Visara LINCS Features - Manual (Page 15)

5
Chapter 2. APPN Network Node
707021-001
Class of Service Definitions (COS)
For a particular COS, APPN determines the importance of eight values that are defined for
every link within the APPN network. The values are:
• Propagation delay
• Cost per byte
• Cost for connect time
• Effective capacity
• Security
• Three optional user defined values
Each COS assigns a particular weight to these values. When an end node requests a route to a
partner, the class-of-service requested is compared against the COSs available along the path.
If the defined weights of a COS at each node meet or exceed the weights for the COS requested,
then the path will be selected. If one node along the path cannot provide the COS requested
(for example: SECURE), the request will be rejected. Configuration and Management
The “Display/Update APPN COS” utility on the Customization Data Menu is used to display
or define your COS parameters. If you are not extremely knowledgeable about SNA and APPN
route selection procedures, you should probably not define your own COSs. Default values
will be used if no COS is defined.
Directory Services
APPN performs dynamic, automatic network definition capability. In an APPN network,
end nodes and the resources they provide (LUs) need only be known by their serving
network node.
A LEN’s resources are defined during LINCS configuration. End nodes inform network nodes
of their resources upon connecting. Directory services maintains a directory database of this
information, plus information about resources outside its own domain as it learns of them.
Aging algorithms remove inactive entrees from the “Safe Stored” directory database to keep it
at a manageable size. LINCS’ APPN supports standard directory services including:
• Network node server – LINCS registers its APPN end node’s resources a local database.
LENs and ENs use this service to locate remote LUs.
• LU registration – LEN LUs can be registered using LINCS’ Central Control. This enables
remote end nodes to find them.
• Directed and broadcast services – LINCS uses directed search requests to obtain domain
path information from a central directory server, typically VTAM, and uses broadcast search
requests when no central directory service is present.
Locating a Resource
APPN end nodes do not need partner definitions. Instead, an end node asks its network node
server (for example LINCS) to find a partner, and to determine the best route to get there. Each
end node tells its network node server which LUs reside in it. By combining all the information
known by all the network nodes, the location of any LU can be determined. When an NN is
requested to find an LU, it first looks within its own directory for the LU’s location. If not