[e2e] end of interest -- BP metadata / binary vs text

Rajesh Krishnan rkrishnan at comcast.net
Sun May 11 08:30:07 PDT 2008


My objective was to provoke discussion on the topic of whether it makes
sense to think of DTN as a session layer, as an overlay above TCP, etc.
from the e2e perspective.  If you feel this topic is unsuitable for
discussion here, I will gladly stop posting on this topic here of

> I am afraid that those who treat the RFCs as scripture from high priests 
> mistake dogma for thoughtfulness.

I am definitely not treating RFCs as scripture.  I am not satisfied with
the explanation that DTN/BP belongs to the "session layer" as the best
or only model.  I find this limiting, since DTN issues span all the way
from applications to the physical "layer".

> The essential valid measure of DTN ideas is that they work, and will 
> continue to work well, *to organize the solution* to an interesting 
> class of real-world problems.   It is irrelevant whether they provide 
> the basis for destroying some "traditional paradigm" and creating a new 
> religion.

Agreed.  If anyone reads my post as being about destroying old religion
and creating a new one, that is missing the point.  It is about getting
out of old shackles though; why keep doing the same thing (like the way
we fit seem to try to fit DTN into the old mold) and expect a different
result?   If we say DTN is in the session layer, we will engineer a
useful DTN session layer alright, but will a DTN session layer solve any
fundamentally new problems?  Does that limit new architectures that
could be explored?

> What made the Internet architecture useful was its attention to 
> "interoperation" and to facilitating support of "unanticipated" 
> applications and implementation technologies.  It framed those things 
> well, making progress possible.  DTN ideas frame a new set of issues 
> well - communcations that occur between entities that occupy 
> discontiguous regions of space-time influence.   Such communications 
> have always existed (books communicate across time in personal and 
> public libraries, postal letters transcend spatial barriers in 
> self-contained form) - DTN's merely ratify their importance by focusing 
> framing on those issues.

Agreed.  In a DTN, among other things, we want to maximize the value of
information exchanged within a transitory encounter, and this can not be
framed entirely as a session-layer issue.  Relegating DTN to the session
layer will completely isolate it from a radio-aware CLA (or whatever
name we want to call it) among other things, which relates to a point
you made earlier.

Hope that clarifies my original post somewhat.

Best Regards,

> Rajesh Krishnan wrote:
> >
> > Granted this matches the viewpoint presented in RFC 5050 of BP's
> > (non-threatening ;) relationship to TCP/IP.
> >
> > By including forwarding and dynamic routing (L3?), retransmissions
> (L4?
> > and L2?), and persistent storage and application metadata tagging
> (L7?)
> > concerns within the same protocol, BP does not fit harmoniously at
> L5 of
> > the TCP/IP Internet, IMHO.  This challenge to traditional layering
> is
> > precisely what I find most fascinating about DTN.
> >
> > With the CLA/BP split, there is still layering in DTN; just that the
> > layering is not congruent to conventional TCP/IP layering.
> Effectively,
> > DTN/BP seems to relate to TCP/IP more or less the same way IP looks
> at
> > other network technologies.  At least that is my interpretation of
> > DTN/BP as an overlay abstraction (TCP/IP is relevant only as
> expedient
> > means for early deployment.  ;)
> >
> > I am speaking only for myself here (not past or present employers or
> > funding agencies or IRTF WGs), and this thread ought to migrate to
> > dtn-interest perhaps.
> >
> > Best Regards,
> > Rajesh

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