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

[Margaret Wasserman <mrw@windriver.com>]

>
>Wrong.
>
>TCP is the reliable transport.

Wrong.  :-).  TCP provides data integrity.  It is impossible
to provide complete reliability over an unreliable medium.
Any application that wishes to maintain a long-lived TCP
connection must be prepared to reestablish the connection
if it drops.  

>Most TCP applications are so stateful that they can not accept a
>loss of bytes.

No TCP application will ever see dropped bytes.  This is
why TCP retransmits.  A TCP application _may_ see a TCP
connection drop during a data transfer.  At that point, the
application will know that the transferred data may be
truncated and should act accordingly -- the best thing to
do in this situation is application specific.

>If you insist that TCP may be unreliable upon multihoming,
>you will end up with construting virtual reliable TCP over
>unreliable TCP.

My above comments aside, it may be a requirement of a site 
multi-homing solution that TCP connections survive an outage 
at one connection point.  Site multi-homing requirements in this
area are completely orthogonal to whether TCP provides
complete reliability.

Margaret