-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Drake Wilson wrote: (snip) > One case that has probably been discussed before (but not in this > thread) is that TCP isn't really good for overlay networks that pass > many concurrent streams. TCP enforces in-order delivery of all the > packets on a connection between two onion routers, when in fact in the > ideal case, this ordering is not required, and only ordering within > streams is necessary. Enforcing full in-order delivery across streams > magnifies the effects of latency and packet loss, and can cause data > rate allocation between streams to be suboptimal; it's literally true > that while one stream is tying up the TCP connection, another cannot > use it at all, even though the streams are effectively preempted after > transferring a certain number of bits in a slice/cell so that the > delay does not become unbounded. (It's rather like pre-emptive > scheduling of multiple tasks on a uniprocessor computer, in fact.) (snip)
This is why in the roadmap for the future of the Tor project, one of the goals is to switch from TCP to UDP as the transport protocol for the overlay connections. Indeed, UDP would be more efficient, since any TCP protocol being tunneled within it would have its own sequencing, etc.; it also would (potentially) allow UDP-based protocols to not only be tunneled, but tunneled efficiently. (It's interesting that this problem was discussed regarding the Hamachi zero-config VPN program; it uses UDP for its encapsulated packets, and allows any enclosed TCP streams to use their own sequencing.) - -- F. Fox Owner of Tor node "kitsune" http://fenrisfox.livejournal.com -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iQIcBAEBCAAGBQJJlXwTAAoJECxKjnsrYHNHqxsP/13Y0IIppWmElZFlUEus1cxY BgB11/nikfAPe5SwyzI7uo7Phm2UbsamqqdpDB34nI4nNrqqLAV+tzyklyOD+mHV 7t8cU5l10w96gdIX9SiBhALPMx0ssKlDLwf1YDBGLwXEJ0VBlhy71GZGwZrYw4UJ LM8JeyyoxxKEsLL6Aaou713B5t8j5lMUyYJ/DmCvHR6gi0JTQLYqXppC3axN1afE afGat+XJCbikOzo/lKnDWQ3Y5BcHNHth1pjYiLBzjhCIs8fjs8WPEVuz/xvPsrGf q7j8Nz2zWuWACca7Td6+Wv3MtajK8uK22cjroHCpbHtef8HLEdUaJ4hgdoF1Vkg2 V8s7XfkX/yaL28cOld4UN+QDm1Uub3+PqUUCyZvMVGuRKj2JKyiPvTf4CfLtyUe5 W1aDUorzml5/i8dAGPgski3PrEmZV6Egrxsh8n5+ed6Bi9xX/885yfjGNXQWyARF fG6dKyjHVVcylVFDYEiGLyiJJsHEKCcCvmj2GKmsMkrJ0igGpJ8jwfaunL3f/LsJ ZIDJITwuJd7+2pKsT3H5SfumBMrsI5PTuAZlVgFUzEcWE3SVZRl1hinGxfxneIw2 QyEEznAYvc+5Uyfzv3g4dY9hPqzKo5ZGZf171WItH0lQXjE98sHwaPSKksPHNx/E /foC+o+3I+PwSfnE8jhJ =X67u -----END PGP SIGNATURE-----
