Configuring ISG Policies for Session Maintenance

Last Updated: December 19, 2012

Intelligent Services Gateway (ISG) is a Cisco IOS XE software feature set that provides a structured framework in which edge devices can deliver flexible and scalable services to subscribers. This module describes how to configure a session timer and connection timer through a service policy map. Additionally, the Internet Engineering Task Force (IETF) RADIUS attributes Session-Timeout (attribute 27) and Idle-Timeout (attribute 28) can be used in service profiles on an authentication, authorization, and accounting (AAA) server to configure the same session maintenance control.

IP subscriber session keepalive support is configured for monitoring session data traffic in the upstream direction for idleness. Address Resolution Protocol (ARP) is used for Layer 2 connected subscribers. For routed host (Layer 3 connected) subscribers, the protocol defaults to Internet Control Message Protocol (ICMP). ICMP is also used in configurations where the access interface does not support ARP.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Prerequisites for ISG Policies for Session Maintenance

A traffic class is required only if an idle timer or session timer is being installed on a service that has a traffic class definition in it. If the timer is installed on a session or service that has no traffic class, a traffic class is not required. See the "Configuring ISG Subscriber Services" module for information about how to configure a traffic class.

Restrictions for ISG Policies for Session Maintenance

For an idle timeout that is applied on an IP session (rather than on a PPP session), there is currently no way to specify the direction. By default, the direction in which the idle timer is applied is always outbound.

Information About ISG Policies for Session Maintenance

Session Maintenance Timers

ISG provides two commands (each of which can be set independently) to maintain control over a session and its connection. The timeout absolute command controls how long a session can be connected before it is terminated. The timeout idle command controls how long a connection can be idle before it is terminated. Both commands detect both PPP and IP sessions and can be applied in a non-traffic-class-based service, on a per-session basis, or in a flow (traffic-class-based service). All subscriber traffic will reset the timers; however, non-network traffic such as PPP control packets will not reset the timers.

The scope of the session timers and connection timers is determined by the type of service within which the timer is specified. If specified in a service profile for which no traffic class is defined, the timer action will be to terminate the session or connection. If a traffic class specifier resides in the service profile, the timer action will be to deactivate the service.

Benefits of Session Maintenance Timers

The PPP idle timeout functionality has been replaced by the ISG idle timeout feature. The idle timer is a generic feature that can be set to detect idle traffic in both PPP and IP sessions.

You set the idle timer in a service profile that is installed on a session to control how long that service stays installed before it is removed from the session because no traffic is flowing through that service. If the service has traffic class parameters associated with it, that traffic class is terminated when this timer expires, or when the session itself is terminated.

The same is true for the session timer, except that this timer determines how long the session or service stays up, regardless of traffic flowing through it.

Monitoring Sessions

The IP subscriber session's data traffic in the upstream direction can be monitored for idleness using a keepalive feature configured for the subscriber. If a session is idle for a configured period of time, keepalive requests are sent to the subscriber. This action verifies that the connection is still active. The protocol to use for the keepalive request and response can be configured based on the IP subscriber session type. If it is a directly connected host (Layer 2 connection), ARP is used. For routed host (Layer 3 connected) subscribers, ICMP is used. If the access interface does not support ARP, the keepalive protocol defaults to ICMP.

ARP for Keepalive Messages

When a session is established and the keepalive feature is configured to use ARP, the keepalive feature saves the ARP entry as a valid original entry for verifying future ARP responses.


Note
In cases where the access interface does not support ARP, the protocol for keepalives defaults to ICMP.

When ARP is configured, the ARP unicast request is sent to the subscriber. After a configured interval of time, the ARP response (if received) is verified. If the response is correct and matches the original entry that was saved when the subscriber was initially established, the keepalive feature continues monitoring the data plane for the configured interval of time. If the response is not correct, the keepalive feature resends the ARP request until a correct response is received or the configured maximum number of attempts is exceeded.

ICMP for Keepalive Messages

If ICMP is configured, the ICMP "hello" request is sent to the subscriber and checked for a response, until the configured maximum number of attempts is exceeded.

