Session 1332
Planning and Analyzing
Wireless LANs and Mobile IP
Networks
Network Analysis, Planning, and
Troubleshooting
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Session Abstract
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Agenda
 Wireless LAN (WLAN) overview
 WLAN model support
 Capabilities
 Node models
 Attributes
 Statistics
 WLAN nodes architecture
 Lab 1: Hidden node scenario
 Lab 2: Infrastructure Extended Service Set (ESS)
 Lab 3: PCF access mode
 Mobile IP
 Lab 4: Roaming
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Agenda
 Wireless LAN overview
 WLAN model support
 Capabilities
 Node models
 Attributes
 Statistics
 WLAN nodes architecture
 Lab 1: Hidden node scenario
 Lab 2: Infrastructure ESS
 Lab 3: PCF access mode
 Mobile IP
 Lab 4: Roaming
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Why Wireless LAN?
 Mobility
 Users do not have to be plugged in
 Real-time data from anywhere in the organization
 Ease of installation
 No need for cabling through/around walls
 Can go where wires cannot
 Reduced cost-of-ownership
 Easier to move, add, and change
 Uses license-free radio spectrum
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Wireless LAN support in OPNET
 Based on IEEE 802.11 and IEEE 802.11b standards
 Modeled data rates
 1.0 Mbps
 2.0 Mbps
 5.5 Mbps
 11.0 Mbps
 Supported physical layers
 Direct-sequence spread-spectrum (DSSS)
 Frequency Hopping spread-spectrum (FHSS)
 Infrared light (IR)
 DCF MAC operation: Contention based (CSMA/CA)
 PCF MAC operation: Poll based
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Distributed Coordinated Function
(DCF)
Sense the medium
If the medium is busy,
defer
When the medium
becomes idle again,
transmit after a
random backoff
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Point Coordination Function (PCF)
Operation
 Requires centralized coordination
 Introduces contention free period
(CFP)
 Use for “near” real-time services
 Forces a “fair” access to the medium
during the CFP
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Wireless LAN Topologies
 Basic building block:
Basic Service Set (BSS)
 Independent BSS
 Infrastructure BSS
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Wireless LAN Topologies (cont.)
 Infrastructure Extended Service Set (ESS)
BSS 1
BSS 2
BSS 3
Internet
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Agenda
 Wireless LAN overview
 WLAN model support
 Capabilities
 Node models
 Attributes
 Statistics
 WLAN nodes architecture
 Lab 1: Hidden node scenario
 Lab 2: Infrastructure ESS
 Lab 3: PCF access mode
 Mobile IP
 Lab 4: Roaming
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
WLAN OPNET Model: Typical Use Cases
 Study wireless LANs as an alternate/supplemental local area
network technology
 Analyze network performance by varying the network demand
(e.g., number of nodes, application traffic)
 Evaluate optional protocol-specific features like fragmentation
and reassembly or RTS/CTS frame exchange against various
network conditions
 Set up independent and infrastructure BSS networks and
evaluate their performance under different traffic and
configurations
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
WLAN OPNET Model: Typical Use Cases
(contd.)
 Tune PCF parameters to achieve maximum performance for
different applications
 Study the impact of mobility on applications running at mobile
node and efficiency of the wireless LANs being visited
 Modify the logic of standard WLAN algorithms to conduct
experiments with new ideas and prospective improvements
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Node Models
Wireless LAN Station (Non-IP based)
Wireless LAN Workstation
Wireless LAN Server
Bridge with WLAN Port (Access Point)
Router with WLAN interface (Access Point*)
* Unless the interface belongs to a WLAN backbone
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Attributes
Node Attributes
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Model Attribute Definitions
RTS Threshold (bytes)
 Set the packet size threshold for which the ready
to send (RTS)/clear to send (CTS) WLAN
mechanism will be used
 Solution to hidden terminal problem
 Prevent large packets to be dropped
 Overhead due to the RTS/CTS frame exchange
Short Retry Limit
 Maximum transmission attempts for data frames
with a size shorter than or equal to RTS
Threshold
 High values for retry limit will produce a more
reliable transmissions but will create overhead
Long Retry Limit
 Maximum transmission attempts for data frames
with a size greater than RTS Threshold
 Set a lower value than Short Retry Limit will
help to decrease the amount of buffer required
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Model Attribute Definitions (cont.)
Fragmentation Threshold (bytes)
 MSDU > Threshold => fragmentation
occurs
 Smaller packet size reduces packet loss but
increase overhead
Large Packet Processing
 Action taken in the case: higher layer packet
size > maximum allowed data size
 Based on this, a packet will be dropped or
fragmented
 Outside the scope of the standard
Max Receive Lifetime (seconds)
 Maximum time for a packet to wait to be
reassembled at receiver’s reassembly buffer
Buffer Size (bits)
 Maximum length of higher-layer data
arrival buffer
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Model Attribute Definitions (cont.)
