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Is an Office Without Wires Feasible?

This study evaluates the feasibility of all-wireless offices without wires, switches, or APs, focusing on small setups with 10-100 PCs for rapid deployment. It examines performance, user wait times, hardware selection, routing metrics, and more. The methodology involves capturing diverse traffic types from office users, replaying on a testbed, and analyzing various design choices. Results show differences in hardware, band effectiveness, server placement impact, and routing metrics. This ACM Mobisys study from June 2006 presents findings, open issues, and potential limitations, offering insights for implementing wireless office setups effectively.

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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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