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 1.6.0. 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
- Implicit Registration
- Load Regulation
- 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 is not affected 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 1.6.0 – 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
The changes to the inter-node interfaces are listed in Table 1.
The description of impact is as follows:
- No Impact means that the new version can be installed without affecting other nodes.
- Minor Impact means that there are changes, but with extra configuration the previous behavior can be kept.
- Major Impact implies that the change has made an interface backward incompatible.
- New Interface indicates that the interface did not exist in the previous revision.
- Obsolete means that the interface no longer exists.
|
Interface |
Protocol |
Impact |
Description of Change Compared To vCSCF 1.6.0 |
|---|---|---|---|
|
Gm and Mw |
No Impact |
The Public User Identities can be sorted in different orders. The sorting depends on the configuration of parameter scscfPAssociatedUriBehavior in the S-CSCF, see also Table 3. |
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 2.
|
Attribute Name |
Description In vCSCF 1.6.0 |
Description In vCSCF 1.8.2 |
|---|---|---|
|
Graceful Shutdown | ||
|
scscfRegisteredUsersThreshold |
scscfRegisteredUserThreshold is set to 0, the CSCF automatically enters the administrative state Locked when the threshold is reached. For non-zero values, the CSCF automatically enters the administrative state Unlocked when the threshold is reached. This attribute is not access aware. Default value: 0 |
If scscfRegisteredUserThreshold is set to 0, the CSCF automatically enters the administrative state LOCKED when the threshold is reached. For non-zero values, the CSCF automatically enters the administrative state UNLOCKED when the threshold is reached. This attribute is not access-aware. This attribute must not be set with a value larger than 0 when scscfShuttingdownBehavior is FORCED_TO_LOCKED. Default value: 0 |
|
Load Regulation | ||
|
cscfSipOverloadControlReactingTrafficPriorities |
This attribute is used to map the outgoing SIP requests to SIP overload control reacting internal priority levels. 16 priority levels are supported, where value 0 is the highest one. This attribute is only applicable when cscfSipOverloadControlReactingEnabled is true. This attribute is not access-aware. This attribute can be configured as a string, where the priority is provided first and then a list of SIP request groups. The possible groups are Emergency, RphWps0, RphWps1, RphWps2, RphWps3, RphWps4, Inside, and Default. Default value is 0:RphWps0,RphWps1;1:RphWps2,RphWps3;2:RphWps4;3:Emergency;6:Inside;15:Default. |
This attribute is used to map the outgoing SIP requests to SIP overload control reacting internal priority levels. 16 priority levels are supported, where value 1 is the highest priority and 15 is the lowest. All SIP requests with priority 0 are never redirected or rejected. This attribute is only applicable when cscfSipOverloadControlReactingEnabled is true. This attribute is not access-aware. This attribute can be configured as a string, where the priority is provided first and then a list of SIP request groups. The possible groups are Emergency, RphWps0, RphWps1, RphWps2, RphWps3, RphWps4, Inside, and Default. Default value is 0:Inside,RphWps0,RphWps1;1:RphWps2,RphWps3;2:RphWps4;3:Emergency;15:Default. |
|
cscfSipOverloadControlReportingFairnessBehavior |
This attribute controls if the CSCF rejects a volume of incoming traffic from a node that does not support SIP overload control. The volume of incoming traffic is corresponding to the percentage level of how much traffic that a node supporting SIP overload control reduces traffic towards the CSCF node. This attribute is only applicable when cscfSipOverloadControlReportingEnabled is set to true. This attribute is not access-aware. Default value is Sip503Response. |
This attribute controls if the CSCF rejects a volume of incoming traffic from a node that does not support SIP overload control. The volume of incoming traffic is corresponding to the percentage level of how much traffic that a node supporting SIP overload control reduces traffic towards the CSCF node. This attribute is only applicable when cscfSipOverloadControlReportingEnabled is set to true. This attribute is not access-aware. Default value is NoFairness. |
|
cscfSipOverloadOnset |
This attribute is used to configure the average cluster resource utilization level that must be exceeded to activate the SIP overload control reporting function. This attribute is only applicable when cscfSipOverloadControlReportingEnabled is set to true. This attribute is not access-aware. This attribute can be configured with a value between 0–100. Default value is 75. |
This attribute is used to configure the average cluster resource utilization level that must be exceeded to activate the SIP overload control reporting function. This attribute is only applicable when cscfSipOverloadControlReportingEnabled is set to true. This attribute is not access-aware. This attribute can be configured with a value between 0–100. Default value is 85. |
|
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 3.
