5.5.2 Node Interface

To connect to the above interfaces of routing module, a node provides a similar set of interfaces:

• In order to know which module to register during creation, the Node class keeps a list of modules as a class variable. The default value of this list contains only the base routing module. The Node class provides the following two procs to manipulate this module list: rX [name]Node::enable-module & If module RtModule/[name] exists, this proc puts [name] into the module list.
  [name]Node::disable-module & If [name] is in the module list, remove it from the list. When a node is created, it goes through the module list of the Node class, creates all modules included in the list, and register these modules at the node.

  After a node is created, one may use the following instprocs to list modules registered at the node, or to get a handle of a module with a particular name: rX []Node::list-modules & Return a list of the handles (shadow objects) of all registered modules.
  [name]Node::get-module & Return a handle of the registered module whose name matches the given one. Notice that any routing module can only have a single instance registered at any node.

• To allow routing modules register their interests of routing updates, a node object provide the following instprocs: rX [module]Node::route-notify & Add module into route update notification list.
  [module]Node::unreg-route-notify & Remove module from route update notification list.
  Similarly, the following instprocs provide hooks on the attachment of transport agents: rX [module]Node::port-notify & Add module into agent attachment notification list.
  [module]Node::unreg-port-notify & Remove module from agent attachment notification list.
  Notice that in all of these instprocs, parameter module should be a module handle instead of a module name.
• Node provides the following instprocs to manipulate its address and port classifiers:
  • [module, clsfr, hook]Node::insert-entry inserts classifier clsfr into the entry point of the node. It also associates the new classifier with module so that if this classifier is removed later, module will be unregistered. If hook is specified as a number, the existing classifier will be inserted into slot hook of the new classifier. In this way, one may establish a ``chain'' of classifiers; see Figure 5.2 for an example. NOTE: clsfr needs NOT to be a classifier. In some cases one may want to put an agent, or any class derived from Connector, at the entry point of a node. In such cases, one simply supplies target to parameter hook.
  • [module, clsfr, hook]Node::install-entry differs from Node::insert-entry in that it deletes the existing classifier at the node entry point, unregisters any associated routing module, and installs the new classifier at that point. If hook is given, and the old classifier is connected into a classifier chain, it will connect the chain into slot hook of the new classifier. As above, if hook equals to target, clsfr will be treated as an object derived from Connector instead of a classifier.
  • [demux, port]Node::install-demux places the given classifier demux as the default demultiplexer. If port is given, it plugs the existing demultiplexer into slot port of the new one. Notice that in either case it does not delete the existing demultiplexer.