Browse Prior Art Database

Node Buffer Manager

IP.com Disclosure Number: IPCOM000107254D
Original Publication Date: 1992-Feb-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 5 page(s) / 195K

Publishing Venue

IBM

Related People

Glatz, MW: AUTHOR

Abstract

Disclosed is a process for over committing real memory dedicated to APPN PU 2.1 sessions and links as buffer resource space. Overview

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Node Buffer Manager

       Disclosed is a process for over committing real memory
dedicated to APPN PU 2.1 sessions and links as buffer resource space.
Overview

      In APPN, the Node Buffer Manager (NBM) component is the buffer
resource manager for all APPN components.  APPN architecture states
that buffer resources exist when permission to send is granted, i.e.,
receiving node has storage capacity in real memory or disk space to
accept the data transmission.  This buffer space is allocated (when
the session or link is being activated) and dedicated to service that
link's/session's paced window size.  For example, for a session
desiring a 4K rusize on each half-session, NBM would reserve 8K of
memory space specifically for that one session's private use.
Therefore, eight megabytes of buffer space would be required to
support 1000 2.1 sessions (each half-session having a 4K rusize).

      An alternative process for APPN Nodes that are limited in the
amount of real storage and disk capability (and perhaps processor
speed) is to provide a "logical buffer pool" facility.  The "logical
buffer pool" process will allow an APPN Node to support many more
links and sessions than would be the case if buffer space were not
over committed.  Since a "logical buffer pool" structure would over
commit storage, "fairness" algorithms are also needed to restrict
allocation of buffer resources when they become limited/critical.
The following description shows how the logical buffer pool process
is able to over commit real storage by a factor of eight, i.e., for
1000 2.1 sessions, only one megabyte of storage is required instead
of eight megabytes.
Logical Buffer Pool Description

      Assuming 1000 2.1 sessions are to be supported, then one buffer
(capable of holding 512 bytes of RU information) is created per half-
session.  For each buffer a "buffer header control block" is created,
containing the following:
           POINTER TO NEXT BUFFER HEADER
           POINTER TO BUFFER DATA AREA
           POINTER TO NBM LOGICAL POOL CONTROL BLOCK
           POINTER TO DLC LOGICAL POOL CONTROL BLOCK
           PRODUCT-SPECIFIC FLAGS AND CONTROL INFO

      For each of the 1000 sessions two NBM logical pool control
blocks are created (one per half-session).  For every DLC that the
APPN Node supports, one NBM logical pool control block is created.  A
DLC can be thought of as an adapter that is used for receiving and
transmitting data, i.e., SDLC TP adapter, Token_Ring LAN adapter.
The NBM logical pool control block has the following fields:
           POINTER TO NEXT CONTROL BLOCK
           GET COUNT
           FREE COUNT
           BUFFER IN USE COUNT
           INITIAL LOGICAL BUFFER COUNT
           CURRENT LOGICAL BUFFER COUNT
           RE-RESERVE SIZE
           NBM CONTROL FLAGS
           PO...