1. Categorization
of C++ Classes
in NS2
N S 2 U l t i m a t e . c o m
b y
T e e r a w a t I s s a r i y a k u l

2. OUTLINE
Conventional Class Categorization
Simulation Class Categorization
Example: Packet transmission
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3. Conventional Class
categorization
Two-language structure
NS2 consists of two languages: C++ and OTcl
The simplest form ➠ Standalone classes
C O
C.1 C.2 O.1 O.2
C++ classes OTcl classes
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4. Conventional class
categorization
But clearly, there can be more than on class
hierarchy in both the domains
C O
C.1 C.2 O.1 O.2
C++ classes OTcl classes
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5. Conventional class
categorization
But clearly, there can be more than on class
hierarchy in both the domains
D P
D.1 D.2 P.1 P.2
C O
C.1 C.2 O.1 O.2
C++ classes OTcl classes
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6. Conventional object
categorization
Classes in the C++ domain can be bound to
class in the OTcl domain
D P
D.1 D.2 P.1 P.2
C O
C.1 C.2 O.1 O.2
bind
C++ classes OTcl classes
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7. Conventional class
categorization
And, binding can be quite arbitrary
D P
D.1 D.2 P.1 P.2
bind
C O
C.1 C.2 O.1 O.2
bind
C++ classes OTcl classes
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8. Conventional class
categorization
Now we have two categories of classes:
“bound” and “standalone”
D P
D.1 D.2 P.1 P.2 Standalone
bind OTcl classes
C O
Standalone
C++ classes
C.1 C.2 O.1 O.2
bind
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9. Conventional class
categorization
Now we have two categories of classes:
“bound” and “standalone”
D P
D.1 D.2 P.1 P.2 Standalone
bind OTcl classes
bound
C O
Standalone classes
C++ classes
C.1 C.2 O.1 O.2
bind
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10. Conventional class
categorization
Bound C++ = Compiled classes
Bound OTcl = Interpreted classes
Standalone
bind OTcl classes
C O
Standalone
C++ classes
C.1 C.2 O.1 O.2
bind
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11. Conventional class
categorization
Bound C++ = Compiled classes
Bound OTcl = Interpreted classes
Standalone
bind OTcl classes
C O
Standalone
C++ classes
C.1 C.2 O.1 O.2
bind
Compiled Interpreted
classes classes
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12. Conventional class
categorization
C++ OTcl
Compiled Interpreted
Bound
classes classes
Standalone C++ classes OTcl classes
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13. OUTLINE
Conventional Class Categorization
Simulation Class Categorization
Example: Packet transmission
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14. Simulation class
categorization
Six main categories
Base C++ Class Characteristic
TclObject Compiled classes
Handler Default actions
NsObject Receive packets
Packet Packet reception event
Event scheduler: put events on the simulation time line
Scheduler
and execute default actions at the right time.
Others None of the above, e.g., Routing, timers, etc.
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15. related objects were discussed in Chapter 4. The packet-related objects will
Simulation class
be discussed in Chapter 8. The main helper objects will be discussed in
Chapter 15.
categorization
5.1.2 C++ Class Hierarchy
This section gives an overview of C++ class hierarchies. The entire hierarchy
consists of over 100 C++ classes and struct data types. Here, we only show
Six main categories
a part of the hierarchy (in Fig. 5.1). The readers are referred to [18] for the
complete class hierarchy.
OTcl Interface Default Action
TclObject Handler
Simulator PacketQueue NsObject AtHandler QueueHandler
RoutingModule
Network Component
Classifier Connector LanRouter
Uni-directional Point-to-
point Object Connector
Queue Agent ErrorModel LinkDelay Trace
Fig. 5.1. A part of NS2 C++ class hierarchy (this chapter emphasizes on classes
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in boxes with thick solid lines).

16. Simulation class
categorization
Six main categories
Base C++ Class Characteristic
TclObject Compiled classes
Handler Default actions
NsObject Receive packets (= Default action)
Packet Packet reception event
Event scheduler: put events on the simulation time
Scheduler
line and execute default actions at the right time.
Others None of the above, e.g., Routing, timers, etc.
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17. OUTLINE
Conventional Class Categorization
Simulation Class Categorization
Example: Packet transmission
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18. example: packet
transmission
Sending a packet from an Agent object to a
Queue object
Packet
Agent Queue
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19. example: packet
transmission
Class hierarchy
NsObject ➠ Agent and Queue
Event ➠ Packet
NsObject
Event
Packet
Agent Queue
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20. For more
information
about NS2
P l e a s e s e e
t h i s b o o k
f r o m
S p r i n g e r
T. Issaraiyakul and E. Hossain, “Introduction to Network Simulator NS2”, Springer 2009
or visit www.ns2ultimate.com