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This feature enables a router to negotiate X.25 throughput parameters on behalf of end devices, thereby making it possible
for X.25 calls to reach devices that may not themselves be able to negotiate throughput.
History for the X.25 Throughput Negotiation Feature
Release
Modification
12.3(11)YN
This feature was introduced.
12.4(4)T
This feature was integrated into Cisco IOS 12.4(4)T.
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Restrictions for X.25 Throughput Negotiation
This feature currently supports only basic throughput classes; extended throughput classes are not supported.
Information about X.25 Throughput Negotiation
In order for end devices in a network to support X.25 calls, they need to be able to negotiate X.25 throughput parameters.
This feature enables a router to handle that negotiation on behalf of end devices that cannot do it themselves.
Figure 1. Router Negotiating Throughput Between a Network and an End Device
The router does this by stripping out or inserting values, as appropriate for each case, in the "throughput facility field"
of the X.25 calls’ setup and confirmed messages (specifically, in the Call Request, Incoming Call, Call Accepted, and Call
Confirmed packets).
In order to insert values appropriately, the router interface connected to the end device must earlier have been configured
with the input and output bit rates that are intended to be used by the eventual X.25 call.
The rules according to which the router removes or inserts those bit rates are set by the
x25 subscribe throughput command, which can have three distinct states:
no ,
basic or
never . These forms of the command work as follows when the router receives a call from the network and forwards that call onward
to the end device:
If the router has been configured by the command
no x25 subscribe throughput , it will make
nochange to the values it receives in the call’s facility field. The router merely forwards the message, and those values, onward.
If the router has been configured by the
25 subscribe throughput basic form of this command, the router will
insert the bit rate values previously configured on its interface into the call’s facility field. (The only exception is when those
values are larger than the call’s values, in which case the router will leave the call’s smaller values in place when it forwards
the message.)
In cases when the router has substituted its own configured values for the values it detected in the incoming call, the router
also reports those new values in a Call Confirmed packet back out through the network to the source device.
If the
x25 subscribe throughput never form of the command has been entered, the router will
remove the values it receives in the call’s facility field. (And if the values previously configured on the router’s interface are
smaller than those contained in the call, the router will also replace the call’s values with those smaller ones when it forwards
the end device’s Call Confirmed packet back out to the network.)
How these behavior rules apply to each possible case is presented in the first table below.
When calls originate not in the network but in the end device, this command’s three states can have somewhat different results,
which are detailed in the second table below.
Table 1. Router Treatment of Throughput Facility Field in Incoming Call
Incoming call’s ‘Call Request’ packet
Cisco IOS commands applied
Results
Is interface configured with throughput values?
How is Serial Line’s throughput subscription configured?
Within ‘Incoming Call’ packet
Within ‘Call Confirmed’ packet
Contains throughput facility field
YES :
"x25 facility throughput
xxxyyy
no x25 sub throughput
Facility field in message from network is sent to end device unmodified.
End device includes no facility field in its Call Accepted packet to the router. And the router includes no facility field
in the Call Confirmed packet it sends out to the network.
x25 sub throughputnever
Router strips out facility field, then forwards message to end device.
Router sends values out to network only if the values configured on its interface are
smaller than those received in network call.
x25 sub throughputbasic
Router compares values in message with those configured on its interface, and sends to end device the lower set.
Router sends that lower set out to the network.
Has no throughput facility field
no x25 sub throughput
No facility field sent to end device.
No facility field sent out to network.
x25 sub throughputnever
No facility field sent to end device.
No facility field sent back out to network.
x25 sub throughputbasic
Router inserts facility field into message, and forwards that to the end device.
No facility field sent back out to network.
Contains throughput facility field
NO :
"no x25 facility throughput"
no x25 sub throughput
Facility field sent to end device.
End device includes no facility field in its Call Accepted packet to the router. And the router includes no facility field
in the Call Confirmed packet it sends out to the network.
x25 sub throughputnever
Router strips out facility field, then forwards message to end device.
No facility field sent back out to network.
x25 sub throughputbasic
Facility field sent on to end device.
No facility field sent back out to network.
Has no throughput facility field
no x25 sub throughput
No facility field sent to end device.
No facility field sent out to network.
x25 sub throughputnever
No facility field sent to end device.
No facility field sent back out to network.
x25 sub throughputbasic
No facility field sent to end device.
No facility field sent out to network.
*Shaded rows (in PDF version) describe calls that contain no throughput facility field before they reach the router.
Table 2. Router Treatment of Throughput Facility Field in Outgoing Call
Outgoing call’s ‘Call Request’ packet
Cisco IOS commands applied
Results
Is interface configured with throughput values?
