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The Addressing Structure in NS
The Default Address Format
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32 lower bits for port-id, 1 higher bit for
mcast and the rest 32 higher bits for nodeid.
$ns set-address-format def
The Hierarchical Address Format
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Default Hierarchical Setting
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$ns set-address-format hierarchical
3 levels of hierarchy
Specific Hierarchical Setting
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$ns set-address-format hierarchical 2 8 15
The Expanded Node-Address
Format
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address space to 30 bits, allocating 22
higher bits to node-id and lower 8 bits to
port-id.
this command is now obsolete given that
node address and port address spaces are
32 bits wide.
Errors in setting address format
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if number of bits specified is less than 0.
if bit positions clash (contiguous number of
requested free bits not found).
if total number of bits exceed MAXADDRSIZE_.
if expand-port-field-bits is attempted with portbits
less than or equal to the existing portsize.
if number of hierarchy levels do not match with
number of bits specified (for each level).
Hierarchical Address Format-ex
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set ns [new Simulator]
$ns set-address-format hierarchical
AddParams set domain_num_ 區域數
AddParams set cluster_num_ 群組數
AddParams set nodes_num_ 節點數
design topology
Mobile Networking in ns
Mobile Networking
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Mobile node
Routing mechanisms
Network components
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Channel
Network interface
Radio propagation model
MAC protocols
Interface Queue
Link Layer
ARP
The basic wireless model in ns
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MobileNode object is a split object.
The C++ class MobileNode is derived from
parent class Node. (ref ch5)
Difference
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added functionalities of a wireless
mobile node like ability to move within a given
topology
not connected by means of Links to other nodes or
mobilenodes.
Routing mechanisms
Mobilenode Object
Implemented in C++
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The mobility features
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node movement
periodic position
updates
maintaining topology
boundary
etc
implemented in Otcl
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MobileNode itself
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Classifiers
Dmux
LL
Mac
Channel
etc
Creating Node movements
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Start position:
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$node set X_ <x1>
$node set Y_ <y1>
$node set Z_ <z1>
Future destinations:
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$ns at $time $node setdest <x2> <y2> <speed>
Ex:
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ns at 3.0 "$node (0) setdest 48.0 38.0 5.0
the third dimension (Z) is not used.
Creating Node movements
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random movement
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$mobilenode start
Set topology
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set topo [new Topography]
$topo load_flatgrid $opt(x) $opt(y)
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opt(x) and opt(y) are the boundaries used in
simulation
Network Components in a
mobilenode
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MobileNode method add-interface() in
~ns/tcl/lib/ns-mobilenode.tcl
MN components
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Link Layer-(ref.14)
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ARP
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O-writes it into the mac header of the packet
X-broadcasts an ARP query
Interface Queue
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ARP module connected to it which resolves all IP to
hardware (Mac) address conversions
priority to routing rotocol packets
Mac Layer
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carrier sense
MN components-cont.
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Tap Agents
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Network Interfaces
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mobilenode to access the channel.
implemented Phy/WirelessPhy
Radio Propagation Model
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defined in mac.h
register themselves with the mac object using method
installTap()
Friss-space attenuation (1/r2)
Two ray Ground (1/r4)
Antenna
MAC layer protocols
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802.11MAC protocol
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See ~ns/mac-802_11.{cc,h} for implementation details.
Preamble based TDMA protocol
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ns supports a single hop, preamble-based TDMA MAC
protocol
multi-hop environment are not considered
TDMA frame contains
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preamble
data transmission slots
avoid unnecessary power consumption
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set_node_sleep().
Routing Agents
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DSDV
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messages are exchanged between neighbouring
mobilenodes
~ns/dsdv directory and ~ns/tcl/mobility/dsdv.tc
DSR
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checks every data packet for source-route information.
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~ns/tcl/mobility/dsr.tcl
TORA
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X-Routing queries
ns/tora directory and ns/tcl/mobility/tora.tcl
AODV
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ns/aodv and ns/tcl/lib/ns-lib.tcl
Trace Support
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cmu-trace objects are of three types
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CMUTrace/Drop
CMUTrace/Recv
CMUTrace/Send
~ns/trace.{cc,h} and ~ns/tcl/lib/nscmutrace.tcl.
tracing all packets that are sent out in a
router
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set sndT [cmu-trace Send "RTR" $self]
Example for wireless
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Default Script Options
Main Program
produce some simple node movements
simulation ends
Trace Support-cont.
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The cmu-trace object CMUTrace is derived
from the base class Trace.
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tracing packets
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See Chapter 26 for details on class Trace
dropped, received and sent by agents, routers,
mac layers or interface queues in ns.
All traces are written to the buffer wrk_.
Trace Support-cont.
An example of a trace for a tcp packet is as
follows:
r 160.093884945 _6_ RTR --- 5 tcp 1492 [a2
4 6 800] ------- [65536:0 16777984:0 31
16777984] [1 0] 2 0
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Revised format for wireless traces
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cmu-trace objects
This command should be called before the
universal trace command
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$ns trace-all <trace-fd>
Currently this new trace support is available
for wireless
new trace format
new trace format
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Event type
In the traces above, the first field (as in the
older trace format) describes the type of
event taking place at the node and can be
one of the four types:
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s send
r receive
d drop
f forward
new trace format
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General tag
The second field starting with "-t" may
stand for time or global setting
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-t time
-t * (global setting)