ECS is an enhanced or extended premium service. The System Administration Guide provides basic system configuration information, and the product administration guides provide information to configure the core network service functionality. It is recommended that you select the configuration example that best meets your service model, and configure the required elements for that model before using the procedures in this chapter.
The ECS is an in-line service that is integrated within the system. ECS enhances the mobile carrier’s ability to provide flexible, differentiated, and detailed billing to subscribers with Layer 3 through Layer 7 packet inspection, and the ability to integrate with back-end billing system. Active Charging Subsystem (ACS) is responsible for providing the ECS functionality.
The ECS has analyzers that examine uplink and downlink traffic and rules that define what packet content to take action on and what action to take when the rule is true. The analyzers also generate usage records for the billing system.
Traffic analyzers in ECS are based on configured rules. Rules used for traffic analysis analyze packet flows and form usage records. Usage records are created per content type and forwarded to a prepaid server or to a billing system.
The Traffic Analyzer function can perform shallow (Layer 3 and Layer 4) and deep (above Layer 4) packet inspection of IP packet flows. It is able to correlate all layer 3 packets (and bytes) with higher layer trigger criteria (for example, URL detected in an HTTP header). It also performs stateful packet inspection for complex protocols like FTP, RTSP, and SIP that dynamically open ports for the data path and this way, user plane payload is differentiated into “categories”. Traffic analyzers can also detect video streaming over RTSP, and image downloads and MMS over HTTP and differential treatment can be given to the Vcast traffic.
Traffic analyzers work at the application level as well, and perform event-based charging without the interference of the service platforms.
The ECS content analyzers are capable of inspecting and maintaining state across various protocols at all layers of the OSI stack. ECS supports inspecting and analyzing the following protocols:
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File analysis: examination of downloaded file characteristics (for example, file size, chunks transferred, etc.) from file transfer protocols such as HTTP and FTP.
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Shallow packet inspection is defined as inspection of the layer 3 (IP header) and layer 4 (for example, UDP or TCP header) information in the user plane packet flow.
Shallow inspection is examining the IP header (Layer 3) or UDP or TCP header (Layer 4). Deep packet inspection is typically the examination of Uniform Resource Identifier (URI) information (Layer 7). Shallow packet analyzers typically determine the destination IP address or port number of a terminating proxy, where deep packet analyzers typically identify the destination of a terminating proxy.
In some cases, Layer 3 and 4 analyzers that identify a trigger condition are insufficient for billing purposes, so layer 7 is used.
For example, the Web site www.companyname.com corresponds to IP address 1.1.1.1. The stock quote page (www.companyname.com/quotes) and the company page (www.companyname.com/business) are chargeable services. All other pages on this site are free. Since all parts of this Web site corresponds to a destination address of 1.1.1.1 and port number 80 (http), so determination of chargeable user traffic is possible through the actual URL (Layer 7) only.
Deep packet inspection performs packet inspection beyond Layer 4 inspection and is typically deployed for:
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Identification of true destination in the case of terminating proxies, where shallow packet inspection would only reveal the destination IP address / port number of a terminating proxy such as the OpCo’s WAP gateway
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ECS is a licensed feature, the features described in this chapter are only available if you have purchased and installed the required license:
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[600-00-7526] Enhanced Charging Bundle 1 1k Sessions — To enable and configure ECS functionality
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[600-00-7574] Enhanced Charging Bundle 2 1k Sessions — To enable and configure Diameter and DCCA functionality with ECS
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Apart from an ECS license, you may need other licenses for supported features. For more information contact your designated sales or service representative.
Enhanced charging functionality is managed by the Session Controller (SessCtrl) and Session Manager (SessMgr) subsystems. The following figure depicts the ECS architecture.
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Content Service Steering: Redirects incoming traffic to the ECS subsystem
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Protocol Analyzer: Performs the inspection of incoming packets
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Rule Definitions: Specifies the packets to inspect or the charging actions to apply to packets based on content
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Rulebases: Allows grouping one or more number of rule definitions together to define the billing policies for individual subscribers or group of subscribers
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Content Service Steering (CSS) directs selective subscriber traffic into the ECS subsystem (in-line services internal to the system) based on the content of the data presented by mobile subscribers.
