Subject: Re: rfc2493 updates

From: Subrahmanya Hegde <[email-masked]>
Date: Sun, 17 Mar 2002 08:40:29 -0800

Hi,
 I am looking for suggestions for the following issue Related to RFC2493:
[http://search.ietf.org/internet-drafts/draft-ietf-atommib-rfc2493bis-00.txt]

PerfIntervalCount TC[RFC 2493] is defined as Gauge32. This is used in DS3/DS1
MIB and SONET MIBs.

In case of OC-192 Interfaces, these Gauge32 values will wrap around
within 15 Minutes. To support Large value for these interfaces, there is
no Counter64 equivalent of these Intervals. Can we use 'Counter64' to
support OC-192 interfaces?

Appreciate any feedback on this.

Thanks
Subra

Kaj Tesink wrote:

> I-D Archive - Please post attached revision of RFC2493 as
> draft-ietf-atommib-rfc2493bis-00.txt
>
> AToMMIB WG - For your consideration; no technical
> changes; just boiler plate updates. Thanks to Mike
> for the review & help.
>
> Faye, Nathan - Implementation reports of the trunk mibs that use these
> TCs should be sufficient (assuming that all TCs have been
> used) to advance this spec together with the other trunk mibs.
>
> Kaj
>
>   ------------------------------------------------------------------------
>
>    trunktc.txtName: trunktc.txt
>               Type: Plain Text (text/plain)
>
>   ------------------------------------------------------------------------
>
> _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
>
> Kaj Tesink
> Telcordia Technologies. In.
> 331 Newman Springs Road
> Red Bank, NJ 07701
> Email: kaj @research.telcordia.com
> Tel: (732) 758-5254
> Fax: (732) 758-4177
>
> _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/

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From: "C. M. Heard" <[email-masked]>
Date: Sun, 17 Mar 2002 11:03:19 -0800 (PST)

> support OC-192 interfaces?

Subra,

I don't think that such a change is necessary.  The only performance
parameter that could be in danger of wrapping is the count of line layer
CVs (code violations), where at the OC-N rate it is theoretically possible
for up to N*64000 BIP-N errors to occur each second (at the section and
path layer at most 64000 BIP-8 errors can occur in one second).  However,
CVs are supposed to be accumulated only during 1-second intervals that do
not count as SESs (severely errored seconds) or as unavailable time.  The
requirement to inhibit CV counts during SESs was unfortunately not made
explicit in RFC 2558, but it is stated in the latest SONET-MIB draft.

The following table shows the line SES threshold definitions from ANSI
T1.231-1997 for various rates.  These are the values used if
sonetSESthresholdSet has the value ansi1997(5).

         Table 16.  Value for x for SONET line SES definition
           Rate                                          x
           OC-1                                         51
           OC-3                                        154
           OC-12                                       615
           OC-24                                      1229
           OC-48                                      2459
           OC-192                                     9835

From this one sees that if the inhibiting of line layer CVs is properly
applied, then at the OC-192 rate the line layer CV count for a 15-minute
interval should always be less than 900*9835 = 8851500 (0x87102C), which
will easily fit into a 32-bit gauge.

For those who are implementing to SDH instead of SONET standards the
story is a little different.  The performance parameter analogous to
the SONET CV count is the so-called background block error (BBE) count,
which is a count of errored blocks not occurring during severely errored
seconds or unavailable time.  My understanding is that G.829 states
that the 8 BIP-1s contained in the B2 byte of an STM-0 multiplex section
pertain to 8 different blocks within a 125 us frame, and that the 24*N
BIP-1s contained in the B2 bytes of an an STM-N (N = 1, 4, 16) multiplex
section pertain to N x 24 different blocks within a 125 us frame, and so
the multiplex section BBE count is equivalent to the line layer CV count.
However, the SDH multiplex section SES threshold (according to G.784) is
15% errored blocks.  At the STM-16/OC-192 rate the threshold value is
1843200, and so the upper bound on MS-BBE is 1658880000 (0x62E08000),
which still fits into a 32-bit gauge.

Regards,

Mike

---

From: Subrahmanya Hegde <[email-masked]>
Date: Sun, 17 Mar 2002 11:19:48 -0800

Thanks for the explanation.
If we are storing the values of some of these counters for 15 Minute intervals,
[xxIntervalTable in SONET-MIB] , then is it still can be accomodated in
Counter32/Gauge32?

Subra

---

From: "C. M. Heard" <[email-masked]>
Date: Sun, 17 Mar 2002 11:19:05 -0800 (PST)

On Sun, 17 Mar 2002, Subrahmanya Hegde wrote:

> If we are storing the values of some of these counters for 15 Minute
> intervals, [xxIntervalTable in SONET-MIB] , then is it still can be
> accomodated in Counter32/Gauge32?

Yes, if the CV counts are inhibited during SESs as they are supposed
to be, them at any rate up to and including OC-192 all of the current,
previous, and recent interval parameters can be accomodated in Gauge32
objects without overflow.

Mike