[ndnSIM] Route metrics

Alex Afanasyev alexander.afanasyev at ucla.edu
Fri Mar 15 13:54:48 PDT 2013

Hi Natalya,

Metric is just a int32_t value, which can be (but not necessarily) be interpreted similar to OSPF routing metric for this prefix for this face.  The lower value of this "metric" the more preferred the face is to route Interest towards the prefix.  For example, BestRoute forwarding strategy picks a face with minimal "metric".  Other interpretations are possible, if you're using a customized forwarding strategy.

Regarding metric field in topology file.  This field basically defines how preferred a particular link is. Interpretations can vary, but the lower value, the more preferred the link is.  The "metric" that is specified for a specific face in FIB entry ("FIB metric) is basically an aggregated sum (minimal sum) of "link metrics" to reach a specific prefix using this face.  Btw, "link metric" is uint16_t value to prevent overflow of "FIB metric".

Let me show an simple example:

Client ------- Router-1 -------- Producer (/prefix)
  |                                 |
  +--------- Router-2 --------------+

If topology file specified that "link metrics" are the following:
Client Router-1   10
Client Router-2   100
Router-1 Producer 1
Router-2 Producer 1

Then "FIB metrics" on the Client will be:
Face 0 (to router-1): 11
Face 1 (to router-2): 101

On Router-1:
Face 0 (the only face): 1

On Router-2:
Face 0 (the only face): also 1


On Mar 15, 2013, at 1:38 PM, Natalya Rozhnova <natalya.rozhnova at lip6.fr> wrote:

> Hi Alex,
> I'm using topologyReader to create desired network topology. Then I manually configure the FIB entries in my ns3 script like this: ndnHelper.AddRoute(c1, "/c1", r1, 1) etc.
> I'm just curious what is the field "metric" in 'link' section of TopologyReader and what is the difference of this parameter from metric added to my FIB entries as above?
> Thanks,
> Natalya
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