[e2e] end of interest

Jon Crowcroft Jon.Crowcroft at cl.cam.ac.uk
Thu May 15 05:40:20 PDT 2008

for me, modularisation in layers is
part of hierachical categorisation,
which is fine for librarians -
categories (as in women, fire and
dangerous things) led to a more
complex way of modularisation which
ended up being the OO paradigm
with multiple inheritence - as an
implementation pardigm, this turned
out to be too hard for the hard of
thinking, so most OO languages
restricted inheritence and refinement 
to hierarchiy again - but in most
programmes, one is concerned with a
much lower dimensionality problem
space tha the multi-stakeholder system
that is a network architecture where
a more suble and messay abstraction
may be fine - for example one might
just have constraints on
resources and different constraints on
identiifers, and different constrains
on reliability and the way solutions
are componentized across a set of
nodes (hosts, routers, if you must)

an architecture that was purely
constraint based (i.e. just said what
you DONT do) would be very

In missive <a06240808c44cf2bbbebf@[]>, 
John Day typed:

 >>At 10:52 -0400 2008/05/11, David P. Reed wrote:
 >>>Snooping honors the Layeristi - granting them rhetorical power they 
 >>>never deserved.   It sounds like "cheating" or "illegal" operation. 
 >>>The Internet was born without layers - it used architectural
 >>See previous note.  No matter how you cut it. Whether you call them 
 >>layers or framing.  If you have to look at stuff that doesn't belong 
 >>to you, you haven't done something right or there is something you 
 >>don't understand.
 >>>framing differently (e.g., one arch principle illustrative: 
 >>>encapsulation is not layering, and even survives as IP gets 
 >>>encapsulated in TCP port 8 VPNs, much to the chagrin of the 
 >>>Layeristi purists who explain it as a "bug", rather than looking at 
 >>>its roots in passing IP datagrams over SNA and NCP virtual circuits).
 >>Gosh. How is this a bug?  Sounds right to me!
 >>>I'd suggest that first-principles thinking is harder than Jon thinks.
 >>Well, it is hard.  I can testify to that!  Not sure it is harder than 
 >>Jon thinks.  Jon seems to think pretty hard much of the time. 
 >>Although he doesn't want it to show.  ;-)
 >>>It's not just a matter of choosing sides in a war, or acting as an 
 >>>arms merchant to both sides.   It's about thinking more squarely 
 >>>about the real underlying issues that comprise communications . In 
 >>>fact, as some of us have suggested, perhaps the idea that 
 >>>communications can be considered as a "pure" 
 >>>architectural/linguistic frame independent of storage and 
 >>>computation and sensing is the real issue we ought to be addressing 
 >>>today, with pervasive comms/storage/computational elements capable 
 >>>of all three.
 >>No, it is a question of learning to listen carefully to what the 
 >>problem is telling you and not imposing your own ideas on it.  (I 
 >>will admit that I have found that we do the later it is often wrong. 
 >>Embarrassing when it happens.  But if you are careful when you write 
 >>it up no one notices!)  ;-)
 >>>John Day wrote:
 >>>>At 9:08 +0100 2008/05/11, Jon Crowcroft wrote:
 >>>>>nice example of 0nership by warring protocol layer factions
 >>>>>mesh wifi people need to learn to do layer 3 snooping
 >>>>>same way telecom people did...
 >>>>The need to do snooping is an indication of the current model's 
 >>>>inability or refusal to innovate.  A failure to dig more deeply 
 >>>>into the model.  (Or a fear to challenge their religion.)
 >>>>(It turns out once there is a complete architecture, not one of 
 >>>>these DOS look-a-likes, snooping isn't necessary.)
 >>>>>there's a great e2e topic -
 >>>>>we have sort of gotten out of the
 >>>>>denial phase on middle boxes and
 >>>>>we're probably ok with multicast's niches now ...
 >>>>Middleboxes are alos an artifact of an incomplete architecture.  In 
 >>>>a full (shall we say, a wff) architecture, they aren't necessary.
 >>>>>but should we raise the
 >>>>>art of _snooping_ to being a
 >>>>>first class component of any decent
 >>>>>postmodern internet architecture?
 >>>>No, snooping is an admission of failure.  Calling it a component of 
 >>>>a "decent" internet architecture is merely making excuses for our 
 >>>>>multicast group members locations from lookin at IGMP traffic from "below"
 >>>>>is one exxaple (think dslams too) but another would be
 >>>>>P2P aware Traffic Engineering, for example
 >>>>Recognizing that a multicast address is the name of a set deals 
 >>>>with most of this.  (Of course, this means that strictly speaking 
 >>>>multicast addresses aren't really addresses but names.) A multicast 
 >>>>or anycast address must always resolve at some point to a normal 
 >>>>address.  The idea of a multicast address as an ambiguous address 
 >>>>is fundamentally broken.
 >>>>>"layer violations" as taught in protocls #101 has traditionally
 >>>>>been restricted to upper layer tweaking layer-2 operating parameters
 >>>>>(think Application/TCP causing Dial up), rather than
 >>>>>vice versa - but the other way round stretches
 >>>>>programming API paradigms more athletically
 >>>>>so may be condusive to progress...
 >>>>If I understand what you are alluding to, this is addressed by not 
 >>>>ignoring the existence of the enrollment phase in communication.
 >>>>What I have found is that in a wff architecture there are no need 
 >>>>for layer violations.  In other words, if you have layer 
 >>>>violations, you are doing something wrong some place.  Either in 
 >>>>how you are trying to do what you want to do, or in what you think 
 >>>>a layer is.  In this case it seems to be a bit of both.
 >>>>Take care,
 >>>>>In missive <1210445625.6167.138.camel at jg-laptop>, Jim Gettys typed:
 >>>>>  >>On Sat, 2008-05-10 at 12:18 -0400, David P. Reed wrote:
 >>>>>  >>
 >>>>>  >>> There are huge aspects of that future that depend on getting the
 >>>>>  >>> low-level abstractions right (in the sense that they match 
 >>>>>real physical
 >>>>>  >>> reality).  And at the same time, constructing a stack of abstractions
 >>>>>  >>> that work to maximize the utility of radio.
 >>>>>  >>>
 >>>>>  >>
 >>>>>  >>First hand reality in the OLPC project: use of multicast/broadcast based
 >>>>>  >>protocols when crossed with nascent wireless protocols (802.11s), can
 >>>>>  >>cause spectacularly "interesting" (as in Chinese curse) interactions.
 >>>>>  >>
 >>>>>  >>First hand experience is showing that one had better understand what
 >>>>>  >>happens at the lowest wireless layers while building application
 >>>>>  >>middleware protocols and applications....  Some existing protocols that
 >>>>>  >>have worked well on wired networks, and sort of worked OK on 802.11abc
 >>>>>  >>networks, just doesn't work well (or scale well) on a mesh designed to
 >>>>>  >>try to hide what's going on under the covers.
 >>>>>  >>
 >>>>>  >>While overlays are going to play an important role in getting us out of
 >>>>>  >>the current morass (without transition strategies, we're toast; that was
 >>>>>  >>what got the Internet out of telecom circuit switching as the only
 >>>>>  >>mechanism), I have to emphatically agree with Dave that we'd better get
 >>>>>  >>moving on more fundamental redesign and rethinking of networking....
 >>>>>  >>                           - Jim
 >>>>>  >>
 >>>>>  >>--
 >>>>>  >>Jim Gettys <jg at laptop.org>
 >>>>>  >>One Laptop Per Child
 >>>>>  >>
 >>>>>  cheers
 >>>>>    jon



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