Re: Network layer reqt? [was Re: Transport level multihoming]

[Brian E Carpenter <brian@hursley.ibm.com>]

Masataka Ohta wrote:
> 
> Greg;
> 
> > > You miss the point.
> > >
> > > > > Most TCP applications are so stateful that they can not accept a
> > > > > loss of bytes.
> > >
> > > Neither SVC nor TCP reconnection restores lost data.
> >
> > No. But today, connections with TCP/IPv4 and typical IP multi-homing get
> > dropped and data gets lost when the prefered path fails. Traffic is lost
> > until the routing reconverges which is usually long enough to back TCP off
> > into oblivion.
> 
> You are not saying reconnection is good enough but saying reconnection
> is unnecessary.
> 
> That's not a Brian's point.

My point is that reliable apps today are built on the basis that TCP
sessions can break. They contain all the checkpoint/restart machinery
to deal with it today. Furthermore, it is application-dependent machinery
which would be very complex to build into a transport system. Restoring 
network level connectivity after an outage is necessary and sufficient.

> 
> Note also that you are assuming large, thus, slow to converge,
> routing table.

Unfortunately that is the only safe assumption, until we find a multihoming
solution that doesn't punch holes.

   Brian