BSS Identifier
 Identifies the BSS to which a WLAN MAC belongs to
 If set to “Auto Assigned,” the entire OPNET subnet will be considered as a single
BSS
 If configured for one WLAN node, then it needs to be configured for all WLAN
nodes in the network
Access Point Functionality
 Enable or disable access-point operation in the node
 Used to configure BSS and ESS topologies
 Required to be Enabled for PCF operation
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Model Attribute Definitions (cont.)
Data Rate (bps)
 Support for 1.0 Mbps, 2.0 Mbps, 5.5 Mbps, and 11.0 Mbps
 Networks with higher data rate are more sensitive to external interference
 Different data rates are supported in the same BSS
Physical Characteristics
 Set the physical layer used by the model: Frequency Hopping, Direct Sequence
or Infrared. Internal attributes like interframe spacing values and MAC header
are dependent on the physical layer.
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Model Attribute Definitions (cont.)
 Packet Reception Power Threshold
 Defines the received power threshold value in Watts at the radio receiver
for arriving WLAN packets
 Packets with a power less than threshold will be considered as noise
 Will not change the status of the receiver to "busy" from the point of
view of the MAC layer
 Sensitivity indicator
 Vendor specific
 PCF Parameters
 Configure PCF operation mode
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Model Attribute Definitions (cont.)
 PCF Parameters
 PCF Functionality
 Enables / disables use of PCF
 Beacon Interval
 Specifies how often the beacons will be transmitted
 CFP Interval
 The length of each contention free period in seconds
 CFP Beacon Multiple
 Specifies the number of beacons between two CFPs
 Max Failed Polls
 Specifies the maximum
number of consecutive polls
by the AP without a valid
acknowledgement from
MAC that is being polled
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Auto-allocation of WLAN channels to
BSSs (New in 10.0)
 Channel Settings
 Bandwidth and frequency settings
 Default value “Auto Assigned”
 A WLAN channel will be assigned to each BSS automatically
 Manual assignments are supported: pre-defined “channels” or any value
 Must be consistent across the BSS
 Example
 5 BSSs: from “BSS A” to BSS “E” where A < B < C < D < E
BSS A  Ch1
Ch 1
Ch 2
2.401 MHz
Ch 3
Ch 4
BSS B  Ch6
Ch 5
BSS D  Ch2
Ch 6
Ch 7
Ch 8
Ch 9
BSS C  Ch11
Ch 10
BSS E  Ch7
Ch 11
2.451 MHz
2.473 MHz
Reserved Frequency Band for WLAN Channels in U.S.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Roaming (New in 10.0)
 Needed when the connection is weakened/lost with AP
 Two approaches for scanning for a new AP
 Based on signal strength (monitors AP’s periodic beacons)
 Realistic
 Based on distance
 Efficient
 Configure the simulation attribute to determine the approach to be used
 WLAN Beacon Efficiency Mode (default: Enabled)
 WLAN AP Connectivity Check Interval (default: 10 seconds)
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Statistics
Global Statistics
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
Node Statistics
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Statistics (cont.)
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Agenda
 Wireless LAN overview
 WLAN model support
 Capabilities
 Node models
 Attributes
 Statistics
 WLAN nodes architecture
 Lab 1: Hidden node scenario
 Lab 2: Infrastructure ESS
 Lab 3: PCF access mode
 Mobile IP
 Lab 4: Roaming
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Lab #1: Hidden Node
 Objective
 Show the impact of the RTS/CTS mechanism as a measure to prevent
the hidden node problem
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Agenda
 Wireless LAN overview
 WLAN model support
 Capabilities
 Node models
 Attributes
 Statistics
 WLAN nodes architecture
 Lab 1: Hidden node scenario
 Lab 2: Infrastructure ESS
 Lab 3: PCF access mode
 Mobile IP
 Lab 4: Roaming
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Lab #2: Infrastructure BSS
 Objective
 Become familiar with WLAN model
attributes needed to configure BSSs
 Use the model to select an
appropriate WLAN topology
according to the application traffic
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Break
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Agenda
 Wireless LAN overview
 WLAN model support
 Capabilities
 Node models
 Attributes
 Statistics
 WLAN nodes architecture
 Lab 1: Hidden node scenario
 Lab 2: Infrastructure ESS
 Lab 3: PCF access mode
 Mobile IP
 Lab 4: Roaming
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Lab #3: PCF Access Mode
 Objective
 Use PCF mechanism to improve the performance of real-time
applications over WLAN
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Agenda
 Wireless LAN overview
 WLAN model support
 Capabilities
 Node models
 Attributes
 Statistics
 WLAN nodes architecture
 Lab 1: Hidden node scenario
 Lab 2: Infrastructure ESS
 Lab 3: PCF access mode
 Mobile IP
 Lab 4: Roaming
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Mobile IP
 A new model in 10.0
 Implementation based on the following RFCs:
 RFC 3220: IP Mobility Support for IPv4
 RFC 2003: IP Encapsulation Within IP
 RFC 1256: ICMP Router Discovery Messages
 Supported features
 Dynamic tunneling endpoints
 Mobile IP router based networks (legacy end nodes)
 Registration/Deregistration over UDP
 Foreign agent care of address
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Mobile IP (cont.)
