The IP over ATM Mailing List Archive by date

[sudha@fourier.bellcore.com (Sudha Ramesh 21431)]

Pedro PAIVA writes ...

 > ATMers,
 > 
 >   In our UNI 3.0 implementation (RFCs 1577/1483) there's a point that
 > is not clear regarding repeated IEs in a signalling message.
 >   According to 5.4.5.1 Coding Rules and Table 5-5 and its notes (pp.
 > 187-191 of UNI 3.0) my interpretation is that a Broadband Repeat Indi-
 > cator should be included (mandatory) with a repeated Broadband-Low Layer
 > Information IE and is optionally included with a Cause IE.
 >   Any opinions and or implementations having decided ?
 > 
 >   Thanks
 > 
 >   Pedro PAIVA
 >   Swiss Federal Institute of Technology



Here is Q.port's view.  For those who do not know, Q.port(TM) is
Bellcore's ATM signaling software. Q.port implements ATM Forum
UNI-3.0 and UNI-3.1 Specification.

Broadband Low-layer Information Element:
Section 5.4.5.1, 5.3.1.7(Note 3), and C.4 can be interpreted to mean that
the Broadband Repeat Indicator is mandatory with repeated Broadband
Low-layer information elements. But, since the Repeat Indicator is
labelled optional, it could be missing in the SETUP message.  In such
a case, the first occurence of the information element is accepted and
the subsequent repititions are ignored as per 5.5.6.6.2.
The Broadband Repeat Indicator prioritizes the low-layer information
elements that follow it (ref to 5.4.5.1(b) and C.4).  To avoid any
confusion and to account for different interpretations of the
Specification, in Q.port, the following is done.
Whenever the low-layer information element is repeated in an outgoing
message, we always include a Broadband Repeat Indicator.  However,
in an incoming SETUP message, we do accept multiple low-layer information
elements even when the Broadband Repeat Indicator is not used.

As for the Cause, the text in UNI-3.0 and UNI-3.1 suggest that the use
of Broadband Repeat Indicator with the Cause IE is optional.  The
procedures described in UNI-3.0 and UNI-3.1 require repitition of
Cause information element only when the timer T308 or T398
expires. Refer to Section 5.5.4.3, 5.5.4.4., 5.6.3.3 and 5.6.3.4.1.
In these cases, optionally, a second Cause can be included in the
RELEASE or the DROP PARTY ACKNOWLEDGE message sent.  But in these two
messages, Broadband Repeat Indicator information element is not
present.  Therefore, in Q.port, when the Cause information element is
repeated in an outgoing RELEASE or DROP PARTY ACKNOWLEDGE, the
Broadband Repeat Indicator is not included.  If the Cause information
element is repeated in an incoming RELEASE or DROP PARTY ACKNOWLEDGE
message preceded by a Broadband Repeat Indicator information element,
that Repeat Indicator is treated as an unexpected recognized
information element as per 5.5.6.8.3.

In a nutshell, when Q.port transmits a SETUP message, the Broadband
Repeat Indicator is deemed mandatory when the low-layer information
element is repeated.  But when it receives a SETUP message, it is
deemed non-mandatory.  And while transimitting or receiving repeated
Cause information elements in RELEASE or DROP PARTY ACKNOWLEDGE
message, Broadband Repeat Indicator is not used.

Sudha Ramesh
(for the Q.port Team)

PS: If you need more information about Q.port's interpretation of the
Specification, you can contact us at:
qport-support@bellcore.com
201-829-5973