Contents
1 Introduction
This Network Impact Report (NIR) describes how the Virtual Call Session Control Function (vCSCF) 1.8.2 with new and enhanced commercial features affects the vCSCF 1.7.0. The NIR also describes the impact on the overall network, including all affected products and functions.
In this document, the term "vCSCF" refers to the product and the term "CSCF" refers to the CSCF application, independent of being deployed in a native or virtual environment.
- Note:
- The vCSCF product is a software-only product. It is not bundled with any hardware platform or virtualization software.
This document covers the following enhanced features:
- Emergency Call Handling
- Graceful Shutdown
- OAM Management (virtualized)
- SIP Request Handling
- Traceability and Troubleshooting
- Transit Support
- VNF Scaling
2 General Impact
This section describes the general impact owing to the introduction of the vCSCF 1.8.2.
2.1 Backward Compatibility
The vCSCF is backward compatible.
2.2 Capacity and Performance
The subscriber capacity increases by the introduction of the vCSCF 1.8.2 if the same version of cloud environment is used.
The performance improves by the introduction of the vCSCF 1.8.2.
2.3 Hardware and Platform
The vCSCF is a software-only product.
The demands on the hardware and platform are specified in Virtual CSCF Infrastructure Requirements.
2.4 Upgrade Impact
Smooth upgrade is supported for the vCSCF 1.7.0 – vCSCF 1.8.2 upgrade.
2.5 Deprecated Features
There are no deprecated features.
2.6 Obsolete Features
There are no obsolete features.
2.7 Other Network Elements
The Northbound Interface (NBI) is modified, which may affect external management systems, for example the Operation and Support System Radio and Core (OSS-RC).
3 Interfaces
This section describes interface changes between the existing and new revisions of the product. The changes to interfaces described here can require changes to the operator systems, technical plans, training of operator personnel, and so on.
No impact indicates that no changes are needed.
3.1 Inter-Node Interface
There are no changed inter-node interfaces.
3.2 Operation and Maintenance
This section describes changes to attributes, alarms, and counters.
3.2.1 Provisioning and Configuration
This section lists changed, deleted, and new attributes.
Further information on attributes can be found in the following documents:
3.2.1.1 Changed Attributes
The changed attributes are described in Table 1.
|
Attribute Name |
Description In vCSCF 1.7.0 |
Description In vCSCF 1.8.2 |
|---|---|---|
|
OAM Management (virtualized) | ||
|
cscfAdministrativeState |
This attribute indicates the current administrative state of the CSCF. This attribute is used to set the node state to 0 (Locked), 1 (Unlocked), or 2 (Shutting down). A short description of the behavior of CSCF at different states of cscfAdministrativeState is given here. When the node is in state: 0 (Locked), the CSCF is to be taken out of service as soon as possible. Established sessions, except emergency sessions, are released, users are deregistered, and new SIP requests are rejected. When the node is in state: 1 (Unlocked), the CSCF node handles requests and performs functions normally. When the node is in state: 2 (Shutting down), the CSCF is gracefully taken out of service with minimal traffic disturbance. As long as users are registered, non-register traffic is processed as when in Unlocked state. Users are de-registered/re-distributed when handling registration traffic. When all users are de-registered/re-distributed and all sessions are terminated, the CSCF automatically transits from Shutting down to Locked state. The default value is 0 (Locked). |
This attribute indicates the current administrative state of the CSCF. This attribute is used to set the node state to 0 (Locked), 1 (Unlocked), or 2 (Shutting down). A short description of the behavior of the CSCF at different states of cscfAdministrativeState is given here. When the node is in state: 0 (Locked), the CSCF is to be taken out of service as soon as possible. cscfAdministrativeState is not allowed to change from Locked to Unlocked when cscfLockedbehavioris FORCED and still in active state. It is also not allowed to change cscfAdministrativeState from Locked to Shutting down. When the node is in state: 1 (Unlocked), the CSCF node handles requests and performs functions normally. When the node is in state: 2 (Shutting down), the CSCF is gracefully taken out of service with minimal traffic disturbance and the CSCF automatically transits from Shutting down to Locked or Unlocked, depending on the configuration. The default value is 0 (Locked). |
|
Transit Support | ||
|
extNetSelPoolMode |
This attribute defines if the pool is considered to be in allocated number mode.
