|
|
This feature module describes the Public Switched Telephone Network (PSTN) Fallback feature. It includes information on the benefits of the new feature, supported platforms, related documents, and so on.
This document includes the following sections:
The goal of PSTN fallback is to provide a mechanism to monitor congestion in the IP network and either redirect calls to the PSTN or reject calls based on the network congestion.
PSTN fallback does not provide assurances that a call which proceeds over the IP network is protected from the effects of congestion. This is the function of the other QoS mechanisms such as IP RTP Priority or LLQ.
PSTN fallback:
Once the ICPIF values are calculated, they are stored in a fallback cache where they remain until they age out or the cache overflows. Until an entry ages out, probes are sent for that particular destination periodically. This time interval is user configurable.
When attempting a call to a destination, PSTN fallback looks into the fallback cache to see if it already has an ICPIF value for that destination. If the ICPIF value is below the threshold, the call is admitted. If the existing ICPIF value exceeds the threshold, the call is rejected and could go to the PSTN. If an ICPIF value does not exist for that particular destination, a probe is sent to the destination and based on the results of the probe, the call is accepted or rejected.
When a probe is initiated, the VoIP call is put in a wait state until the ICPIF value is returned. This leads to a trade-off in Post Dial-Delay as opposed to gaining network congestion information. This same scenario is applied if the delay and loss thresholds are configured.
This feature is supported on the following Cisco platforms:
Standards
No new or modified standards are supported by this feature.
MIBs
No new or modified MIBs are supported by this feature.
RFCs
No new or modified RFCs are supported by this feature.
Before you can configure PSTN fallback, you must have already configured Voice over IP (VoIP). For more information, see the Cisco IOS Multiservice Applications Configuration Guide and
Cisco IOS Multiservice Applications Command Reference for Cisco IOS Release 12.1.
See the following sections for configuration tasks for the PSTN fallback feature. Each task in the list is identified as either optional or required:
| Command | Purpose | |
|---|---|---|
Step 1 | Router# conf term | Enters global configuration mode. You have entered global configuration mode when the prompt changes to |
Step 2 | Router(config)# call fallback | Enables the PSTN fallback feature. |
| Command | Purpose | |
|---|---|---|
Step 1 | Router# show call fallback config | Shows the current configuration. |
Error Message:%FALLBACK-4-CACHE_OVERFLOW:Cache has overflowed.
Explanation Fallback cache has overflowed and deleted 1/4 of the entries.
Action Increase the fallback cache size.
Explanation Only one test probe can run at a time.
Action Wait until the first test probe is finished.
Explanation No available voice RTP ports were found.
Action Contact your technical support representative.
Explanation No statistic information was returned with probe.
Action Contact your technical support representative.
Explanation A probe error occurred. Possibly, responce time reporter (RTR) responder on remote router is not enabled, or an interface from the source to the destination is down.
Action Check the destination router configuration and status of interfaces from the source to the destination.
| Command | Purpose |
|---|---|
Router# clear call fallback cache | Clears the current ICPIF estimates for all IP addresses in the cache. |
Router# show call fallback stats | Shows the call fallback stats. |
Router# show call fallback config | Shows the current configuration. |
This section provides the following configuration examples:
The following example configures PSTN fallback with default fallback configuration values on Router1 for VoIP over Frame Relay. The direction of the calls is from Router1 to Router2. No MD5 authentication is configured. Additionally, RTR responder is configured on Router2 to answer the probes from Router1. When the number 3666 is called from Router1 and there is congestion on the link between 1.6.6.77 and 1.6.6.78, the call is not admitted. The user will hear a busy tone since there is only one dial peer, 3666, and the IP network that is connected to it is congested. Configure the
call fallback active command (see "call fallback") to enable PSTN fallback.
**** Topology ****
|1.6.6.77 1.6.6.78 |
Router1 3640 | -----------------VoIP over FR -------------| 3660 Router2
| (CIR = 100K) |
**** Router1 'sh run' ****
Current configuration:
!
version 12.0
service timestamps debug datetime msec localtime
service timestamps log uptime
no service password-encryption
!
hostname Router1
!
!
!
!
!
voice-card 3
!
ip subnet-zero
no ip domain-lookup
!
frame-relay switching
!
!
!
call fallback active
!
!
!
!
interface Ethernet0/0
ip address 1.3.22.77 255.255.0.0
no ip directed-broadcast
!
interface Serial0/0
no ip address
no ip directed-broadcast
encapsulation frame-relay
load-interval 30
no keepalive
frame-relay traffic-shaping
frame-relay inverse-arp interval 15
!
interface Serial0/0.1 point-to-point
ip address 1.6.6.77 255.255.0.0
no ip directed-broadcast
frame-relay interface-dlci 100
class frs0
!
!
interface Ethernet0/1
ip address 1.4.4.77 255.255.0.0
no ip directed-broadcast
load-interval 30
!
