Subject: MINUTES OF ARCHITECTURE REFERENCE SIG AT AIW5

From: "Ralph Case" <[email-masked]>
Date: Mon, 18 Jul 94 18:28:38 EDT

_____________________________________________

  This SIG discusses clarifications, fixes, and minor
  enhancements to the APPN architecture.  The focus is on
  improving the quality and interoperability of APPN
  Implementations.

  The session was presented by members of IBM's APPN
  Architecture Team:  Ralph Case, Candy Elder, Tim Hefel,
  and Tom Moore.

  If we've missed something from the meeting, or if you
  have additional questions or comments, please post them
  here or send them directly to us.

ARCHITECTURE UPDATES

  This is a summary of key points raised during the SIG
  meeting.  These notes are intended to supplement the
  handouts in the AIW5 binder.

Generalized ODAI Use

  A limitation was noted (by Dave Finnie, Insession) that a
  Boundary Function must always be on a primary link
  station node.  While this is not stated in the
  architecture, addressing clashes can result if a BF is on
  a secondary link station node.

  A proposal was presented to address this in two parts:

  1.  Clarify the base architecture to state the existing
      restriction.

  2.  Architect a new option for generalizing ODAI usage to
      dependent flows.

  Philip Dickinson, Insession, indicated that this would
  resolve their concern.

Adaptive BIND Pacing

  Tom discussed the way NCP handles BIND pacing.  He
  described the reasons for this, and clarified that nodes
  attaching to NCP need to handle the BIND pacing support
  as indicated in NCP's XID negotiation.

  There was a question about adaptive BIND pacing support
  for dependent vs. independent LUs.  The level of support
  for BIND pacing is indicated by byte 10, bits 6-7 in
  XID3.

CP-CP Session Activation

  CP-CP session activation enhancements is an option for
  APPN V1 EN and NN and base function for APPN V2 for EN
  and NN.  It is documented in the SNA APPN Architecture
  Reference (SC30-3422-3).  Candy clarified how it works in
  scenarios where one node does not support this function.

  Candy also went over some sense data values for errors in
  capabilities exchange.  Some of these are new, and are
  documented in the arch7844 files on the architecture
  repository.

SS Processing of Cdinit on Locate Message

  A Locate message is limited to a total length of 1024
  bytes due to the size of pre-allocated buffers for the
  RECIEVE_NETWORK_SEARCH_TP transaction program.  If there
  are so many Session Endpoint TGs in a Cdinit that the
  length of the entire Locate message exceeds 1024, SS
  should prune some TGVs.  This may only be done on a TGV
  pair boundary.  An entire CV46-CV47 pair must be present
  for each TGV.

  It was mentioned that there are other flows where size
  limitations may impact network operation.  A general
  solution is an area for future architecture work.

LU 6.2 Security

  There is an LU 6.2 rule that security must match on all
  sessions between two partner LUs.  If security is
  required on LU-LU sessions and CP name = LU name, then
  security must be specified on the Bind for CP-CP sessions
  as well, even though Attach security should not be
  specified for conversations on CP-CP sessions.

APPN Format Handling

  Format parsing rules for unrecognized information was
  reviewed.

  There was a question about where to store unrecognized
  CVs received in a TDU.  Topology information should be
  stored where it belongs, but there are no rules now to
  clarify the hierarchy of unrecognized CVs.  There are no
  such CVs, so this is not a problem today, but an
  architecture clarification is warranted.

  When a Network Node server builds a broadcast Locate
  message for a Locate received from a served End Node, it
  applies the rules for an intermediate node - all
  unrecognized CVs are copied and propagated.

  The rules discussed here apply to BIND flows as well.

Modifications to Session Route Building

  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.

  There was a comment that it might be easier to
  specifically delete a resource rather than do this
  special processing.

  It was noted that topology garbage collection
  enhancements to the architecture should be considered.

Assigning FRSN Values to Resources During Topology Exchange

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

Calculating Routes Through VRNs

  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.

TRS Clarification - FRSN-Wrapping

  This is an architecture change to define the rules for
  FRSN wrapping.

DLC Clarifications

  There have been several questions about this area of the
  architecture.  It seems that these questions are the
  result of several factors

  o   The confusing way the architecture is defined
  o   Architected functions that were designed with
      limitations in mind that are no longer relevant
  o   Additional functions products have developed to
      support additional requirements
  o   Requests for architecture changes to support
      additional requirements

  The intent of this section was to clarify what the
  architecture currently supports and focus on areas for
  enhancements and improvements.  There was a lot of lively
  discussion, I think mostly because of the factors I've
  listed above.  I've tried to list the requirements that
  were discussed here.  I'd like to encourage further
  discussion of these requirements and architecture on the
  mail group.

  o   Allow limited resource link stations on nonswitched
      ports.

  o   Allow a link station to be defined at one end, but
      not the other.

  o   Allow CP-CP sessions over limited resource links.

  o   Remove the port type distinctions of "nonswitched",
      "switched", and "SATF".

  o   Allow switched and nonswitched link stations on the
      same port.

  o   Add a source SAP parameter to
      DEFINE_CONNECTION_NETWORK and DEFINE_LINK_STATION.

  o   Allow a range or list of SAPs on the DEFINE_PORT
      command.  This would allow link stations to be
      dynamically created for a given port using a range of
      allowed SAPs.

Message Transport Services

  Dave Bryant, 3Com, presented a general idea about a
  generic message transport service to allow new network
  transaction programs communicate with each other over the
  existing CP-CP sessions.  Dave stated that he will submit
  a proposed architecture to this SIG if there is enough
  interest in the capability.

STATUS

  As of this meeting, there are six changes to the APPN
  architecture.  These are all published and available on
  networking.cary.ibm.com in the
  /pub/standards/aiw/appn/reference/architecture directory.
  Many other topics have been discussed at this and
  previous AIWs.  These other topics are not changes.  They
  are intended to clarify the architecture or answer
  questions that were deemed to be of general interest.
  Such clarifications are posted in the APPNQA*.TXT files
  or in the mail exploder log.

  We are now starting to see a new category of item -
  proposed changes.  These will also be posted as separate
  files.  The index will clearly list their status as
  proposals.

  I will post a list of all architecture changes discussed.
  This will include the current status - proposed or
  approved.

  We agreed to continue several discussions on the mail
  exploder, and I see that has already started.

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