Subject: T1.231 VT1.5 and VTG parameters ?

From: Ken Chapman <[email-masked]>
Date: Mon, 15 Jun 1998 10:29:35 -0400

In ANSI T1.231-1997 clause 8.4.4.2 states: 

"The definitions of the far-end parameters are consistent with 

their near-end counterparts."  and lists AISS-LVFE as one of the

parameters.  However there is no AISS-LV defined in 8.4.3.2, but

clause 8.4.3.2.6 defines SEFS-LV which has no counterpart in

8.4.4.2.  Same is true for VTG counterparts.  

What gives? 

	Ken

==============================================

<color><param>0000,8080,0000</param>Ken Chapman               Argon
Networks, Inc.

[email-masked]        25 Porter Road

tel: 978-486-0665 x146    Littleton, MA  01460

fax: 978-486-9379         http://www.Argon.com

</color>==============================================

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From: "C. M. Heard/VVNET, Inc." <[email-masked]>
Date: Mon, 15 Jun 1998 13:00:21 -0700 (PDT)

> 8.4.4.2.  Same is true for VTG counterparts.

Looking at my copy of T1M1.3/97-011R8 (the final pre-publication draft
of ANSI T1.231-1997) I see that Section 8.4.4.2 lists the parameters

CV-LVFE + BBE_LVFE
ES_LVFE
ESA_LVFE
SES_LVFE
AISS_LVFE
UAS_LVFE

and says that they are defined in Table 13.  That is incorrect.  The
correct reference is to Table 14.  The same error exists in clause
8.4.4.3, which discusses the VTG counterparts of these parameters
(and also in 8.4.4.1, which discusses STS-n line layer parameters).

Table 14 does not list AISS-LV or AISS-LVG (and I found no mention of
these parameters anywhere else in the document), but it _does_ list
AISS_LVFE and AISS_LVG.  The abbreviated definitions for these parameters
are "RDI-LV > 1" and "RDI-LVG > 1", and the corresponding text subclause
references for the full definitions are 8.4.4.2 and 8.4.4.3.

I think this is a bug in the document :-)

I think it is possible to divine the intended meaning by looking at the
AISS-L and AISS-LFE parameters, whose abbreviated definitions in Table 14
are "AIS-L > 1" and "RDI-L > 1" respectively and whose text subclause
references are 8.4.3.1.7 and 8.4.4.1.  Clause 8.4.3.1.7 defines the
AISS-L parameter as "a count of 1-second intervals containing one or
more AIS-L defects."  8.4.4.1 has the same structure as 8.4.4.2, except
for stating that far end parameters are not incremented (and the invalid
data flag is raised) during intervals in which AIS-L defects are present.

So, I think we can safely say the "RDI-x > 1" expands to "a count of
one second intervals containing one or more RDI-x defects" (where
RDI-x can be any of RDI-L, RDI-LV, RDI-LVG, etc.).

There is something else I would like to say.  AISS-L, AISS-LFE, and their
VT and VTG kin are all listed in Table 14 as optional (O).  Allow me to
point out that the existing trunk MIBs (including the SONET MIB in
particular) deliberately excluded such stuff.  I strongly recommend that
the supplemental SONET MIB contain the _required_ objects that are missing
from the present MIBs, and nothing more.  There are already enough of those!

                                  ==

In order to track down why SEFS-LFG and SEFS-LVGFE don't exist I looked
at the definitions of the defects SEF-LV and SEF-LVG, which are in
clauses 8.1.3.2.1 and 8.1.3.3.1 respectively.  In both cases the
answer is "Under study"!

In fact, _all_ of the VT and VTG line stuff is new in T1.231-1997, i.e.,
it was not present in T1.231-1993.  Its purpose is to deal with the
sub-STS-1 rates and formats which were introduced in T1.105-07-1996.
This is an _entirely new_ set of transport formats, distinct from
the OC-n/STS-n hierarchy.  The VT 1.5 line rate is 2.048 Mbps and
the VTG line rate is 7.488 Mbps.  Their primary purpose is transport
VT path signals in an intraoffice environment.

Is this stuff even in scope for the SONET supplemental MIB?  Does
anyone out there implement these rates and formats?

Mike
--
C. M. Heard/VVNET, Inc.
[email-masked]