Re: session layers, was Re: Renumbering ... Should we consider an association that spans transports?

[Fred Baker <fred at cisco.com>]

Dumb question of the month. With the exception of the last claim  
("...can prioritize..."), this could just as easily describe SCTP.  
What here is new? And define "prioritize"?

On Sep 17, 2007, at 2:02 AM, Lars Eggert wrote:
> You might be interested in Bryan Ford's SST paper from this year's  
> SIGCOMM:
>
> Structured Streams: a New Transport Abstraction. Bryan Ford. ACM  
> SIGCOMM 2007, August 27-31, 2007, Kyoto, Japan. http:// 
> www.brynosaurus.com/pub/net/sst-abs.html
>
> Abstract: Internet applications currently have a choice between  
> stream and datagram transport abstractions. Datagrams efficiently  
> support small transactions and streams are suited for long-running  
> conversations, but neither abstraction adequately supports  
> applications like HTTP that exhibit a mixture of transaction sizes,  
> or applications like FTP and SIP that use multiple transport  
> instances. Structured Stream Transport (SST) enhances the  
> traditional stream abstraction with a hierarchical hereditary  
> structure, allowing applications to create lightweight child  
> streams from any existing stream. Unlike TCP streams, these  
> lightweight streams incur neither 3-way handshaking delays on  
> startup nor TIME-WAIT periods on close. Each stream offers  
> independent data transfer and flow control, allowing different  
> transactions to proceed in parallel without head-of-line blocking,  
> but all streams share one congestion control context. SST supports  
> both reliable and best-effort delivery in a way that semantically  
> unifies datagrams with streams and solves the classic “large  
> datagram” problem, where a datagram's loss probability increases  
> exponentially with fragment count. Finally, an application can  
> prioritize its streams relative to each other and adjust priorities  
> dynamically through out-of-band signaling. A user-space prototype  
> shows that SST is TCP-friendly to within 2%, and performs  
> comparably to a user-space TCP and to within 10% of kernel TCP on a  
> WiFi network.
>
> Lars_______________________________________________
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