Subject: TDM Hairpinning; Re: [Megaco] Hairpin case A/u Law conversion

From: [email-masked]
Date: Wed, 25 Feb 2004 15:24:39 +0100

Dear Zhao Bo,

because there isn't any "hairpinning" definition in MEGACOP/H.248 standards
("please correct if I'm wrong"), I'd like to use the following one for
responding your questions:

***********************************************************************************
Definition:
TDM Hairpinning
? is a scenario whereby a call is being made between two TDM endpoints on a
    single media gateway. The media comes in on one TDM channel and goes
    out on another TDM channel through the use of an internal loop in the
    media gateway.

Note 1: due to the fact that there are local call types at local exchanges
(CLASS5), and transit exchanges (CLASS4) in legacy TDM networks (PSTN,
NISDN, etc), there is a variety of TDM-to-TDM connection types behind the
general "TDM hairpinning" capability (dependent on required type of IWF,
etc.) in corresponding H.248 MG types

Note 2: H.248/MEGCOP perspective
TDM Hairpinning = Single H.248 Context with 2 H.248 TDM Terminations
************************************************************************************

Based on this hairpinning understanding, my answers are:

(1) Speech telephony service: G.711 companding formats are a property of
the corresponding H.248 TDM termination

[Note: dependent on MG architecture and implementation, property might be
signalled or preprovisioned. Of course, G.711 companding law is an inherent
property of your DS0 channel at your PDH/SDH/SONET framer; the way, how
this DS0 property is associated with the corresponding H.248 TDM
Termination property may only realized MG-internally for very specific MG
architectures. Generally it is up to the MGC, particularly if some (or all)
DS0's are ISDN B channels.]

(2) Voiceband Data services: same as in (1)

[Note: VBD according new ITU-T V.152 -> "... For purposes of
interoperability, a V.152 compliant implementation shall support at least
both G.711 A-law and G.711 ì-law codecs as VBD codecs. "]

(3) ISDN UDI = all ISDN Teleservices with ISDN I.231. bearer service
requirement
=> H.248 TDM Termination property must be signalled by MGC, if not, MG may
not guarantee UDI capability (i.e., fully transparent 64-kbit/s bearer
channel) in TDM hairpinning scenarios ...

Conclusion:
IF your MG is supporting
PSTN lines (= H.248 ALN Termination),
PSTN trunks (= H.248 TDM Termination), and
ISDN B channels (= H.248 TDM Termination)

AND IF you've such services and interworking requirements

THEN you should generally signal the corresponding properties ...

... in case of
TDM hairpinning,
ALN hairpinning, or
ALN-to-TDM connection types.

Regards,
Albrecht

ALCATEL

                      Zhao Bo                                                                                                                       
                      <[email-masked]>         To:      [email-masked]                                                                             
                      Sent by:                 cc:                                                                                                  
                      megaco-admin@iet         Subject: [Megaco] Hairpin case A/u Law conversion                                                    
                      f.org                                                                                                                         

                      25.02.2004 08:11                                                                                                              

In this case, the A/u law format of a TDM ciruit can be provisioned,  but
the MG doesn't know the service type of a call, thus
has no way to know if a conversion is needed. For speech service conversion
may be needed; for data service like isdn UDI, conversion is not permitted.
Is there any method to solve this problem?

Zhao Bo

*****************************************************************
This e-mail and its attachments contain confidential information from
HUAWEI, which is intended only for the person or entity whose address is
listed above. Any use of the information contained herein in any way
(including, but not limited to, total or partial disclosure, reproduction,
or dissemination) by persons other than the intended recipient(s) is
prohibited. If you receive this e-mail in error, please notify the sender
by phone or email immediately and delete it!
*****************************************************************

_______________________________________________
Megaco mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/megaco

_______________________________________________
Megaco mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/megaco