440 Chapter 12: SNA Technology
Figure 12-5
Subarea Concepts
Subarea Nodes
Subarea nodes are either PU type 5 or 4. The main components in an SNA domain are the
mainframe (5) and the FEP (4). Subarea nodes can communicate with other subarea nodes and
their peripheral devices, but peripheral nodes can communicate only with the subarea node to
which they are connected.
There are two main types of subarea nodes: host (or mainframe) and FEP:
·
Host or mainframe--This type of node sits at the top of the network and contains the
CPU. This device is in charge of the network and is sometimes referred to as the master.
This is from where all resources in the network are controlled. Software that runs on the
mainframe is called VTAM. The mainframe typically is connected to a FEP by a channel.
A channel can be copper bus and tag or fiber ESCON connector:
-- VTAM (Virtual Telecommunications Access Method)--A software package
developed by IBM that runs on the mainframe. It directly controls the
transmission of data to and from the network.
-- ESCON (Enterprise System Connection)--The ESCON Channel Port
Adapter provides a single channel attachment interface for connecting Cisco
7200-series routers to an ESCON director or to a mainframe channel. This
interface can eliminate the need for a separate front-end processor (FEP). The
SSCP
Subarea 1
Subarea node
PU 5
Peripheral node
Subarea 2
PU 4
Front-end processor
Subarea node
IBM 3745
IBM 3X74
PU 2
PU 2
IBM printer
Cluster controller
Peripheral node
PU 2
IBM 3745
Subarea 3
PU 4
PU 5
Subarea 5
Subarea node
SSCP
IBM S/370
IBM 3X74
PU 2
PU 4
PU 2
Subarea 4
Subarea node
IBM 3745
87200333.book Page 440 Wednesday, August 22, 2001 2:53 PM