AT&T 2500 series, 7500 series Circuit-Switched Public Data Networks, SDS and Sddn Applications

8-22PUBLIC AND PRIVATE DATA NETWORK CONNECTIONS

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ports, although Memotec also has higher capacity units. (See figure 8-13.)

ASYNC

ENDPOINTS

SYSTEM

85

7400A,	MEMOTEC
7400B,		X.25	MODEM OR	APS	X.25	∙
ADU, OR	SP/630		PRIVATE LINE
MPDM	PAD
						X.25 HOST
APS	ACCUNET PACKET SERVICE - AT&T X.25 PDN

Figure 8-13.ACCUNET Packet Service

∙REDI-ACCESS— For relatively low-volumes of data and intermittent APS access, a less expensive alternative might be dial-up access to shared facilities. Control Data Corporation’s REDI-ACCESS service offers you asynchronous, dial-up access to shared facilities that interface directly with APS.

Circuit-Switched Public Data Networks

AT&T offers two circuit-switched digital data network services for public access. These services are the ACCUNET Switched Digital Services (SDS), and the Software Defined Digital Network (SDDN).

AT&T provides switched access to both SDS and SDDN. In addition, both SDS and SDDN offer two transmission options: Switched 56 Service (SW56), and Switched 64 Service (SW64).

∙SW56 is a dial-up 56-kbps data transmission service that allows DTEs to communicate with each other. Access to the service is via analog line service, dedicated DATAPHONE Digital Service [DDS] private lines, or T1.5 shared access lines. Access facilities are ordered from the LEC. The facilities connect a System 75, System 85, Generic 1 or 2 communications system to SDS or SDDN at the AT&T point- of-presence (POP).

∙SW64 is a dial-up 64-kbps service that requires dedicated T1.5 ISDN-PRI access for connection of your communications system to the AT&T POP.

SDS and SDDN Applications

SDS and SDDN applications include:

∙Video conferencing — Low bit-rate, color video can be transmitted via SDS or SDDN. PICTURETEL, Optel, and Compression Labs (CLI) build video equipment that interfaces with your communications system for the transmission of video data over SDS or SDDN.

∙High-speed facsimile — Facsimile equipment that interfaces with your communications system for the transmission of facsimiles over SDS or SDDN can transmit a single page in 3 seconds.

∙Bulk data transfer — SDS and SDDN support file transfers from PC to PC, mainframe to PC, and mainframe to mainframe. DSP is a company that builds plug-in cards for personal computers that facilitate the transfer of files from the PC, through your communications system, over SDS or SDDN.

∙ALLIANCE 3000 service — This AT&T service provides interactive teleconferencing with as many as 59 locations.