For IP subnet sessions, the peer (destination) IP address to be used for ICMP "hello" requests will be all the IP addresses within the subnet. This means "hello" requests will be sent sequentially (not simultaneously) to all the possible hosts within that subnet. If there is no response from any host in that subnet, the session will be disconnected.

Another option is to configure ICMP directed broadcast for keepalive requests. If the subscriber hosts recognize the IP subnet broadcast address, the ISG can send the ICMP "hello" request to the subnet broadcast address. The subscribers need not be on the same subnet as the ISG for this configuration to work. A directed broadcast keepalive request can work multiple hops away as long as these conditions are satisfied:

  • The group of subscribers identified by the subnet must have the same subnet mask provisioned locally as the subnet provisioned on the subnet subscriber session on the ISG. Otherwise, the subscriber hosts will not recognize the subnet broadcast address.
  • The router directly connected to the hosts must enable directed-broadcast forwarding, so that the IP subnet broadcast gets translated into a Layer 2 broadcast.

When these two conditions are satisfied, you can optimize the ICMP keepalive configuration to minimize the number of ICMP packets.


Note
Because enabling directed broadcasts increases the risk of denial of service attacks, the use of subnet directed broadcasts is not turned on by default.

How to Configure ISG Policies for Session Maintenance

Configuring the session maintenance timers requires two separate tasks, one to set the idle timer and one to set the session timer. Either one or both of these tasks can be performed in order to set session maintenance control. The following tasks show how to set these timers in a service policy map and in a RADIUS AAA server profile:

Configuring the Session Timer in a Service Policy Map

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    policy-map type service policy-map-name

4.    [priority] class type trafficclass-map-name

5.    timeout absolute duration-in-seconds

6.    end


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
policy-map type service policy-map-name


Example:

Router(config)# policy-map type service policy1

 

Enters policy map configuration mode so you can begin configuring the service policy.

 
Step 4
[priority] class type trafficclass-map-name

Example:

Router(config-control-policymap)# class type traffic class1

 

Associates a previously configured traffic class with the policy map.

 
Step 5
timeout absolute duration-in-seconds


Example:

Router(config-control-policymap-class-control)# timeout absolute 30

 

Specifies the session lifetime, in seconds.

 
Step 6
end


Example:

Router(conf-subscriber-profile)# end

 

Returns to privileged EXEC mode.

 

What to Do Next

You may want to configure a method of activating the service policy map or service profile; for example, control policies can be used to activate services. For more information about methods of service activation, see the module "Configuring ISG Subscriber Services".

Configuring the Session Timer on a AAA Server

Perform this task to set the session timer on a AAA server profile.

SUMMARY STEPS

1.    Session-Timeout= duration-in-seconds


DETAILED STEPS
  Command or Action Purpose
Step 1
Session-Timeout= duration-in-seconds
 

Sets the IETF RADIUS session timer (attribute 27) in a user or service profile, in a range from 30 to 4294967 seconds.

 

Configuring the Connection Timer in a Service Policy Map

Perform this task to set the connection timer in a service policy map.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    policy-map type service policy-map-name

4.    [priority] class type trafficclass-map-name

5.    timeout idle duration-in-seconds

6.    end


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
policy-map type service policy-map-name


Example:

Router(config)# policy-map type service policy1

 

Enters policy map configuration mode so you can begin configuring the service policy.

 
Step 4
[priority] class type trafficclass-map-name

Example:

Router(config-service-policymap)# class type traffic class1

 

Associates a previously configured traffic class to the policy map.

 
Step 5
timeout idle duration-in-seconds


Example:

Router(config-control-policymap-class-traffic)# timeout idle 3000

 

Specifies how long a connection can be idle before it is terminated. The range is platform and release-specific. For more information, use the question mark (?) online help function.

 
Step 6
end


Example:

Router(config-control-policymap-class-traffic)# end

 

Returns to privileged EXEC mode.

 

What to Do Next

You may want to configure a method of activating the service policy map or service profile; for example, control policies can be used to activate services. For more information about methods of service activation, see the module "Configuring ISG Subscriber Services".

Configuring the Connection Timer on a AAA Server

Perform this task to set the connection timer on a AAA server profile.