|
Attribute Name |
Description |
|---|---|
|
Graceful Shutdown | |
|
scscfShuttingdownBehavior |
This attribute configures when the S-CSCF automatically sets cscfAdministrativeState from SHUTTINGDOWNto LOCKED. The configured value takes effect when cscfAdministrativeState is set to SHUTTINGDOWN and is valid for the whole shutting down period. This attribute is not access-aware. Do not configure the attribute scscfShuttingdownBehavior to FORCED_TO_LOCKED when the threshold value for number of registered users scscfRegisteredUsersThreshold is larger than 0 and the other way around. Default value: GRACEFUL. |
|
scscfShuttingdownPhasePeriodTimer |
This attribute configures the phase length in minutes during which a percentage of the registered users is redirected when the S-CSCF is in shutting down mode. The configured value takes effect when cscfAdministrativeState is set to SHUTTINGDOWN and is valid for during the whole shutting down period. Changing cscfRegistrationRefreshMax during the shutting down period does not affect the shutting down phase period. This attribute is not access-aware. When the parameter scscfShuttingdownPhasePeriodTimer is set to 0, the phase length is set to the maximum registration period cscfRegistrationRefreshMax. Default value: 0. |
|
scscfShuttingdownPhases |
This attribute configures the number of phases that are used to redirect registered users when the S-CSCF is in shutting down mode. The length of one phase is set in scscfShuttingdownPhasePeriodTimer or cscfRegistrationRefreshMax. The configured value takes effect when cscfAdministrativeState is set to SHUTTINGDOWN and is valid for the whole shutting down period. This attribute is not access-aware. Default value: 0. |
|
Implicit Registration | |
|
scscfPAssociatedUriBehavior |
This parameter configures the behavior of the S-CSCF to determine the sorting order of unbarred public identities in the list of P-Associated-URI that is added to the REGISTER response. The sorting order is applied on public identities (IMPUs) in the Service Profile that is associated with the public identity and is presented in the To header in the registration request. In the sorting, the first non-barred SIP URI in the Service Profile is added as the first entry in the list of URIs in the P-Associated-URI header. The first non-barred tel URI in the Service Profile is added as the second entry. Other non-barred public identities in the Service Profile are added to the header in a random way.
The following are possible parameter values: The default value is 0. |
|
Load Regulation | |
|
cscfSipOverloadAbatement |
This attribute defines the threshold of the average cluster resource utilization percentage that triggers the decrement of the oc parameter value. The CSCF periodically decreases the reported oc parameter value, while the average cluster resource utilization level value is smaller than this threshold. This attribute is only applicable when cscfSipOverloadControlReportingEnabled is true. This attribute is not access-aware. This attribute is an integer between 0–100. The value must not be larger than the value of cscfSipOverloadOnset. The default value is 75. |
|
cscfSipOverloadDecrementStep |
The attribute defines the value of the step with which the oc parameter value is decreased. This attribute is only applicable when cscfSipOverloadControlReportingEnabled is true. This attribute is not access-aware. This attribute is an integer between 0–100. The default value is 1. |
|
cscfSipOverloadIncrementStep |
The attribute defines the value of the step with which the oc parameter value is increased. This attribute is only applicable when cscfSipOverloadControlReportingEnabled is true. This attribute is not access-aware. This attribute is an integer between 0–100. The default value is 2. |
|
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 4.
|
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
The changed counters are described in Table 5.
|
Counter Name |
Description of Change |
|---|---|
|
Graceful Shutdown | |
|
cscfConcurrentRegistrations |
The description and condition of counter cscfConcurrentRegistrations are changed to reflect the use of this counter in a better way. There is no functional change of this counter. |
|
cscfConcurrentRegisteredUserProfiles |
The condition of counter cscfConcurrentRegisteredUserProfiles is changed to reflect the use of this counter in a better way. There is no functional change of this counter. |
|
cscfPeakConcurrentRegistrations |
The description and condition of counter cscfPeakConcurrentRegistrations are changed to reflect the use of this counter in a better way. There is no functional change of this counter. |
|
cscfPeakConcurrentRegisteredUserProfiles |
The condition of counter cscfPeakConcurrentRegisteredUserProfiles is changed to reflect the use of this counter in a better way. There is no functional change of this counter. |
|
scscfConcurrentUnregisteredUserProfiles |
The condition of counter scscfConcurrentUnregisteredUserProfiles is changed to reflect the use of this counter in a better way. There is no functional change of this counter. |
|
scscfPeakConcurrentUnregisteredUserProfiles |
The condition of counter scscfPeakConcurrentUnregisteredUserProfiles is changed to reflect the use of this counter in a better way. There is no functional change of this counter. |
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
The new counters are described in Table 6.
|
Attribute Name |
Description |
|---|---|
|
Load Regulation | |
|
cscfSipReportingOverloadControlDuration |
This counter shows the number of seconds that the node spent in the overload condition during a Granularity Period. |
|
cscfSipReportingOverloadControlPeriods |
This counter shows the number of times when the node entered the overload operation mode during a Granularity Period. |
4 Summary of Impacts per Feature
This section summarizes the impact per feature when the feature is turned off, as listed in Table 7.
