We are having some issues with our WAN, where users are saying that things
such as opening Word docs and opening e-mails with attachments are much
slower since a new server was installed last May. The network people say
that the performance is normal. I'm interested in getting some opinions
about whether what they're saying is true.
The WAN goes from Philadelphia to New York. It is a T1 line (not
point-to-point), but uses dedicated bandwidth. It supposedly has 1.5 Mbps up
and 1.5 Mbps down, which are combined for a total theoretical bandwidth of
3.0 Mbps.
Here are some times we're getting.
* To open an e-mail with a 1.3 MB photo attached, it takes about 15-20
seconds.
* To open a Word doc (from within MS Word, using File | Open):
- 20 KB doc: 3 seconds
- 1,800 KB doc: 5.5 seconds
- 20,000 KB doc: 70 seconds.
Similarly, copying the 20,000 KB doc from a network drive to a local C drive
over the WAN takes 70 seconds.
Here's what our network guy says:
"For a 1-byte file, I saw 43 packets between the servers. There's a
minimal delay of about 30ms for each packet (that's counting the
propagation at the speed of light through all the cables and the time
it passes through all the routers between Philly and NY). 30ms isn't
bad by the way. I agree that just taking into account the distance at
the speed of light, a straight wire should be able to cover the
distance in about 2-3ms. So the other 90% of that time must be spent
in packet switching.
"The answer here is that in order to make network disk faster between
the two offices, you either need a faster link with less latency. But
it's actually the latency that is killing us here.
"With larger files, the number of packet exchanges grows. You can see
that simply the distance between NY and Philly is a large contributing
factor to the file opening times."
I don't know if 30 ms is a normal time for a packet to travel between those
two cities, or if the times we're getting are normal, so any feedback is
appreciated. But I do know that there was a definitely slowdown when the new
server was installed last May (though we don't have any times from before
things got slow to compare to), though they're denying that there was.
Thanks.
Neil
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