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T1/E1 Digital Voice Port Adapter Installation and Configruation
OL-3592-02
Chapter 1 Overview
Features
support Voice over IP involves a series of protocols and features geared toward quality of service (QoS).
Traffic shaping considerations must be taken into account to ensure the reliability of the voice
connection.
Features
The PA-VXA, PA-VXB, and PA-VXC have the following features:
•
Universal ports—One interface port (PA-VXA) or two interface ports (PA-VXB and PA-VXC) per
port adapter are configurable as either T1 (with integrated CSU/DSU) or E1 (with integrated
G.703/G.704 120-ohm interface). Additionally, a port may be configured on a per-DS0 basis for
voice termination, time-division multiplexing (TDM) pass-through (cross-connect), or packet data.
•
High-density digital signal processor (DSP) technology—Full support exists for low-bit-rate voice
compression (down to 5.3 kbps) on all T1/E1 port channels.
•
Multiservice Interchange (MIX) support—Voice channels can be TDM-switched between port
adapter slots in the Cisco 7200 VXR chassis. This allows DSP resources to be shared between port
adapters in the same chassis or for port-to-port DS0 cross-connect between port adapter slots.
•
DS0 drop and insert—Flexible TDM cross-connect capability between ports and the MIX bus is
available.
•
VoIP and VoFR termination—Full VoIP and Voice over Frame Relay (VoFR) gateway functionality
for mixed environments is available.
•
Full-featured DSP firmware—Support exists for eight standard-compression algorithms plus echo
cancellation, full dual tone multifrequency (DTMF)/MF tone detection and generation, and
dial-pulse generation.
•
Silence suppression—To conserve network bandwidth, voice activity detection (VAD) prevents
sending data when no voice is present. Comfort-noise generation prevents uncomfortable dead
silence on the receiving end.
•
Multiple clocking options—Ports can be clocked internally from the network, or the network clock
from one port can be sent to the other port on the card or to other cards across the MIX bus in
the VXR chassis.
•
Flexible signaling support—Channel-associated signaling (CAS) and common channel signaling
(CCS) support is available for both E1 and T1 applications in H.323 environments.
DSP features:
•
Coders/decoders (codecs):
G.711 (a-law/u-law), G.729/G.729.a (with b variant), G.723.1, G.728, G.726
•
Fax relay through T.30 support:
V.17, V.29, V.27
•
Echo cancellation—32 milliseconds meeting G.165
•
DTMF/R2/MF/SF/CP tone detection and generation
•
Dial-pulse detection and generation
•
Energy-based voice activity detection (VAD) and codec-specific VAD
•
Comfort noise generator
