MAC Interface in ns-2

General Architecture of a mobile node in ns-2:



the relationship of MAC could be found in ns-mobilenode.tcl. The source code:

........ # # The following setups up link layer, mac layer, network interface # and physical layer structures for the mobile node. # Node/MobileNode instproc add-interface { channel pmodel lltype mactype \ qtype qlen iftype anttype topo inerrproc outerrproc fecproc} { $self instvar arptable_ nifs_ netif_ mac_ ifq_ ll_ imep_ inerr_ outerr_ fec_ ....... # # Link Layer # $ll arptable $arptable_ $ll mac $mac $ll down-target $ifq if {$imepflag == "ON" } { $imep recvtarget [$self entry] $imep sendtarget $ll $ll up-target $imep } else { $ll up-target [$self entry] } # # Interface Queue # $ifq target $mac $ifq set limit_ $qlen if {$imepflag != ""} { set drpT [$self mobility-trace Drop "IFQ"] } else { set drpT [cmu-trace Drop "IFQ" $self] } $ifq drop-target $drpT if { $namfp != "" } { $drpT namattach $namfp } # Mac Layer # $mac netif $netif $mac up-target $ll if {$outerr == "" && $fec == ""} { $mac down-target $netif } elseif {$outerr != "" && $fec == ""} { $mac down-target $outerr $outerr target $netif } elseif {$outerr == "" && $fec != ""} { $mac down-target $fec $fec down-target $netif } else { $mac down-target $fec $fec down-target $outerr $err target $netif }

Actually, from top to down path, the structure is  ll  --->  ifq ----> mac ---> netif . for packets going up, it is netif ---> mac --->ll. Thus, ifq is only used for down path of . however, a scheduler is also only useful to handle outgoing packets. Thus, if we want to implement a scheduler, we have to use something to replace this "ifq" and remake the interface in tcl script.