Subject: Re: [PWE3] Transport of CAS over CESoPSN [RFC 5086]

From: <[email-masked]>
Date: Sun, 29 Nov 2009 20:55:13 +0000

Hola  Javi,

Thank you for some clarification, I have some more questions in-line [hvh[

> > --- What happens if instead of CAS CCS is used for the signalling?
> 
> Yoy may transport CSS signalling in transparent mode (as another bearer 
> channel) or in HDLC mode (RFC 5087)
>
> > --- E1 CAS uses a multiframe which includes RAI (note this is different from
> >     the E1 RAI, how is this transferred?
>
> "5.4.  Trunk-Specific NxDS0 Services with CAS" carry CAS signalling from TDM multiframe in CAS substructures, including error indicators (detailed RCFC 5086, CESoPSN)
> 

[hvh] RFC5086 only mentions the TS0 RAI (in the M bits), it does not mention the TS16 RAI.

[hvh] in addition there is no mention how the S1-S5 bits in TS0 are transferred,
       they can contain propriatary information and timing (SSM) information.

> > --- Currently transport of most E1 is checked with CRC-4 how it this transferred?
>
> Flags L, R, M are used to indicate error in transmission and reception. 
> Also, sequence numbers of SAR-PDUs (AAL.1) and CPS-PDU (AAL.2) may be 
> used to detect losses.

[hvh] CRC-4 is used for PM as well  to determine the BER, how is this related to
       loss detection?

> > --- CRC-4 errors are reported by using REI, this is not mentioned at all, why?
> >
> > Has this RFC been liaised to the ITU-T SG15 experts for review?
>
> ITU-T Y.1453 coincides with the transport of TDM data over a PSN UDP/IP, 
> without mentioning the concept Pseudowire.

[hvh] why is Y.1453 not mentioned in this RFC?

Regards, Huub.

===============
> >> According to RFC 5086, the mechanism:
> >>
> >> + "5.3.  Extending Basic NxDS0 Services with CE Application Signaling": 
> >> it may transport the state signalling of CEs, e.g., CAS for the 
> >> telephony applications.
> >>
> >> + "5.4.  Trunk-Specific NxDS0 Services with CAS": it transport CAS 
> >> signalling for the telephony applications.
> >>
> >> In principle, both represent two distinct possibilities. However:
> >>
> >> a) Apart from CAS for the telephony applications, what other real 
> >> example of CE Application Signaling may be proposed?
> >>
> >> b) If the mechanism 5.3 necessary, why is not covered by the RFC 5087 
> >> (TDMoIP) for AAL.1?