!
ip classless
ip route 0.0.0.0 0.0.0.0 Ethernet0/0
ip route 1.5.0.0 255.255.0.0 1.4.4.78
ip route 223.255.254.254 255.255.255.255 Ethernet0/0
no ip http server
!
!
map-class frame-relay frs0
no frame-relay adaptive-shaping
frame-relay cir 100000
frame-relay bc 560
frame-relay mincir 100000
frame-relay fair-queue
frame-relay fragment 100
frame-relay ip rtp priority 16384 16383 75
!
!
!
line con 0
exec-timeout 35791 0
transport input none
line aux 0
line vty 0 4
password ard
login
!
!
voice-port 1/0/0
!
voice-port 1/0/1
!
voice-port 1/1/0
!
voice-port 1/1/1
!
dial-peer voice 10 pots
destination-pattern 6666
port 1/0/0
!
dial-peer voice 20 pots
destination-pattern 6777
port 1/0/1
!
!
dial-peer voice 300 voip
destination-pattern 3...
no vad
session target ipv4:1.6.6.78
!
dial-peer voice 60 pots
destination-pattern 6111
port 1/1/0
!
end
**** Router2 'sh run' ****
Current configuration:
!
version 12.0
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Router2
!
!
!
voice-card 4
!
ip subnet-zero
!
isdn voice-call-failure 0
!
!
!
interface FastEthernet0/0
no ip address
no ip directed-broadcast
shutdown
duplex auto
speed auto
!
interface FastEthernet0/1
no ip address
no ip directed-broadcast
shutdown
duplex auto
speed auto
!
interface Ethernet1/0
ip address 1.3.22.80 255.255.0.0
no ip directed-broadcast
!
interface Serial1/0
no ip address
no ip directed-broadcast
encapsulation frame-relay
load-interval 30
no keepalive
clockrate 256000
frame-relay traffic-shaping
frame-relay inverse-arp interval 15
!
interface Serial1/0.1 point-to-point
ip address 1.6.6.78 255.255.0.0
no ip directed-broadcast
frame-relay interface-dlci 100
class frs0
!
interface Ethernet1/1
ip address 1.5.5.74 255.255.0.0
no ip directed-broadcast
!
!
map-class frame-relay frs0
frame-relay fragment 100
frame-relay ip rtp priority 16384 16383 75
no frame-relay adaptive-shaping
frame-relay cir 100000
frame-relay bc 1000
frame-relay mincir 100000
frame-relay fair-queue
!
!
voice-port 2/0/0
!
voice-port 2/0/1
!
voice-port 2/1/0
!
voice-port 2/1/1
!
voice-port 3/0/0
!
voice-port 3/0/1
!
voice-port 3/1/0
!
voice-port 3/1/1
!
dial-peer voice 10 pots
destination-pattern 3111
port 2/0/0
!
dial-peer voice 20 pots
destination-pattern 3222
port 2/0/1
!
dial-peer voice 100 voip
destination-pattern 6...
no vad
session target ipv4:1.6.6.77
!
dial-peer voice 60 pots
destination-pattern 3999
port 3/0/0
!
dial-peer voice 70 pots
destination-pattern 3888
port 3/0/1
!
rtr responder
!
line con 0
exec-timeout 0 0
transport input none
line aux 0
line vty 0 4
login
!
end
The following example configures PSTN fallback for VoIP over MLPPP for Router1. The direction of the calls is from Router1 to Router2. MD5 authentication is configured. Also RTR responder is configured on Router2 to answer the probes from Router1. When the number 6666 is called from Router1 and there is congestion on the link between Router1 and Router2, the call is sent to port 3/0/1 and hence to Router2 over the PSTN.
Probes are sent every 20 seconds (default) with 15 packets in each probe, and are sent in the priority queue with the other voice packets after ip rtp priority is enabled. Also, the delay and loss threshold command is configured with delay threshold of 150 and loss threshold of 5%, and the cache aging timeout is 10,000 seconds. The link is configured for 128K, and 80K is reserved for voice using the
ip rtp priority command.
(Router1) 3660 ----------VoIP over MLPPP---------- 3640 (Router2)
3/0/1 | | 1/0/0
PSTN-------------------------------------PSTN
Router1:
Current configuration:
!
version 12.0
service timestamps debug datetime
service timestamps log datetime
no service password-encryption
!
hostname Router1
!
!
!
!
!
!
voice-card 4
!
ip subnet-zero
!
call fallback probe-timeout 20
call fallback threshold delay 150 loss 5
call fallback jitter-probe num-packets 15
call fallback jitter-probe priority-queue
call fallback cache-timeout 10000
call fallback active
!
!
