[bittorrent] Choking based on network closeness?
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.
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