CSS uses Access Control Lists (ACLs) to redirect selective subscriber traffic flows. ACLs control the flow of packets into and out of the system. ACLs consist of “rules” (ACL rules) or filters that control the action taken on packets matching the filter criteria.
ACLs are configurable on a per-context basis and applies to a subscriber through either a subscriber profile (for PDSN) or an APN profile (for GGSN) in the destination context.
IMPORTANT: For more information on CSS, refer to the Content Service Steering chapter of the System Enhanced Feature Configuration Guide.IMPORTANT: For more information on ACLs, refer to the IP Access Control Lists chapter of the System Enhanced Feature Configuration Guide.The Protocol Analyzer is the software stack responsible for analyzing the individual protocol fields and states during packet inspection.
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Shallow Packet Inspection: Inspection of the layer 3 (IP header) and layer 4 (for example, UDP or TCP header) information.
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Deep Packet Inspection: Inspection of layer 7 and 7+ information. Deep packet inspection functionality includes:
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Detection of Uniform Resource Identifier (URI) information at level 7 (for example, HTTP, WTP, RTSP URLs)
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Identification of true destination in the case of terminating proxies, where shallow packet inspection would only reveal the destination IP address / port number of a terminating proxy
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De-encapsulation of upper layer protocol headers, such as MMS-over-WTP, WSP-over-UDP, and IP-over GPRS
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The Protocol Analyzer performs a stateful packet inspection of complex protocols, such as FTP, RTSP, and SIP, which dynamically open ports for the data path, so the payload can be classified according to content.
The Protocol Analyzer is also capable of determining which layer 3 packets belong (either directly or indirectly) to a trigger condition (for example, URL). In cases where the trigger condition cannot be uniquely defined at layers 3 and 4, then the trigger condition must be defined at layer 7 (i.e., a specific URL must be matched).
Every packet that enters the ECS subsystem must first go through the Protocol Analyzer software stack, which is comprised of individual protocol analyzers for each of the supported protocols as shown in the following figure.
Each analyzer consists of fields and states that are compared to the protocol-fields and protocol-states in the incoming packets to determine packet content.
Rule definitions (Ruledefs) are user-defined expressions, based on protocol fields and/or protocol-states, which define what actions to take when specific field values are true. Expressions may contain a number of operator types (string, =, >, etc.) based on the data type of the operand. For example, “string” type expressions like URLs and host name can be used with comparison operators like “contains”, “!contains”, “=”, “!=”, “starts-with”, “ends-with”, “!starts-with” and “!ends-with”. Integer type expressions like “packet size” and “sequence number” can be used with comparison operators like “=”, “!=”, “>=”, “<=”. Each ruledef configuration consists of multiple expressions applicable to any of the fields or states supported by the respective analyzers.
Each ruledef can be used across multiple rulebases, and up to 2048 ruledefs can be defined in a charging service.
Ruledefs have an expression part, which matches particular packets based upon analyzer field variables. This is a boolean (analyzer_field operator value) expression that tests for analyzer field values.
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Routing Ruledefs: Routing ruledefs are used to route packets to content analyzers. Routing ruledefs determine which content analyzer to route the packet to when the protocol fields and/or protocol-states in ruledef expression are true. Up to 256 ruledefs can be configured for routing.
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Charging Ruledefs: Charging ruledefs are used to specify what action to take based on the analysis done by the content analyzers. Actions can include redirection, charge value, and billing record emission. Up to 2048 ruledefs can be configured for charging.
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Post-processing Ruledefs: Used for post-processing purposes. Enables processing of packets even if the rule matching for them has been disabled.
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By default, if rule-application is not specified when the ruledef is configured, the system configures the ruledef as a charging ruledef.
Ruledefs support a priority configuration to specify the order by which the ruledefs are examined and applied to packets. The names of the ruledefs must be unique across the service or globally. Up to 2048 ruledefs for both categories can be defined for an ECS charging service. A ruledef can be used across multiple rulebases.
