[openib-general] [ANNOUNCE] Contribute RDS(ReliableDatagramSockets) to OpenIB

[Grant Grundler]

On Wed, Nov 09, 2005 at 12:45:17PM -0800, Caitlin Bestler wrote:
>  
...

Caitlin,
I'm having problems reading the quoting "style" too.
Please, can you take a look at "quotefix"?
	http://home.in.tum.de/~jain/software/outlook-quotefix/

thanks,
grant



> ________________________________
> 
> 	From: openib-general-bounces at openib.org
> [mailto:openib-general-bounces at openib.org] On Behalf Of Michael Krause
> 	Sent: Wednesday, November 09, 2005 12:21 PM
> 	To: Rick Frank; Ranjit Pandit
> 	Cc: openib-general at openib.org
> 	Subject: Re: [openib-general] [ANNOUNCE] Contribute
> RDS(ReliableDatagramSockets) to OpenIB
> 	
> 	
> 
> 		One could be able to talk to the remote node across
> other HCA but that does not mean one has an understanding of the state
> at the remote node unless the failure is noted and a resync of state
> occurs or the remote is able to deal with duplicates, etc.   This has
> nothing to do with API or the transport involved but, as Caitlin noted,
> the difference between knowing a send buffer is free vs. knowing that
> the application received the data requested.  Therefore, one has only
> reduced the reliability / robustness problem space to some extent but
> has not solved it by the use of RDS.
> 		
> 		
> 
> Correct. When there are point-to-point credits (even if only
> enforced/understood
> at the ULP) then the application can correctly infer that message N was
> successfully processed because the matching credit was restored. A
> transport
> neutral application can only communicate restoration of credits via ULP
> messaging. When credits are shared across sessions then the ULP
> has a much more complex task to properly communicate credits.
>  
> The proposal I presented at RAIT for multistreamed MPA had a
> non-highlighted
> option for a "wildcard" endpoint. Without the option multistream MPA is
> essentially
> the SCTP adaptation for RDMA running over plain MPA/TCP. It achieves the
> same reduction in reliable transport layer connections that RDS does,
> but
> does not reduce the number of RDMA endpoints. The wildcard option 
> reduces the number of RDMA endpoints as well, but greatly complicates
> the RDMA state machines. RDS over IB faces similar problems, but solved
> them slightly differently.
>  
> Over iWARP I believe these complexities favor keeping the point-to-point
> logical connection between QP and only reducing the number of L4 
> connections (from many TCP connections to a single TCP connection
> or SCTP association). The advantage of that approach is that the API
> from application to RDMA endpoint (QP) can be left totally unchanged.
> But I do not see any such option over IB, unless RD is improved or a
> new SCTP-like connection mode is defined.
>  
> In my opinion the multi-streaming is the most important feature here,
> but over IB I do not think there is a natural adaptation that provides
> multi-streaming without also adding the any-to-any endpoint semantics.
> Multistream MPA and SCTP can both support the any-to-any endpoint
> semantics by moving the source to payload information rather than
> transport information (by invoking "wildcard status" in MS-MPA or
> by duplicating the field for SCTP). So the RDS API strikes me as
> the best option for a transport neutral application. MS-MPA and SCTP
> reductions in transport overhead would be available without special
> API support.
>  

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