Subject: APPN Architecture Changes

From: "Ralph Case" <[email-masked]>
Date: Thu, 8 Sep 94 13:41:14 EDT

At the last AIW, we agreed that there is a need for a list
of all the changes to APPN architecture since the reference
was published.  It would also be useful to catalog all the
items discussed at the APPN reference SIG.  I have posted
architem.psbin to the networking repository that should satisfy
both of these requirements.  It is also available in ascii
form as architem.txt, and I have included it below.

Ralph Case                    [email-masked]    (919)254-1882
APPN Architecture
IBM Networking Hardware Division

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   This file is regularly updated to reflect the current
   status of the APPN architecture.  This file is current
   as of August 31, 1994.

   This is a list of all APPN architecture items discussed
   at the AIW.  It is divided into sections:

   o   "Approved Changes" are considered part of the APPN
       architecture of record.  Specific documentation for
       these items is, or will shortly be, available on the
       networking repository.  This file points to the
       documentation.  See the index file for a list of
       individual files.

   o   "Proposed Changes" have been submitted to the AIW for
       consideration.  Documents will be available for these
       items for the AIW to approve.

   o   "Clarifications and Answers" just list topics that
       have been discussed at the AIW.  These are not
       considered changes to the architecture.
       Documentation for these may be available as
       appropriate.  See the SIG handouts and minutes.

   To ask a question or propose a change, submit it to the
   AIW Architecture Reference SIG on the aiw-appn-reference
   mail exploder.

APPROVED CHANGES
________________

   These changes are Closed Pages (CP) and part of the APPN
   Architecture of record.

TOPOLOGY AWARENESS OF CP-CP SESSIONS

   ABSTRACT:  Topology awareness of CP-CP sessions enables
   TRS to keep current status for TGs carrying CP-CP
   sessions.  If a CP-CP session becomes inactive, SS no
   longer has to signal CS to invoke nonactivation XIDs and
   CS no longer has to signal TRS that a CP-CP session is
   not active or supported on that TG.  Operator
   intervention is no longer needed to deactivate and
   reactivate a link in order to activate a new CP-CP
   session on that link.  With thin enhancement, SS signals
   TRS when a CP-CP session is active or inactive.  An
   operator interface enables manual activation and
   deactivation of CP-CP sessions.  An operator may
   reactivate a deactivated CP-CP session.  An operator may
   choose to move CP-CP sessions in order to take advantage
   of a higher speed link between two APPN nodes.

   STATUS:  Documented in arch7844 files.  This is a change
   to the base architecture.

   Presented at AIW3.

STRIP NETID FROM RSCV

   ABSTRACT:  This item allows APPN Network Nodes (NN) to
   save space in Route Selection Control Vectors (RSCVs)
   when building routes, allowing more hops to fit in an
   RSCV.  The modification requires NNs to strip off the
   NetID portion (9 bytes) from each TG Descriptor CV for
   every TG Descriptor that connects two nodes having the
   same NetID, when building the RSCV.

   STATUS:  Documented in arch7860 files.  This is base
   (required) architecture for future releases.

   Presented at AIW4.  "RSCV 'next hop' Determination"
   presented at AIW3.

INCREMENTING RSN DURING INITIAL TOPOLOGY EXCHANGE

   ABSTRACT:  This APPN modification reduces the number of
   TDUs that are generated within APPN networks when an NN
   performs topology exchanges with multiple partner NNs.
   The specific modification is within the TRS component and
   includes two new actions:

   1.  When performing a topology exchange, the NN does not
       increment its own RSN when including its node update
       in a TDU.
   2.  Safe storing NNs must increment the RSN of their node
       record whenever reading their TDBs back into memory
       from permanent storage.  This prevents the
       possibility of an NN being garbage collected
       (Time-to-Live decrements to 0), because previously
       the requirement that NNs increment their own RSNs in
       topology exchanges was the safeguard for this
       happening.

   STATUS:  Documented in arch7880 files.  This is base
   (required) architecture for future releases.

   Presented at AIW4.  "TRS Performance Optimizations"
   presented at AIW3.

INTERPRETING MODE OR COS NAMES

   ABSTRACT:  Modify interpretation rules to

   o   Allow blank mode or COS names to be used in route
       requests (required of future releases)
   o   Allow unrecognized mode or COS names to be mapped to
       default COS (optional to implement)
   o   Allow operators the ability to define own default COS
       through the NOF DEFINE_CLASS_OF_SERVICE command
       (optional to implement)

   STATUS:  Documented in arch7893 files.

   Presented at AIW4.  "Mode to COS Mapping Clarifications"
   presented at AIW3.