!
interface Multilink1
ip address 1.10.10.1 255.255.0.0
no ip directed-broadcast
no ip route-cache
no ip mroute-cache
no keepalive
fair-queue 64 256 0
no cdp enable
ppp multilink
ppp multilink fragment-delay 20
ppp multilink interleave
multilink-group 1
ip rtp priority 16384 16383 80
!
interface FastEthernet0/0
no ip address
no ip directed-broadcast
shutdown
duplex auto
speed auto
!
interface FastEthernet0/1
no ip address
no ip directed-broadcast
shutdown
duplex auto
speed auto
!
interface Ethernet1/0
ip address 1.3.22.80 255.255.0.0
no ip directed-broadcast
!
interface Serial1/0
bandwidth 128
no ip address
no ip directed-broadcast
encapsulation ppp
no ip route-cache
no ip mroute-cache
load-interval 30
no fair-queue
clockrate 125000
ppp authentication chap
ppp multilink
multilink-group 1
!
interface Ethernet1/1
ip address 1.5.5.74 255.255.0.0
no ip directed-broadcast
!
ip classless
ip route 0.0.0.0 0.0.0.0 Ethernet1/0
ip route 1.4.0.0 255.255.0.0 1.5.5.78
ip route 223.255.254.254 255.255.255.255 1.3.0.1
no ip http server
!
!
voice-port 2/0/0
!
voice-port 2/0/1
!
voice-port 2/1/0
!
voice-port 2/1/1
!
voice-port 3/0/0
!
voice-port 3/0/1
!
voice-port 3/1/0
!
voice-port 3/1/1
!
!
dial-peer voice 10 pots
destination-pattern 3111
port 2/0/0
!
dial-peer voice 20 pots
destination-pattern 3222
port 2/0/1
!
!
dial-peer voice 60 pots
destination-pattern 3999
port 3/0/0
!
dial-peer voice 70 pots
destination-pattern 6666
port 3/0/1
!
dial-peer voice 200 voip
destination-pattern 6...
session target ipv4:1.10.10.1
!
!
line con 0
exec-timeout 0 0
transport input none
line aux 0
line vty 0 4
exec-timeout 0 0
login
!
end
To enable PSTN fallback, use the call fallback global configuration command. To disable PSTN fallback, use the no form of this command.
call fallbackSyntax Description
This command has no arguments or keywords.
Defaults
Disabled
Command Modes
Global configuration
Command History
12.1(3)T This command was introduced.
Release
Modification
Examples
The following example enables the call fallback feature:
Router(config)#call fallbackRouter(config)#
When call fallback is not configured:
Router(config)# call fallback
When call fallback is configured:
Router(config)# call fallback
Fallback subsystem is already on
Related Commands
show call fallback config Shows the call fallback configuration.
Command
Description
To specify the call fallback cache size, use the call fallback cache-size global configuration command. To restore the default value, use the no form of this command.
call fallback cache-size number
Syntax Description
number Specifies the cache size in number of entries. The valid range is
1 to 256.
Defaults
128
Command Modes
Global configuration
Command History
12.1(3)T This command was introduced.
Release
Modification
Usage Guidelines
Overflow process deletes up to one fourth of the cache entries to allow for additional calls beyond the specified cache size. This command is utilized only when call fallback is off.
Examples
The following example specifies the call fallback cache size of 120:
Router(config)# call fallback cache-size 120
When call fallback is not configured:
Router(config)# call fallback cache-size 128
When call fallback is already configured:
Router(config)# call fall cache-size 128
Cache size left unchanged (can be changed only when Fallback is OFF (use no call
fallback))
Related Commands
call fallback cache-timeout Specifies the time after which the cache entry will be purged. show call fallback cache Shows the current ICPIF estimates for all IP addresses in the cache.
Command
Description
To specify the time after which the cache entry will be purged, use the call fallback cache-timeout global configuration command. To restore the default value, use the no form of this command.
call fallback cache-timeout seconds
Syntax Description
seconds Specifies the cache timeout value in seconds. The valid range is
1 to 2,147,483.
Defaults
600 seconds
Command Modes
Global configuration
Command History
12.1(3)T This command was introduced.
Release
Modification
Usage Guidelines
The probes are continued in the background as long as the entry remains in the cache.
The timeout only happens when there are no active calls on that cache entry for the timeout period. As long as there are active calls, the timer will be reset.
Examples
The following example specifies the call fallback cache-timeout of 1200:
Router(config)# call fallback cache-timeout 1200
Related Commands
call fallback cache-size Specifies the call fallback cache size. show call fallback cache Shows the current ICPIF estimates for all IP addresses in the cache.
Command
Description
To specify the call fallback value weight, use the call fallback instantaneous-value-weight global configuration command. To return to the default values, use the no form of this command.
call fallback instantaneous-value-weight weight
Syntax Description
weight Specifies the instantaneous value weight. The valid range is 0 to 100.
