How can I test actual modem performance?
How do I check for line noise on a phone line?
How do I upgrade from my current 56k to V.90?
How does the V.90 technology work?
What are typical 56K connect speeds?
What can the MTU settings do for my Internet connection?
What is MTU?
What is the difference between KB/s and Kb/s?
Why can't I find Dial-Up Networking on my system?
Why do I connect fast but seem to slow down after
a while?
Why do I need TCP/IP installed?
Why does it say that I'm connected at 115,200 bps?
Why does my modem connect at 26,400 bps or slower?
Why does my modem continue to connect at slow speeds?
Why does my modem keep getting disconnected?
Why does my USR Sportsters get slower and slower,
and then suddenly disconnect?
Why doesn't my connection ever connect at 56K speeds?
How can I test actual modem performance?
If done correctly, file downloads are an excellent way to test
modem performance. The trick is to make sure you're really testing
the modem's raw transfer rate, and not some other factor that
you're not aware of.
Here are some guidelines for download testing:
· USE AN FTP PROGRAM
Web browsers often fluctuate to much to accurately measure download
rates. FTP is more reliable. Note that some FTP programs reports
download speeds in Kilobits per second (Kbps), while others use
Kilobytes per second (KBps).
· DOWNLOAD A COMPRESSED .ZIP FILE
If the file you download isn't compressed, hardware data compression
in the modem will kick in, leading to erroneous results. Different
file types compress to different degrees, so if you download a
Microsoft Word file as opposed to a QuickTime movie, there's no
way to compare the results. Use a .zip (PKZip/WinZip) file for
your tests.
· DOWNLOAD A FILE THAT'S AT LEAST 200K
A file size of at least 200K will help minimize the effects of
a slow start. The larger the file, the more accurate the results.
· DOWNLOAD FROM YOUR LOCAL FTP SERVER OR UNIX DIRECTORY
A local server is one that's run by your ISP, not on the other
side world. If you download a file from across the Internet, you're
testing your ISP's connectivity to the Internet just as much as
you're testing your modem.
Our FTP site is ftp.konnections.com
How do I check for line noise
on a phone line?
Listening for noise:
First you need to get rid of the dial tone so you can really
listen to the line. Dial a number, any number but obviously one
which is valid for your area, so that you don't get the dial tone
replaced by a busy signal. The easiest and most common across
all areas is a '1'. Is your dial tone gone? Now listen and really
concentrate, because you are only going to get 30 seconds, before
times run out and gets replaced by a busy signal.
This is the first major step to checking if you have a good line
for a modem or not. Is it quiet? No pops, bangs, crackles, creaking,
or faint voices in the background from other people's conversations.
All or any of these noises will cause you a problem on a high
speed modem.
Just what are these noises?
Well, it can be something as simple as a loose screw on a connector
block somewhere between you and the exchange, or water getting
into one of Telco’s cable ducts and the waterproofing (around
the cable joints) has started to break down. You could have a
bad connection in the house somewhere, and not necessarily on
the line extension that's feeding your modem. Other people's conversations
(called 'crosstalk') are not so easy to pin down, and are usually
more likely to be further 'into the system' before the source
becomes apparent.
Check the Phone
Let's presume you have one of these noises to some greater or
lesser degree. Next you need to check the phone itself. After
all, if it's just the phone causing the noise, it won't affect
the quality you get from the modem now. If you have a spare phone,
take it and plug it into the same socket and then check for noise
again. If you don't have a spare phone, it might be worth heading
to the local electronics store to pick up an inexpensive phone.
Checking the Modem connector
Let's assume now that you are happy with the perceived 'quietness'
of the line. Now you move to the modem. How can you check if you
have a dodgy plug or socket associated with the modem? Well, surprisingly,
it's reasonably simple but you'll need to be fairly quick in carrying
out the next 'test'.
What you are going to do is to get the modem to go on line,
but not actually dial out a full number (similar to what you did
just now but using the modem instead). To do this you'll also
need to have a phone plugged in, too, that's fairly near to where
your PC/Modem are. Don't pick up the phone yet.
