Subject: Re: [multipathtcp] TCP modification vs switching to SCTP

From: Aleksi Suhonen <[email-masked]>
Date: Mon, 15 Jun 2009 06:34:23 +0300

Bryan Ford wrote:
> I think this "multipath TCP versus multipath SCTP" question is 
> important, but still misses a larger issue: SCTP and TCP are different 
> transports providing substantially different application-visible 
> semantics, but we would really like to have multipath support for _both_ 
> of those transports (and perhaps others).

One thing I haven't noticed yet in these discussions is interaction with 
other multi-pathing protocols underneath or on top of TCP.

For example, if you run TCP over HIP, you get multi-pathing from HIP.
Or if you run iSCSI over TCP, iSCSI itself takes care of multi-pathing.

What happens to these protocol combinations if TCP starts to behave 
differently too?

 > It's a pain for TCP
> applications to switch to SCTP because it involves programmers learning 
> a new API with different semantics:

This is why operating systems that support SCTP have two separate APIs, 
one that provides an identical interface as TCP with the exception of 
one parameter to one function call, and one that is substantially 
different and offers much more control over the finer features of SCTP, 
isn't it?

--
	Aleksi Suhonen