Subject: Flow Control SIGlet Minutes - Sept. AIW

From: [email-masked] (Shannon Nix)
Date: Wed, 20 Oct 93 18:01:06 EST

Fellow controllers of flow:

I apologize for the delay in posting the minutes of the flow control SIGlet at 
the September AIW.  Here they are:

Meeting convened in parallel with the meeting for the connect SIGlet.

The agenda was presented and discussed:

Technical Contributions were presented:

    a.  Adaptive Pacing Proposal - Peter Gayek, IBM
    b.  Out-of-band Flow Control Proposal - Paul Gacek, Novell
    c.  Buffer Management Policy Proposal - Shannon Nix, Netlink
    
Hardcopy of slides were made available for (a) and (c) as well as a supporting 
paper for (c).  If anyone did not attend the meeting and would like a copy of 
these items drop me a direct note with your address included ([email-masked]).

Contribution (a) has been presented earlier on the mailing list by Peter Gayek 
of IBM.
Contribution (b) has been presented earlier on the mailing list by Anand Subramanian 
of Novell.

In addition to the scheduled contributions, Ed Stern of Proteon presented a 
case for using the ENTERBUSY/EXITBUSY mechanism defined by the 6611 
implementation (also described earlier on the mailing list by David Miller of 
IBM)

The meeting broke for dinner and reconvened in the evening.  In the 
evening the working group focused on identifying points of consensus and 
outstanding issues.  Rather than recounting a blow-by-blow description of the 
session I will summarize the outcome below:

CONSENSUS ITEMS

1.    A circuit-level flow control mechanism should be included in the 
      base function set. 
      
2.    An additional flow control mechanism to be exerted on a transport
      connection (above and beyond any native transport capability) should
      be included in the base function set.
      
3.    The scope of this working group shall be to define a "back pressure 
      mechanism" for Switch-to-switch Protocol (SSP) rather than to describe 
      a policy to enforce "end-to-end" flow control and fairness among
      circuits.
      
4.    An adaptive pacing mechanism, similar to the one proposed by Peter, 
      should be defined as an option.
      
OPEN ISSUES:

1.    Exactly what mechanism should be included in the base set to exert
      circuit-level flow control?  Two primary schools-of-thought:
      
      a.  Fixed pacing mechanism
      b.  ENTERBUSY/EXITBUSY mechanism
      
2.    Transport Connection mapping to transport sessions.  Possibilities are:

      a.  Use 6611 mechanism:  One simplex connection in each direction 
          over which both data and control packets are sent.
          
      b.  Use a single full duplex connection over which data and control 
          packets are sent in both directions.
          
      c.  The Novell proposal: Use two full duplex connections and use one
          channel in each direction for data and the remaining channel in
          each direction for control.
          
      d.  Have multiple full duplex connections in each direction for data.
      
      It was generally agreed that (d) and possibly (c) had implications in
      all of the following working groups:
      
      Flow Control, COS, Connect, Capabilities
      
3.    Patent Issue! IBM is still cogitating on whether they shall assert an
      patent right on the concept of adaptive pacing ( APPN sessions use a
      similar mechanism).  The general consensus of the group is that we will
      not incorporate technology over which any vendor holds patent rights.
      
      Jane Munn of IBM has agreed to supply a timely answer to group stating 
      IBM's position on this issue.

The group also agreed to hold a teleconference in November to discuss these 
issues and advance the consensus.  Paul Gacek of Novell has offered to host 
this teleconference.  

Paul has suggested, and it seems eminently sensible, that the issues need 
more definition/discussion prior to scheduling this teleconference.

Comments?

Go forth and discuss,
Shannon