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eager
Guest
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 Posted: Thu Dec 20, 2007 11:00 am Post subject: ISDN PRI - 1.544 Mbps or 1.536 Mbps ? |
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"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 .... |
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robertwessel2@yahoo.com
Guest
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| Posted: Thu Dec 20, 2007 11:00 am Post subject: Re: ISDN PRI - 1.544 Mbps or 1.536 Mbps ? |
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On Dec 19, 11:00 pm, "eager" <ea...@beaver.it> wrote:
| Quote: | "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 ....
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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). |
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eager
Guest
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| Posted: Thu Dec 20, 2007 1:43 pm Post subject: Re: ISDN PRI - 1.544 Mbps or 1.536 Mbps ? |
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<robertwessel2@yahoo.com> wrote in message
news:cdd97e9b-aed7-47d0-8e48-7dfe09f02ef7@i12g2000prf.googlegroups.com...
| Quote: | On Dec 19, 11:00 pm, "eager" <ea...@beaver.it> 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. |
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Hubert Wi¶niewski
Guest
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| Posted: Thu Dec 20, 2007 1:54 pm Post subject: Re: ISDN PRI - 1.544 Mbps or 1.536 Mbps ? |
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eager wrote:
| Quote: | robertwessel2@yahoo.com> wrote in message
news:cdd97e9b-aed7-47d0-8e48-7dfe09f02ef7@i12g2000prf.googlegroups.com...
On Dec 19, 11:00 pm, "eager" <ea...@beaver.it> 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.
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Hi,
24 * 64kbps + 8kbps management channel used by telco
Hubert |
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robertwessel2@yahoo.com
Guest
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| Posted: Thu Dec 20, 2007 9:28 pm Post subject: Re: ISDN PRI - 1.544 Mbps or 1.536 Mbps ? |
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On Dec 20, 1:43 am, "eager" <ea...@beaver.it> wrote:
| Quote: | 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. |
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eager
Guest
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| Posted: Fri Dec 21, 2007 12:32 pm Post subject: Re: ISDN PRI - 1.544 Mbps or 1.536 Mbps ? |
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<robertwessel2@yahoo.com> wrote in message
news:a923bdbf-2cab-4cdb-bcf3-978f03ed409c@n20g2000hsh.googlegroups.com...
| Quote: | On Dec 20, 1:43 am, "eager" <ea...@beaver.it> 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.
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Thank you! |
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