Dialup UK Article - Dial-up
Modem FAQ's (Part 2)
Q: Why do my dialup connections
“pause" in between?
A: This is a kind of problem that dialup
connection users encounter often. You are online on perhaps
in contact with a distant system over the Internet or accessing
a BBS, or transferring data or typing in commands, when suddenly
communications “pauses”. Then after some time
it starts again…
There are a many factors that can cause this kind of pausing
and determining the real cause can often be difficult, sometimes
very difficult. More importantly, the cause of this kind of
pause may be out of your control. Here is a list of possible
1. Network problems
A TCP/IP network like the Internet transmits data in small
packets through the network. When the network gets overloaded,
the network routers deal with the problem by discarding data
packets. The sender does get to notice that the receiver has
not received packets that have been sent and to resend those
packets. The result is a pause in data transmission. In extreme
cases packet loss can go as high as 30% or more, bringing
transmission down to a crawling speed with hardly any data
flowing most of the time.
This problem can be diagnosed using "ping" and
"traceroute" tools. The only way to resolve this
problem is by negotiating with the network administrator.
There may not be much that can be done if the epicenter of
the pause is outside of the local network.
Similar can happen when you are connected with a remote server5.
Remote servers can handle a limited load. When the load gets
excessive, there is a general slowdown to all those using
the server. This may result in small to long pauses when the
server is busy serving other users.
As the usage of Internet increases, the amount of data transfer
increases. This is becoming an ever-increasing problem for
popular web sites that gets hundreds and thousands of hits
per day. The only way to deal with this problem is to access
the server when there is possibility of fewer loads on the
2. Routing and other problems
As the load on the internet grows, larger networks are adopting
certain data transmitting policies. These networks may be
giving access to small ISPs who operate in small local area.
What these networks do is that during periods of peak load,
they may drop many packets or route them onto slower links
with more traffic. In extreme case, the network may refuse
to let the data pass them altogether. The only way to deal
with this problem is to be sure that your ISP has good connectivity.
3. Modem firmware problems
Certain modems may have a problem that can cause the modem
to "pause". This particularly happens when the modem
is being used in an interactive mode on a normal dialup connection.
This is often observed while connected to a Bulletin Board
System (BBS) or asynchronous dialup UNIX shell. In most cases,
the "pause" will last up to about a minute. The
solution is mostly specific to modems.
Incompatibilities between certain modems can result in a
variety of problems, including "pausing." In this
kind of case, you probably have an interoperability problem.
A firmware upgrade that corrects the problem may be available
for your modem.
4. Computer problems
Hardware conflicts are a frequent cause of both long and
short pauses. When two COM ports are set to the same I/O address
or IRQ this issue could arise. For example, sometimes moving
the mouse will cause modem data to flow, but in other cases
the modem may not work at all.
A UART port, it can cause all sorts of communications problems,
including both long and short pauses when you access your
If flow control is not configured properly in both the comm
software and the modem, the result is “overruns”.
These overruns result in lost data, which can cause "pauses"
as well as delays due to data retransmission.
5. Line connection problem:
This problem may be happening because the cause is present
in your modem connection. Normally, when a transmission error
occurs, error correcting modems automatically retransmit the
affected data. Under normal conditions, the retransmission
is faster. When connections are slower like a dial up connection,
the retransmissions can result in "pauses" while
the data is being retransmitted.
Certain modems will help you detect and diagnose this kind
of problem. This cause is mostly out of control and the possible
solution is to get better connections. But, the diagnostic
utility may help in reducing the frequency of errors).
While modems are having this error due to a poor connection,
data will sparingly flow. Although, in most cases, a pause
will lasts only a few seconds but multiple error recovery
processes can go on for much longer. This will give you impression
that the connection has just stopped.
6. Software problems
Improper TCP/IP configuration can lead to packet fragmentation
and other problems that may be manifested as "pausing."
Software configuration and interference
Errors in comm software applications can also result in "pausing."
The only solution is to ensure that all comm applications
are configured properly.
It is also possible for two software applications or device
drivers particularly network drivers to interfere with each
other. This lockup is enough to cause a "pause”.
The solution is to eliminate one of the applications involved
Sometime the operating system suddenly needs a lot more memory
to run an application. The OS may need to swap megabytes of
data between memory and a disk drive. On less sophisticated
operating systems like Windows versions, this can result in
a "pause" in communications during the swapping.
The symptom of this problem is a large burst of disk activity.
Q: Why the Call Waiting does
not interrupt my modem connection?
A: Call Waiting is a phone service
option that allows you to be interrupted by an incoming call
while you are using the phone line. If you are using the phone
line for data or fax, the "beep" that signals the
incoming call can cause an abrupt disconnection, which can
be a problem.
To enable or disable call waiting you have to dial an access
number mostly specific to the phone company. Check with your
local phone company to be sure. Some comm programs have an
option to insert the special code automatically.
You may want Call Waiting feature to be enabled to interrupt
a data or fax call, so that you do not miss an important incoming
call. However, there are some modems like V.34 modems designed
to overcome line interrupts. They may not be disconnected
by the interrupt. However, there are some modems that do come
with this facility. If your work requires you to get interrupts
then make sure that you have a modem with call waiting feature.
Make sure it is enabled when you go online.
Q: How do I keep my data/fax
call from getting interrupted?
A: Some people may have a single telephone
line with multiple extensions. You can use this line for both
voice and fax/data. But there is a danger…
If you are online, doing some large data transfer and someone
else picks an extension, your connection is lost and so as
your data. The solution to this problem is to install a "Line
Protector" for each extension phone. When you are online,
the Line Protector will automatically prevent the attached
phone from interrupting your connection.