Defaults
66
Command Modes
Global configuration
Command History
12.1(3)T This command was introduced.
Release
Modification
Usage Guidelines
To make decisions based on the current probe, use the weight of 100. To assign a weight to the existing value, use a lower weight.
Examples
The following example specifies the call fallback instantaneous value weight for 50:
Router(config)# call fallback instantaneous-value-weight 50
Related Commands
show call fallback config Shows the call fallback configuration.
Command
Description
To specify the number of packets for jitter, use the call fallback jitter-probe num-packets global configuration command. To restore the default value, use the no form of this command.
call fallback jitter-probe num-packets number
Syntax Description
number Specifies num-packets value. The valid range is 2 to 50.
Defaults
15
Command Modes
Global configuration
Command History
12.1(3)T This command was introduced.
Release
Modification
Usage Guidelines
To get a more realistic estimate on the network congestion, increase the number of packets. Use fewer packets when you need to focus on bandwidth.
Examples
The following example specifies the call fallback jitter-probe num-packets to 20:
Router(config)# call fallback jitter-probe num-packets 20
Related Commands
call fallback jitter-probe precedence Specifies the jitter-probe precedence. call fallback probe-timeout Sets the interval between RTR probes for network statistics.
Command
Description
To specify the jitter-probe precedence, use the call fallback jitter-probe precedence global configuration command. To restore the default value, use the no form of this command.
call fallback jitter-probe precedence precedence
Syntax Description
precedence Specifies the jitter probe precedence.
Defaults
2
Command Modes
Global configuration
Command History
12.1(3)T This command was introduced.
Release
Modification
Usage Guidelines
Setting the precedence field sets the IP Precedence (TOS) on this packet.
Examples
The following example specifies the call fallback jitter-probe probe precedence of 5:
router(config)# call fallback jitter-probe precedence 5
Related Commands
show call fallback config Shows the call fallback configuration.
Command
Description
To assign a priority-queue setting, use the call fallback jitter-probe priority-queue global configuration command. To return to default values, use the no form of this command.
call fallback jitter-probe priority-queueSyntax Description
This command has no arguments or keywords.
Defaults
This command is disabled by default.
Command Modes
Global configuration
Command History
12.1(3)T This command was introduced.
Release
Modification
Usage Guidelines
This command is only applicable if the queuing method used is IP RTP Priority. This command is unnecessary when LLQ is used, because these packets will follow the PQ path (or not) based on the LLQ classification criteria and not this command.
The command works by choosing between sending the probe on an odd or even RTP port number.
Examples
The following example specifies the call fallback jitter-probe priority queue setting:
Router(config)# call fallback jitter-probe priority-queue Warning:In order for this command to have any affect on the probes, IP priority queueing must be set for UDP voice ports 16384-32767.
Related Commands
ip rtp priority Provides a strict priority queueing scheme for delay-sensitive data. show traffic-queue For VoIP over Frame Relay.
Command
Description
To specify MD5 configuration, use the call fallback key-chain global configuration command. To restore the default values, use the no form of this command.
call fallback key-chain name-of-chain
Syntax Description
name-of-chain Specifies the name of the chain. This line is to be alphanumeric and case-sensitive text.
Defaults
No call fallback key-chain is defined.
Command Modes
Global configuration
Command History
12.1(3)T This command was introduced.
Release
Modification
Usage Guidelines
This command is used to enable RTR Probe authentication using MD5. If authentication is used, the keys on the sender and receiver routers must match.
Examples
The following example specifies the call fallback key-chain of cisco:
Router(config)# call fallback key-chain cisco
Related Commands
key chain Enables authentication for routing protocols by identifying a group of authentication keys. key-string Specifies the authetication string for a key.
Command
Description
To specify a router that keeps a cache table (by IP addresses) of distances for several destination peers sitting behind it, use the call fallback map address-list global configuration command. To restore the default values, use the no form of this command.
call fallback map map target ip-address address-list ip-address1 ip-address2 up to ip-address7
Syntax Description
map Specifies the fallback map. The valid range is 1 to 16. target ip-address Specifies the target IP address. address-list ip-address1 to ip-address7 Lists the IP addresses that will be kept in the cache table. The maximum number of IP addresses is seven.
Defaults
No call fallback maps are defined.
Command Modes
Global configuration
Command History
12.1(3)T This command was introduced.
Release
Modification
Usage Guidelines
Use this command when several destination peers are sitting behind one common node.
Call fallback map setup allows the decongestion of traffic caused by a high volume of call probes sent across a network to query a large number of dial peers. One router/common node can keep the distances in a cache table to numerous IP addresses/destination peers in a network. When the fallback is queried for network congestion to a particular IP address (that is, the common node), the map addresses are searched in order to find the target IP address. If a match is determined, the probes are sent to the target address rather than to the particular IP address.