You're about to enter a command string to the modem, so you'll
need to have the PC powered up and talking to the modem with whatever
piece of communication software you use. Don't dial out a number.
The following steps will require AT commands to be sent to the
modem.
Now type this: 'ATX0D1;' (without the quotes) and what you should
hear (if you have the modem's speaker on) is that the modem will
pick up the line (dial tone heard), then dial a 1 and finally
drop back to command mode (OK prompt on your screen) while holding
the line open. The next bit is easy or more difficult depending
on the accessibility of your modems’ leads. i.e. internal
or external modem. Now pick up the phone and listen.
This time, it's going to be your modem that may 'time out' before
your phone line does. Check the modem's lead, plugs and sockets
by physically getting hold of them and just gently pushing and
pulling on the lead at both ends. You'll find on these type of
plugs that there is possibly a couple of millimeters of 'play'
even when the plug is fully seated in it's socket. This is enough
for our purposes. Again, be gentle. If there is a dodgy connection,
it won't take a lot of movement before it becomes apparent in
the phone you are listening to.
No noise? If the modem hasn't already timed out, drop the line
send the 'ATH' command. If you did hear some crackling from that,
then you'll need to get that lead replaced. It could be just the
contacts of the plugs that have become a little tarnished. A good
ink eraser with a fairly sharp edge should clean these up nicely
Test for Line level and Eye Quality Monitor.
Modems With a Rockwell Chipset:
You've carried out all the above and you are still getting poor
speed connections with your modem. Now it's going to matter exactly
what type of modem you have, and whether it has a Rockwell chipset
in it or not. How do you find out? The easiest way (and most standard)
is to type either AT&V or ATI4. If you have a Rockwell chipset,
you'll see a complete configuration dump starting with 'Active
Profile' then 'Stored Profile 0' followed by 'Stored Profile 1'
and finally 'Telephone Number Stores'. The latter should return
a couple of rows of checksum digits (up to 4 rows) which are the
capabilities of the modem in 'hex.'
If you have a Rockwell chipset, follow this procedure:
1. Dial into another modem [a BBS or other service provider]
from a terminal screen (not automatic with a script - manually)
2. Do whatever you need to get your Login prompt [if your service
does immediate PPP or immediate TELNET, use a different service].
3. Pause (do nothing) for at least 1 second.
4. Type '+++' (without the quote marks - just the pluses)
5. The modem should now have dropped back into command mode and
you should be looking at an 'OK' prompt *but* you will still be
online. (You'll need to be fairly sprightly, as you may lose the
connection if you aren't quick enough...)
6. NOW you can type AT%L%Q [Return]. The modem should return
2 figures on successive lines like 20 8 or something. These are
the Line Level (%L) in -dbm and the Eye Quality Monitor (%Q) index.
In the example above, that would be -20dbm (reasonable) and 8
(also reasonable). Higher figures mean worse connections. Anything
higher than about -24 with the first, and you'll be seeing bad
connections or possibly none at all. Higher than 15 on the second,
and you've got real line problems on your circuit that your Telco
should be able to sort out.
When you've finished, you might like to go back online with ATO
(not zero) and then log off normally. You *may* find you get logged
off anyway after you've got the response to %L%Q. If you do get
bad figures from these tests, you'll need to contact your Telco
to try and get your line improved.
Other Modems:
If you have a USR based modem (and there are some 'badge engineered'
models about), then chances are you will be able to use ATI6 for
your checking. This can be done either online (see above for how
to stay online but get back to command mode...) or offline, as
the USR chipset 'remembers' the figures it got from the last connect
you made. The bits you are interested in are BLERS. These are
'Bit Link Error RateS'. Ideally, this figure should be 0. If it
is 1 or 2 after you have been online for a while, then you probably
have nothing to worry about. If it climbs much higher over, say,
a 3-4 minute connect, then you are probably suffering from noise
or low level or both, as in the Rockwell situation above. If you
want to know what the rest of the figures mean, consult your modem
manual. Unfortunately, the USRs do not give an indication of the
actual received carrier level in decibels/milliwatt (dbm).