When changing pool mode, all data in the pool that is not used in the new pool mode is automatically erased.
Possible Values and Meanings: |
This attribute defines the result type of the External Network Selection analysis.
When changing pool mode, all data in the pool that is not used in the new pool mode automatically is erased.
Possible Values and Meanings: |
|
tcscfBehavior |
This attribute controls if HSS (LIR) Lookup(s) are performed or not, on the terminating side of I-CSCF. The attribute cscfISPBehavior must be configured to 1 (standalone I-CSCF) when tcscfBehavior is enabled. This attribute is preparing to introduce a new Transit Function CSCF (also referred to T-CSCF). |
This attribute controls if HSS (LIR) lookups are performed, not performed, or transit verification is done on the terminating side of the I-CSCF. The attribute cscfISPBehavior must be configured to 1 (standalone I-CSCF) when tcscfBehavior is ENABLED.
Possible Values and Meanings: |
|
VNF Scaling | ||
|
cscfProcessBehaviourAtClusterReconfiguration |
This parameter is used to indicate the CSCF process termination behavior during Cluster Reconfiguration.
Cluster Reconfiguration occurs during:
Possible Values and Meanings: The default value is IMMEDIATE. |
This parameter is used to indicate the CSCF process termination behavior during Cluster Reconfiguration.
Cluster Reconfiguration occurs during:
Possible Values and Meanings: The default value is DELAYED. |
3.2.1.2 Deleted Attributes
There are no deleted attributes.
3.2.1.3 Deprecated Attributes
There are no deprecated attributes.
3.2.1.4 Obsolete Attributes
There are no obsolete attributes.
3.2.1.5 New Attributes and Environment Variables
The new attributes are described in Table 2.
|
Attribute Name |
Description |
|---|---|
|
OAM Management (Virtualized) | |
|
cscfLockedBehavior |
This attribute describes the behavior of the CSCF during the Locked state. The configured value takes effect when cscfAdministrativeState is set to 0 (LOCKED). This attribute is not access-aware. Possible values are GRACEFUL, IGNORE_REQUESTS, and FORCED. The default value is GRACEFUL. |
|
SIP Request Handling | |
|
cscfBlacklistingThresholdInterval |
This attribute defines the measurement period, in seconds, for blacklisting thresholds.
This attribute applies to the following SIP blacklisting reasons: Accepted range: 0 – 86400 When it is set to 0, only CscfDestinationUnavailabilityTimer (or the Retry-After header for SIP 503 responses with Retry-After) is used as measurement period for blacklisting thresholds and blacklisting period. |
|
cscfBlacklistingThresholdIntervalDest |
This attribute defines the measurement period, in seconds, for blacklisting thresholds for specific destinations in the network.
This attribute applies to the following SIP blacklisting reasons: Possible values: default or [0–9]{1,10} Accepted length: 1–7 When it is set to default, there is no specific configuration for the destination. |
|
Transit Support | |
|
extNetSelectionInitialTransitTableName |
This parameter must be configured with the name of the ENS table to indicate where to start a navigating table for transit verification. The referenced table must be configured before this parameter can be changed. A defined ENS navigation and matching for transit verification. For example: SipMessage:[tableName], calling:[tableName], P-Asserted-Identity:[tableName], CIC:[tableName], RN:[tableName] or called:[tableName]. Default value: None. |
There are no new environment variables.
3.2.2 Fault Management
This section describes alarms that have been changed, deleted, or added.
3.2.2.1 Changed Alarms
The new alarms are described in Table 3.
|
Alarm Name |
Description of Change |
|---|---|
|
Transit Support | |
|
CSCF External Network Selection Initial Table Incorrectly Configured |
The alarm also is raised when the extNetSelectionInitialTransitTableName parameter is set to an empty table that does not contain any entries, or when some other configuration error is discovered in the ENS tables. For the initial table extNetSelectionInitialTableName, the Additional Text field states Configured Initial Table <table type>:<tablename> is empty. For the initial transit table extNetSelectionInitialTransitTableName, the Additional Text field states Configured Initial Transit Table <table type>:<tablename> is empty. |
|
CSCF External Network Selection Memory Limit Reached |
When this alarm is raised, any transit verification causes all SIP messages to be handled as non-transit. |
|
CSCF External Network Selection Table Loop Detected |
This alarm indicates if a loop was detected in the transit verification analysis or in the External Network Selection analysis. The Additional Info field is extended as R:SipMessage=[INVITE tel:+468000000000 SIP/2], SdpMediaType=[]” or T:SipMessage=[INVITE tel:+468000000000 SIP/2], SdpMediaType=[], where R stands for External Network Selection and T stands for transit verification. |
3.2.2.2 Deleted Alarms
There are no deleted alarms.