In Figure 1, the three routers (1, 2, and 3) keep the cache tables of distances for the destination peers behind them. When a call probe comes from somewhere in the IP cloud, the cache routers will check their distance tables for the IP address/destination peer where the call probe is destined. This limits congestion on the networks behind these routers by directing the probe to the particular IP address and not to the entire network.
Examples
The following example specifies call fallback map address-list configurations for 172.32.10.1 and 172.46.10.1:
Router(config)#call fallback map 1 target 172.32.10.1 address-list 172.32.10.2 172.32.10.3 172.32.10.4 172.32.10.5 172.32.10.6 172.32.10.7 172.32.10.8Router(config)#call fallback map 2 target 172.46.10.1 address-list 172.46.10.2 172.46.10.3 172.46.10.4 172.46.10.5 172.46.10.6 172.46.10.7 172.46.10.8
Related Commands
Specifies a router that will keep a cache table (by subnet addresses) of distances for several destination peers sitting behind it. Shows the call fallback configuration.
Command
Description
To specify a router that keeps a cache table (by subnet addresses) of distances for several destination peers sitting behind it, use the call fallback map subnet global configuration command. To restore the default values, use the no form of this command.
call fallback map map target ip-address subnet ip-network netmask
Syntax Description
map Specifies the fallback map. The valid range is 1 to 16. target ip-address Specifies the target IP address. subnet ip-network Specifies the subnet IP address. netmask Specifies the netmask.
Defaults
No call fallback maps are defined.
Command Modes
Global configuration
Command History
12.1(3)T This command was introduced.
Release
Modification
Usage Guidelines
Use this command when several destination peers are sitting behind one common node.
Call fallback map setup allows the decongestion of traffic caused by a high volume of call probes sent across a network to query a large number of dial peers. One router/common node can keep the distances in a cache table to numerous IP addresses within a subnet (destination peers) in a network. When the fallback is queried for network congestion to a particular IP address (that is, the common node), the map addresses are searched in order to find the target IP address. If a match is determined, the probes are sent to the target address rather than to the particular IP address.
In Figure 2, the three routers (1, 2, and 3) keep the cache tables of distances for the destination peers behind them. When a call probe comes from somewhere in the IP cloud, the cache routers check their distance tables for the subnet address/destination peer where the call probe is destined. This limits congestion on the networks behind these routers by directing the probe to the particular subnet address and not to the entire network.
Examples
The following example specifies the call fallback map subnet configuration for 209.165.201.225:
Router(config)#call fallback map 1 209.165.201.225 subnet 209.165.201.224 255.255.255.224Router(config)#call fallback map 2 209.165.202.225 subnet 209.165.202.224 255.255.255.224
Related Commands
Specifies a router that will keep a cache table (by IP addresses) of distances for several destination peers sitting behind it. Shows the call fallback configuration.
Command
Description
To set the interval between RTR probes for network statistics, use the call fallback probe-interval global configuration command. To restore the default value, use the no form of this command.
call fallback probe-interval seconds
Syntax Description
seconds Specifies the interval in seconds. Valid values are 1 to 2,147,483.
Defaults
30 seconds
Command Modes
Global configuration
Command History
12.1(3)T This command was introduced.
Release
Modification
Usage Guidelines
To reduce the bandwidth taken up by the probes, increase the probe-timeout interval.
Examples
The following example configures the call fallback probe-interval for a 120 second interval:
Router(config)# call fallback probe-interval 120
Related Commands
call fallback jitter-probe num-packets Specifies the inter-packet interval and number of packets for jitter.
Command
Description
To specify the ICPIF threshold, use the call fallback threshold icpif global configuration command. The ICPIF is calculated and used as per the ITU G.113 specification. To restore the default value, use the no form of this command.
call fallback threshold icpif value
Syntax Description
value Sets the threshold value. The valid range is 0 to 34.
Defaults
5
Command Modes
Global configuration
Command History
12.1(3)T This command was introduced.
Release
Modification
Usage Guidelines
A lower value of ICPIF tolerates less delay/loss. Use lower values for higher quality of voice. Configuring a value of 34 equates to 100% packet loss.
Examples
The following example sets the call fallback threshold icpif to 20:
Router(config)# call fallback threshold icpif 20
Related Commands
call fallback threshold delay Specifies fallback threshold.
Command
Description
To specify call fallback threshold delay and loss values, use the call fallback threshold delay global configuration command. To restore the default value, use the no form of this command.
call fallback threshold delay value loss value
Syntax Description
delay value Sets the delay value. The valid range is 1 to 2,147,483,647 msec. loss value Sets the loss value. The valid range is 0 to 100%.
Defaults
None
Command Modes
Global configuration
Command History
12.1(3)T This command was introduced.
Release
Modification
Usage Guidelines
Use lower values of delay and loss for higher quality of voice.
