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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.
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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 Agent MIB Request MIB Reply Trap Reply Trap Trap Ack
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 RCX 0 1 2 Sensor Motor Memory 0 Touch Light Temperature 1 2 S1 S2 S3 S1 S2 S3 S1 S2 S3 0 1 2 0 1 2 0 1 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