Appendix F: LAN Auto-find & Proxy configuration

How about an "auto-find" feature for servents running in a LAN?

The idea: Multiple servents running in a LAN could easily find each other and connect automatically. Perhaps on a LAN party or in a home network, servents will find each other without running an additional hostcache or manual configuration (plug'n'play). Similar to multiplayer games where you click on "LAN games" and then you'll see all running servers, no need to configure IP/port manually.

Implementation: Each servent sends a UDP broadcast [1] on startup to the LAN (only internal LAN devices, not to the internet) and every servent will answer with an UDP "pong". The binary data within those UDP datagrams should be identical with Gnutella's ping/pong descriptor (for reusing the existing methods/code!).

There's more... supplementary idea 2: It may usefull to define a servent which is the link to another network segment or to the internet, a superpeer with proxy/tunneling ability. All clients in the LAN will auto find this servent (LAN UDP broadcast again) and then use this superpeer all together to connect to the internet, instead of each and everyone connect on their own.
I think this last feature is very important for two reasons: a) Internet bandwith is used more efficient and b) a superpeer proxy could increase download succes for people behind a NAT router. A NAT router usually allows no incoming connections, peers behind two different NAT routed networks can not share files (also not via Gnutella's push, see here). Such hosts are the majority following Limewire's host statistics [2]. A superpeer proxy in the LAN could be the missing link and reroute/tunnel those requests to the correct servent = more shared files, higher download rate.

Implementation: Similar to UDP broadcasts above, a proxy servent will set the equivalent GUID features bits (bSuperpeer, bProxyTunnel) before answering with an UDP "pong". Additional handshaking headers are needed to negotiate proxying and tunelling [3] between clients and superpeer, topic for further investigations.

Notes: Do also cross check with the 'Your-IP' handshake header in Appendix A, this header is used to tell the local peer (or tunneling proxy peer) the external IP of your NAT router (IPs could be dynamic since most ppl do not have a static IP). Furthermore see Apendix B, the GUID tagging Byte 9 Bits 0-1 define the mentioned superpeer and proxy/tunelling ability.

Result: We achieve a full automatic LAN client find + automatic proxy configuration (elimination of today existing bottlenecks with NAT routers, traffic minimization).

[1] UDP Broadcasts - http://tangentsoft.net/wskfaq/interm...html#broadcast
[2] Limewires's Gnutella Network Size - http://www.limewire.com/index.jsp/size
[3] Gnutella Tunneling - http://groups.yahoo.com/group/the_gd..._discusion.txt (Yahoo account required)