Visara FEP-4600 Planning Guide - Manual (Page 66)

Chapter 6. Support of PU 4 Connections
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Transmission Group Support on the FEP-4600
The FEP-4600 currently supports only single link Transmission Groups. When migrating
from a 37x5 FEP where multilink Transmission Groups are currently used, it should be
considered, why are multilink Transmission Groups currently being used? There are
probably only two answers.
1. To provide increased bandwidth for data traffic.
2. To provide a redundant path, in case one link becomes inoperative.
Increased Bandwidth: Traditional 3745 Front Ends were stingy on link speeds due to
the technologies commonly in use at the time they were developed. The FEP-4600 makes
use of newer technologies, and easily provides ample bandwidth over a variety of
interfaces:
 FICON
 ESCON
 100 Mbps and 1000 Mbps Ethernet
 100 Mbps Token Ring
 T1/E1 capable Serial Links
Redundant Paths: Although the FEP-4600 does not support multilink Transmission
Groups, it will support parallel single link Transmission Groups, allowing you to set up
multiple Explicit Routes between subareas.
If multilink transmission groups are currently in use between the 37x5 that the FEP-4600
is replacing and a remote NCP, it will be necessary to make changes to the gen of the
remote NCP.
If the connection to the remote 37x5 is via DLSw, the routed IP network usually provides
the needed redundancy within the IP network architecture.
TG Numbering: Each interface on the FEP-4600 can be configured to match the TG
number defined in VTAM or can be matched to the definition in the remote NCP. TG
numbers must match for the physical interfaces that the FEP-4600 shares with the
adjacent subareas. The TG number assigned to the ESCON interface for a PU4 circuit
must match the TG number assigned in the adjacent VTAM for the corresponding Link
Station definition. On the remote link (such as SDLC or Token Ring) the TG number
must match the TG number assigned on the remote NCP. The TG on the ESCON side
does not have to match the TG number on the remote interface side of our circuit. The
FEP-4600 will take care of linking the upstream TG to the downstream TG.
When multiple PU4 paths are defined through the FEP-4600, it is possible to assign a
single subarea to the FEP-4600 and use a different TG number for each of the remote
destinations. It is also possible to assign a different subarea number to each destination
and use the same or different TG numbers for each destination.