Tema: Re: Apie Zebra ir CERT
Autorius: locked
Data: 2009-08-11 16:05:56
kad Comcast smaukosi su p2p tai tiesa, bet realiai tai kas cia aprasyta nera
ribojimas, jei kai kuriuos connectionus praleidzia, vistiek appsas retryina
tiek kiek jam reikia, ir pagaliau ivykus susijungimui, vistiek greiti galu
gale pasiekia koks galimas. kaip pabaigoje raso kad "it relies on the P2P
protocol being used to either find another peer (hopefully a Comcast one)",
tai toks ispudis kad visa sita smaukyma daro norint trafika koncentruoti
labiau ISP viduje, bet tada kyla klausimas kodel tiesiog neriboja greicio
ISP-OUTSIDE sessionams, paliekant ramybeje ISP viduje (atrenkant pagal IP
range) cirkuliuojancius connectionus, ir vietoje to pisasi su VISAIS p2p 
connectionais _tikedamiesi_ kazkokio efekto, tikedamiesi kad kitas 
connectionas jau kreipsis i viduje ISP esanti peera, nebent cia kazkoks 
useriukas tiesiog kreivai aprase procesa.

"Bone Daddy" <.info@bonedaddy.serveftp.com> wrote in message
news:h5rn85$b33$1@trimpas.omnitel.net...
"PxYra" <nera@nebus.net> wrote in message
news:h5rl9l$7r9$1@trimpas.omnitel.net...
>
> daugiau kuo shustresne versija tada ir vaidenas visokie leti uzsieniai P2P
> ribojimai ir kitos nesamones,   ? ? ?

HOW IT WORKS:

- The Sandvine application reads packets that are traversing the network
boundary

- If the application senses that outbound P2P traffic is higher than a
threshold determined by Comcast, Sandvine begins to interrupt P2P protocol
sequences that would initiate a new transfer from within the Comcast network
to a peer outside of the Comcast network

- The interruption is accomplished by sending a perfectly forged TCP packet
(correct peer, port, and sequence numbering) with the RST (reset) flag set.
This packet is obeyed by the network stack or operating system which drops
the connection.

In eDonkey connections, for example, queued UPLOADS (to others) will not be
honored to some percentage of non-Comcast P2P users. Immediately after the
peer requests ranges to be transferred, the connection is dropped in the
above manner. Gnutella transfers are similarly affected in the same manner.

In BitTorrent connections, the RST message is sent well after the handshake,
and often after some data has been exchanged. The Sandvine filter interferes
during lulls (NOOP and HAVE commands) as well as the moment of transition
from the ending of sending one complete piece. When I am not using Comcast,
BitTorrent disconnections due to peer resets (RST flag) are 3%. Using
Comcast, 39% of connections are terminated using the RST flag.

In Summary: The Sandvine filter has taken steps to try to make the filtering
experience innocuous (nearly invisible) to the user. Some transfers are
allowed, the interruption seems to come from the distant peer, and it relies
on the P2P protocol being used to either find another peer (hopefully a
Comcast one) or retry that peer later.