[ih] Separation of TCP and IP

[Brian E Carpenter]

Woof woof woof!

I was just curious to see where OSI stood on this question in the
1980 Zimmermann paper. No trace of datagrams really, at that time,
except as a possible future addition. But on the session layer, he
wrote:

"Protocols for the Session Layer
No standard exists and no proposal has been currently available,
since in most networks, session functions were often considered as
part of higher layer functions such as Virtual Terminal and File
Transfer.
A standard Session Layer Protocol can easily be extracted
from existing higher layer protocols."

There is no suggestion that the session layer was intended
to provide resilience and/or security, which I think is
how we'd look at it today. In their own ways, SCTP, MPTCP,
TLS and QUIC are all about that.

All the same, I think Zimmermann was right - what OSI conceived
of as session layer functions have always been mainly embedded
in apps, and the same goes for the elusive Presentation Layer.

Regards
    Brian Carpenter

On 24-Jun-22 13:52, Dave Crocker via Internet-history wrote:
> On 6/23/2022 6:41 PM, Jack Haverty via Internet-history wrote:
>> and they have no need for "sessions".
> 
> 
> This is a squirrel and I'm inclined to chase after it.
> 
> In the context you've used this clause, sure.  But I suspect we'd be in
> better shape if we'd actually taken advantage of the construct more
> generally.
> 
> I was intrigued to discover, some years back, that TLS is actually
> specified within a session layer model, though this bit of generality
> has apparently not been otherwise exploited.
> 
> The benefit of this layer is the tiresome one of indirection. The
> current reality is that one process interacts with another through a
> transport protocol. If this interaction is based on continuing state,
> there is no convention for maintaining process-process context if that
> transport interaction is lost. So the interaction has no robustness
> against outages or mobility.
> 
> A session layer can fix that, hiding changes from one transport
> 'connection' to another. Move from Wi-Fi access to cell-based access and
> the applications see only some performance hiccups, but no loss of
> the... session.
> 
> woof.
> 
> d/
>