SUMMARY STEPS

1.    Idle-Timeout= duration-in-seconds


DETAILED STEPS
  Command or Action Purpose
Step 1
Idle-Timeout= duration-in-seconds
 

Sets IETF RADIUS (attribute 28) in a user or service profile, in a range from 1 to 4294967 seconds.

 

Verifying the Session and Connection Timer Settings

Perform this task to verify that the timers have been installed correctly.

SUMMARY STEPS

1.    enable

2.    show subscriber session all

3.    end


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
show subscriber session all


Example:

Router# show subscriber session all

 

Displays current subscriber information, including reports about the timers that are enabled.

 
Step 3
end


Example:

Router# end

 

Returns to privileged EXEC mode.

 

Troubleshooting the Session and Connection Timer Settings

The following sections describe the debug commands that can be used to troubleshoot the session maintenance timers:

Prerequisites for Troubleshooting the Session Maintenance Timers

Before performing the task in this section, it is recommended that you be familiar with the use of Cisco IOS debug commands described in the introductory chapters of the Cisco IOS Debug Command Reference. Also see the module "Troubleshooting ISG with Session Monitoring and Distributed Conditional Debugging."

Restrictions for Troubleshooting the Session Maintenance Timers


Caution

Because debugging output is assigned high priority in the CPU process, it can render the system unusable. For this reason, use the Cisco IOS debug commands only to troubleshoot specific problems or during troubleshooting sessions with Cisco technical support staff. Moreover, we recommend that you use debug commands during periods of lower network traffic and fewer users, or on a debug chassis with a single active session. Debugging during these periods decreases the likelihood that increased debug command processing overhead will affect system use.

Debug Commands Available for the Session Maintenance Timers

The table below lists the debug commands that can be used to diagnose problems with the session maintenance timers.

Table 1 Debug Commands for Troubleshooting Session Maintenance Timers

Command

Purpose

debug subscriber feature error

Displays general Feature Manager errors.

debug subscriber feature event

Displays general Feature Manager events.

debug subscriber feature name idle-timer error

Displays idle timer errors.

debug subscriber feature name idle-timer event

Displays idle timer events.

debug subscriber feature name session-timer error

Displays session timer errors.

debug subscriber feature name session-timer event

Displays session timer events.

Configuring a Session Keepalive on the Router

This task describes how to configure the keepalive feature on the router, using either ARP or ICMP.

Because the session keepalive feature is checking for the subscriber's health and presence, this feature is applied only to the session as a whole and not per-flow.


Note
  • If a service profile includes an ISG traffic class configuration, the keepalive feature will be ignored.
  • If this feature is applied to a non-IP session, for example, a PPP over Ethernet (PPPoE) or PPP over ATM (PPPoA) session, this feature application will fail and the following applies:
    • If the feature is applied at a session-start event, both the feature application and the session will fail.
    • If this feature is pushed onto a session after the session-start event, the push will fail.
SUMMARY STEPS

1.    enable

2.    configure terminal

3.    policy-map type service policy-map-name

4.    keepalive [idle idle-seconds] [attempts max-retries] [interval retry-seconds] [protocol {ARP | ICMP [broadcast]}]

5.    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
policy-map type service policy-map-name


Example:

Router(config)# policy-map type service policymap1

 

Enters service policy map configuration mode.

 
Step 4
keepalive [idle idle-seconds] [attempts max-retries] [interval retry-seconds] [protocol {ARP | ICMP [broadcast]}]


Example:

Router(config-service-policymap)# keepalive idle 7 attempts 3 interval 1 protocol arp

 

Enables keepalive messages and sets the maximum idle period, number of requests, interval between requests, and protocol for keepalive messages.

  • The ranges and default values for the idle, attempts, and interval keywords are platform and release-specific. For more information, use the question mark (?) online help function.
  • protocol --For Layer 2 connections, the default is ARP; for routed connections, the default is ICMP.
  • broadcast --This option is disabled by default.
Note    If this command is applied to a non-IP session, the command will fail. If the command is applied to a non-IP session at the session-start event, the session will also fail.
 
Step 5
exit


Example:

Router(config-service-policymap)# exit

 

Returns to global configuration mode.

