Browse Prior Art Database

SS7 Level 2 Protocol Two-Out-Of-Three Checking for Link Integrity With Discarded Signal Units

IP.com Disclosure Number: IPCOM000101306D
Original Publication Date: 1990-Jul-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Horlacher, BC: AUTHOR [+3]

Abstract

This article describes a technique for checking for two-out-of-three invalid signal units when "like" signal units are discarded and only the number of like signal units are kept for further evaluation.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 69% of the total text.

SS7 Level 2 Protocol Two-Out-Of-Three Checking for Link Integrity With Discarded Signal Units

       This article describes a technique for checking for
two-out-of-three invalid signal units when "like" signal units are
discarded and only the number of like signal units are kept for
further evaluation.

      In the technique disclosed herein, each signal unit (SU) is
screened independently, and any SU that is identical to its immediate
predecessor is tallied.  Upon the occurrence of a "different from its
immediate predecessor" SU, the tally is included in an entry field
called "signal units discarded" SUD in the receive queue, as shown in
Fig. 1.

      In performing two-out-of-three checking to determine a faulty
link, the two fields that are checked independently are the forward
indicator bits (FIBs) and the backward indicator bits (BIBs).  Two
variables, UNF (unreasonable FIB) and UNB (unreasonable BIB) are used
in link evaluation. The algorithm used for both is identical.  The
FIB check is explained herein in detail.

      Referring to Fig. 2, a signal unit is received.  If it is good
(the FIB is valid), then if the variable UNF = 0, it is a good
link. If UNF = 1, then at least two good SUs in a row have
been bad, UNF is decremented (it will now = 0).  If UNF = 2 (the
last evaluated SU was bad), a further check is made to see if there
were any more like the bad one that was discarded during screening
(the SUD field).  IF SUD = 0, then UNF is dec...