Computing Your Internet Speed?

john_uy asks: "I am from the Philippines working in a university. We currently have a frame relay E1 link to the Internet. The actual rate that we are subscribed for is 1Mbp/s (CIR) with an option to burst to 2Mbp/s (E1). Internet connectivity is very expensive and we pay around $9,000 every month. I want the best for the university and I just want to make sure that they aren't getting cheated." There are some hard and fast statistics in the article, so please read it to get the details. Based on these numbers, is the University getting the proper bandwidth for it's bucks?

"Here is the situation. On normal days, we get an average throughput of around 250kbp/s on some sites and 700kbp/s on others. This is done using bandwidth testers on around 20 different sites around the world. The 700kbp/s is around the best that we can get on a single computer with a single file download (from Microsoft, CNet, Tucows, Netscape, etc.) For multiple file downloads, we can get a max of around 1984kbp/s (that is if we download around 3-4 files or we download from the telecom company's test server.)

Is this an acceptable service? Initially, I thought having a bandwith this size will give us a download capacity of at least 1024kbp/s with an option to go full blast during the night. What are your experiences with links of similar line rates? What makes a single file download that slow. I know for sure that there may be congestion, router failures, routing instability, etc. If problem existed, it should be temporary (since we test on almost a daily basis.) I have heard from other forums that people can really download at E1 rates even in a Cable/DSL connection.

A hearty 'Thank you!' to you all for your help."

So if you see a broadband connection that offers {x} kbps/downstream and {y} kbps upstream, what kind of speeds are you likely to expect if you are getting your money's worth?

Comments

This says it all

[chuckfee]

>For multiple file downloads, we can get a max
>of around 1984kbp/s (that is if we download
> around 3-4 files or we download from the
> telecom company's test server.)

An E1 connection is 2.048 mbit/s. 1984 kbit/sec
is 1.9375 mbit/sec. 1.9375/2.048 = 94.60%
utilization. Since that 2.048 mbit/sec is the
raw, layer 2 wire speed of the connection
and the 1984kbit/sec is the speed of a
layer 3/4 tcp/ftp transfer you're probably doing
even better than 94.60% since you are not counting
the overhead of TCP/IP and packet sizes.

Also, note that your ISP is only guaranteeing
you E1 speed over the link from you to them. After
that all bets are off. The only valid data
transfers would be from your LAN to theirs and
even then they should be done so that disk
issues aren't skewing the results.

This is what I usually do:

Inside ftp)

ftp> get bigfilename.tar.gz /dev/null

note transfer speed

repeat exactly the same transfer. This should
make sure the remote file is now in disk cache
and should be served to you without any disk
accesses.

ftp> get bigfilename.tar.gz /dev/null

now note the transfer speed here. It might be
a bit higher.

As you've also seen, single transfers won't max
out the connection. If you can run multiple
simultaneous tests and sum teh results you will
probably see slightly higher results.

That being said, I dont' think you have much to
worry about if you are getting 1984kbit/sec over
a 2.048 mbit/sec E1.

If it were me, I'd be running MRTG on the snmp
stats of your router so that you can see exactly
the amount of bandwidth being used. go to
www.mrtg.org, download, compile, install and
sit back. note that mrtg will report direct byte
counts so that you'll get a consistent layer 2
data transfer number rather than mixing layers.

Re:This says it all

[M-G]

Definitely use MRTG to get an idea of your usage. There are also a number of utilities that can make estimates of pipe size between routers: pathchar, bing, etc. These so happen to be covered in a sample chapter on O'Reilly's site:

http://www.oreilly.com/catalog/nettroubletools/c ha pter/ch04.html

Re:This says it all

[morzel]

An E1 connection is 2.048 mbit/s. 1984 kbit/sec is 1.9375 mbit/sec.

I'm afraid I'll have to correct you on your calculations:

An E1 connection is 2048 kbit or 2 mbit - not 2.048 mbit/s.

E1 is actually a bundle of 32 64kbit channels (timeslots) over the same physical medium, where it is either possible to use all 32 timeslots for data (unframed E1), or where 1 64kbit timeslot is being used to transmit timeslot information to the interface placed by the telco (framed E1) - thus having an actual data rate of 2048-64=1984 kbit.

A 1984 kbit connection could well be what the university has ordered, if the telco is using 1 channel for timeslot synchronisation (very common here in Belgium).

Using a large compressed file over FTP for speedtesting is indeed a good way to have an indication of the linespeed, but doesn't cut it to get a good picture.

Using MRTG on your router (probably cisco 2600-ish) will yield far more correct results