If you have neither of these types of modem, then you are going
to have to consult your manual.
If you've got noise and a low line level, you need to contact
your Telco provider. Explain to them that you are using a modem
on your line, you are getting poor cct quality figures from your
modem, and that the line level is low. You are entitled to have
this problem corrected. Make sure that you say there is nothing
wrong with your normal voice communications (if that is the case...),
otherwise they will just do a normal line check. If you are on
a digital exchange, ask them if you can have the AGC (Automatic
Gain Control) turned OFF and your line setting at the exchange,
set to position '5'. In most cases this should give you a good
cct and level and cure your connect problems at a stroke.
How do I upgrade from my current
56k to V.90?
Here's an easy guide to upgrading a 56k modem to the ITU's V.90
56Kbps Standard.
Step #1:
Find out if your ISP has upgraded to V.90. Before 56K modem owners
can connect to their ISP using the ITU's new V.90 56Kbps standard,
the ISP first must implement V.90 in its central-site modem equipment.
Those ISPs who have not yet offered any type of 56Kbps Internet
access service are also expected to very quickly implement V.90
in the coming weeks and months. Most believe it will be several
months until the majority of ISPs finish their upgrade to V.90.
Before and after that upgrade is completed, all ISPs who previously
offered 56K service will continue to offer 56K service.
Step #2:
Decide if you're really a candidate for an immediate V.90 upgrade
-- if you're already happy with your ISP's 56K service and have
no immediate plans to switch to another ISP, there is no immediate
need to upgrade to V.90.
Step #3:
If you do decide to upgrade to V.90, check with your modem manufacturer
regarding specific procedures. The most common procedure will
likely be a simple software download from your modem manufacturer's
web site, but the exact procedure is up to each manufacturer.
Step #4:
Also have your modem manufacturer describe how your 56K modem
will allow you to easily alternate between V.90 and 56K, if necessary.
The upgrade path that many modem manufacturers have developed
for their customers is designed to give modem owners backward
compatibility with 56K, even after they have upgraded to V.90.
The advantage here is that different ISPs will complete their
V.90 upgrades on different timetables and this type of upgrade
path will ensure that an upgraded 56K/V.90 modem will always make
a reliable 56K or V.90 connection at any point during the industry's
transition to V.90. Again, the smartest move is to postpone your
V.90 upgrade until you have confirmed that your ISP has upgraded
to V.90.
Step #5:
Start benefiting from your V.90 56Kbps modem.
If you're already getting great service at one of the thousands
of Points of Presence (POPs) supporting 56K, there is nothing
else you need to do. If your ISP has upgraded to V.90 and you
want the universal interoperability that V.90 offers, then check
with your modem manufacturer to get the upgrade details.
How does the V.90 technology
work?
Traditional modems assume that both ends of a connection to the
public switched telephone network are analog. Data signals are
converted from digital to analog and back again, limiting transmission
speeds to 33.6 Kbps.
V.90 technology makes a different assumption in that one end
of the modem conversation has a pure-digital connection to the
phone network (which Internet Service Providers and corporations
already use for remote access) and takes advantage of that high
speed digital connection.
By viewing the public switched telephone network as a digital
network, V.90 technology is able to propel data downstream from
the Internet to your computer at speeds of up to 56 Kbps. *In
this way V.90 technology is different than other high speed modems
-- because data is digitally encoded downstream instead of modulated.
This is an asymmetrical method, so upstream transmissions (mostly
keystroke and mouse commands from your computer to the central
site, which require less bandwidth) continue to flow at the conventional
rate of 33.6 Kbps.
V.90 technology is ideal for serious Internet users, because
you really need the 56 Kbps speed for downloading those Web pages
with sound, video and other large files.