Examples
The following example configures the call fallback threshold delay to 20 msec and loss to 50%:
Router(config)# call fallback threshold delay 20 loss 50
Related Commands
call fallback threshold icpif Specifies the ICPIF threshold.
Command
Description
To clear the current ICPIF estimates for all IP addresses or a specific IP address in the cache, use the clear call fallback cache EXEC command.
clear call fallback cache [ip-address]
Syntax Description
ip-address (Optional) Specifies the target IP address.
Defaults
None
Command Modes
EXEC
Command History
12.1(3)T This command was introduced.
Release
Modification
Usage Guidelines
If no IP address is specified, the command will clear the cache of all ICPIF estimates for all IP addresses.
Examples
The following example clears the cache of the ICPIF estimate for IP address 209.165.200.225.
Router# clear call fallback cache 209.165.200.225
Related Commands
show call fallback cache Shows the current ICPIF estimates for all IP addresses in the cache.
Command
Description
To clear the call fallback stats, use the clear call fallback stats EXEC command.
clear call fallback statsSyntax Description
This command has no arguments or keywords.
Defaults
None
Command Modes
EXEC
Command History
12.1(3)T This command was introduced.
Release
Modification
Examples
The following example clears the call fallback:
Router# clear call fallback stats
Related Commands
show call fallback stats Shows the call fallback stats.
Command
Description
To see the current ICPIF estimates for all IP addresses in cache, use the show call fallback cache EXEC command. To clear all entries in the cache, use the clear call fallback ca che form of this command.
show call fallback cache [ip-address]
Syntax Description
ip-address (Optional) Specifies a specific IP address.
Defaults
None
Command Modes
EXEC
Command History
12.1(3)T This command was introduced.
Release
Modification
Examples
The following example dislpays output from the show call fallback cache command:
Router# show call fallback cache
Probe IP Address Codec Delay Loss ICPIF Reject Accept
----- ---------- ----- ----- ---- ----- ------ ------
1 1.1.1.4 g729r8 40 0 0 0 9
2 122.24.56.25 g729r8 148 10 5 1 4
2 active probes
Field Description
------- ------------
Probe Probe number
IP Address IP Address to which the probe is sent
Codec Codec Type of the probe
Delay Delay in milliseconds that the probe incurred
Loss Loss in % that the probe incurred
ICPIF Computed ICPIF value for the probe
Reject Number of times that calls of Codec Type <Codec>
were rejected to the IP Address
Accept Number of times that calls of Codec Type <Codec>
were accepted to the IP Address
active probes Number of destinations being probed
Router# show call fallback cache 1.14.115.53
Probe IP Address Codec ICPIF Reject Accept
----- ---------- ----- ----- ------ ------
1 1.14.115.53 g729r8 0 0 2
1 active probes
Related Commands
show call fallback stats Shows the callfallback stats.
Command
Description
To see the call fallback configuration, use the show call fallback config EXEC command.
show call fallback configSyntax Description
This command has no arguments or keywords.
Defaults
None
Command Modes
EXEC
Command History
12.1(3)T This command was introduced.
Release
Modification
Examples
The following example displays output from the show call fallback config command:
Router# show call fallback config
VoIP fallback config:
Fallback is ON
Using ICPIF threshold:
ICPIF value timeout:20 seconds
ICPIF threshold:20
Number of packets in a probe:20
IP precedence of probe packets:2
Fallback cache size:2 entries
Fallback cache timeout:240 seconds
Instantaneous value weight:65
MD5 Keychain:secret
Related Commands
call fallback Enables the PSTN fallback feature.
Command
Description
To see the call fallback stats, use the show call fallback stats EXEC command. To remove all values, use the clear call falback stats command.
show call fallback statsSyntax Description
This command has no arguments or keywords.
Defaults
None
Command Modes
EXEC
Command History
12.1(3)T This command was introduced.
Release
Modification
Examples
The following example displays output from the show call fallback stats command:
Router# show call fallback stats VOIP Fallback Stats: Total accepted calls:3 Total rejected calls:1 Total cache overflows:1 Field Description ------- ------------ Total accepted calls Number of times that calls were successful over IP. Total rejected calls Number of times that calls were rejected over IP. Total cache overflows Number of times that the fallback cache overflowed and requied pruning.
Related Commands
Clears the call fallback stats. show call fallback cache Displays the current ICPIF estimates for all IP addresses in the cache.
Command
Description
To test a probe to a particular IP address and see the ICPIF RTR values, use the test call fallback probe EXEC command. This command has no impact on the cache.
test call fallback probe ip-address [codec 711/729]
Syntax Description
ip-address Specifies the target IP address. codec 711/729 (Optional) Specifies a specific codec type.
Defaults
None
Command Modes
EXEC
Command History
12.1(3)T This command was introduced.
Release
Modification
Examples
The following example demonstrates a test probe to IP address 1.1.1.4, and shows that the ICPIF value to 1.1.1.4 is 0.
