what is a OOF(Out Of Frame) in "show controller e1"??

Sanghee Han · ‎12-03-2009

Hi all,

I wander about oof in show controller e1.

Router# show controllers e1

E1 4/1 is up.

  No alarms detected.

  Framing is CRC4, Line Code is hdb3

  Data in current interval (0 seconds elapsed):

     0 Line Code Violations, 0 Path Code Violations 0 Slip Secs, 0 Fr Loss Secs,

     0 Line Err Secs, 0 Degraded Mins 0 Errored Secs, 0 Bursty Err Secs,

     0 Severely Err Secs, 0 Unavail Secs

  Total Data (last 79 15 minute intervals):

     0 Line Code Violations, 0 Path Code Violations, 0 Slip Secs, 0 Fr Loss Secs,

     0 Line Err Secs, 0 Degraded Mins, 0 Errored Secs, 0 Bursty Err Secs,

     0 Severely Err Secs, 0 Unavail Secs

in above output,

"Fr Loss Secs" meas

- Indicates the number of seconds an Out Of Frame (OOF) error is detected.

but I can't understand the exact meaning of "the number of seconds an out of frame error".

is there anyone to explain about this easily?

what is a OOF??

Thanks.

Giuseppe Larosa · ‎12-04-2009

Hello,

an out of frame event happens when it is not possible to recognize the organisation of the data stream.

An E1 uses a framed structure is not a simple bit stream is formed by 32 B channels each 64 kbps. The channels are multiplexed in the time domain.

see this line in sh controller:

>>

Framing is CRC4, Line Code is hdb3

CRC4 is a type of framing.

a definition of all these errors is present in an RFC that describes the associated SNMP MIB variables.

Simply put if errors concentrated in a small time interval the receiver cannot understand the stucture of the bit stream.

see

http://www.rfc-editor.org/rfc/rfc1406.txt

section

3.3.2.  Performance Defects

For E1 links, an Out Of Frame defect is declared when
          three consecutive frame alignment signals have been
          received with an error (see G.706 Section 4.1 [17]).

          Once an Out Of Frame Defect is declared, the framer
          starts searching for a correct framing pattern.  The Out
          of Frame defect ends when the signal is in frame.

          In-frame occurs when there are fewer than two frame bit
          errors within 3 msec period for ESF signals and 0.75 msec


Hope to help
Giuseppe

Sanghee Han · ‎12-06-2009

Thanks for your help.

It's a good answer for me.

thank Giuseppe always.