Re: LAN - where is the invisible node created

[Yuri Pryadkin <yuri@who.isi.edu>]

Anand,

the LAN (virtual) node is created in tcl/lan/vlan.tcl.  It is not
really a node, but a very light-weight object.  In fact, it is used
only as a container for LAN shared objects: Channel, MCL, etc.  Its
purposes are:

	1) make ns routing work with LANs
	2) make LAN architecture more scalable

It's worth noting that the cost of 3->1 (i.e. 3->4->1) is still 1 hop.

In most cases it should be transparent.

You can find further info about it in nsDoc.

  -Yuri

anandr@cs.ucsb.edu (Anand P. Rangarajan) writes:

> hi
> 
>   i'm printing the next hop information for some 
>   topologies.
> 
>   if all the links in the network were just 
>   point-to-point links
>   the table has exactly the same number of nodes
>   as in the topology. but if there is a LAN, there
>   seems to be another node which connects the nodes
>   in the LAN and the other part of the topology.
> 
> Example:
> 
> Topology:
>   
>    3
>    |
>    |
>  -----
>    |
>    |
>    1-------2-------0
> 
> 
> In the above topology, 3 is the only node in the LAN 
> and 1 is the router between the LAN and the other part
> of the network.
> 
> 
> Dumpingng Routing Table: Next Hop Information
>         0       1       2       3       4
> 0       --      2       2       2       2
> 1       2       --      2       4       4
> 2       0       1       --      1       1
> 3       4       4       4       --      4
> 4       1       1       1       3       --
>  
> 
> one can see a new node "4" in the table that connects 3 
> and 1.
> 
>   i wish to know where( in the ns source code) and 
>   why this new node is created.
> 
>   i'd appreciate if someone throws light on this.
> 
> 
> Thanks,
> Anand