Router(config)# test call fallback probe 1.1.1.4 Running a test RTR probe.... ICPIF value for the test probe is 0
Related Commands
call fallback Enables the PSTN fallback feature.
Command
Description
This section documents new debug commands related to the PSTN fallback feature. All other commands used with this feature are documented in the Cisco IOS Release 12.1 command reference publications.
To see details of the voice fallback, use the debug call fallback detail EXEC command. To disable debugging output, use the no form of this command.
debug call fallback detailSyntax Description
This command has no arguments or keywords.
Defaults
Debugging is not enabled.
Command Modes
EXEC
Command History
12.1(3)T This command was introduced.
Release
Modification
Examples
The following example depicts a call coming in to 1.1.1.4 with codec g729r8. Because there is no cache entry for this destination, a probe is sent and values are inserted into the cache. A lookup is performed again, entry is found, and fallback decision is made to admit the call.
Router# debug call fallback detail
When cache is empty:
debug call fallback detail:
2d19h:fb_lookup_cache:1.1.1.4, codec:g729r8
2d19h:fb_lookup_cache:No entry found.
2d19h:fb_check:no entry exists, enqueueing probe info... 1.1.1.4, codec:g729r8
2d19h:fb_main:Got FB_APP_INQ event
2d19h:fb_main:Dequeued prob info: 1.1.1.4, codec:g729r8
2d19h:fb_lookup_cache:1.1.1.4, codec:g729r8
2d19h:fb_lookup_cache:No entry found.
2d19h:fb_cache_insert:insert:1.1.1.4, codec:g729r8
2d19h:fb_cache_insert:returning entry:1.1.1.4, codec:g729r8
2d19h:fb_initiate_probe:Creating probe... 1.1.1.4, codec:g729r8
2d19h:fb_initiate_probe:Created and started on probe #13, 1.1.1.4, codec:g729r8
2d19h:fb_lookup_cache:1.1.1.4, codec:g729r8
2d19h:fb_lookup_cache:Found entry.
2d19h:fb_check:returned FB_CHECK_TRUE, 1.1.1.4, codec:g729r8
2d19h:fb_main:calling callback function with:TRUE
The following example depicts a call coming in to 1.1.1.4 with codec g729r8. A lookup is performed, entry is found, and fallback decision is made to admit the call.
Router# debug call fallback detail
When cache is full:
2d19h:fb_lookup_cache:1.1.1.4, codec:g729r8
2d19h:fb_lookup_cache:Found entry.
2d19h:fb_check:returned FB_CHECK_TRUE, 1.1.1.4, codec:g729r8
2d19h:fb_main:calling callback function with:TRUE
To see details of the voice fallback probes, use the debug call fallback probes EXEC command. To disable debugging output, use the no form of this command.
debug call fallback probesSyntax Description
This command has no arguments or keywords.
Defaults
Debugging is not enabled.
Command Modes
EXEC
Command History
12.1(3)T This command was introduced.
Release
Modification
Examples
The following example depicts a call coming in to 1.1.1.4 and codec type g729r8. Because there is no cache entry for this IP Address, a g729r8 probe is initiated. The probe consists of 20 packets returns an average delay of 43 ms. The "jitter out" is jitter from source to destination router and "jitter in" is jitter from destination to source router. The delay, loss, and ICPIF values following g113_calc_icpif are the instantaneous values, whereas those values following "New smoothed values" are the values after applying the smoothing with weight 65.
Router# debug call fallback probes
2d19h:fb_initiate_probe:Probe payload is 32
2d19h:fb_main:NumOfRTT=20, RTTSum=120, loss=0, delay=43, jitter in=0, jitter out=0->
1.1.1.4, codec:g729r8
2d19h:g113_calc_icpif(delay (w/codec delay)=43, loss=0, expect_factor=10) Icpif=0
2d19h:fb_main:Probe timer expired, 1.1.1.4, codec:g729r8
2d19h:fb_main:NumOfRTT=20, RTTSum=120, loss=0, delay=43, jitter in=0, jitter out=0->
1.1.1.4, codec:g729r8
2d19h:g113_calc_icpif(delay (w/codec delay)=43, loss=0, expect_factor=10) Icpif=0
2d19h:fb_main:New smoothed values:inst_weight=65, ICPIF=0, Delay=43, Loss=0 -> 1.1.1.4,
codec:g729r8
ABCD signaling—Four-bit telephony line signaling coding in which each letter of "ABCD" represents one of the four bits. This is often associated with CAS or Robbed-Bit signaling on a T1 or E1 telephony trunk.
Cisco-trunk (private line) call—A Cisco trunk (private line) call is established by the forced connection of a dynamic switched call. A Cisco-trunk call is established during configuration of the trunk and stays up for the duration of the configuration. Optionally, it provides a pass-through connection path to pass signaling information between the two telephony interfaces at either end of the connection.
