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Cisco ATA 187 Analog Telephone Adaptor Administration Guide for SIP (Version 1.0)
OL-21862-01
Chapter 1 Cisco ATA 187 Analog Telephone Adaptor Overview
Software Features
Secure Real-Time Transport Protocol
Secure Real-Time Transport Protocol secures voice conversations on the network and provides
protection against replay attacks.
Name Signaling Event based passthrough
Name Signaling Event (NSE)-based passthrough is simply thet transport of fax or modem
communications using the G.711 codec.
The ATA 187 does not support NSE-based modem passthrough.
Transport Layer Security Protocol
Transport Layer Security (TLS) is a cryptographic protocol that secures data communications such as
e-mail on the Internet. TLS is functionally equivalent to Secure Sockets Layer (SSL).
T.38 Fax Relay
The T.38 fax relay feature enables devices to use fax machines to send files over the IP network. In
general, when a fax is received, it is converted to an image, sent to the T.38 fax device, and converted
back to an analog fax signal. T.38 fax relays configured with voice gateways decode or demodulate the
fax signals before they are transported over IP. With the SIP call control protocol, the T.38 fax relay is
indicated by Security Description (SDP) entries in the initial SIP INVITE message. After the initial SIP
INVITE message, the call is established to switch from voice mode to T.38 mode. Cisco Unified
Communications Administration allows you to configure a SIP profile that supports T.38 fax
communication.
Voice Codecs Supported
The ATA 187 supports these voice codecs (check your other network devices for the codecs they
support):
• G.711µ-law
• G.711A-law
• G.729A
• G.729B
• G.729AB
Other Supported Protocols
The ATA 187 supports these additional protocols:
• 802.1Q VLAN tagging
• Cisco Discovery Protocol (CDP)
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