What does "bandwidth" mean in cached-routers?

Scott Bennett bennett at cs.niu.edu
Mon Mar 24 03:56:25 UTC 2008


     On Mon, 24 Mar 2008 09:11:40 +0800 "Jackie" <g06b08120301 at email.nbu.edu.cn>
wrote:
>When looking at network maps in Vidalia, we can see the bandwidth of the =
>router denoted as "1286KB/s". But when looking up corresponding records =
>in the "cached-routers" located in tor data directory, it reads in the =
>form of "bandwidth 1024000 2048000 1316902". What does it mean? Does it =
>have any relation with "1286KB/s"?

     1316902 B/s / 1024 B/KB = 1286 KB/s + 38 B/s.  Isn't 1286 KB/s close
enough to satisfy you?  How would you prefer to see it displayed by
Vidalia instead?
>
>Another question about the bandwidth of circuits: I see routers in a =
>circuit having different bandwidth, from xxKB/s to xxxxKB/s. Is the =
>bandwidth of the circuit as a whole determined by the router with the =
>lowest bandwidth? For example: a circuit containing 3 nodes whose =
>bandwidth are 4328, 4317, 327KB/s respectively. Can we say that the =
>bandwidth of this circuit is 327KB/s?

     No, of course not.  Your circuit may well be only one of many circuits
passing through each of those routers.  The sum of the traffic over all
of those circuits passing through a router at a given time is what is
recorded as the "Bandwidth"--which was a really poorly chosen word to
refer to data transmission rates, but which also is now so firmly embedded
in the common parlance that there no hope of correcting it.
>
>By adding "ExcludeNodes" to torrc to remove low-bandwidth routers, can =
>we speed up tor?

     You might improve your own client's performance at the expense of
the rest of the tor-using community's experience.  You might also reduce
the security of your client's anonymity.  It's much the same situation as
for those who wish to limit their client's choices of exit servers.

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><DIV><FONT size=3D2>When looking at network maps in Vidalia, we can see =
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>bandwidth of the router denoted as "1286KB/s". But when looking up =
>corresponding=20

     In the future, please don't post MIME headers or HTML to mailing lists.
It's very wasteful and hard on the eyes, too.


                                  Scott Bennett, Comm. ASMELG, CFIAG
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