Sorry for the previous mail, didn't mean to give anyone a headache. This
one is lined up much better:)
Port Error Counters
The PortMaster keeps count of errors detected on its port
which are useful when debugging a problem or when trying to
detect a problem. Below are sample screen shots of some
PortMaster ports with links to definitions of the various errors.
Sample synchronous port output
Command> show w1
----------------------- Current Status - Port W1 ---------------------------
Status: ESTABLISHED
Input: 915287284 Abort Errors: 56/1
Output: 3214289999 CRC Errors: 27
Pending: 0 Overrun Errors: 0
TX Errors: 0 Frame Errors: 15
Modem Status: DCD+ CTS+
Sample asynchronous port output
Command> show s10
----------------------- Current Status - Port S10 --------------------------
Status: ESTABLISHED
Input: 1392900 Parity Errors: 0
Output: 453743 Framing Errors: 0
Pending: 0 Overrun Errors: 0
Modem Status: DCD+ CTS+
Abort Errors
An abort error means that a connection did not establish on the
synchronous port and it is trying again. Each time it tries again it
increments the error count by one.
When you see a slash in the Abort Error (Abort Errors: 56/1)
count the first number represents framing errors, the second
number represents device errors.
Framing Errors count is incremented when:
The receiver chip reports a framing error
The receiver chip reports an abort
Device Errors count is incremented when:
When frame size is 0.
When frame size is greater than the maximum size of a
PPP frame.
When frames overlap each other
CRC Errors
Means the data received did not pass a verification routine.
Cyclical Redundancy Check - Is a check on the data to make
sure that it has arrived ok. The checking mechanism is a hashing
algorithm. The CRC hashes the large set of all possible binary
numbers onto the smaller set of all possible CRC codes. Hashing
by nature loses data so at least two different blocks must
produce identical CRC. So CRC is very good at detecting
changes in data blocks caused by typical erros occurring during
serial transmission (Which is what Portmasters use it for) but a
clever programmer could slip a virus through one that was being
used to scan disk files for virus (Which the Portmaster does
NOT do).
Overrun Errors
If a character is received sent to the buffer to be processed
before the previous character has been read by the processor the
previous character is destroyed or overwritten. Basically
someone is force-feeding characters to a port greater than the
port speed.
Frame Errors
Basically, the frame was munged in transit. Almost always caused
by a hardware failure in a line or modem, etc.
A frame is considered invalid if it does not terminate with at least
1 STOP bit. If a framing error occurs the counter is incremented,
and the portmaster automatically attempts to resynchronize by
assuming that the incorrect STOP bit was actually the start bit for
the next character. A new character is then constructed beginning
with this new START bit.
On synchronous ports the "Frame errors" is sometimes followed
by two numbers separated by a slash.
Frame Errors: small packets/large packets
Large packets count is incremented when receive
character counter overflow (packet too big - drop it).
Small error count is incremented when a short frame is
received.
Troubleshooting Framing Errors
What to watch for?
See if the framing errors are rising constantly or just
sometimes.
You need to know if your framing errors are incrementing
at a constant rate or if your framing errors are ocurring all
at once. If they are incrementing at a constant rate, by how
much? How quickly? If they happen all at once and are
not on the rise then they were probably caused by a single
event. Unplugging a serial cable from the PortMaster can
result in a jump of framing errors.
Determine if the framing errors are limited to one port
If you notice a particular port has numerous framing errors
on the rise then swap the serial cable, device (modem,
CSU/DSU), phone wire with that of another port. If the
problem follows the port then check the Livingston. If the
problem follows the line then begin swapping cables,
modems, etc to narrow down the source of the framing
errors.
What to do?
Make sure your power cables are perpindicular to your
data cables.
Electricity passing through a cable generates a magnetic
field. The electro-magnetic fields generated by the power
cables can disrupt information passing through the data
cables. By running your power cables perpendicular to
your data cables you minimized the contact with the
electro-magnetic fields.
Check your serial cables
The cable (and possibly connectors and adapters)
between the PortMaster and (modem or CSU/DSU)
should be shielded to minimize noise from other serial
cables and power connectors.
Try swapping the cable and/or adapters. Sometimes a
cable will have a short. Usually serial cables come bad in
batches since they are all manufactured at the same time.
When swapping cables try to use store bought cables to
prevent human error. Be especially suspicious of DB25 to
RJ45 connects as these often have problems.
Have your lines tested for noise
Analog, ISDN, T1, etc lines are all susceptable to noise at
the telephone company. This is OFTEN the cause of many
framing errors and the noise test is generally free. Noise
can come and go so you will want to see when the framing
errors are occuring.
Check the enviornment
Other devices can cause noise as well that can result in
framing errors. Be sure to keep your data cables away
from monitors, magnets, old color TV's, arc welders and
low flying UFOs.
Verify Modem/CSU/DSU
Modems and CSU/DSU's can also cause framing errors if
they are defective or misconfigured.
Verify Phone Wire and block
Check the wiring in your building, in the block and from
the block to the modem. If this is wired poorly, or you
have bare copper running or ordinary phone wiring running
for a few feet will make you susecpable to framing errors.
--- jstorms@livingston.com Diplomacy: The art of saying good doggie while seaching for a big rock.