*Actual speeds vary depending on line conditions. Due to FCC
limitations, speeds in the U.S. are limited to 53 Kbps.
V.90 also incorporates something called "Line Probing"
The connection sequence also known as "line probing"
establishes the clarity of the phone connection. The key to line
probing is the assessment of line quality - not necessarily the
quality of the connection. The signal to noise ratio improves
with the accuracy of the line probe, lowering error rates and
improving throughput rates.
What are typical 56K connect
speeds?
Although your results will depend heavily on many different factors
(phone line quality, ISP connection types, traffic, etc…)
typical results are:
· 42,000bps to 46,666bps for modems using the Rockwell
K56flex chipset.
· 44,000bps to 52,000bps for modems using the 3COM X2
chipset.
What can the MTU settings do for
my Internet connection?
Here's a simple analogy. TCP/IP takes a web page and cuts it
into nice neat squares (packets). It puts each piece in an envelope
with the address (header) of where it’s going for the routers
to send it along its way. Then all the letters are delivered to
your mailbox. So:
MSS = the size of each cut square of paper
MTU = the size of the envelope (which must be slightly bigger
than the square of paper)
RWIN = the size of the mailbox which "receives" the
letters
The maximum speed of TCP/IP transfers through a SLIP (Serial
Line Protocol) or PPP (Point To Point Protocol) connection is,
first and foremost, limited by the speed of the modem. In an ideal
world, for an already compressed file, you should be able to get
3.2 Kbytes/sec transfers with a 28.8 Kbps (kilobits per second)
connection; 2.7 Kbytes/sec with a 24 Kbps connection; 1.6 Kbytes/sec
with a 14.4 Kbps connection; etc. Roughly speaking, each one Byte/sec
of delivered TCP data rate requires 9 bps of modem connect rate.
The data transfer speeds mentioned are the ideal speeds one can
achieve, but this is often thwarted by fragmentation which may
occur in the transmission of packets of data.
As you visit various web sites, you will encounter at least one
router on the download path with an IP default MTU of only 576
bytes. This is the most common MTU setting in use and is generally
referred to as the "Internet Standard". If you are using
the Windows 95 default MTU setting of 1500, this will likely result
in packet fragmentation slowdown (since you are trying to use
TCP segments (MSS) larger than 536 bytes.) Avoiding fragmentation
has a major effect on file download speed, whether we are talking
about html and image files from the web or straight text data
bits in your e-mail program.
What is MTU?
MaxMTU Explained:
Data on the Internet is sent in chunks called packets. The Internet
standard packet size is 576 bytes (including 40 bytes for address
information). This packet size is known as the Maximum Transmission
Unit, or MTU. The 536 bytes of data remaining after the address
information is subtracted are known as the Maximum Segment Size
(MSS).
The problem is that the default setting for Windows 95 Dial-Up
Networking is an MTU of 1,500 bytes. This setting is ok for Internet
connections made through a LAN. But since most consumers use a
dial-up connection (via modem) it tends to slow down the download
time while it resends the packets to accommodate the mismatched
packet size.
MTU is usually set in conjunction with MSS, the Maximum Segment
Size, and RWIN, the TCP Receive WINdow. MSS is the largest segment
of TCP data that the Winsock is prepared to receive on that connection.
MSS must be smaller than MTU by at least 40 bytes, the size of
the header and trailer information. The tool will automatically
adjust MSS when the user changes MTU. RWIN determines how much
data the receiving computer is prepared to receive. If RWIN is
set too large it will result in greater loss of data if a packet
is lost or damaged. If it is set too small (e.g. 1x MSS), transmission
will be very slow. Normally RWIN is set to either 4x, 6x or 8x
the MSS value which is 40 bytes less the MTU.
Adjusting the MaxMTU:
The Manual Tune-Up provides access to the MTU adjustment. When
the program is first run the MTU value will be grayed. If the
user used a third party program to adjust this value the currently
selected value will be displayed. If the value set matches 576
or 1500 then that button will also be highlighted. The user can
adjust to any value they wish by pressing the top (to increase)
or bottom (to decrease) of the round button. The user must press
the "Apply" button to set the new value.
