AT&T 7500 series, 7100 series manual 12.LAN/SNA Connectivity, Communication System as a LAN Backup

8-20LOCAL AREA NETWORK CONNECTIONS

____________________________________________________________________________________________________________________________
_
		S75/85/G1/G2		S75/85/G1/G2
				T-1
LAN	3B2 OR 6386				3B2 OR 6386	LAN
	X.25	MPDM		MPDM	X.25
WITH						WITH
	ROUTER				ROUTER
StarGROUP						StarGROUP
NAU		X.25		X.25		NAU
		CARD		CARD
		Figure 8-11.	X.25/StarGROUP Connectivity

			S75/85/G1/G2	S75/85/G1/G2
LAN	X.25		T-1
	ROUTER	MPDM	. . . .	MPDM
WITH
StarGROUP
3270 EMULATION
PROGRAM FOR
END USER ACCESS
				HOST
		X.25	LAN	F
				E
		ROUTER	WITH
				P
			StarGROUP
				PCS CARD
				PC GATEWAY SOFTWARE

Figure 8-12.LAN/SNA Connectivity

The Communication System as a LAN Backup

In work environments that are totally dependent upon real-time computer interaction, it is very important that access to the LAN server be highly reliable. One of the most simple reliability schemes is redundancy. For a LAN, total redundancy may be too expensive. Offering the same required redundancy, however, is independent access to a communications system for each LAN node. This approach provides a more economical alternative to a second LAN since the communications system is necessary to basic business operations and runs concurrently at most LAN sites.

To equip the LAN for this type of redundancy, in addition to each node being connected to the LAN, each node must also have its own RS-232 connection with a modem or data module for access to the server through the communications system. In addition, each node must have terminal emulation software available that will enable it to communicate with the server. For example, communication with a server from 6386 PC StarLAN nodes may require that LAN Manager Remote Gateway software be available at each PC.