What mean D-bit?

[pelikan81]

Hello all,
i have on my switch aplication/command that can measure PCM alarm, and set counters according that. I have in output these parameters:

D-BIT D-Bit in service word
SD-Bit D-Bit in multiframe service word
SN-Bit N-Bit in multiframe service word

Does anybody know what is these bits good for?
thanx a lot
mario

output for example:

PCM ALARM COUNTERS PDCLNK = 0- 6-3

TIME COUNTER 12-50MS 50-100MS 100-2000MS >2000MS
-------------+---------+----------+------------+--------
AIS 0 0 0 0
SYN 0 0 0 0
SSYN 0 0 0 0
D-BIT 255 155 63 0
SD-BIT 0 0 0 0
SN-BIT 0 0 0 0
INC LOSS 0 0 0 0
AIS MULT 0 0 0 0

 

[SYQUEST]

How does the manual or the manufacturer describe it??

Is the PCM related to a DS1?

....JIM....

 

[pelikan81]

it is E1 2Mbp/s

 

[SYQUEST]

Since I am only familiar with the US DS1/T1 standards, you might want to get E1 standards or references to identify all the types of error conditions that it is susceptible and what they mean.

....JIM....

 

[Trotski]

T1 and E1 have equivilent standards saving that E1 uses 30 X 64Kbit Channels

 

[hawks]

Take a look here

http://www.faxswitch.com/Definitions/telecom_dictionary_s.html

 

[pelikan81]

Exactly i found something about D-bit:
"Multiple ISDN user devices can be physically attached to one circuit. In this configuration, collisions can result if two terminals transmit simultaneously. Therefore, ISDN provides features to determine link contention. When an NT receives a D bit from the TE, it echoes back the bit in the next E-bit position. The TE expects the next E bit to be the same as its last transmitted D bit."

http://cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/isdn.htm

but this is cover for Basic Rate Interface BRI, for Primary Rate PRI i didn't find anything, in G.703,G.704 recommendation also nothing

 

[pelikan81]

ok, i found it out:

D-bit is sent to the remote end in the service word of the pulse frame in odd byte in multiframe in the third bit MSB. (in timeslot 0 - in synchronization byte)
D = dringend = critical alarm

Possible causes:
- Loss of pulse frame alignment at the remote end
- Loss of the incoming 2-Mbit/s signal at the remote end
- Excessive bit error rate at the remote end

(i found that bit also like A-bit)

mario