1. 7DS Seven Degrees of Separation Suman Srinivasan IRT Lab Columbia University

2. Problems with Wide Area Wireless 802.11 currently hard to deploy across city or large area Problem: How can mobile devices / gadgets get information? Solution: 7DS!

3. Concept Use local peer-to-peer wireless networks to exchange information –Peers can get information they do not have from another peer Once wireless 7DS network set up, it could be used for any purpose –Getting web pages from peers –Sending e-mails –File transfer to selected client

4. Illustration In the absence of the Internet, nodes can exchange information amongst themselves Internet

5. Design Peer-to-peer network set up using zeroconf –Protocol enables devices to get IP address and communicate without a DHCP / other server Proxy server serves content –If connected to Internet, functions normally –If not connected, connects to peers to get information

6. Design Search engine –Allows self / peers to search within the device’s database for necessary information Multicast querying system –Allows peers to query systems in peer- to-peer network –Searches can be for files or keywords Transport System –To forward e-mail

7. Design

8. Connection & Proxy Server Connection set up using zeroconf protocol –Similar to AppleTalk, Microsoft NETBIOS, Novell IPX –Uses link-local addressing, multicast DNS, DNS service discovery Proxy server –Peer’s user client uses localhost proxy server by default –Detects Internet connection availability –If Internet, normal network operation –No Internet, peer-to-peer data exchange

9. Search Engine Provides ability to query self for results Searches the cache index using Swish-e library Presents results in any of three formats: HTML, XML and plain text Similar in concept to Google Desktop

10. Query Multicast Engine Used to actually exchange information among peers Requesting peer broadcasts a query to the network Responding peers reply if they have information –Send encoded string with list of matching items Requesting peer retrieves suitable information

11. Conclusion 7DS allows data retrieval and transmission, even in absence of Internet Exchange of information within local network –Nodes that eventually connect to larger network facilitate new information exchange No user intervention unless absolutely necessary New step in practical, large-scale wireless networking with gadgets? –Remains to be seen