[e2e] Switched Ethernet is Not an End-to-End System; was Protocols breaking the end-to-end argument

[Jon Crowcroft]

well to be specific,
TCP retransmission times
and 
TCP congestion control
were NOT designed in from day 1

early TCPs had fixed retransmit until the RSRE algorithm
and then it was still some time before the Karn/Partridge
improvements kicked in
plus 
early TCPs had no congestion control at all 
until '87

however, since then 
the adaptation of timers
and the adaption of flow rates 
makes the interweb
look very much like a giant contention ethernet - 
in fact for exactly the same reason as voice on ethernet
never  was a big deal, voice on the interweb
requires you to have a path running at releatively 
low utilisation otherwise delays diverge...and loss kicks in

one thing 
(van pointed this out in a talk here a couple of days ago)
that saves it from the same fate as pure contention systems
is that there's a packet conservation principle...
again NOT something designed in the original TCP

so that's 3 new principles within the end2end system that
actually weren't in the original design of the protocols
that I count...there's a few other ones lurking inside
IP too, but thats to do with routing, and as Bob Braden
so wisely says, "we don't do routing in e2e"


In missive <4AED9B58.30809 at reed.com>, "David P. Reed" typed:

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 >>There are probably also lessons in the evolution from networks that are 
 >>synchronized with clocks that must have timing with parts-per-billion 
 >>accuracy (the "Bell System" architecture - e.g. SONET) to networks that 
 >>allow for internal retiming, buffering, etc.
 >>
 >>That doesn't mean that it is a fact that IP is a thin layer over such 
 >>clock-synchronized networks, which still exist and carry IP traffic.  
 >>Nor is TCP designed to be corrective of such networks brittle 
 >>unreliability, which leads to rerouting over alternate paths that may 
 >>cause transient out-of-order delivery, duplication, and a need to 
 >>reallocate resources.
 >>
 >>TCP and IP were designed to handle heterogeneity and best efforts, and 
 >>the idea that they were either designed to remedy Aloha or evolved so 
 >>that they only run on Ethernet - that is nonsense, a just so story.
 >>
 >>On 11/01/2009 05:10 AM, Jon Crowcroft wrote:
 >>> There definitely are lessons
 >>> in the evolution from
 >>> end-mediated contention to
 >>> switch-mediated access
 >>> in ethernet-land.
 >>>
 >>> The oft-perceived analogy
 >>> of the whole internet as a big ethernet,
 >>> a huge shared resource
 >>> with contention mainly mediated
 >>> by end systems, is alluring.
 >>>
 >>> So the move to
 >>> net/switch-centric resource allocation/control
 >>> in the local,
 >>> might suggest some similar move
 >>> in the wide area...
 >>> until you actually think about the
 >>> heterogeneity in the
 >>> topology, in capacity and in latency,
 >>> of the system -
 >>>
 >>> Plenty of enterprise nets and small ISPs
 >>> (e.g. UK size) can consider
 >>> a carrier-grade switched ether
 >>> control philosophy (e.g.
 >>> esp. to replace
 >>> complicated MPLS setups:)
 >>> but it doesn't subsume/replace e2e
 >>> resource sharing -
 >>>
 >>> It doesn't address
 >>> multihomeing, multipath, mobility or multicast
 >>> in any useful way either...it doesn't
 >>> speak to swarms and CDNs much either.
 >>>
 >>> There were other lan technologies
 >>> which didn't have built in collapse
 >>> as part of the media-sharing protocols
 >>> so the lesson wasn't as widely
 >>> necessary as the e2e monoculture
 >>> pretends (people who built
 >>> token and slotted rings
 >>> had other views of the world
 >>> too:)
 >>>
 >>> On the other hand, it would be instructive
 >>> to see how many end&edge systems are now on
 >>> wireless ethernet and to see if the balance has
 >>> swung back once again in "favour" of
 >>> shared media/contention.
 >>>
 >>> aloha
 >>>
 >>> jon
 >>>
 >>>    
 >>
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 >><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
 >><html>
 >><head>
 >>  <meta content="text/html; charset=ISO-8859-1"
 >> http-equiv="Content-Type">
 >></head>
 >><body text="#000000" bgcolor="#ffffff">
 >><font face="Helvetica, Arial, sans-serif">There are probably also
 >>lessons in the evolution from networks that are synchronized with
 >>clocks that must have timing with parts-per-billion accuracy </font>(the
 >>"Bell System" architecture - e.g. SONET) to networks that allow for
 >>internal retiming, buffering, etc.<br>
 >><br>
 >>That doesn't mean that it is a fact that IP is a thin layer over such
 >>clock-synchronized networks, which still exist and carry IP traffic.&nbsp;
 >>Nor is TCP designed to be corrective of such networks brittle
 >>unreliability, which leads to rerouting over alternate paths that may
 >>cause transient out-of-order delivery, duplication, and a need to
 >>reallocate resources.<br>
 >><br>
 >>TCP and IP were designed to handle heterogeneity and best efforts, and
 >>the idea that they were either designed to remedy Aloha or evolved so
 >>that they only run on Ethernet - that is nonsense, a just so story.<br>
 >><br>
 >>On 11/01/2009 05:10 AM, Jon Crowcroft wrote:
 >><blockquote cite="mid:E1N4XOe-0000FR-00 at mta2.cl.cam.ac.uk" type="cite">
 >>  <pre wrap="">There definitely are lessons 
 >>in the evolution from 
 >>end-mediated contention to 
 >>switch-mediated access
 >>in ethernet-land.
 >>
 >>The oft-perceived analogy
 >>of the whole internet as a big ethernet,
 >>a huge shared resource 
 >>with contention mainly mediated
 >>by end systems, is alluring.
 >>
 >>So the move to 
 >>net/switch-centric resource allocation/control
 >>in the local, 
 >>might suggest some similar move
 >>in the wide area...
 >>until you actually think about the
 >>heterogeneity in the
 >>topology, in capacity and in latency,
 >>of the system - 
 >>
 >>Plenty of enterprise nets and small ISPs
 >>(e.g. UK size) can consider
 >>a carrier-grade switched ether
 >>control philosophy (e.g. 
 >>esp. to replace
 >>complicated MPLS setups:)
 >>but it doesn't subsume/replace e2e
 >>resource sharing - 
 >>
 >>It doesn't address 
 >>multihomeing, multipath, mobility or multicast
 >>in any useful way either...it doesn't
 >>speak to swarms and CDNs much either.
 >>
 >>There were other lan technologies
 >>which didn't have built in collapse
 >>as part of the media-sharing protocols
 >>so the lesson wasn't as widely
 >>necessary as the e2e monoculture
 >>pretends (people who built 
 >>token and slotted rings
 >>had other views of the world 
 >>too:)
 >>
 >>On the other hand, it would be instructive
 >>to see how many end&amp;edge systems are now on
 >>wireless ethernet and to see if the balance has
 >>swung back once again in "favour" of 
 >>shared media/contention. 
 >>
 >>aloha
 >>
 >>jon
 >>
 >>  </pre>
 >></blockquote>
 >></body>
 >></html>
 >>
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 cheers

   jon