How is Serial Line’s throughput subscription configured?
Within outgoing ‘Call Request’ packet
Within received ‘Call Confirmed’ packet
Contains throughput facility field
YES :
"x25 facility throughput
xxxyyy
no x25 sub throughput
Router forwards facility field it receives in the end device’s Call Request packet out to the network unmodified.
Router forwards facility field it receives in the Call Confirmed packet from the network on to the end device unmodified.
x25 sub throughputnever
Router refuses to forward call on to the network, and cancels it, sending back to the end device a Clear Request packet with
the Cause Code field set to 3 (‘3’ stands for "Invalid Facility Request"). Router also sends to the end device a Diagnostic
Code field set to 65 (which stands for "Facility Code Not Allowed").
x25 sub throughputbasic
Router compares values in message with those configured on its interface, and sends to network the lower set.
Router sends that lower set to the end device, unless still different values are received in
theCallConfirmedmessage from the network. In that case, the router forwards that network set to the end device.
Has no throughput facility field
no x25 sub throughput
No facility field sent to network.
No facility field sent to end device.
x25 sub throughputnever
Router sends values configured on its interface out to the network.
No facility field sent to end device.
x25 sub throughputbasic
Router inserts facility field into message, and forwards that to the network.
Router sends the inserted facility field to the end device.
Contains throughput facility field
NO :
"no x25 facility throughput"
no x25 sub throughput
Router forwards facility field it receives in the end device’s Call Request packet out to the network unmodified.
Router forwards facility field it receives in the Call Confirmed packet from the network on to the end device unmodified.
x25 sub throughputnever
Router refuses to forward call on to the network, and cancels it, sending back to the end device a Clear Request packet with
the Cause Code field set to 3 (‘3’ stands for "Invalid Facility Request"). Router also sends to the end device a Diagnostic
Code field set to 65 (which stands for "Facility Code Not Allowed").
x25 sub throughputbasic
Facility field sent on to network.
Facility field sent back to end device.
Has no throughput facility field
no x25 sub throughput
No facility field sent to network.
No facility field sent to end device.
x25 sub throughputnever
No facility field sent to network.
No facility field sent to end device.
x25 sub throughputbasic
No facility field sent to network.
No facility field sent to end device.
*Shaded rows (in PDF version) describe calls that contain no throughput facility field before they reach the router.
How to Configure X.25 Throughput Negotiation
Configuring X.25 Throughput Negotiation
Before you begin
If you choose the
basic keyword of the
x25 subscribe throughput command below, you must first configure the interface with the appropriate class negotiation values for input and output
throughput across the network by using the
throughput inout keyword and arguments of the
x25 facility command . For more information about the
x25 facility command, see the Cisco IOS Wide-Area Networking Command Reference.
SUMMARY STEPS
enable
configure terminal
interface interface-id
x25 subscribe throughput { never | basic }
exit
DETAILED STEPS
Command or Action
Purpose
Step 1
enable
Example:
Router> enable
Enables privileged EXEC mode.
Enter your password if prompted.
Step 2
configure terminal
Example:
Router# configure terminal
Enters global configuration mode.
Step 3
interface interface-id
Example:
Router(config)# interface serial2/0
Specifies the interface which is connected to the end device, and enters interface configuration mode.
Step 4
x25 subscribe throughput { never | basic }
Example:
Router(config-if)# x25 subscribe throughput basic
Enables the router to negotiate X.25 throughput for the end device.
(In this example, the end device always expects the throughput facility field to be present in incoming call setup packets).
Step 5
exit
Example:
Router(config-if)# exit
Exits interface configuration mode.
Examples
In this example, the end device never expects the throughput facility field to be present in incoming call setup packets:
In this example, the active throughput negotiation capability on the just-illustrated interface (Serial 0/0) gets turned off:
Router(config)# interface serial0/0
Router(config-if)# no x25 subscribe throughput
Router(config-if)# exit
Configuration Examples for X.25 Throughput Negotiation
Basic example
In this example, the end device always expects the throughput facility
field to be present in Incoming Call packets. The router inserts its configured
bit rate values--unless they are larger than the values in the incoming call.
In this example, the end device never expects the throughput facility field to be present in Incoming Call packets. The router
removes the facility field from incoming calls.
Router# configure terminal
Router(config)# interface serial2/0
Router(config-if)# x25 facility throughput 300 300
Router(config-if)# x25 subscribe throughput never
Router(config-if)# end
Router#
Additional References
Related Documents
Related Topic
Document Title
Configuring X.25 throughput facilities
Cisco IOS Wide-Area Networking Command Reference
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