AT&T 7500 series, 7100 series manual Private Data Networks, Terrestrial Private Data Network Links

8-26PUBLIC AND PRIVATE DATA NETWORK CONNECTIONS

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PRIVATE DATA NETWORKS

AT&T leases facilities to private companies for nonswitched connections to private network endpoints. Applications for these connections include high-volume data transmission, bulk voice and data transmission to multiple locations, interactive computer-aided design, and so forth. The leased facilities over which the connections are made may be either terrestrial or satellite.

Terrestrial Private Data Network Links

The terrestrial services that AT&T offers for nailed-up connections are listed below.

∙ACCUNET T1.5 service — With this service, a dedicated T1 trunk is connected between private communications systems, between private communications systems and a central office, and between

central offices. Access is through a private communications system, a switched public data network, the DATAPHONE Digital Data Service, or the SKYNET® Digital Service.

∙ACCUNET T45 service — This service provides fiber-optic digital transmission from a DS1 port to a M28 multiplexer that multiplexes up to 28 DS1 trunks or 672 DS0 lines. From the M28, signals travel at the DS3 level to the AT&T POP. At the POP, the transmission is demultiplexed and can access the switched public data network, T1.5 service, the DATAPHONE Digital Data Service, and so on.

∙ACCUNET Spectrum of Digital Services (ASDS) — Access to ASDS can be through analog or digital facilities. Access need not be at the DS1 level — subrate channels as well as multiple DS0 channels may be accommodated. Through ASDS, digital transmission is furnished at speeds ranging from 9.6, 56, or 64 kbps, up to the DS1 speed of 1.544 Mbps. This service is sometimes called fractional T1.

Private Connections Through ACCUNET T1.5 and T45

Connections through these facilities present their own special set of requirements. Figures 8-17through 8-20show some typical private data network connections. Table 8-7lists the requirements for the illustrated connections.

DTE

MPDM/M1*

OR

7500B

S75/S85

G1/G2

T1.5

PRIVATE DATA

NETWORK

T1.5

S75/S85

G1/G2

MPDM/M1*

OR

7500B

DTE

Figure 8-17.Private Data Network with Robbed Bit Trunks (Mode 1)