MultiBuildingMessaging

Multi-building (or multi-node) messaging is implemented as a service-style agent. Its use is optional and it can be enabled/disabled by simply enabling/disabling the multibuilding service agent. It is easily configured using the service configuration file and provides several new topics for use in the local agent exchange bus.

Configuration

The service configuration file may contain the declarations below:

• building-publish-address: A ØMQ address on which to listen for messages published by other nodes. Defaults to 'tcp://0.0.0.0:9161'.

• building-subscribe-address: A ØMQ address on which to listen for messages subscribed to by other nodes. Defaults to 'tcp://0.0.0.0:9160'.

• public-key, secret-key: Curve keypair (create with zmq.curve_keypair()) to use for authentication and encryption. If not provided, all communications will be unauthenticated and unencrypted.

• hosts: A mapping (dictionary) of building names to publish/subscribe addresses. Each entry is of the form:

  "CAMPUS/BUILDING": {"pub": "PUB_ADDRESS", "sub": "SUB_ADDRESS", "public-key": "PUBKEY", "allow": "PUB_OR_SUB"}
  

  • CAMPUS/BUILDING: building for which the given parameters apply
  • PUB_ADDRESS: ØMQ address used to connect to the building for publishing
  • SUB_ADDRESS: ØMQ address used to connect to the building subscriptions
  • PUBKEY: curve public key of the host used to authenticate incoming connections
  • PUB_OR_SUB: the string "pub" to allow publishing only or "sub" to allow both publish and subscribe

• cleanup-period: Frequency, in seconds, to check for and close stale connections. Defaults to 600 seconds (10 minutes).

• uuid: A UUID to use in the Cookie header. If not given, one will be automatically generated.

Sending and Receiving Inter-building Messages

Three topics are provided for inter-building messaging:

• building/recv/CAMPUS/BUILDING/TOPIC: Agents can subscribe to to this topic to receive messages sent to TOPIC at the building specified by CAMPUS/BUILDING.

• building/send/CAMPUS/BUILDING/TOPIC: Agents can send messages to this topic to have them forwarded to TOPIC at the building specified by CAMPUS/BUILDING.

• building/error/CAMPUS/BUILDING/TOPIC: Errors encountered during sending/receiving to/from the above two topics will be sent over this topic.

Limitations and Future Work

• Requires opening multiple listening ports: It would be nice to multiplex all inter-building communications over a single port to decrease the attack footprint and ease firewall administration.

• There is limited authorization: a remote host can either publish or publish and subscribe. Perhaps a filter list can be included to limit which topics a host may subscribe to or publish on.

• Remote host lookup is kept in a static file: Ideally, host lookup would be done through some central directory service, but that is not currently implemented.