Transcript PC - RCX Management Application

• PC – RCX Management Application
FEATURES
• This is an application similar to SNMP, for
managing the RCX brick from a PC.
• PC queries/sets the status of the various
objects on the brick.
• The RCX brick can report any failures to
the PC.
COMPONENTS
• Agent – RCX.
The device which is managed.
• MIB – Management Information Base
This is a hierarchical arrangement of the various objects on
the agent that can be monitored.
• NMS – Network Management Station (PC)
This refers to the manager which sends the queries/set
messages to the agent.
COMMUNICATION
• Protocol for communication is based on
LLC.
• 2 layers involved
– LLC
– LLC Reliable Handler
• RCXPort()
• IR forms the physical layer for
communication.
ARCHITECTURE
NMS
MIB
Agent
Request
Reply
Trap Reply
Trap
Trap Ack
MIB
MESSAGES
• Request Message
– Sent from NMS to Agent
– Get / Set Messages
– Each request message is sent as a series of
bytes
– Message Size, Id Size, Identifier, Type of
Message, Tag Value, Extra Data
MESSAGES(contd..)
• Reply Message
- Get Message – Value written as a short
integer in two bytes.
- Set Message – No reply sent back.
MESSAGES ( contd..)
• Trap Message
– Sent in emergency situations
– Used to notify the NMS about its situation so
that some recovery action could be taken up by
the NMS.
– Unique Identifier
MESSAGES ( contd..)
• Trap Reply Message
- Sent from the NMS to the Agent.
- Specifies the recovery action to be taken.
• Trap Ack Message
– Sent back from the agent to the NMS once the agent
has recovered.
– Helps notify the NMS to start its normal querying.
MIB
• Managed objects comprise the MIB.
• A managed object in the RCX is a component
whose status can be queried or set.
• Egs., of managed objects in the RCX
– Sensor, Motor,Memory
– Types of Sensors – Touch, Light
– Instances of Sensors are S1, S2, S3
– Instances of Motors are A, B, C
MIB ORGANISATION
1
0
RCX
1
Sensor
2
Motor
Memory
0
1
Touch
S1
0
S2
1
S3
2
Light
Temperature
S1 S2 S3
0
1
2
S1 S2
2
0
1
S3
2
Eg: Identifier for touch sensor S1: 1.0.0.0.
PARAMETERS ASSOCIATED WITH THE OBJECTS
• Memory
– Retrieves the amount of free memory available
• Status of the motors
– flt()
– forward()
– backward()
– reversedirection()
– setPower()
– Stop()
• Sensors
– A sensor can be activated or passivated
TRAP SITUATIONS
• A trap message could be sent in the
following situations
– When voltage is getting low
– When the brick is low on memory
TRAP MESSAGES
• When an emergency situation arises, a trap message is sent
to the NMS.
• The agent suspends all other activities of receiving queries
from the NMS.
• When the NMS receives a trap it suspends its other
activities and begins to process the trap message.
• A trap reply message will then be sent to the agent,
depending on the type of trap request.
• On receiving the reply message the agent sends back a trap
ack message.
FORMAL VERIFICATION
• UPPAAL will be used for verification
• Properties to be verified
– Deadlock free