Cell Relay Archive

["Saso Stojanovski" <sasos@nortelnetworks.com>]

rajagopalan,



rajagopalan.sampath@wipro.com wrote:

> 2. My assumption is, the pointer ( P-format ) is always send in the PDU with Seq
> Count '0'? Is this right? If the pointer is sent in the first PDU of a cycle (

wrong. the P-format may be used with *any* of the following sequence numbers: 0, 2,
4 or 6.

however, you should use it only *once* within a sequence of 8 consecutive cells.

the single case where the pointer position is fixed is when the structure size is
bigger than 8 PDUs, so that there is no structure boundary within the 8-cell
sequence. in such cases, the pointer value of 127 *must* be in position no.6.


> i.e. the PDU with Sequence count 0 ), what'll be sent in the remaining PDUs of
> the same cycle ( i.e in the PDUs with Seq Count 2, 4, 6 )? Can we send a Non-P
> format cells in place of P-format cells? i.e. the whole PDU ( 47 bytes)

> will  be filled only with user information irrespective of the sequence number?
> Is there any hard and fast rule like the Non-P format cells should be sent only
> with Seq Count 1, 3, 5 and 7?

yes, you can send non-P format cells in even-numbered PDUs.
again, you may use the P-format *only once* in a sequence of 8 consecutive cells.
hence, the remaining 7 cells are necessarily non-P format.



> If I'm wrong, what the mechanism, in which the AAL1 user sends data to the AAL1.
>
> Also, in a Voiceband signal service, only one 64kbps voice channel is used, in
> which the data doesn't use any structure information. In this case, how the DATA
> is passed to the AAL1?
> The data always sent in Non-P format in a cycle, except the 7th PDU with Seq
> Count '6'. In which the pointer always takes the value "127" ( the default )
> value.

there are no pointers when emulating a single channel (not even "default"
pointers).


cheers,
    v
--saso



> Can I assume that, at transmit side, the AAL1 user guarantees CBR? So, partial
> filling of PDUs will not be needed at CS layer to compensate the "cell assembly
> delay".
>
> Plse tell, whether my understanding is correct.
>
> Thanks in advance.
>
> -Rajagopalan.
>