SNA Network Addressing

Names and addresses are assigned during system generation to identify network resources to end users and the path control network.
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Two levels of addressing are used by the path control network:
  • Network Addresses - used to route messages between subareas and between NAUs in subarea nodes
  • Local Addresses - used to route messages between subareas and peripheral nodes, and between NAUs in peripheral node
  • SNA Network Interconnection (SNI)

Network Addresses

Network addresses uniquely identify NAUs (SSCPs, LUs, PUs, links, and so on). Network addresses are made up of two parts: the subarea address and the element address.
Subarea addresses contain the subarea number of the subarea Node. The subarea number is user-assigned at system definition.
Element addresses are unique only within a subarea. They are assigned during system generation, network reconfiguration, activation of switched resources, or initiation of parallel LU-LU sessions.
Extended addressing uses a 23-bit address field for the network address. The extended address is divided into 8 bits for the subarea address and 15 bits for the element address. Previous addressing schemes used a total of 16 bits for the network address with a user-selected length for the subarea portion.

Local Addresses

Local addresses uniquely identify NAUs within a peripheral node. These addresses are used only to identify resources within a peripheral node and are not the same as the element addresses discussed above.
Network addresses are translated to local addresses by the boundary function, which resides in the subarea node. Thus, the boundary function insulates the peripheral node from network address changes resulting from reconfigurations.
Network Names
End users avoid having to know network addresses by referring to NAUs by symbolic names. These names are translated into addresses for the path control network by directory services in the SSCP. The use of network names insulates the end user from address changes in the network.

SNA Network Interconnection (SNI)

SNA network interconnection allows end users in two separate SNA networks to communicate with each other without requiring unique addresses of network names in both networks. The interconnection is effected by a gateway consisting of a gateway node and at least one gateway SSCP. Network addresses are translated by the gateway node and network names are translated by the gateway SSCP. To ensure that addresses and names are unique among interconnected networks, gateways prefix them with a network identifier. The network identifiers are uniquely assigned during system generation.
The
MICS Network Analyzer
Option distinguishes between interconnected networks by retaining the network name in a common data element, NETWRKID. For the
MICS
files derived from NPM data, NETWRKID may be set to the value of the NPM data field PLUNETID. An additional network identifier, SLUNETID, is carried in the
MICS
NPM User Activity File. The Network Identifier Exit Routine, SNTNIDRT, is explained in the Network Identifier Exit (SNTNIDRT) section.