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

2. 2.JUNE.200622 All-Wireless Office No wires No switches No APs

3. 2.JUNE.200633 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

4. 2.JUNE.20064 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. 2.JUNE.200655 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

6. 2.JUNE.200666 Don’t We Already Know? Typical evaluation –Select sender, receiver at random; 1 TCP flow, 2 mins –Repeat 100 times, calculate median

7. 2.JUNE.200677 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

8. 2.JUNE.200688 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)

9. 2.JUNE.200699 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

10. 2.JUNE.200610 Mesh Testbed CentralDistantExtreme User 01203 User 02205 User 03207206 User 04208 208,207 User 05209 209,210 User 06211 211,214 User 07226215215,216 User 08225217217,202 User 09218 218,204 User 10227219219,225 User 11204220220,226 Domain Controllers214,215204,226201,227 Source Depots217227201,227 Exchange220202201,227 Proxies216,219201,225201,227 Config Netgear WG Netgear WAB/G ORiNOCO Proxim Transmit Power RTS / CTS Aa-56a-36 100% Ba-56a-36 100%on Ca-56g-10 100% D g-10a-56100% E g-10a-5650% F g-10a-5612.50%

11. 2.JUNE.200611 Light Load, Central Placement

12. 2.JUNE.200612 Heavy Load, Distant Placement

13. 2.JUNE.200613 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"Feasibility Study of Mesh Networks for All-Wireless Offices"

14. 2.JUNE.200614 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