As with BRI, you have several switch types to select from. Check with your provider to configure
the correct one. Otherwise, you might have to reboot your router for the switch type change
to take effect.
Table 26.3 shows the typical available switch types used with PRI.
TABLE 2 6 . 3
PRI Switch Types
Switch Type Typically Used
PRIMARY-5ESS AT&T 5ESS switch type for the U.S.
PRIMARY-4ESS AT&T 4ESS switch type for the U.S.
PRIMARY-DMS100 Northern DMS-100 switch type for the U.S.
PRIMARY-NET5 NET5 switch type for the U.K. and most of Europe
VN3 VN3 and VN4 switch types for France
PRIMARY-NTT Japanese ISDN PRI switches
PRIMARY-NI AT&T National ISDN switch type for the U.S.
T-1– and E-1–based PRIs use different line-coding and framing schemes. A T-1–based PRI
uses binary eight-zero substitution (B8ZS) for encoding and Extended Super Frame (ESF) for
framing. An E-1–based PRI uses high-density bipolar Order 3 (HDB3) for encoding and cyclic
redundancy check, level 4 (CRC-4) for framing.
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