Verilink 9000 Series (34-00271) Product Manual - Manual (Page 135)

7
B
ISYNC
2780/3780
AND
3270
Introduction This chapter provides specific information for the Bisync 2780/3780 and 3270
protocols and how they operate using the TXPORT MultiPro platform and NMCS
software.
Bisync
Principles and
Concepts The Bisync protocols belong poll/select to the family. The basic concept of
poll/select operation is simple. All information is stored at the central site for all
branch sites to use. The centralized mainframe where this information is stored is
commonly referred to as the host. All branch-site locations extract and send
information commonly from terminals, therefore these locations are referred to as
terminals. Two examples of non-terminal devices are ATM machines and printers.
They communicate with the network poll/select protocol being used. The host site
polls all terminal devices at the branch sites, querying whether there is data to
receive from them. Upon being polled, the terminal device transmits some
indication to the host as to whether there is information to be transmitted or
received. The host, having an indication of a terminal device needing service,
selects that terminal device, and the transaction is completed. Polling then resumes
from the host site.
TXPORT MultiPro platforms support the Bisync protocols. These protocols follow
the same concepts as other poll/select-type protocols. If a port is connected to a
host end on the TXPORT device, that port should be configured using that
particular protocol’s host port parameters. If the port selected is connected to a
terminal end on the TXPORT device, that port should be configured using that
particular protocol’s terminal parameters. All host TXPORT device ports must
have a list of which terminal addresses to service. Likewise, each terminal
TXPORT device port must have a unique host name where the terminal data
should be sent.
All host and terminal TXPORT device ports emulate a host or terminal
respectively, thereby only passing non-polling sequences through the transport
(WAN) connection. This protocol emulation is commonly referred to as spoofing.
Spoofing allows more efficient use of the WAN connection, freeing up bandwidth
as well as keeping bandwidth costs down, particularly in the frame relay
environment.
Figure 7-1 on page 114 shows a typical Bisync network using Frame Relay as the
transport medium. This figure shows addressing information as address table
information for Port 4 on unit 002 and unit 003, Port 1 Frame Relay Endpoint
Lists for all units, and the Host name field on unit 001’s Port 4.