 

Example

The following example configures the keepalive feature on a router using ARP: 

policy-map type service accting_service
 class type traffic ALL
 !
  keepalive interval 3 protocol ARP
!

Configuring a Session Keepalive on a RADIUS Server

This task describes how to configure the session keepalive parameters on a RADIUS server.

SUMMARY STEPS

1.    Service-Name password = "cisco"

2.    Cisco-Avpair = "subscriber:keepalive = [idle period1] [attempts Max-retries] [interval period2] [protocol ICMP [broadcast] | ARP}"


DETAILED STEPS
Step 1   Service-Name password = "cisco"
Step 2   Cisco-Avpair = "subscriber:keepalive = [idle period1] [attempts Max-retries] [interval period2] [protocol ICMP [broadcast] | ARP}"

Configures the allowable idle period, maximum number of attempts to connect, the interval between attempts, and the communication protocol to be used.

The ranges and defaults are as follows:

  • Idle period: range is 5 to10 seconds; default is 10 seconds.
  • Attempts: range is 3 to 10; default is 5.
  • Interval: default is 1 to 10 seconds.
  • Protocol: for Layer 2 connections, the default is ARP; for routed connections, the default is ICMP.
  • Broadcast option: by default this option is disabled.
Note    If a service profile includes an ISG traffic class configuration, the keepalive feature will be ignored.

Configuration Examples for ISG Policies for Session Maintenance

Example: Session Timer Configuration in a Service Policy Map

The following example limits session time in a service policy map to 4800 seconds (80 minutes): 

class-map type traffic match-any traffic-class
 match access-group input 101
 match access-group output 102
policy-map type service video-service
 class traffic-class
  police input 20000 30000 60000
  police output 21000 31500 63000
  timeout absolute 4800
 class type traffic default
 drop

Example: Connection Idle Timer Configuration in a Service Policy Map

The following example limits idle connection time in a service policy map to 30 seconds: 

class-map type traffic match-any traffic-class
 match access-group input 101
 match access-group output 102
policy-map type service video-service
 class type traffic traffic-class
  police input 20000 30000 60000
  police output 21000 31500 63000
  timeout idle 30
 class type traffic default
 drop

Example: Session Timer Show Command Output

The following example shows the settings for the session timer displayed by the show subscriber session all privileged EXEC command: 

Current Subscriber Information: Total sessions 1
--------------------------------------------------
Unique Session ID: 3
Identifier: user01
SIP subscriber access type(s): PPPoE/PPP
Current SIP options: Req Fwding/Req Fwded
Session Up-time: 00:02:50, Last Changed: 00:02:53
AAA unique ID: 4
Interface: Virtual-Access2.1
Policy information:
  Context 02DE7380: Handle 1B000009
  Authentication status: authen
  User profile, excluding services:
    Framed-Protocol      1 [PPP]
    username             "user01"
    Framed-Protocol      1 [PPP]
    username             "user01"
  Prepaid context: not present
Non-datapath features:
 Feature: Session Timeout
  Timeout value is 180000 seconds
  Time remaining is 2d01h
Configuration sources associated with this session:
Interface: Virtual-Template1, Active Time = 00:02:52

Example: Connection Idle Timer Show Command Output

The following example shows the settings for the idle timer as displayed by the show subscriber session all privileged EXEC command: 

Current Subscriber Information: Total sessions 1
--------------------------------------------------
Unique Session ID: 4
Identifier: user01
SIP subscriber access type(s): PPPoE/PPP
Current SIP options: Req Fwding/Req Fwded
Session Up-time: 00:01:44, Last Changed: 00:01:46
AAA unique ID: 5
Interface: Virtual-Access2.1

Policy information:
  Context 02DE7380: Handle AD00000C
  Authentication status: authen
  User profile, excluding services:
    Framed-Protocol      1 [PPP]
    username             "user01"
    Framed-Protocol      1 [PPP]
    username             "user01"
  Prepaid context: not present
Session outbound features:
 Feature: PPP Idle Timeout
  Timeout value is 2000		
  Idle time is 00:01:44	

