MASTER-TO-MASTER COMMUNICATIONS

A single master with all of its consoles is known as a LSO group. To share data outside of a group requires master-to-master data sharing. Data sharing between groups is done through the configuration file.

Following are two parts of configuration files that are sharing data between groups.

table1

In this NTLIST both the source and the global fields should be set to Yes. When a master receives updates for this tag it will share the updates with other masters on the network.

table1

In this NTLIST the source field is set to No. The destination master must have this NT definition in order to receive and relay update information for this tag.

LSO allows a master the capability of broadcasting data packets to masters within one group and/or masters in a different group. The MTRGROUP is the name of the master group which the master belongs to. All the masters within the same group can send data to and receive data from each other. If master A in GROUP1 needs to send data to master B in GROUP2, the ALTERNATE_MTRGROUP of A's configuration should be set to GROUP2. This will allow A to broadcast data to masters (including master B) in GROUP2 as well as broadcasting data to masters in GROUP1.

LSO provides 3 NCBs for each master group by default if the master group is specified. These NCBs are subtracted from the number of NCBs allocated to LSO via the NCBS parameter. For a master, 3 NCBs are allocated for MTRGROUP (whose default name is MTR_GRP) by default. If ALTERNATE_MTRGROUP is not specified, no NCB will be allocated for ALTERNATE_MTRGROUP. You can modify the number of NCBs allocated for a master group.

LSO also provides a packet broadcasting reliability scheme to guarantee packets to be delivered reliably among masters. In essence, a packet broadcasted by master A will be received by other masters if they are defined as within the broadcasting scope of master A. Even if one master is dead, the data transfer among masters will not be affected. Therefore, this scheme allows data transfer among master groups to continue independent of any console groups.

LSO provides four new system parameters to support master groups. They are as follows:

WORKSTATIONID

Each master must have a unique identifier and it should be numbered sequentially from 1 to 32.

MTRGROUP

MTRGROUP is the name of the master group in which the current master belongs to.

ALTERNATE_MTRGROUP

ALTERNATE_MTRGROUP is the name of an alternate master group that will be able to receive broadcasts from this master.

ALTMTRNCBS

ALTMTRNCBS is the number of NCBS dedicated to communicating with the alternate master group.

LSO provides a global demand-cancel system which allows a console in a console group to request data from another console in any other console group by using a global network tag. It also allows a console to cancel its demand for a network tag in another console in any other console group so that it will not receive the data value of that network tag. In essence, the system makes transparent to a console the way LSO broadcasts data packets among masters.

If a network tag NT1 is defined as Global in console C, whenever the condition of the input list in which NT1 is specified turns TRUE, C will send a demand for NT1 to its master M. M will broadcast this demand to all the other masters within its broadcasting scope. After a master N receives this demand, it will register this demand. If NT1 is defined as the SOURCE by one of N's consoles, N will immediately send the current value it has for NT1 to M, and M relays it to C. Whenever N receives data for NT1, it will broadcast the data to M, and M relays it to C.

If the condition of the input list in which NT1 is specified turns FALSE, C will send a demand cancel for NT1 to its master M and M broadcasts it to other masters. After receiving this demand-cancel, N removes the demand for NT1 from its memory. If this is the only demand for NT1 that N has, N will not broadcast the value for NT1 after receiving it from its consoles. This Global Demand-Cancel system is fully compatible with the LSO Masterto-Master support.

Whenever a master is started, it will broadcast the demands for global network tags it receives from its consoles to other masters within its broadcasting scope so that all the other masters can register the demands. Whenever a master connects to a console and receives all the NT definitions from the console, this master will broadcast a message to other masters within its broadcasting scope so that the other masters can send their NT demands to this master. In this way, no matter when a master is started, the Global Demand-Cancel system, along with the LSO Master-to-Master support, guarantees data transfer to be performed reliably and transparently among masters.


Prev Next