 Why use Mobile IP?
 Uninterrupted service for mobile users
 Transparent to transport layer and applications
 IP level roaming between different IP subnets/providers
 Operational implementations
 Cisco Mobile IP routers
 Various Linux implementation (for Laptops and PDAs)
 Future enhancements
 Co-located care of address
 Route optimization
 IPv6 support
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Mobile IP Example
 Mobile node at the home network
 No tunneling is required
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Mobile IP Example (cont.)
 Mobile node at a foreign network
 Data from server is tunneled by home agent to foreign agent
IP Tunnel
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Mobile IP Attributes: Router
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Mobile IP Attributes: Router (cont.)
 Home Agent
 Interface Name
 Name of a physical or loopback interface to enable the home agent
service
 IP address has to be pre-assigned to the interface
 Agent Type
 Home Agent
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Mobile IP Attributes: Router (cont.)
 Foreign Agent
 Interface Name
 Name of a physical or loopback interface to enable the foreign agent
service
 Usually a roaming capable (e.g. radio) interface
 Agent Type
 Foreign Agent
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Mobile IP Attributes: Router (cont.)
 Mobile Router
 Interface Name
 Name of a physical or loopback interface to enable the Mobile Router
service
 Need to be a loopback interface if more than one roaming interfaces
 The interface must have an IP address that falls into the same IP subnet
as the HA
 Agent Type
 Mobile Router
 Home Agent IP Address
 IP address of the HA interface
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Mobile IP Attributes: Host
 Mobile Node
 Interface Name
 Name of a physical or loopback interface to enable the Mobile Node
service
 The interface must have an IP address that falls into the same IP subnet
as the HA
 Home Agent IP Address
 IP address of the HA interface
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Agenda
 Wireless LAN overview
 WLAN model support
 Capabilities
 Node models
 Attributes
 Statistics
 WLAN nodes architecture
 Lab 1: Hidden node scenario
 Lab 2: Infrastructure ESS
 Lab 3: PCF access mode
 Mobile IP
 Lab 4: Roaming Mobile IP
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Lab #5: Roaming Mobile IP
 Objective
 Configure Mobile IP network utilizing WLAN roaming capabilities
 Adjust Mobile IP handoff parameters to achieve less communication
interrupts
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Takeaway Points
 RTS/CTS option can help alleviate the hidden node problem
 Additional APs provides more capacity and support scalability
 Use PCF option to provide QoS
 Use roaming feature to model mobile scenarios
 OPNET provides extensive modeling support for modeling
wireless LAN networks:
 Discrete Event Simulation for modeling protocol algorithms, optional
standard features, transient effects, protocol overhead traffic, deployment of
explicit traffic sources (TCP/IP-based applications or raw traffic
generators) over WLAN technology, etc.
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Additional Resources
 Wireless LAN Model Usage Guide
 Click on “Help” menu and select “Product Documentation”
 “Model Descriptions  Model Usage Guides Wireless LAN (802.11)”
 Wireless LAN FAQs
 Go to “Support Center” at OPNET’s WWW site
 http://www.opnet.com/support
 Click on “FAQs” link under “Technical Resources”
 Search the FAQ database using the keywords “Wireless LAN” or “WLAN”
Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
References
 IEEE 802.11 standard
 RFC 3220 IP Mobility Support for IPv4
 Gast, Matthew S., 802.11 Wireless Networks: The Definitive
Guide, O’Reilly & Associates, April 2002
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1332 Planning and Analyzing Wireless LANs and Mobile IP Networks
Related Wireless Sessions
 Session 1529: Understanding WLAN Model Internals and
Interfaces
 Session 1318: Planning and Analyzing UMTS Networks
 Session 1807: Introduction to Next Generation Wireless
Technologies
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