Re: Multicast Questions

[Lloyd Wood <eep1lw@surrey.ac.uk>]

On Sat, 27 Sep 2008, jamester wrote:

> My first question :
> 
> 	It seems like "$ns set-address-format expanded" and multicast
> 	do not go together. 

>       When I use expanded address I get errors similar to "_o57:
>       no target for slot 128".  This error occurs when I generate
>       only 100 nodes with expanded address format, but not without
>       expanded address format.  Anyone knows anything about this?

What version of ns are you using? I spent some time
discovering and pointing this particular gotcha out on the mailing
list circa 2.1b3[*]

Instead of set-address-format, stick to Node expandaddr.

Take a look through the ns mailing list archive[+]

http://www-mash.CS.berkeley.EDU/dist/archive/ns-users/9809/0066.html
http://www-mash.CS.Berkeley.EDU/dist/archive/ns-users/9901/0072.html

There's a forwarded note giving some indication why (no idea where
that came from) at:
http://www-mash.CS.Berkeley.EDU/dist/archive/ns-users/9901/0084.html

and addressing has been improved more recently (although afaik the
various addressing modes are not all some aspect of hierarchical
addressing - one level of hierarchy would give a flat space, and one 
overall type of addressing might simplify interactions), so this
should be less of a problem in recent ns.

When in doubt, try Node expandaddr.

For your second problem below, make sure you're using Node allocaddr
if you're using expanded addressing - 0x8002 is only valid as a
multicast address for the slowly-being-deprecated small address space
when you have 128 nodes or less. Assuming you aren't using expanded
addressing...

...well, I've never seen get-mcast-tree before - where is that
defined? I can't find it in my recent snapshot or 2.1b5 or the docs.

thanks,

L.

[*] these days I tend to stick to pointing out that DV routing is
    broken, that the only person who has got it working again can't
    remember how he did it, and can we have it functional again for
    2.1b6, please?

[+] hang on, ht://dig currently isn't generating header/footer
    parts of search result pages when it's not returning no data, so
    you're limited to the first ten results; you'd never be able to
    turn this stuff up.

<L.Wood@surrey.ac.uk>PGP<http://www.ee.surrey.ac.uk/Personal/L.Wood/>

> My second question :
> 	Is there any way I can see routes from source to destination nodes in
> 	multicast?  I tried following :
> 
> 	set mproto DM
>            	set mrthandle [$ns mrtproto $mproto {}]
>            	........
>            	$ns join-group receiver_agent group            
> 	$ns get-mcast-tree $node($src) $group #src is srouce node id
> 
> 	I do not get multicast tree but following error messages.
> 	
> 	ns: _o3 get-mcast-tree _o53 0x8002]: can't read "GROUP_": no such variable
>     	while executing
> 	"error "No replicator for $GROUP_ at [$src id]""
>     	(procedure "_o3" line 7)
>     	(Simulator get-mcast-tree line 7)
>     	invoked from within
> 	"_o3 get-mcast-tree _o53 0x8002]"
> 
> Any help is greatly appreciated.
> Thanks in advance.
> 
> -James Kwon