31.3 Commands at a glance
Following is a list of commands used for multicast simulations:
set ns [new Simulator -mcast on]
This turns the multicast flag on for the the given simulation, at the time of
creation of the simulator object.
This like the command above turns the multicast flag on.
This returns true if multicast flag has been turned on for the simulation
and returns false if multicast is not turned on.
$ns_ mrtproto mproto optional:nodelist
This command specifies the type of multicast protocol <mproto> to be used
like DM, CtrMcast etc. As an additional argument, the list of nodes <nodelist>
that will run an instance of detailed routing protocol (other than
centralised mcast) can also be passed.
$ns_ mrtproto-iifs mproto node iifs
This command allows a finer control than mrtproto. Since multiple mcast
protocols can be run at a node, this command specifies which mcast protocol
<mproto> to run at which of the incoming interfaces given by <iifs> in the <node>.
This returns a new/unused multicast address that may be used to assign a multicast
address to a group.
THIS COMMAND IS OBSOLETE NOW
This command expands the address space from 16 bits to 30 bits. However this
command has been replaced by "ns_ set-address-format-expanded".
$node_ join-group agent grp
This command is used when the <agent> at the node joins a particular group <grp>.
$node_ leave-group agent grp
This is used when the <agent> at the nodes decides to leave the group <grp>.
This command starts multicast routing at all nodes.
This stopd mcast routing at all nodes.
$node_ enable-mcast sim
This allows special mcast supporting mechanisms (like a mcast classifier) to
be added to the mcast-enabled node. <sim> is the a handle to the simulator
In addition to the internal methods listed here there are other methods specific to
protocols like centralized mcast (CtrMcast), dense mode (DM), shared tree
mode (ST) or bi-directional shared tree mode (BST), Node and Link class
methods and NetworkInterface and Multicast classifier methods specific to
multicast routing. All mcast related files may be found under
- Centralised Multicast
- A handle to the CtrMcastComp object is
returned when the protocol is specified as `CtrMcast' in mrtproto.
Ctrmcast methods are:
$ctrmcastcomp switch-treetype group-addr
Switch from the Rendezvous Point rooted shared tree to source-specific
trees for the group specified by group-addr. Note that this method cannot
be used to switch from source-specific trees back to a shared tree for a
$ctrmcastcomp set_c_rp node-list
This sets the RPs.
$ctrmcastcomp set_c_bsr node0:0 node1:1
This sets the BSR, specified as list of node:priority.
$ctrmcastcomp get_c_rp node group
Returns the RP for the group as seen by the node node for the multicast
group with address group-addr. Note that different nodes may see different
RPs for the group if the network is partitioned as the nodes might be in
$ctrmcastcomp get_c_bsr node
Returns the current BSR for the group.
This recomputes multicast routes in the event of network dynamics or a
change in unicast routes.
- Dense Mode
- The dense mode (DM) protocol can be run as PIM-DM (default) or DVMRP
depending on the class variable CacheMissMode. There are no methods
specific to this mcast protocol object. Class variables are:
- Timeout value for prune state at nodes. defaults to
- Used to set PIM-DM or DVMRP type forwarding rules.
- Shared Tree
- There are no methods for this class. Variables are:
- RP_ indexed by group determines which node is the RP for a
- Bidirectional Shared Tree
- There are no methods for this class. Variable is same as that of Shared
Tree described above.