Changes between Version 5 and Version 6 of LayoutAspect

Timestamp:

Oct 15, 2013 11:14:48 AM (11 years ago)

Author:

faber

Comment:

--

LayoutAspect

@@ -73 +73 @@
 This is probably more intuitive with an example.  Here is a topology:
 
+[[Image(Recursion.png)]]
+
+And here is the fragment F1.  The fragment and the top level topology are exactly the same, including the fragment recursively including itself in each of the regions in it.
+
+[[Image(Recursion_Frag.png)]]
+
+When the testbed (or a tool) expands the topology the first time, this topology results.  The labels are the level variable of each region.
+
+[[Image(Recursion1.png)]]
+
+Note that he two regions on the right side have level 0.  We have left them in the diagram to show how recursions terminate.  As we expend the regions again, below, we see that the level 0 regions are removed, as are the substrates that they were attached to.  A substrate with one interface does not really constitute a communications context - there's no one to talk to.  Removing the level 0 regions would be part of the first region expansion; level 0 regions never appear in real topologies.
+
+[[Image(Recursion2.png)]]
+
+And those last remaining level 1 regions expand into single computers just as the first one did, leaving the full topology:
+
+[[Image(Recursion3.png)]]
+
+=== Naming and Recursion ===
+
+We have been vague about how names are assigned to elements and substrates in recursions.  In the simplest case, where the topology specifier does not care how those names are assigned, they can be assigned by the testbed (or tool).  If the user wants a specific layout of names the pathname system can be used.
+
+Each element or substrate in a topology was either named directly (at the top level) or results from an expansion of a region.  By prepending the name of an element with the name of the region from which it was expanded, each substrate or element acquires a unique path name.  That assumes that each expansion preserves the property than element and substrate names are unique, but the system can enforce this.
+
+Should a user need control over each name, that user must supply an an explicit map of fragment name to topology name at each region element.  The maps are bound to regions by pathname of the region.
+
+The model supports hybrid solutions, where some areas of a topology include user-specified name maps and some regions of the topology are named by the testbed (or tool).  The rule is that testbed-assigned names are provisional and can be overriden by specific user assignments.
+
+=== Views ===
+
+The previous sections have described topologies mostly in terms of constructing them, but a significant part of the model's power is in its ability to present topologies in different ways for different audiences.
+
+Consider the following scenario:  a researcher studying the propagation of a security compromise makes use of a recursive tool to create a topology that reflects a particular scenario for study.  Because it was generated by a recursive tool, a natural representation is in recursive regions, but those regions may not be useful to the researcher.
+
+The researcher has a different breakdown of the experiment. In their mind the topology consists of a routing backbone, some enterprise networks, and a set of enterprise networks containing compromised computers.  This breakdown of the topology can also be characterized in terms of elements (including regions) and substrates where the regions are defined, not by the workings of the construction algorithm, but by the semantics of the researcher's experiment.
+
+Finally, when the testbed realizes the topology, it will assign physical resources to each element and substrate.  If the topology is heavily virtualized it may be helpful for the researcher (or testbed staff) to see the topology broken into regions that map to physcial machines in the testbed.
+
+We call these different descriptions of the same topology ''