Ping times with Tor running

Scott Bennett bennett at
Mon Jun 29 04:07:55 UTC 2009

     On Sat, 27 Jun 2009 08:47:01 -0700 Kris Linquist <kris at>
>The answer to this may be "yeah, duh.", just thought I'd ask :).   I've 
>got a residential cable connection where I am guaranteed 22mbit down, 
>5mbit up.   My Tor relay BandwithRate is 1000 KB  bursting up to 2000 KB.

     A word of caution is in order here.  In the U.S., some cable ISPs
(e.g., Comcast) falsely market their services, so that you think you are
getting data-rate-based pricing of their services.  I.e., they offer
several different, guaranteed data rates (sometimes with higher burst rates,
though of unspecified duration/conditions for the bursts to get the higher
rates) at different price levels.  What these companies are not telling the
(potential) customers is that what they are *really* selling is a fixed,
maximum amount of data to be transferred, a total of bytes transmitted and
received, per month and that the different price levels are simply different
prices you can pay to use up the monthly limit in longer or shorter times,
none of which amount to more than a small fraction of a month at the
guaranteed data rate.
     If the customer exceeds the maximum amount of data transmitted and
received in a month, the customer will receive a phone call from a division
of that company (possibly previously unknown to employees in other parts of
the company, e.g., marketing, sales, technical support, customer service).
In the case of Comcast, the phone call serves to warn the customer that if
the customer ever exceeds the monthly data allocation again, the customer
will be disconnected for a minimum of twelve months.  The call may arrive at
a time during the month after the initial violation late enough that a second
violation may have already occurred.  In the case of Comcast, the company
division making the call claims to have no knowledge regarding the portion
of the current month's allocation the customer has already used, leaving the
customer totally in the dark.
     The upshot is that a tor node operator on such a network needs to have
read every word of the ISP's acceptable use policy and any other rules lists
the ISP provides in order to find out whether the ISP in question does have
a cap.  Comcast has a 250 GB/mo. cap.  The limit applies to the *total* of
all bytes received plus all bytes transmitted in a calendar month.  Multiply
the average rate of (bytes in + bytes out)/s times the number of seconds in
a month to see what your expected monthly usage is.  Then divide the ISP's
cap by the number of seconds in a 31-day month to see what limit *you* should
apply to your rates to stay out of trouble with your ISP (if your ISP has a
cap).  If your ISP sets a monthly usage cap and you make these calculations,
you will see that the rates you've been marketed are vastly greater than the
rates you've been sold.  Basically, it amounts to fraud, but it would be
difficult to get a prosecution started if the ISP has a cap buried in the
acceptable use policy or other obtuse document.
>While Tor is running, incoming and outgoing pings to the nearest hop 
>goes from ~15ms to ~300+ms.  This is very obvious when browsing.
>Is this expected or do you think it's poor performance by either my ISP 
>or cable modem at accepting many connections?
     Yes, it is normal, as other respondents have already posted.  If you
find it a problem, you will need to apply some sort of traffic shaping/
prioritization.  You didn't mention the operating system you're using, so
recommendations made already may be inapplicable.

                                  Scott Bennett, Comm. ASMELG, CFIAG
* Internet:       bennett at                              *
* "A well regulated and disciplined militia, is at all times a good  *
* objection to the introduction of that bane of all free governments *
* -- a standing army."                                               *
*    -- Gov. John Hancock, New York Journal, 28 January 1790         *

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