[bittorrent] Choking based on network closeness?

Elliott Mitchell ehem at m5p.com
Tue Jul 12 18:49:51 EDT 2005

>From: Bill McGonigle <bill at bfccomputing.com>
> On Jul 11, 2005, at 14:46, Justin Cormack wrote:
> > It came up on the list before, and there were some uses for it. The 
> > main problem is that no one seems to have enough information to 
> > measure closeness, unless you actually work for a large ISP or run 
> > BGP.
> I've looked at a few different techniques that might apply - 
> traceroute, pathchar, packet-tailgating.  Assuming 'closeness' is only 
> one decision criterion I'm not seeing a reason why traceroute wouldn't 
> be sufficient (but tell me otherwise).  You'd have to make some 
> assumptions about how many hops are behind those * * * routers but the 
> core internet routers seem to always respond properly, and that gets 
> you most of the useful big-picture topology.

Much more likely option, you /might/ be able to get the TTL. You don't
want to know about where all the hops are, merely the length of the

> There are certainly broken routers, some edge routers that won't honor 
> the ICMP packets, and probably an OS that won't allow the user to send 
> ICMP packets.  But there is probably enough information most of the 
> time to make a good guess.  And, you'd always fall back to the 'fastest 
> peer' algorithm in the absence of other data.

More pertinent question, how many OSes /will/ allow users to send ICMP
packets? Allowing users to send ICMP packets is a massive security hole,
no serious OS will allow you to do so.

(\___(\___(\______          --=> 8-) EHM <=--          ______/)___/)___/)
 \BS (    |         EHeM at gremlin.m5p.com PGP 8881EF59         |    )   /
  \_CS\   |  _____  -O #include <stddisclaimer.h> O-   _____  |   /  _/
    \___\_|_/82 04 A1 3C C7 B1 37 2A*E3 6E 84 DA 97 4C 40 E6\_|_/___/

More information about the BitTorrent mailing list