Cisco AS5800 Especificaciones descargar pdf (Pagina 91)

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Cisco AS5800 Operations, Administration, Maintenance, and Provisioning Guide

DOC-7810814=

Chapter 3 Operations

Verifying Modem Performance

• Exactly one digital to analog conversion must exist in the circuit. The digital line must connect into

a digital switch, not a channel bank. V.90 requires PRI (64k clear-channel DS0s). Channel banks

destroy V.90 by adding additional analog-to-digital conversions. Telcos occasionally refer to

channel banks as line-side services. Digital switches are sometimes referred to as trunk-side

services. Figure 3-5 shows this.

Figure 3-5 No Channel Banks for V.90

•

In the local loop, less than three miles of twisted-pair copper line with no load coils is ideal. Load

coils limit frequencies (passband). V.90 requires a 3000 Hz passband. A circuit that does not deliver

a 3200 Hz passband will most likely not deliver V.90. Load coils are common in long loops in

North America (at the 3.5 mile mark).

• Sometimes the PSTN switch fabric is extended by a digital carrier. It is then converted to analog by

a SLC. This setup complies with V.90. The digital-to-analog conversion is moved closer to the

subscriber. However, non-integrated or universal SLCs do not comply to V.90.

• Use a recommended V.90 client modem.

• Electrical house wiring sometimes causes V.90 trainup to fail. For details, see the “V.34 Basic

Rules” section on page 3-7.

Initiating a Modem Loopback Test Call

Test the access server’s ability to initiate and terminate a modem call. Similar to sending a ping to the

next-hop router, this test verifies basic connectivity for modem operations. Successfully performing this

test gives you a strong indication that remote clients should be able to dial into the NAS. Figure 3-6

shows this test.

After completing this test, dial into the EXEC from a client PC and a client modem (no PPP).

Table 3-3 V.90 Supported Cisco IOS Releases

Chassis Modem Type Cisco IOS Release

Cisco AS5800 MICA 11.3(6+)AA

12.0(1+)T

Line side service

Channel bank

Trunk side service

Digital switch

Digital switch NAS

NAS

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Cisco AS5800 Especificaciones Pagina 91