3.2.2.3 Deprecated Alarms
There are no deprecated alarms.
3.2.2.4 Obsolete Alarms
There are no obsolete alarms.
3.2.2.5 New Alarms
There are no new alarms.
3.2.3 Events and Notifications
This section describes events and notifications that have been changed, deleted, or added.
3.2.3.1 Changed Events and Notifications
There are no changed events and notifications.
3.2.3.2 Deleted Events and Notifications
There are no deleted events and notifications.
3.2.3.3 Deprecated Events and Notifications
There are no deprecated events and notifications.
3.2.3.4 Obsolete Events and Notifications
There are no obsolete events and notifications.
3.2.3.5 New Events and Notifications
There are no new events and notifications.
3.2.4 Counters
This section describes counters that have been changed, deleted, or added.
3.2.4.1 Changed Counters
There are no changed counters.
3.2.4.2 Deleted Counters
There are no deleted counters.
3.2.4.3 Deprecated Counters
There are no deprecated counters.
3.2.4.4 Obsolete Counters
There are no obsolete counters.
3.2.4.5 New Counters
There are no new counters.
4 Summary of Impacts per Feature
This section summarizes the impact per feature when the feature is turned off, as listed in Table 4.
The description of impact is as follows:
- Major Impact means that the feature has done an incompatible change so that another node requires an update.
- Minor Impact means that the feature has caused changes that affect other nodes, but with extra configuration, the previous behavior can be kept.
- No Impact means that the feature has no impact on the system.
|
Feature |
Impact |
Basic or Optional New or Enhanced |
Included in Value Packs |
Relation to Other Features or Nodes | ||
|
Major |
Minor |
No | ||||
|
Emergency Call Handling |
X |
Optional Enhanced |
Voice. Service Identity SIP Trunking Dynamic User |
|||
|
Graceful Shutdown |
X |
Basic Enhanced |
Voice Messaging Service Identity SIP Trunking Transit Dynamic User |
|||
|
OAM Management (virtualized) |
X |
Basic Enhanced |
Voice Messaging Service Identity SIP Trunking Transit Dynamic User |
|||
|
SIP Request Handling |
X |
Basic Enhanced |
Voice Messaging Service Identity SIP Trunking Transit Dynamic User |
SIP Nodes | ||
|
Traceability and Troubleshooting |
X |
Basic Enhanced |
Voice Messaging Service Identity SIP Trunking Transit Dynamic User |
Core Networks Operations Manager | ||
|
Transit Support |
X |
Optional Enhanced |
Transit |
|||
|
VNF Scaling |
X |
Basic Enhanced |
Voice Messaging Service Identity SIP Trunking Transit Dynamic User |
|||
5 Impact on CSCF Features
This section shows the impact on the CSCF features when the feature is turned on.
5.1 Emergency Call Handling
This section describes the enhanced feature Emergency Call Handling.
5.1.1 Description
If an emergency call is rejected by the last Public Safety Answering Point (PSAP) assigned by the Location Repository Function (LRF), and the default PSAP is not configured or the call is a service test call, the Emergency Call Session Control Function (E-CSCF) forwards the SIP error response that it received from the last failed PSAP to the caller. This behavior applies to an E-CSCF with a SIP-based Ml interface.
5.2 Graceful Shutdown
This section describes the enhanced feature Graceful Shutdown.
5.2.1 Description
To get a faster graceful shutdown behavior and not prevent the Serving Call Session Control Function (S-CSCF) to automatically transit from Shutting Down to Locked state, a new behavior for the unregistered users is introduced.
