Text 4284, 128 rader
Skriven 2012-10-01 17:21:38 av Roy Witt (1:387/22)
   Kommentar till text 4274 av Michiel van der Vlist (2:2/2.0)
Ärende: FidoNews 29:40 [02/06]: General Articles
================================================
18 Aug 03 15:10, FidoNews Robot wrote to All:

Great article, Michiel...Go NADs!


 FR> =================================================================
 FR>                         GENERAL ARTICLES
 FR> =================================================================

 FR>                 Notes on a topless echomail distribution system.
 FR>                 By Michiel van der Vlist, 2:280/5555


 FR> Fidonet echomail distribution is traditionally based on top down
 FR> structures. While Fidonet itself was designed as a peer to peer
 FR> network, echomail terminology is full of terms like uplink, downlink,
 FR> hubs and backbones. For a specific echomail area, a node has one
 FR> uplink and zero or mode downlinks. Peering links are only found at
 FR> the top of the so called backbone if it consists of a backbone ring.
 FR> AKA a fully connected polygon.

 FR> Such a rigid structure is needed to avoid so called dupes. Messages
 FR> arriving more than once. Dupes can happen when there is more then one
 FR> path between nodes. One way to prevent dupes is to ensure that there
 FR> is only one path between the downlinks and the uplinks.


 FR>                             Backbone
 FR>                              /   \
 FR>                             /     \
 FR>                            /       \
 FR>                          Hub       Hub
 FR>                         /  \      /   \
 FR>                        /    \    /     \
 FR>                      node  node node  node

 FR> Another one is dupe prevention by seen-by.

 FR>                         A----------B
 FR>                         | *      * |
 FR>                         |   *  *   |
 FR>                         |   *  *   |
 FR>                         | *      * |
 FR>                         C----------D


 FR> These four nodes form a so called fully connected polygon. They are
 FR> all connected to each other. The seen-bys prevent that a message from
 FR> A arriving at B will be sent on to C and D, because they are already
 FR> in the seen-by.

 FR> There is no theoretical limit on the size of a fully connected
 FR> polygon but there are practical limits. Five is about the practical
 FR> maximum.

 FR> A standard echomail topology is a backbone of one to five nodes
 FR> forming a fully connected polygon. Each backbone member feeds a
 FR> number of hubs who in turn feed a number of downlinks.

 FR> Such a configuration works fine for preventing dupes.

 FR> But is has drawbacks.
 FR> It is a top down configuration and one of the drawbacks of that is
 FR> that it has a top from which things can be controlled. The most
 FR> recent example was in the summer of 2011 when the North American
 FR> Backbone tried to grab control of Fodonews, causing a schism in te
 FR> process, but there have been many other examples in the history of
 FR> Fidonet. The R28 CSO wars come to mind.

 FR> The cost sharing wars ended when the main distrubition went from POTS
 FR> to Fido over IP, reducing the cost to almost zero, so there no longer
 FR> was any cost to fight over. We thought that freed Fidonet from the
 FR> power of the distributors to control the distribution of echomal, but
 FR> unfortunately it didn't as the 2011 Fidonews coup has demonstrated.

 FR> So in the summer of 2011 the NAB set all of Fidonet outside of Z1 to
 FR> read only for the Fidonews echo. And than something unexpected
 FR> happened. To circumvent the censoring, sysops all over the world
 FR> starting laying new links. Without any coordinations whatsover. Just
 FR> find a link that is not censored. They knew this was going to cause
 FR> dupes, but the idea was to first restore the links and worry about
 FR> the dupes later. What evolved was what I have named the NADS, the New
 FR> Anarchy Distribution Network. Some have called it GONADS which is
 FR> quite appropriate as it takes balls to knowingly and willingly
 FR> breaking a 25 year old taboo: that of causing dupes. Up until then
 FR> that had been an almost mortal sin.


 FR> Yes, there were some dupes. But not as many as was feared. Not by FAR
 FR> as many. So then the idea arose to lay some more links. And some
 FR> more. Against inituition this did not cause an increase of dupes. In
 FR> retrospect this is not so strange. When everyone links up with
 FR> everyone we are back to a fully connected polygon. So when
 FR> approaching such a configuration one can expect the dupes to go down
 FR> again.

 FR> And there we have it. The NADS. Others have called it the Fidoweb.
 FR> Maybe a better term as that is what it looks like.

 FR> The result is a topless distribution system. No "top" to control it
 FR> from and as a side benefit, it is far less sensitive to SPOF. If
 FR> there is a path that dupes can follow, there is an alternate path in
 FR> case a node drops out. The price is a manageable increase in traffic.
 FR> In the POTS age, that would have increased the cost. In the Fido over
 FR> IP age: who cares?


 FR> ¸ Michiel van der Vlist, all rights reserved.
 FR> Permission to publish in the FIDONEWS file echo, the FIDONEWS
 FR> discussion echo and the FNEWS_PUBLISH echo as originating from 2:2/2



 FR> -----------------------------------------------------------------

 FR> --- Azure/NewsPrep 3.0
 FR>  * Origin: Home of the Fidonews (2:2/2.0)

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