IMPORTANT: Ruledef priorities control the flow of the packets through the analyzers and control the order in which the charging actions are applied. The ruledef with the lowest priority number invokes first.For routing ruledefs, it is important that lower level analyzers (such as the TCP analyzer) be invoked prior to the related analyzers in the next level (such as HTTP analyzer and S-HTTP analyzers), as the next level of analyzers may require access to resources or information from the lower level.
Priorities are also important for charging ruledefs as the action defined in the first matched charging rule apply to the packet and ECS subsystem disregards the rest of the charging ruledefs.
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rule-for-http has been defined with the expressions: tcp either-port = 80
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ruledef port-80
rule-application routing
ruledef bbc-news
http url starts-with http://news.bbc.co.uk
rule-application charging
ruledef catch-all
ip any-match = TRUE
rule-application charging
charging-action free-site
content-id 100
charging-action charge-by-duration
content-id 101
rulebase standard
The following figure illustrates how ruledefs interact with the Protocol Analyzer Stack and Action Engine to produce charging records.
Packets entering the ECS subsystem must first pass through the Protocol Analyzer Stack where routing ruledefs apply to determine which packets to inspect. Then output from this inspection is passed to the Charging Engine, where charging ruledefs apply to perform actions on the output.
The following figure and the steps that follow describe the details of routing ruledef application during packet inspection.
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The packet redirected to ECS based on the ACLs in the subscriber’s APN template and packets enter ECS through the Protocol Analyzer Stack.
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Packets entering Protocol Analyzer Stack first go through a shallow inspection by passing through the following analyzers in the order specified below:
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IMPORTANT: In the current release of ECS, traffic routes to the ICMP, TCP, and UDP analyzers by default. Therefore, defining routing ruledefs for these analyzers are not required now.|
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The fields and states found in the shallow inspection are compared to the fields and states defined in the routing ruledefs in the subscriber’s rulebase.
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As stated the ruledefs priority determines the order in which the ruledefs are compared against packets.
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When the protocol fields and states found during the shallow inspection match those defined in a routing ruledef, the packet is routed to the appropriate layer 7or 7+ analyzer for a deep packet inspection.
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The output of that analysis flows into the Charging Engine, where an action can be applied. Applied actions include redirection, charge value, and billing record emission.
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This section describes the details of how charging ruledefs are applied to the output from the Protocol Analyzer Stack.
The following figure and the steps that follow describe the process of charging ruledefs and charging engines.
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In the Classification Engine, the output from the deep packet inspection is compared to the charging ruledefs. The priority configured in each charging ruledef specifies the order in which the ruledefs are compared against the packet inspection output.
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When a field or state from the output of the deep packet inspection matches a field or state defined in a charging ruledef, the ruledef action is applied to the packet. Actions can include redirection, charge value, or billing record emission. It is also possible that a match does not occur and no action will be applied to the packet at all.
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Group-of-Ruledefs enable grouping ruledefs into categories. When a group-of-ruledefs is configured in a rulebase, if any of the ruledefs within the group matches, the specified charging-action is performed, any more action instances are not processed.
A group-of-ruledefs may contain optimizable ruledefs. Whether a group is optimized or not is decided on whether all the ruledefs in the group-of-ruledefs can be optimized, and if the group is included in a rulebase that has optimization turned on, then the group will be optimized.
When a new ruledef is added, it is checked if it is included in any group-of-ruledefs, and whether it needs to be optimized, etc.
A rulebase is a collection of ruledefs and their associated billing policy. The rulebase determines the action to be taken when a rule is matched. A maximum of 512 rulebases can be specified within an Active Charging Service.
It is possible to define a ruledef with different actions. For example, a Web site might be free for postpaid users and charge based on volume for prepaid users. Rulebases can also be used to apply the same ruledefs for several subscribers, which eliminate the need to have unique ruledefs for each subscriber.
IMPORTANT: Features described in this section are license enabled. If you have not previously purchased licenses for these services, contact your sales representative for more information.In conjunction with ST Series platforms, ECS provides a high-level network flow and bandwidth control mechanism through Session Control system of the chassis. ECS Session Control feature uses the interaction between SessMgr subsystem and Static Traffic Policy Infrastructure support of the ST Series platforms to provide an effective method to maximize network resources and enhancement to overall user experience.