Configuration sources associated with this session:
Interface: Virtual-Template1, Active Time = 00:01:47

Example: Session Timer Debug Output

The following example shows output when the session timer debug commands (debug subscriber feature error , debug subscriber feature event, debug subscriber feature name session-timer error , and debug subscriber feature name session-timer event) are enabled: 

*Jan 12 18:38:51.947: SSF[Vi2.1/Abs Timeout]: Vaccess interface config
update; not per-user, ignore
*Jan 12 18:38:53.195: SSF[Vt1/uid:3]: Install interface configured
features
*Jan 12 18:38:53.195: SSF[Vt1/uid:3]: Associate segment element handle
0x95000002 for session 1191182344, 1 entries
*Jan 12 18:38:53.195: SSF[Vt1/uid:3/Abs Timeout]: Group feature install
*Jan 12 18:38:53.195: SSF[uid:3/Abs Timeout]: Adding feature to none segment(s)

Example: Connection Idle Timer Debug Output

The following example shows output when the idle timer debug commands (debug subscriber feature error, debug subscriber feature event, debug subscriber feature name idle-timer error, and debug subscriber feature name idle-timer event) are enabled: 

*Jan 12 18:43:15.167: SSF[Vt1/uid:4]: Install interface configured
features
*Jan 12 18:43:15.167: SSF[Vt1/uid:4]: Associate segment element handle
0xF4000003 for session 67108875, 1 entries
*Jan 12 18:43:15.167: SSF[Vt1/uid:4/Idle Timeout]: Group feature install
*Jan 12 18:43:15.167: SSF[uid:4/Idle Timeout]: Adding feature to outbound
segment(s)	
*Jan 12 18:43:15.167: Idle Timeout[uid:4]: Idle timer start, duration 2000
seconds, direction: outbound
*Jan 12 18:43:16.327: SSM FH: [SSS:PPPoE:8198:Idle Timeout:4097] created
02DFFDD8
*Jan 12 18:43:16.327: SSM FH: [SSS:PPPoE:8198:Idle Timeout:4097] added
02DFFDD8 [outbound]
*Jan 12 18:43:16.327: SSM FH: [SSS:PPPoE:8198:Idle Timeout:4097]
installed: ok
*Jan 12 18:43:16.327: SSM FH: [SSS:PPPoE:8198:Idle Timeout:4097]
installed: ok
*Jan 12 18:43:19.147: SSM FH: [SSS:PPPoE:8198:Idle Timeout:4097] bound

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS commands

Cisco IOS Master Commands List, All Releases

ISG commands

Cisco IOS Intelligent Services Gateway Command Reference

ppp timeout idle and timeout absolute PPP timer commands

Cisco IOS Dial Technologies Command Reference

HA commands

Cisco IOS High Availability Command Reference

HA configuration

Cisco IOS XE High Availability Configuration Guide

Technical Assistance

Description

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http://www.cisco.com/cisco/web/support/index.html

Feature Information for ISG Policies for Session Maintenance

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Table 2 Feature Information for ISG Session Maintenance

Feature Name

Releases

Feature Configuration Information

ISG: Session: Lifecycle: Idle Timeout

12.2(28)SB 12.2(33)SRC 15.0(1)S

The ISG idle timeout controls how long a connection can be idle before it is terminated.

In Cisco IOS Release 12.2(33)SRC, this feature was implemented on the Cisco 7600 router.

ISG: Session Protection & Resiliency: Keepalive-ARP, ICMP

12.2(33)SB 12.2(33)SRC 15.0(1)S

IP subscriber session keepalive support is configured for monitoring session data traffic in the upstream direction for idleness. Address Resolution Protocol (ARP) is used for Layer 2 connected subscribers. For routed hosts (Layer 3 connected) subscribers, the protocol defaults to Internet Control Message Protocol (ICMP). ICMP is also used in configurations where the access interface does not support ARP.

In Cisco IOS Release 12.2(33)SRC, this feature was implemented on the Cisco 7200 and Cisco 7600 routers.

In Cisco IOS Release 12.2(33)SB, this feature was implemented on the Cisco 10000 router.

The following command was introduced: keepalive (ISG)

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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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