jamming, routing disruption, resource consumption 14

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