Примечания к выпуску для Cisco Cisco IOS Software Release 12.2(2)XA

PSTN fallback does not provide assurances that a VoIP call that proceeds over the IP network is 
protected from the effects of congestion. This is the function of the other Quality of Service (QoS) 
mechanisms such as IP Real-Time Transport Protocol (RTP) priority or low latency queuing (LLQ).

PSTN fallback includes the following features:

Offers flexibility to define the congestion thresholds based on the network.

Defines a threshold based on Calculated Planning Impairment Factor (ICPIF), which is derived 
as part of International Telecommunication Union (ITU) G.113. 

Defines a threshold based solely on packet delay and loss measurements.

Uses Response Time Reporter (RTR) probes to provide packet delay, jitter, and loss information for 
the relevant IP addresses. Based on the packet loss, delay, and jitter encountered by these probes, an 
ICPIF or delay and loss values are calculated.

Is supported by calls of any codec. Only G.729 and G.711 have accurately simulated probes. Calls 
of all other codecs are emulated by a G.711 probe.

Refer to the following document for additional information:

http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122newft/122limit/122x/122xa/122x
a_2/ft_pfavb.htm

In Cisco IOS Release 12.2(2), the range of the output attenuation command for voice ports has changed 
from 0–14 to –6–14.

To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules, 
go to the Cisco MIB website on Cisco.com at 
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.

Old Cisco MIBs will be replaced in a future release. Currently, OLD-CISCO-* MIBs are being converted 
into more scalable MIBs without affecting existing Cisco IOS products or network management system 
(NMS) applications. You can update from deprecated MIBs to the replacement MIBs as shown in 

.