Re: Overlays and encapsulations (was Re: Engineering discussions )

On 09 Mar 2014, at 22:33, Alia Atlas <akatlas(_at_)gmail(_dot_)com> wrote:

> In the last few years, there seems to be a drive towards overlays and 
> additional
> packet encapsulations.  What problems do you see these as solving?  Is there a
> more focused way to consider the drivers and downsides?
>
> Thoughts?
Oh. Could we have an easier one to start with? Especially on the Sunday after 
an IETF? Because my response to this one right now would be to say lots of 
terribly unkind things about dodgy middleboxes, which is not a very balanced 
approach to the issue and unlikely to be very helpful in steering the list 
toward more productive conversation. But let me try.

It's hard to say anything in general about what "overlay x on y" solves in 
detail (I'll consider encapsulation an implementation detail of overlay for 
now) for all x and y, other than (1) somebody thought that it would provide a 
service that y doesn't on its own that (2) they locally thought they needed at 
the time, and (3) they might actually have been right about (1) and (2). 

The upside is that overlaying allows us to use the abstractions from the higher 
layer of the overlay when all we have is the lower layer.  

The downside is that x over y might not really be the same as x, because you 
miss some assumption inherent in either x or y about the corresponding y or x, 
and you end up breaking something end-to-end. This gets more complicated when 
years later, after all the bugs are worked out, somebody notices the shiny new 
x and decides to overlay z on top of it.

I don't see a more focused way to consider this at this (ridiculously high) 
level of abstraction. A good general considering-the-downsides question might 
be "how well can I run NNTP, SSH, DNS, World of Warcraft, BitTorrent, Windows 
file sharing, and WebRTC over it at the same time in an airplane at rush hour 
on Mars next to my microwave while randomly unplugging stuff?" 

Admittedly this is a rather higher-layer viewpoint. On preview, I suspect you 
might get a more useful (and more concrete) thread out of Eric's response.

Cheers,

Brian

> On Sun, Mar 9, 2014 at 5:29 PM, heasley <heas(_at_)shrubbery(_dot_)net> wrote:
> Sun, Mar 09, 2014 at 11:10:27AM +0000, Dave Crocker:
> > The phrasing of your suggestion presumes that you are currently
> > prevented from having those discussions.  But of course you aren't.
> I believe the point is to separate general technical discussion from the
> general everything else discussion, such as the draft-how-not-to-be-a-
> wanker discussion, so that those here just for the technical aspects of
> IETF need not wade through it.  Which I support.

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