Common MaxMTU values:
The following are values you can experiment with when adjusting
the MTU value manually:
400, 512, 552, 556, 576, 1000, 1006, 1024, 1152, 1500
What is the difference between
KB/s and Kb/s?
The main units of modem speed are:
· KB/s or KBps = kilobytes per second
· Kb/s or Kbps = kilobits per second
When transmitted over a modem, there are ten bits per byte (eight
data bits plus a start bit and a stop bit). So if one modem seems
ten times faster than another, it's because different units are
being used.
Why can't I find Dial-Up Networking
on my system?
Windows 95 does not automatically include Dial-Up Networking
during installation. You can verify and if needed, install Dial-Up
Networking using these instructions:
1. Click on "Start", click on Settings, click on Control
Panel
2. Double click on the "Add/Remove Programs" icon
3. Click on the tab labeled "Windows Setup"
4. In the list of components, highlight "Communications"
5. Click on the "Details" button
6. Verify that the "Dial-Up Networking" component is
selected. If it is not, select it now.
7. Click on Ok until you are back at the Control Panel. You will
probably be prompted to enter your Windows 95 CD-ROM or provide
the location of the Windows 95 installation files and might also
have to restart your system.
8. Once installation is completed, double click on the "My
Computer" icon on the desktop
9. You will see a "Dial-Up Networking" folder. Double
clicking on this will allow you to create a dial-up profile.
Why do I connect fast but seem
to slow down after a while?
Initial connect speed can be deceiving. V.34 and 56K modems can
and do shift their speeds up and down during the course of the
call to respond to changing phone line conditions. Some modems
connect very aggressively at high speeds, but are then are forced
to lower their speed to a more stable level. Others may connect
conservatively and upshift.
For example: Using a 56K modem, you may connect at 50,666bps but
during your time online, congestion causes your connection to
slow down to 28800bps. Once the congestion has cleared your speed
will try to climb back up to the speed you originally connected
at.
Why do I need TCP/IP installed?
TCP/IP is the protocol used by the Internet that makes it possible
for different operating systems and networks to communicate with
each other over long distances.
To connect to the Internet, you must have TCP/IP installed. You
can install TCP/IP when you install Windows 95 using the "Custom
Setup Options", or if Windows 95 is already installed, you
can install it using the 'Network' icon in Control Panel.
To install TCP/IP
1. Open the Windows Control Panel
2. Double-Click on the 'Network' icon, click the Add button.
3. In the 'Select Network Component Type' dialog box, double-click
'Protocol'.
4. In the 'Select Network Protocol' dialog box, in the 'Manufacturers'
list, click 'Microsoft' and in the 'Network Protocols' list, click
'TCP/IP'. Click 'OK'.
Why does it say that I'm connected
at 115,200 bps?
Sometimes the connect speed reported by your dial-up connection
(the DCE) will be mistakenly reported as the DTE value. In other
words, your 33,600bps connection might be mistakenly reported
as a 115,200bps connection. Check your modem's users manual or
web site for information on AT commands that can correct this
mistake.
Why does my modem connect at
26,400 bps or slower?
Telephone line signal quality varies widely from one area to
another and from one call to the next. All V.34 modems probe the
telephone line during the initial 'handshake' sequence to determine
the optimum carrier speed to utilize based upon the quality of
the received signals.
Most name brand 33.6 modems feature a robust V.34 technology that
attempts to connect at the highest possible speed. When calling
local numbers your modem should typically connect at speeds of
26,400 to 33,600 bps. When calling long distance numbers, connect
speeds may vary between 19,200 and 33,600 bps.
Why does my modem continue to
connect at slow speeds?
Modems rarely connect at their rated speed because connection
speeds depend on a variety of items. Here are some considerations:
· Make sure that the ISP you are using has the support
for the modem you are using and is of the same or higher speed
than your own. If you are using a 56K modem, the ISP you are using
must have support for the same 56K modem technology. If not, the
modem will connect at 28,800 bps. If you try to connect a faster
modem with a slower one, it will always default to the slower
speed.
