ISDN PRI - 1.544 Mbps or 1.536 Mbps ? - TCP-IP

This is a discussion on ISDN PRI - 1.544 Mbps or 1.536 Mbps ? - TCP-IP ; "The Primary Rate Interface consists of 23 B-channels and one 64 kbit/s D-channel using a T1 line. Thus, a Primary Rate Interface user on a T1 line can have up to 1.544 Mbit/s service." If you do the math: 23Bchannels ...

Thread: ISDN PRI - 1.544 Mbps or 1.536 Mbps ?

1. ISDN PRI - 1.544 Mbps or 1.536 Mbps ?

"The Primary Rate Interface consists of 23 B-channels and one 64 kbit/s
D-channel using a T1 line. Thus, a Primary Rate Interface user on a T1 line
can have up to 1.544 Mbit/s service."

If you do the math:
23Bchannels x 64 + 1D channel x64 = 1536 kbps or 1.536Mbit/s.
Even if you divide 1536 : 1024 still doesn't give 1.544 Mbps ....

2. Re: ISDN PRI - 1.544 Mbps or 1.536 Mbps ?

On Dec 19, 11:00 pm, "eager" wrote:
> "The Primary Rate Interface consists of 23 B-channels and one 64 kbit/s
> D-channel using a T1 line. Thus, a Primary Rate Interface user on a T1 line
> can have up to 1.544 Mbit/s service."
>
> If you do the math:
> 23Bchannels x 64 + 1D channel x64 = 1536 kbps or 1.536Mbit/s.
> Even if you divide 1536 : 1024 still doesn't give 1.544 Mbps ....

A T1 line has 8000 frames each second of 192 data bits. When
channelized for voice or ISDN PRI, you have 8 bits for each of the 24
channels in each frame. Each frame also has a framing bit. So
193x8000=1.544mb/s, with 8000bps being overhead. Not unlike a 9600bps
async link really being able to transmit 7680bps of "real" data
(assuming N-8-1 format).

3. Re: ISDN PRI - 1.544 Mbps or 1.536 Mbps ?

wrote in message
> On Dec 19, 11:00 pm, "eager" wrote:
>> "The Primary Rate Interface consists of 23 B-channels and one 64 kbit/s
>> D-channel using a T1 line. Thus, a Primary Rate Interface user on a T1
>> line
>> can have up to 1.544 Mbit/s service."
>>
>> If you do the math:
>> 23Bchannels x 64 + 1D channel x64 = 1536 kbps or 1.536Mbit/s.
>> Even if you divide 1536 : 1024 still doesn't give 1.544 Mbps ....

>
>
> A T1 line has 8000 frames each second of 192 data bits. When
> channelized for voice or ISDN PRI, you have 8 bits for each of the 24
> channels in each frame. Each frame also has a framing bit. So
> 193x8000=1.544mb/s, with 8000bps being overhead. Not unlike a 9600bps
> async link really being able to transmit 7680bps of "real" data
> (assuming N-8-1 format).

I do not know where you got that, but even so, PRI _uses_ T1 line, and every
book out there says that PRI consists of 23 B-channels _64kbps_each_ and 1 D
channel also _64kbps.

4. Re: ISDN PRI - 1.544 Mbps or 1.536 Mbps ?

eager wrote:
> wrote in message
>> On Dec 19, 11:00 pm, "eager" wrote:
>>> "The Primary Rate Interface consists of 23 B-channels and one 64 kbit/s
>>> D-channel using a T1 line. Thus, a Primary Rate Interface user on a T1
>>> line
>>> can have up to 1.544 Mbit/s service."
>>>
>>> If you do the math:
>>> 23Bchannels x 64 + 1D channel x64 = 1536 kbps or 1.536Mbit/s.
>>> Even if you divide 1536 : 1024 still doesn't give 1.544 Mbps ....

>>
>> A T1 line has 8000 frames each second of 192 data bits. When
>> channelized for voice or ISDN PRI, you have 8 bits for each of the 24
>> channels in each frame. Each frame also has a framing bit. So
>> 193x8000=1.544mb/s, with 8000bps being overhead. Not unlike a 9600bps
>> async link really being able to transmit 7680bps of "real" data
>> (assuming N-8-1 format).

>
> I do not know where you got that, but even so, PRI _uses_ T1 line, and every
> book out there says that PRI consists of 23 B-channels _64kbps_each_ and 1 D
> channel also _64kbps.
>
>
>

Hi,

24 * 64kbps + 8kbps management channel used by telco

Hubert

5. Re: ISDN PRI - 1.544 Mbps or 1.536 Mbps ?

On Dec 20, 1:43 am, "eager" wrote:
> > A T1 line has 8000 frames each second of 192 data bits. When
> > channelized for voice or ISDN PRI, you have 8 bits for each of the 24
> > channels in each frame. Each frame also has a framing bit. So
> > 193x8000=1.544mb/s, with 8000bps being overhead. Not unlike a 9600bps
> > async link really being able to transmit 7680bps of "real" data
> > (assuming N-8-1 format).

>
> I do not know where you got that, but even so, PRI _uses_ T1 line, and every
> book out there says that PRI consists of 23 B-channels _64kbps_each_ and 1 D
> channel also _64kbps.

Right, but what's your question? Just like I said, each T1 frame of
192 data bits (of which there are 8000 each second), carries eight
bits from each of the 24 (23B+1D) 64kbps channels in a PRI (assuming
the T1 is carrying a PRI, of course). And each frame has a 193rd bit
for framing, which is the source of the 8000bps you were missing.

The 193x8000 frame format is inherent in a T1. You can channelize
that many different ways, but with voice-like circuits, the sub
channels are invariably bit sliced across the frame in such a way that
no jitter, burstyness, or lag is introduced. Remember that basic
voice service is 8000 eight bit samples per second, and that you'll
find line/frame formats all over the (telco) network synchronized in
some fashion to the 8000 samples-per-second rate for the precise
reason that you can carry that data rate without jitter, burstyness,
or lag.

6. Re: ISDN PRI - 1.544 Mbps or 1.536 Mbps ?

wrote in message
> On Dec 20, 1:43 am, "eager" wrote:
>> > A T1 line has 8000 frames each second of 192 data bits. When
>> > channelized for voice or ISDN PRI, you have 8 bits for each of the 24
>> > channels in each frame. Each frame also has a framing bit. So
>> > 193x8000=1.544mb/s, with 8000bps being overhead. Not unlike a 9600bps
>> > async link really being able to transmit 7680bps of "real" data
>> > (assuming N-8-1 format).

>>
>> I do not know where you got that, but even so, PRI _uses_ T1 line, and
>> every
>> book out there says that PRI consists of 23 B-channels _64kbps_each_ and
>> 1 D
>> channel also _64kbps.

>
>
> Right, but what's your question? Just like I said, each T1 frame of
> 192 data bits (of which there are 8000 each second), carries eight
> bits from each of the 24 (23B+1D) 64kbps channels in a PRI (assuming
> the T1 is carrying a PRI, of course). And each frame has a 193rd bit
> for framing, which is the source of the 8000bps you were missing.
>
> The 193x8000 frame format is inherent in a T1. You can channelize
> that many different ways, but with voice-like circuits, the sub
> channels are invariably bit sliced across the frame in such a way that
> no jitter, burstyness, or lag is introduced. Remember that basic
> voice service is 8000 eight bit samples per second, and that you'll
> find line/frame formats all over the (telco) network synchronized in
> some fashion to the 8000 samples-per-second rate for the precise
> reason that you can carry that data rate without jitter, burstyness,
> or lag.

Thank you!