Friday, February 21, 2014

Random Points on Topologies in OPNET

Physical topology is the actual layout of the nodes and links.
Logical topology deals with protocol configuration of the network devices for the establishing channels.
Physical topologies include fully-connected mesh, partially-connected mesh, bus, star, ring, ring and hybrid.

The Object Palette provides access to OPNET models. You can access it through Topology->Object Palette 
  • Node Models consists of hubs, switches, routers etc.
  • Link Models contains models of links e.g. 10BASE-T.
  • Path Models contains model for specifying network paths e.g. Multiprotocol Label Switching (MPLS).
  • Demand Models specify the data flows, IP voice traffic, IP security etc.
  • Wireless Domain models, contains sparse grid, mobility etc.
  • Shared Objects contain models group according to common properties e.g. internet_toolbox group contains node, link etc. for modeling the Internet.
Model naming follows convention like companyabrivation_model_slots_ethernetinterfaces_framerelayinterfaces_...

OPNET also provides some models of complete networks e.g. 10BaseT_LAN models a LAN in which nodes are connected via 10BASE_T Ethernet links.
Nodes like Application Config, IP VPN Config, Profile Config etc. don't represent real-life devices but allows the configuration of various applications and technologies.
ppp_wkstn  and  ethernet_wkstn  are  used  to  model  client  workstations.
ppp_server and ethernet_server are used to model servers.
1000BaseX_LAN, 100BaseT_LAN, and  10BaseT_LAN  models  are  used to simulate Ethernet LANs. By default, each of the above network models simulates the operation of a LAN with 10 end nodes.
ethernet4_slip8_gtwy models a gateway router.
ethernet2_slip8_firewall also models a gateway router but with additional firewall features.
ip32_cloud models an IP cloud and is commonly used to represent the connectivity  of  the  Internet
PPP_28K, PPP_33K, PPP_56K, PPP_DS1, and PPP_DS3 are models of duplex point-to-point links with various data rates.

You can also create custom model by selecting Create Custom Model button in Object Pallet.

Rapid Configuration is a useful tool for creating network topologies with a large number of nodes. You can open it by selecting select Topology > Rapid Configuration…

Select Topology->Verify Links to verify link conectivity.

Select Topology->Fail Selected Objects to fail the selected object during a specific point in simulation and then recover it in other point of time.

With the help of the subnet object, you can arrange nodes in the network in a hierarchical fashion.

In fixed subnet nodes are not allowed to move during the simulation.

Double-click on the subnet icon will take you inside the subnet.

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