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How POS is sent via STM lines?

 
 
Yehavi Bourvine
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      03-28-2006
Hello,

I have a question about packing IP packets inside STM-1 transmision lines
using POS:

The POS standard says (roughly) to take the IP packet, encapsulate it into
PPP and then put this into the VC4 payload. The VC4 payload is 2,340 bytes, so
what is done when there are small packets to send? Are they simply
concatanated one after the other in one payload?
if there is nothing to send (or not enough packets to fill the payload) how
is it padded? with HDLC flags?

Thanks! __Yehavi:
 
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bertklaps@yahoo.com
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      04-01-2006
Yehavi Bourvine 58-4279 wrote:
> I have a question about packing IP packets inside STM-1 transmision lines
> using POS:
>
> The POS standard says (roughly) to take the IP packet, encapsulate it into
> PPP and then put this into the VC4 payload. The VC4 payload is 2,340 bytes, so
> what is done when there are small packets to send? Are they simply
> concatanated one after the other in one payload?
> if there is nothing to send (or not enough packets to fill the payload) how
> is it padded? with HDLC flags?


To map PPP into SDH you need octet-stuffed HDLC encapsulation
(HDLC flag, address/control and FCS). The HDLC frames are send back
to back and inter-frame gap is filled with HDLC flags. The result is
then
scrambled before inserting into the VC-n payload.

Check ITU-T G.707 or RFC 2615.

Regards,
Bert

 
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