CLI—Command line interface.
CODEC—Coder-Decoder. An integrated circuit device that typically uses pulse code modulation to transform analog signals into a digital bit stream and digital signals back into analog signals. In
Voice over IP, Voice over Frame Relay, and Voice over ATM, a DSP software algorithm used to compress/decompress speech or audio signals.
DLCI—Data-link connection identifier.
Dial peer—An addressable call endpoint that contains configuration information including voice protocol, a CODEC type, and a telephone number associated with the call endpoint. There are 5 kinds of dial peers: POTS, VoIP, VoFR, and VoATM.
DSP—Digital Signaling Processor.
DTMF—Dual tone multifrequency. Uses two simultaneous voice-band tones for dial such as touch tone.
DTMF relay—Enables the generation of FRF.11 Annex A frames for a VoFR dial peer. The DSP generates Annex A frames instead of passing a DTMF tone through the network as a voice sample. DTMF relay also applies to VoIP.
Dynamic switched call—A telephone call dynamically established across a packet data network based on a dialed telephone number. The proprietary session protocol runs over FRF.11-compliant subchannels.
E&M—Stands for recEive and transMit (or Ear and Mouth). E&M is a trunking arrangement generally used for two-way switch-to-switch or switch-to-network connections. Cisco's analog E&M interface is an RJ-48 connector that allows connections to PBX trunk lines (tie lines). E&M is also available on E1 and T1 digital interfaces.
E1—European equivalent of T1. 32-64kbps channels include 1-channel for framing and 1-channel for CCS channel information at a 2.048 Mhz clock rate.
FRF—Frame Relay Forum. An association of corporate members consisting of vendors, carriers, users, and consultants committed to implementing Frame Relay in accordance with national and international standards. See http://www.frforum.com.
FXO—Foreign Exchange Office. An FXO interface connects to the PSTN or PBX, and is the interface offered on a standard telephone. Cisco's FXO interface is an RJ-11 connector that allows an analog connection to be directed to the PSTN or to a station interface on a PBX.
FXS—Foreign Exchange Station. An FXS interface connects directly to a standard telephone and supplies ring, voltage, and dial tone. Cisco's FXS interface is an RJ-11 connector that allows connections to basic telephone service equipment, keysets, and PBXs.
ICPIF—Calculated Planning Impairment Factor. Calculated and used as per the ITU G.113 specification.
LLQ—low latency queuing. LLQ brings strict priority queueing to Class-Based Weighted Fair Queueing (CBWFQ). Strict priority queueing allows delay-sensitive data such as voice to be dequeued and sent first (before packets in other queues are dequeued), giving delay-sensitive data preferential treatment over other traffic.
MD5—Message Digest 5. Algorithm used for message authentication in SNMP v.2. MD5 verifies the integrity of the communication, authenticates the origin, and checks for timeliness.
MEL CAS—Mercury Exchange Limited (MEL) Channel Associated Signaling. A voice signaling protocol used primarily in the United Kingdom.
PBX—Private Branch Exchange. A privately owned central switching office.
Permanent calls—Permanent calls are private line calls used for fixed point-to-point calls, connections between PBXs (E&M to E&M), or for remote telephone extensions (FXO to FXS).
POTS—Plain old telephone service. Basic telephone service supplying standard single line telephones, telephone lines, and access to the PSTN.
POTS dial peer—Dial peer connected by a traditional telephony network. POTS peers point to a particular voice port on a voice network device.
PSTN—Public Switched Telephone Network. PSTN refers to the global network, made up of many local and long distance companies, and various categories in between.
RTR—Response Time Reporter.
Switched calls—Switched calls are normal telephone calls when a user picks up a phone, hears a dial tone and enters the destination phone number to reach the other phone.
T1—Digital carrier facility. T1 transmits DS-1-formatted data at 1.544 Mbps through the telephone-switching network by using AMI or B8ZS coding.
Trunk—Service that allows quasi-transparent connections between two PBXs, a PBX and a local extension, or some other combination of telephony interfaces with signaling passed transparently through the packet data network.
Voice over IP—Voice over IP enables a router to carry voice traffic, for example, telephone calls and faxes) over an IP network. In Voice over IP, the DSP segments the voice signal into frames, which are then coupled in groups and stored in voice packets that are transported by using IP. The number of samples in a packet depends on the codec and the configuration settings.
VoIP—Voice over IP.
 |
Note For a list of other internetworking terms, see Internetworking Terms and Acronyms, available on the Documentation CD-ROM and Cisco Connection Online (CCO) at the following URL: http://www.cisco.com/univercd/cc/td/doc/cisintwk/ita/index.htm. |
Posted: Wed Sep 27 12:44:01 PDT 2000
Copyright 1989-2000©Cisco Systems Inc.