[ns] connector related

[billy dimi <kldannys@yahoo.com>]

copied from ns-link.tcl

SimpleLink instproc enable-mcast { src dst } {
    $self instvar iif_ ttl_
    set iif_ [new NetworkInterface]
    $iif_ target [$ttl_ target]
    $ttl_ target $iif_

    $src add-oif [$self head] $self
    $dst add-iif [$iif_ label] $self
}

I would like to ask the followings:

First: Why  ttl_ is ralated with iif_ in such a way??
       As far as i know these two entities have 
different
       physical meanings ( ttl_ = time to live for a
packet
       which is a number decremented at each node) (
iif_ = 
       incoming interface is the interface from which
the 
       packet received).

Second:Shouldn't be
                " $ttl_ target [$iif_ target]" 
       instead of
                " $ttl_ target $iif_ "

       According to "connector.h" we should first set
or get 
       the target_ by declaring  "$arg target" and
then use 
       the arg[2] target method  " $src target $dst "

Third: Why do we connect iif_ with ttl_ AND ttl_ with
iif_ ??

I think i miss something...Can somebody help ??
Thanks
Billy

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