NEGOTIATING FRSN IN INITIAL TOPOLOGY EXCHANGE

   ABSTRACT:  This change fixes a bug that may occur when
   performing a topology exchange with a nonSafe-Store
   network node.

   STATUS:  Documented in arch7945 files.  This is base
   (required) architecture for future releases.

   Presented at AIW4.

ISR HANDLING OF BINDS AND RSP(BIND)S INDICATING TWO-STAGE PACING

   ABSTRACT:  This change removes the restriction that SCM
   may receive BINDs and RSP(BIND)s with the pacing staging
   indicators set to two-stage from subarea boundary
   function only if the BIND or RSP(BIND) is unextended.

   STATUS:  Documented in arch7978 files.

   Presented at AIW4.

CALCULATING ROUTES THROUGH VRNS

   ABSTRACT:  This is a new change to make mandatory the
   suggested method of assigning weights to VRNs and CN TGs.
   This will allow simpler network definition and more
   consistency in route calculation.

   STATUS:  Documented in arch7944 files.  This also
   contains a clarification "Building/Interpreting Routes
   through VRNs" discussed at AIW4.

   Presented at AIW5.  "TG and VRN Weight Determination"
   presented at AIW3.

FRSN WRAPPING

   ABSTRACT:  This change documents how FRSN wrapping is
   detected and handled.

   STATUS:  Documented in arch8116 files.  This is base
   (required) architecture for future releases.

   Presented at AIW5.

TOPOLOGY GARBAGE COLLECTION

   ABSTRACT:  Use an odd RSN and a new bit indicator to
   ensure correct garbage collection.

   STATUS:  Presented at AIW3.

   Will be documented.

LFSID ADDRESS SPACE PARTITIONING

   ABSTRACT:  A "Dependent LU Range" of the LFSID address
   space is unconditionally reserved for dependent LU-LU
   sessions that receive boundary function support over the
   TG.

   STATUS:  Presented at AIW4.

   Will be documented.

ASSIGNING FRSN VALUES TO RESOURCES DURING TOPOLOGY EXCHANGE

   ABSTRACT:  This is a new change to reduce the number of
   TDUs that flow in some cases during an initial topology
   exchange.

   STATUS:  Presented at AIW5.

   This will be documented.

PROPOSED CHANGES
________________

   These changes have been discussed, but have not reached
   final approval yet.

GENERALIZED ODAI USE

   ABSTRACT:  There is an unstated restriction that a
   boundary function must be on the primary link station
   node.  A new option is proposed that allows ODAI usage
   for dependent flows to be the same as for independent
   flows.

   STATUS:  This proposal was discussed at AIW5.  A document
   will be submitted for approval.

MODIFICATIONS TO SESSION ROUTE BUILDING

   ABSTRACT:  This is a proposal for architecture changes to
   solve a problem that could occur when a node changes type
   from NN to EN.  Network nodes remain in the Topology
   database even when not active in the network.  This is
   for efficiency reasons.  Special processing is required
   for the case when a node is still available, but not as a
   network node.

   STATUS:  This proposal was discussed at AIW5.  A document
   will be submitted for approval.

PARALLEL TGS OVER A LAN

   ABSTRACT:  Change DEFINE_LINK_STATION command to include
   local SAP address.

   STATUS:  Proposed at AIW4.

   This proposal is related to the dynamic link station
   discussion that was raised at AIW5.  This item will be
   resolved based on what the SIG decides to do with those
   questions.

CLARIFICATIONS AND ANSWERS
__________________________

   These items have been discussed, but are not considered
   changes to the architecture.

CORRECTING THE TOPOLOGY DATABASE WHEN AN NN BECOMES EN/LEN

   Discussed at AIW4.

LIMIT OF ONE TDU PER CONVERSATION

   Discussed at AIW4.

INTEROPERABILITY WITH BORDER NODES

   Discussed at AIW4.  "RSCV 'next hop' Determination"
   presented at AIW3.

NO DEFAULT NETID

   Discussed at AIW4.

ENCODING MAC ADDRESS IN TG DESCRIPTOR

   Discussed at AIW4.

SEARCH RESULT PREFERENCES

   Discussed at AIW3 and AIW4.

ADAPTIVE BIND PACING

   Discussed at AIW5.

CP-CP SESSION ACTIVATION

   Discussed at AIW5.

SS PROCESSING OF CDINIT ON LOCATE MESSAGE

   Discussed at AIW5.

LU 6.2 SECURITY

   Discussed at AIW5.

APPN FORMAT HANDLING

   Discussed at AIW5.

DLC CLARIFICATION

   Discussed at AIW5.