Download
1 / 15
150 likes | 169 Views
This application for managing the RCX brick from a PC allows querying and setting status of brick objects, with failure reports to the PC. Utilizes Agent-RCX and MIB architecture, with LLC-based communication protocol. Messages like Request, Reply, Trap, and Trap Ack ensure efficient communication between NMS and Agent. The MIB consists of managed objects such as Sensors (Touch, Light), Motors, and Memory. Trap situations like low voltage trigger Trap Messages for emergency notifications. Formal verification using UPPAAL assures deadlock-free operation.
E N D
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