· Sometimes line noise and the quality of the connection
can affect the speed at which you connect. There are four areas
of concern:
1. The inside wiring of the location you using
2. The phone company that routes the call
3. The phone company at the location you are calling
4. The inside wiring of the location you called.
The most likely problems are the wiring of locations you are
located at and the one you are calling. This problem is especially
bad for 56K modems.
· Check to see if the COM port setting is set to the maximum
speed supported by the type of modem installed, most new modems
should have the COM port speed set to 115,200 bps.
· Check the flow control, it should be set to Hardware
(RTS/CTS).
· Check the modem initialization string and verify that
the connect speed has not been set to a specific rate.
Use the following strings to initialize your modem for high-speed
connections with error correction, data compression and hardware
handshaking:
AT&F2 or as an alternative AT \N3 &K3 &Q5 &D
Why does my modem keep getting
disconnected?
· Line noise
If you are attempting to make a long distance connection over
a bad phone line, line noise may be interfering with the signal.
If the place you are trying to call has another number, try calling
it instead.
· If the problem is occurring no matter what number you
dial, check your phone line to make sure there is no extraneous
noise.
Replace the cable going from your modem to the wall jack to make
sure a kink in the cable isn't causing line noise. Check to make
sure no one is picking up an extension. If someone else picks
up the phone, it will corrupt your connection, usually forcing
your modem to hang up.
· If the disconnect problem occurs with an internal modem.
Try moving the modem to another slot, the modem maybe affect by
noise radiated by the adapter next to it. This is especially true
for the inexpensive modems.
· Time Limit restriction
Verify that the location you are calling does not have a time
limit on the connection. This often used when the service does
not have sufficient resources to support a lot of simultaneous
users.
During peak hours (8PM-11PM) most Internet providers will disconnect
customers that have been connected for more than 1 or 2 hours.
This will allow other users to have an opportunity to use the
Internet service. Unfortunately, this is a standard policy throughout
the internet industry, there will always be a growing amount of
clients to serve.
Certain TCP/IP stacks used by Internet access providers will
automatically disconnect the user after a period of inactivity.
Check the manual or contact the manufacturer of your Internet
software to determine if this could be the problem.
· User Settings
The program will verify that the 'Disconnect a call if idle for
more than' check box is not set or it is set to a short time (less
then 15 minutes).
· Call waiting
Review dialing properties for the call waiting. If not set query
the user to determine if they have call waiting feature on the
phone. If they respond yes then make sure that the disable code
has been entered in the Dialing Properties. In Control Panel select
the Modem icon, press the Dialing Properties button and check
the 'To disable call waiting, dial' check box and enter the correct
code for your phone system.
Why does my USR Sportsters get
slower and slower, and then suddenly disconnect?
This is the X2 version of 'Spiral Death Syndrome'.
The fix in most cases is to add S15=128 to the Init string to
disable V.42 hardware error correction.
It may also be necessary to add &K0 to the Init string to
disable V.42bis hardware data compression.
WARNING: Using these tips, your Internet performance may suffer
when downloading non-compressed files.
Why doesn't my connection ever
connect at 56K speeds?
FCC regulations limits performance to 53.3K.
There is an FCC regulation that prevents all devices attached
to the telephone network from exceeding a certain power output.
As a result, the modems have to scale back the output, which has
a direct effect on the speed at which it can transfer data. Currently,
they have the server modem limit set to 53,333 bps. This does
not mean that you will not be able to hit the higher speeds, it
simply decreases the likelihood.
Also, there are many factors that can influence the connection
rate and the speed at which you transfer data. Even though one
end of the connection is pure digital, there are issues that can
hamper an X2 connection, while not necessarily preventing it altogether.
Essentially, the qualities of the phone line plays an essential
role in the speed of the connection.
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