ISG Template-based Policy and Feature Provisioning

The ISG Template-based Policy and Feature Provisioning feature improves CPU utilization and supports higher Cisco Intelligent Services Gateway (ISG) session scale and calls per second (CPS) rates. This module describes how to configure ISG to bring up templates on subscriber sessions for policy and feature provisioning and management.

Prerequisites for ISG Template-based Policy and Feature Provisioning

  • If the Cisco IOS software on the device is upgraded to Cisco IOS XE Release 3.11S or downgraded to a prior version, IP subscriber sessions need to be cleared.
  • Before using the information in this module, it is recommended that you be familiar with how to configure and use ISG control policies. For more information about ISG control policies, see the “Configuring ISG Control Policies” module.

Restrictions for ISG Template-based Policy and Feature Provisioning

  • Subscriber templating is supported only on the Cisco ASR 1000 Series Aggregation Services Routers.
  • Templating is enabled by default in Cisco IOS XE Release 3.11S and later releases. This is applicable even when the Cisco IOS software is upgraded to Cisco IOS XE Release 3.11S or later releases. It is recommended not to disable it.
  • The lawful intercept (LI), per-user access control list (ACL), and per-user QoS features are not supported. However, these features can be provisioned on a session even if they are not provisioned through the template.
  • Performance improvements due to templating are applicable only to IP-based sessions.
  • Software path in IOL is not supported for templating.
  • PPP subscriber sessions are not templated.
  • Lite session limits are handled more gracefully.
  • Sessions cannot be scaled beyond 128k on FP40.
  • Walkby sessions cannot be scaled beyond 1.05M sessions.
  • During ISSU upgrade to Cisco IOS XE Release 3.11S or downgrade to an earlier release, the existing sessions are lost and need to be recreated.
  • The Layer 4 redirect (L4R) feature appears twice in the template.

Information About ISG Template-based Policy and Feature Provisioning

ISG Policy Provisioning Model

Historically, ISG subscriber policies and services were provisioned individually as separate features. There were very few policies that varied from session to session. As most sessions shared common policies, this led to poor utilization of CPU resources and hence a sluggish system.

To enhance system performance, a template of each policy is assigned an ID and provisioned once on the layer. This template policy is then customized for each subscriber session with the features specific to that session. Templating also applies to services where a template service can be provisioned on a layer. In this case, the policy template can be represented by a set of service template IDs. In the event that an applied policy on a session changes (on policy event or CoA), a new policy template is referenced.


Note

Prior to Cisco IOS XE Release 3.11S, the service policy was removed when the number of sessions using it becomes zero. However, after templating is enabled by default, a delay of 5 minutes is introduced to remove the idle service. This prevents the service policy from being modified during this period (that is the new service policy will not be downloaded until the older one gets deleted). As a workaround, the new service policy name can be renamed so that it is treated as a new service and is downloaded immediately.

Benefits of Templating

Templating provides the following advantages:
  • It improves system resource utilization resulting in better performance.
  • It enables better Quantum Flow Processor (QFP) memory usage per single stack or dual stack session.
  • It improves CPS rates and scaling.
  • It enhances CPU utilization and reduces delays due to reduced messaging for policy provisioning on sessions.

Configuration Examples for ISG Template-based Policy and Feature Provisioning

Example: Verifying ISG Template-based Policy and Feature Provisioning

The following examples show sample output generated from the configuration of ISG templating: 

Device# show subscriber template

   Template Id     Associated Sessions    Creation Time
         1                1             4:15:2013 7:38:850
Device# show subscriber template id 1

   Template Id     Associated Sessions    Creation Time
         1                1             4:15:2013 7:38:850

Class-id: 0
Features:      

Idle Timeout:
Dir: In/Out

Keepalive:
Dir: In/Out

Portbundle Hostkey:
Dir: In/Out 

Forced flow Routing:
URL Based Redirection:
Next-Hop Ip: 10.10.0.2

Class-id: 12
Features:   

Accounting:
Dir           Traffic Status
In/Out      Allowed/Not Allowed

Prepaid Idle Time:
Dir: In/Out

Prepaid Volume Monitor:
Dir            Traffic Status
In/Out       Allowed/Not Allowed

Prepaid Time Monitor:
Dir            Traffic Status
In/Out       Allowed/Not Allowed

Class-id: 6
Features:         

L4 Redirect:
Aclnum     Srv_ip   Duration   Frequency
0          3:3:3:1     0           0 

Class-id: 2
Features:

Policing:
Dir           Rate_in    Limit_in   Extended_Limit_in
In/Out        40          480000            960000
Device# show subscriber template state

ISG templating is ON
Total number of templates    		1