Table Of Contents

P-CSCF Support

Contents

Restrictions for Implementing P-CSCF Support

Information About P-CSCF Support

Standard Non-IMS Profile

P-CSCF Access Profile

P-CSCF Core Profile

Implementing P-CSCF Support

Configuring Profiles Inheritance

P-CSCF Support

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The Proxy-Call Session Control Function (P-CSCF) is the first contact point for the users of the Information Management System (IMS). The P-CSCF functions as a proxy server for the user equipment; all Session Initiation Protocol (SIP) signaling traffic to and from the user equipment must go through the P-CSCF. The P-CSCF validates and then forwards requests from the user equipment and then processes and forwards the responses to the user equipment.

The P-CSCF can also function as a user agent in the context of the SIP operating procedures. If an abnormal condition arises in a session, the P-CSCF can unilaterally release the session for the user equipment. The user agent role can also be used to generate independent SIP messages required during the registration, such as sending the user's public and private identities. There may be more than one P-CSCF in the operator's network based on survivability, number of users, expected traffic, and network topology. The P-CSCF can be also referred to as the SIP server.

To implement the P-CSCF support on the Session Border Controller (SBC), users must select an Inherit Profile for a SIP adjacency. The three available Inherit Profiles are:

•Standard Non-IMS Profile

•P-CSCF Access Profile

•P-CSCF Core Profile

Each of these profiles groups a set of IMS-related configuration fields, which can be applied across multiple adjacencies.

If a valid profile is configured, then this profile is applied to an adjacency that does not have a profile configured. If a profile is already selected for a SIP adjacency, that profile is used instead of the entity's profile.

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Note For ACE SBC Release 3.0.00, this feature is supported in the unified model only.

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Feature History for P-CSCF Support

Release	Modification
ACE SBC Release 3.0.00	This feature was introduced on the Cisco 7600 series router along with support for the SBC unified model.

Contents

This module contains the following sections:

•Restrictions for Implementing P-CSCF Support

•Information About P-CSCF Support

•Implementing P-CSCF Support

Restrictions for Implementing P-CSCF Support

The following restrictions and limitations apply to implementing P-CSCF support:

•Since the Visited Network Identifier is not part of an Inherit Profile, you need to configure it independently on a per-adjacency basis.

•This feature does not offer support for securing access links through IPSec or Network Attachment Subsystem (NASS) bundled authentication.

•This feature does not support emergency calls.

Information About P-CSCF Support

This section contains the following subsections:

•Standard Non-IMS Profile

•P-CSCF Access Profile

•P-CSCF Core Profile

Standard Non-IMS Profile

This profile provides compatibility with existing SBC functionality and is used for adjacencies that do not operate in an IMS network. When this profile is applied to an adjacency, the SBC exhibits the following properties:

•Contact headers are rewritten to ensure that the SBC remains on the signaling path.

•Unknown headers, methods, and options are, by default, not allowed to pass through.

•The SBC does not attach Path headers to outbound signals.

•The SBC does not attach Record-Route headers to outbound signals.

•The endpoints on this adjacency do not need to be registered to receive or send Non-REGISTER requests.

•The endpoints do not need to attach a Route header to outbound signals.

•The adjacencies do not generate P-Charging Vector headers for outbound signals.

P-CSCF Access Profile

This profile provides the configurations required to perform the functions of a P-CSCF Access adjacency. When this profile is applied to an adjacency, the SBC exhibits the following properties:

•Contact headers are not rewritten.

•The endpoints on this adjacency need to be registered to receive or send Non-REGISTER requests.

•The endpoints need to attach a Route header to outbound signals, which in turn, matches a Service-Route set from the Registrar.

•The SBC appends Record-Route headers to outbound signals.

•The SBC does not attach Path headers to outbound signals.

•The adjacencies do not generate P-Charging Vector headers for outbound signals.

•The SBC, by default, allows all inbound non-essential headers to pass through, except P-Asserted Identity, Security-Client, Security-Verify, P-Charging-Function Addresses, P-Charging-Vector, and P-Media-Authorization.

•The SBC, by default, allows all outbound non-essential headers, except P-Charging-Function-Addresses, P-Charging-Vector, and P-Media-Authorization.

•The SBC allows all inbound non-essential methods to pass through.

•The SBC allows all outbound non-essential methods to pass through; UEs are not permitted to act as Registrars.

•The Option tags in Supported, Require, or Proxy-Require headers are allowed to pass through in both directions.

P-CSCF Core Profile

This profile provides the configurations required to perform the functions of a P-CSCF Core adjacency. When this profile is applied to an adjacency, the SBC exhibits the following properties:

•Contact headers are not rewritten.

•The SBC, by default, allows all inbound unknown headers, except the P-Charging-Function-Addresses and P-Media-Authorization.

•The SBC appends Record-Route headers to outbound signals.

•The SBC attaches Path headers to outbound REGISTER signals from P-CSCF.

•The adjacencies generate P-Charging Vector headers for outbound signals.

•The endpoints on this adjacency do not need to be registered to receive or send Non-REGISTER requests.

•The SBC, by default, allows all outbound non-essential headers, except P-Charging-Function-Addresses and P-Media-Authorization.

•The SBC allows all unknown methods to pass through.

•The Option tags in Supported, Require, or Proxy-Require headers are allowed to pass through in both directions.

Implementing P-CSCF Support

This section explains how to configure profile inheritance.

Configuring Profiles Inheritance

SUMMARY STEPS

1. configure

2. sbc service-name

3. sbe

4. sip inherit profile {preset-ibcf-ext-untrusted | preset-ibcf-external | preset-ibcf-internal | preset-p-cscf-access | preset-p-cscf-core | preset-standard-non-ims}

5. adjacency sip adjacency-name

6. inherit profile preset p-cscf-access

7. visited network identifier network-name

8. exit

DETAILED STEPS

	Command or Action	Purpose
Step 1	configure Example: host1/Admin# configure	Enables global configuration mode.
Step 2	sbc service-name Example: host1/Admin(config)# sbc mysbc	Enters the mode of an SBC service. •Use the service-name argument to define the name of the service.
Step 3	sbe Example: host1/Admin(config-sbc)# sbe	Enters the mode of a SBE entity within an SBC service.
Step 4	sip inherit profile {preset-ibcf-ext-untrusted | preset-ibcf-external | preset-ibcf-internal | preset-p-cscf-access | preset-p-cscf-core | preset-standard-non-ims} Example: host1/Admin(config-sbc-sbe)# sip inherit profile preset p-cscf-access	Configures the P-CSCF Access Inherit Profile as the global profile.
Step 5	adjacency sip adjacency-name Example: host1/Admin(config-sbc-sbe)# adjacency sip sipadj	Enters the mode of an SBE SIP adjacency. •Use the adjacency-name argument to define the name of the SIP adjacency.
Step 6	inherit profile preset p-cscf-access Example: host1/Admin(config-sbc-sbe-adj-sip)# inherit profile preset-p-cscf-access	Configures the SIP adjacency to use the P-CSCF-Access profile.
Step 7	visited network identifier network-name Example: host1/Admin(config-sbc-sbe-adj-sip)# visited network identifier mynetwork.com	Configures the specified visited network identifier on the SIP adjacency.
Step 8	exit Example: host1/Admin(config-sbc-sbe-adj-sip)# exit	Exits the SIP adjacency mode to the SBE mode.