Intermittently, my internet connection becomes really slow. The download
speed seems to be OK (650 -700 kbps) but I periodically show a latency period
as high as >3600 ms. My ISP says that is normal but I don’t think they know
what they are talking about.
I used to be with your ISP (the original question called out the ISP by
name), and, well … let’s just say I’m no longer with them.
There are several reasons that internet speeds can vary, but in general I
wouldn’t expect latency (the time it takes for a response to arrive) of over
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Off the top of my head, here are some reasons you might be seeing those
Activity on your own machine. I suspect this is not the case, but I do have
to call it out since it could be a biggie. Basically anything else you’re doing
on your machine that accesses the internet could be adversely impacting the
speed tests that you’re running. Of particular note are viruses that may have
planted a spam-bot on your machine. They’ll periodically start sending big
batches of spam which could certainly affect your apparent internet speed.
The quality of your phone line. I ran into this myself some
years ago. Turned out I had a noisy phone line, that was impacted by water
seeping into the wires underground. Once the telephone company came out,
discovered and fixed that, life was good. Even with my more recent T-1
installation, the technicians had to switch the wires used because of the poor
signal quality of the originally selected pair.
ISP Traffic. Even though your DSL connection to your ISP is dedicated only
to you, at some point “upstream” it is aggregated with the internet traffic of
others. Cable users see this most frequently, since their bandwidth is
not dedicated, but rather shared with their immediate neighbors. If
there’s something happening to use up all resources after your connection is
aggregated with others, the impact might well be reduced performance.
Traffic at “the other end”. I’m going to assume that you’re seeing a general
problem across all of your internet connections, but if it’s a problem with one
particular site or service, the issue could easily be at their end.
A poor quality or dying DSL modem. I experienced this as well. Rather than
just fail outright, I have seen DSL modems die a slow death, and performance is
often one of the early warning signs.
Problems with your own network card or equipment. This needs to be included
for completeness. One of the things that most ISP technical support people will
tell you to do is to disconnect everything but one computer from your
connection, and test it that way. It’s annoying, but there’s a reason: this
eliminates all of your other equipment, such as routers, switches and other
computers, from impacting the results. In your case, it would be interesting to do
exactly that, and then see if the result change if you use a different
Unfortunately, as you can see, there are many places to potentially point the
finger. A good ISP will help you diagnose at least somewhat, or perhaps put you
in contact with the data side of your local telephone company that actually
provides the physical connection into your home. (As an aside, even though your
ISP and your telephone company might share a name that does not mean
that they are the same company, or that even if they are that the two divisions
work well together. Often, it’s just the opposite.)