When cscfAdministrativeState is set to SHUTTINGDOWN, unregistered users are started to be deregistered by the S-CSCF. Any new session establishment attempt related to services for unregistered or not-registered users are rejected through a SIP 480 response when scscfRedundantScscfEntry is empty. When scscfRedundantScscfEntry is configured, they are rejected through a SIP 305 response.
When all registered users are deregistered, the S-CSCF automatically sets cscfAdministrativeState to LOCKED, even when any unregistered users remain in the S-CSCF.
5.3 OAM Management (Virtualized)
This section describes the enhanced feature OAM Management (Virtualized).
5.3.1 Description
When the CSCF is in the Administrative State Locked, the new parameter cscfLockedBehavior defines the behavior of the CSCF.
The parameter cscfLockedBehavior has the following settings:
- GRACEFUL
When cscfAdministrativeState is set to 0 (LOCKED), the Serving Call Session Control Function (S-CSCF) responds with a 480 (Temporarily Unavailable) response for initial registration, re-registration, and registration of a new contact. All other SIP requests are rejected by 503 (Service Unavailable) responses that are enhanced with the value 5 mins (300 sec) in the Retry-After header. This triggers the client nodes to redirect or blacklist the CSCF in the state LOCKED, so it disconnects all sessions and deregisters all users. The updated 503 (Service Unavailable) response message is applicable for all other CSCF node types.
- IGNORE_REQUESTS
When cscfAdministrativeState is set to 0 (LOCKED), the S-CSCF does not respond to any incoming initial SIP requests; it does not send 480 (Temporarily Unavailable) to REGISTER requests or 503 (Service Unavailable) to other requests. The S-CSCF still sends BYE messages to terminate all sessions, SAR, 3rd party REGISTER, and NOTIFY requests to de-REGISTER all users.
All other CSCF node types ignore the incoming initial SIP requests when cscfAdministrativeState is set to 0 (LOCKED).
- FORCED
When cscfAdministrativeState is set to 0 (LOCKED), all CSCF nodes immediately close the SIP ports. This means that all external signalling stops. The S-CSCF silently terminates all sessions and removes all registered and unregistered users.
5.4 SIP Request Handling
This section describes the enhanced feature SIP Request Handling.
5.4.1 Description
It is possible to configure the time period for accumulating the blacklisting thresholds interval separately from the blacklisting duration period. The threshold interval can be configured per Fully Qualified Domain Name (FQDN), next to the global configuration.
It applies to the following SIP blacklisting reasons:
- SIP 503 with Retry-After header
- SIP 503 without Retry-After header
- Transaction time-out
- Fatal transport error
If the threshold for one of these reasons is exceeded during the measurement period, the blacklisting period starts. During the blacklisting period, received requests are not forwarded to the blacklisted destination.
5.5 Traceability and Troubleshooting
This section describes the enhanced feature Traceability and Troubleshooting.
5.5.1 Description
The CSCF is enhanced to align the CSCF Health Check output format structure and use with other IP Multimedia Subsystem (IMS) Virtual Network Functions (VNFs). The new XML® output format enables using the results in a networking monitoring tool. The CSCF also supports new command line options for the Health Check script.
5.6 Transit Support
This section describes the enhanced feature Transit Support.
5.6.1 Description
The transit function in a terminating Interrogating Call Session Control Function (I-CSCF) is enhanced with a transit verification function that enables determination if SIP requests must be transited based on configurable criteria. All SIP requests that fulfill the configured criteria are handled as transit requests for which Home Subscriber Server (HSS) queries are suppressed. All SIP requests that do not fulfill the configured criteria are handled as non-transit requests.
For example, when a terminating I-CSCF receives a SIP request with a telephone number in its Request-URI, the transit verification function compares the originating network information in the received Via header and the called number in the received Request-URI with the configured criteria. If extNetSelectionInitialTransitTableName is not configured or the referenced table is misconfigured, all SIP requests are handled as non-transited requests.
The transit verification function is configurable for a standalone I-CSCF and a collocated IS-CSCF.
5.7 VNF Scaling
This section describes the enhanced feature VNF Scaling.
5.7.1 Description
The configuration attribute cscfProcessBehaviourAtClusterReconfiguration can be set to a new value: DELAYED. This new value delays the process termination so the traffic disturbance during Cluster Reconfiguration is reduced.