Re: Application knowledge of transport characteristics (was: Re: Domain Centric Administration)

[Douglas Otis <dotis at mail-abuse.org>]

On Jul 8, 2007, at 10:53 PM, Lars Eggert wrote:

> On 2007-7-5, at 19:07, ext Tom.Petch wrote:
> > If we had a range of transports (perhaps like OSI offered), we  
> > could choose the one most suited.  We don't, we only have two, so  
> > it may become a choice of one with a hack.  But then that limited  
> > choice may be the reason why the Internet Protocol Suite has  
> > become the suite of choice for most:-)
>
> We have four standards-track transport protocols (UDP, TCP, DCCP  
> and SCTP), and, FWIW, SCTP has a concept of record boundaries.
>
> Designers of applications and higher-layer protocols still have a  
> tendency to ignore SCTP and DCCP and the particular features they  
> can offer to applications. This can make applications more complex,  
> because they need to re-invent mechanisms that a more appropriate  
> transport protocol would have provided.

A desire to use TCP or UDP could also be due vested interests in  
existing solutions.  Utilization of transports with poor error  
detection capabilities as found with TCP or UDP checksums, and even  
Fletcher-32, have modulos that can mask fairly common memory or  
interface errors.  SCTP extends error detection and ensures jumbo  
frames are afforded end-to-end error detection equivalent to 1.5 KB  
ethernet LAN packets.  A number of errors go undetected by TCP or  
UDP.  Handling such errors by upper protocols layers is usually not  
robust, if even existent.  When reliability, high availability, low  
latency, and elimination of head of queue blocking matters, SCTP  
offers a clean solution.

-Doug

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