[openib-general] OpenSM

[shaharf]

As I already mentioned, Mellanox released its Simulator. You can find it
in https://openib.org/svn/gen2/utils/src/linux-user/IBMgtSim/ . The
problem is that this Simulator is build to work with the Mellanox Gold
environment. So either you get use Mellanox gold (that is based on gen1)
or port the Simulator to gen2.

 

I am not aware to any other opensource simulators.

 

Shahar

 

 

 

 

________________________________

From: abhijitngpune [mailto:abhijitngpune at indiatimes.com] 
Sent: Wednesday, March 30, 2005 6:52 AM
To: shaharf
Cc: openib-general at openib.org
Subject: Re: RE: [openib-general] OpenSM

 

hi,

  Is there any opensource subnet simulator? Where can i get it?

Abhijeet

"shaharf" wrote: 

	Hi abhijitngpune,

	 

	OpenSM do not know care about the topology of the network. Every
connected graph is valid for it. BTW, fat tree can have cycles too. If I
don't err, the algorithm used by the OpenSM is a variation of some well
known graph algorithm invented by Dijkstra or based on one of Dijkstra's
(I hope I write his name correctly) algorithm. You can find these
algorithms in any graph theory text book - look for "find all shortest
paths" algorithms. (for example :
http://ciips.ee.uwa.edu.au/~morris/Year2/PLDS210/dijkstra.html )

	 

	Very briefly the algorithm that the opensm is using goes like
that:

	 

	1. All switches learn about themselves (hop 0) and any direct
connected hosts (hop 1). They keep this information in a forwarding
table that contains (schematically) the following information (the
actual details are a bit more complicated to be able to support
multipathing) :

	 

	Lid (local port id), out-port, hops

	 

	2. Now you start the hop>1 learning phase that use several
passes over the switches. On every single pass, you go over all switches
(the order does not matter) and within each switch you go examine any
direct attached switch called "neighbor".   For every such neighbor you
compare your forwarding table to neighbor table. If you find a lid that
have hop count less than your hop count +1 (for the extra hop between
you and the neighbor switch)  you change you table entry to route that
lid thought the connecting port.

	 

	3. You repeat the above process until no table is changed during
a complete pass, or until number of switch passes are done.

	 

	The correctness of this algorithm is left to the reader ;-)

	 

	It seems that you are using gen1 stack and Opensm. Please be
aware to the fact that gen1 tree is not supported any more. Please use
gen2.

	The opensm Tcl extension is not supported on gen2 and I don't
know on any plans to support it.

	 

	Regarding the topology example - any connected graph will do. I
guess that most connected graphs are very inefficient traffic wise, but
still all of them are valid.

	 

	Demonstrating that a topology is configured correctly is a bit
of a problem. If you are willing to spend some efforts, you can use the
topology simulator released with Melloanox Gold - look for the IBADM
package. This stuff is not very well documented but it should be
useable. Melloanox released (or about to release) a real subnet
simulator that you can use to run opensm on top of it. Using this
simulator you can test any arbitrary topology. The problem is that you
have to port this simulator to gen2.

	Any volunteers are welcomed...

	  

	Shahar

	 

	
________________________________


	From: openib-general-bounces at openib.org
[mailto:openib-general-bounces at openib.org] On Behalf Of abhijitngpune
	Sent: Tuesday, March 29, 05 3:09 PM
	To: openib-general at openib.org
	Subject: [openib-general] OpenSM

	 

	Hi all, I am a new to infiniband and related issues. I have some
few doubts related to openSM. 1. how does openSM support the non fat
tree (graph having cycles) topologies? (any research paper will do) 2.
Given a graph (it contains cycles) topology how can i demonstrate that
subnet manager working for this topology? 3. What is openSM tcl
extension is used for? does anybody have example code for perticular
(irregular/ non fat tree) topology? Abhijeet 

	
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