Subject: SCSP MIB: Need for extra Hello Interface table

From: Hoylen Sue <[email-masked]>
Date: Tue, 9 Dec 1997 10:45:03 +1000

Cliff,

The SCSP MIB <draft-wang-ion-scsp-mib-00.txt> puts the Hello
Interval and dead factor in with the SCSP instance:

>   ScspLSEntry ::= SEQUENCE {
>	scspLSID                          OCTET STRING(SIZE(0..64)),
>	scspLSHelloInterval               INTEGER,
>	scspLSDeadFactor                  INTEGER,
>	scspLSRowStatus                   RowStatus
>	}

This restricts the SCSP impementation to use one set of values per
SGID+PID+LSID.  Whereas, the SCSP specification does not have this
limitation.  It is conceivable that an operator would wish to run a
server with different Hello Intervals for some of the NBMA addresses it
uses (for example, usage charging or loading of that address e.g. over a
carrier link address).

Also, the user may choose to configure two NBMA addresses to the same
DCS. This is permitted under the SCSP specification, and is one method
to avoid having a single point of failure, e.g. by multiple physical routes.
This means that the combination of SGID+PID+DCSID is not unique.

Thus, the current MIB will not be able to properly handle this.

A natural solution to the above problems is to have an extra table for
representing the Hello Interfaces (e.g. the NBMA addresses or local
hardware I/F).  This table can be indexed by SGID+PID+HIID, where HIID
is a locally unique Hello Interface ID. The ScspDCSEntry table is then
indexed by SGID+PID+HIID+DCSID.

It is apparant that without a protocol and data link layer specific MIB,
SCSP management is not very useful.  One of the most important
configuration operations performed by managers will be to configure the
NBMA addresses, and that will be a data link layer specific operation.
The introduction of the HIID and will eventually be required in some
form to associate the corresponding entities between the SCSP MIB and
the data link layer specific MIB.

Hoylen
__________________________________________________________ Dr Hoylen Sue
[email-masked]                                        +61 7 3259 2222
CiTR Pty Ltd, PO Box 1643, Milton, 4064, Australia. Fax: +61 7 3259 2259
http://www.citr.com.au           http://www.dstc.edu.au/RDU/staff/hoylen