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 |
| ||
|
Implicit Registration |
X |
Basic Enhanced |
Voice Messaging Service Identity SIP Trunking Dynamic User |
| ||
|
Load Regulation |
X |
Basic Enhanced |
Voice Messaging Service Identity SIP Trunking Transit Dynamic User |
SIP nodes supporting the Reporting Role for SIP Overload Control (RFC7339) | ||
|
OAM Management (virtualized) |
X |
Basic Enhanced |
Voice Messaging Service Identity SIP Trunking Transit Dynamic User |
NeLS | ||
|
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
Redirection Distribution of Re-REGISTER Requests
When a standalone S-CSCF or a collocated S-CSCF enters in shutting down state, the S-CSCF distributes the redirection of re-REGISTER requests registered users over the number of phases as configured in scscfShuttingdownPhases. The phase length is set to the maximum registration refresh time as configured in cscfRegistrationRefreshMax or scscfShuttingdownPhasePeriodTimer.
When scscfShuttingdownPhases is 0, the user redistribution function is triggered without considering the value of scscfShuttingdownPhasePeriodTimer and scscfShuttingdownBehavior.
When the limit intensity of redirected register requests is triggered, the behavior of the S-CSCF can be configured by setting scscfShuttingdownBehavior to one its two options, see CSCF Configuration Management
Unregistered Users In Shutting Down State
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 Implicit Registration
This section describes the enhanced feature Implicit Registration.
5.3.1 Description
Through Implicit Registration, the S-CSCF is able to sort the IP Multimedia Public Identities (IMPUs) in the list of the P-Associated-URI that is added to the REGISTER response. The sorting is done based on the Home Subscriber Server (HSS) Service Profile that the IMPU belongs to at registration: the registration Service Profile.
To support multi-SIM service for emergency calls, a secondary device must not get the IMPU of the primary device as its top IMPU. Therefore, the S-CSCF allows the IMPUs that are found in the Service Profile of the registering IMPU to return in the top of the P-Associated-URI list.
In the sorting, the first non-barred SIP URI in the Service Profile is added as the first entry in the list of URIs in the P-Associated-URI header. The first non-barred tel URI in the Service Profile is added as the second entry. Other non-barred public identities in the Service Profile are added to the header in a random way. The value of scscfPAssociatedUriBehavior determines if the S-CSCF sorts only the IMPUs from emergency registrations or the IMPUs from all registrations.
5.4 Load Regulation
This section describes the enhanced feature Load Regulation.
5.4.1 Description
Reporting Role for SIP Overload Control
The calculation of the percentage level of the value of the oc parameter is based on the average cluster Resource Utilization Information (RUI) and the previous oc value.
The oc value is adjusted according to the following rules:
- At the initial phase, the oc value is set to 0. This indicates no SIP server overload.
- The oc value is increased
and decreased as follows (see also Figure 1):
- The oc value increases when the resource utilization level is larger than the Overload Onset (OO) threshold.
- The oc value remains unchanged when the resource utilization level is between the Overload Onset (OO) threshold and Overload Abatement (OA) threshold.
- The oc value decreases when the resource utilization level is lower than the Overload Abatement (OA) threshold.
The following Configuration Management parameters can be used to adjust the oc value:
- cscfSipOverloadOnset
When the RUI reaches the Overload Onset threshold, the CSCF increases oc value.
- cscfSipOverloadAbatement
When the RUI falls below the Overload Abatement (OA) threshold, the CSCF decreases oc value.
- cscfSipOverloadIncrementStep
The step value with which the CSCF increases the value of oc.
- cscfSipOverloadDecrementStep
The step value with which the CSCF decreases the value of oc with.
When upgrading from an older CSCF version that supports SIP Overload Control, some existing CM parameter values are overwritten with new default values.
If the parameter cscfSipOverloadOnset is already configured in the system, evaluate its value considering the modified calculation of the oc value. The new default value provides a better behavior in general.
Reacting Role for SIP Overload Control
All SIP requests with priority level 0 in the Configuration Management parameter cscfSipOverloadControlReactingTrafficPriorities are never redirected or rejected.
5.5 OAM Management (Virtualized)
This section describes the enhanced feature OAM Management (Virtualized).
5.5.1 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.
For the License Management, the allowed period in Autonomous Mode is increased from 7 to 90 days.
5.6 SIP Request Handling
This section describes the enhanced feature SIP Request Handling.
5.6.1 Description
Network-Initiated De-Registration
At network-initiated de-registration, the S-CSCF releases early dialogues that are associated to the de-registered contact by sending CANCEL in the downstream direction. The CANCEL procedure is managed through the non- INVITE transaction failover timer and can generate a SIP 408 (Timeout) response for the INVITE dialog if there is a transaction time-out of the CANCEL transaction.
Time Period for Accumulating the Blacklisting Thresholds
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.
5.7 Traceability and Troubleshooting
This section describes the enhanced feature Traceability and Troubleshooting.
5.7.1 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.
5.8 Transit Support
This section describes the enhanced feature Transit Support.
5.8.1 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.
5.9 VNF Scaling
This section describes the enhanced feature VNF Scaling.
5.9.1 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.