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Flow Control Functionality: This functionality provides the ability to define and manage the number of simultaneous IP-based sessions and/or the number of simultaneous instances of a particular application permitted for the subscriber.
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If a subscriber begins a packet data session and system is either pre-configured or receives a subscriber profile from the AAA server indicating the maximum amount of simultaneous flow for a subscriber or an application is allowed to initiate. If subscriber exceeds the limit of allowed number of flows for subscriber or type of application system blocks/redirect/discard/terminate the traffic.
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Subscriber-Level Session Quota: Configurable on a per-rulebase basis
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Application-Level Session Quota: Configurable on a per-charging-action basis
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Bandwidth Control Functionality: This functionality allows the operator to apply rate limit to potentially bandwidth intensive and service disruptive applications.
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Using this feature the operator can police and prioritize subscribers’ traffic to ensure that no single or group of subscribers’ traffic negatively impacts another subscribers’ traffic.
For example, if a subscriber is running a P2P file sharing program and the system is pre-configured to detect and limit the amount of bandwidth to the subscriber for P2P application. The system gets the quota limit for bandwidth from PDP context parameter or individual subscriber. If the subscriber’s P2P traffic usage exceeds the pre-configured limit, the Session Control discards the traffic for this subscriber session.
Session Control feature in ECS also provides the controls to police any traffic to/from a subscriber/application with the ST Series platforms.
ECS supports Time-based Charging (TBC) to charge customers on either actual consumed time or total session time usage during a subscriber session. TBC generates charging records based on the actual time difference between receiving the two packets, or by adding idle time when no packet flow occurs.
PDP context charging allows the system to collect charging information related to data volumes sent to and received by the MS. This collected information is categorized by the QoS applied to the PDP context. FBC integrates a Tariff Plane Function (TPF) to the charging capabilities that categorize the PDP context data volume for specific service data flows.
Service data flows are defined by charging rules. The charging rules use protocol characteristics such as:
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FBC provides multiple service data flow counts, one each per defined service data flow. When FBC is configured in the ECS, PDP context online charging is achieved by FBC online charging using only the wildcard service data flow.
When further service data flows are specified, traffic is categorized, and counted, according to the service data flow specification. You can apply wildcard to service data flow that do not match any of the specific service data flows.
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Start of PDP context: Upon encountering this event, a Credit Control Request (CCR) starts, indicating the start of the PDP context, is sent towards the Online Charging Service. The data volume is captured per service data flow for the PDP context.
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Start of service data flow: An interim CCR is generated for the PDP context, indicating the start of a new service data flow, and a new volume count for this service data flow is started.
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Termination of service data flow: The service data flow volume counter is closed, and an interim CCR is generated towards the Online Charging Service, indicating the end of the service data flow and the final volume count for this service data flow.
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End of PDP context: Upon encountering this event, a CCR stop, indicating the end of the PDP context, is sent towards the Online Charging Service together with the final volume counts for the PDP context and all service data flows.
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Expiration of an operator configured time limit per PDP context: This event triggers the emission of an interim CCR, indicating the elapsed time and the accrued data volume for the PDP context since the last report.
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Expiration of an operator configured time limit per service data flow: The service data flow volume counter is closed and an interim CCR is sent to the Online Charging Service, indicating the elapsed time and the accrued data volume since the last report for that service data flow. A new service data flow container is opened if the service data flow is still active.
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Expiration of an operator configured data volume limit per PDP context: This event triggers the emission of an interim CCR, indicating the elapsed time and the accrued data volume for the PDP context since the last report.
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Expiration of an operator configured data volume limit per service data flow: The service data flow volume counter is closed and an interim CCR is sent to the Online Charging Service, indicating the elapsed time and the accrued data volume since the last report for that service data flow. A new service data flow container is opened if the service data flow is still active.
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Change of charging condition: When QoS change, tariff time change are encountered, all current volume counts are captured and sent towards the Online Charging Service with an interim CCR. New volume counts for all active service data flows are started.
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Administrative intervention by user/service also force trigger a chargeable event.
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A Flow Data Record (FDR) is generated for each of the above events. These generated records are stored in an EDR/UDR/FDR (xDR) and eG-CDR format (for GGSN platforms) and retrieved by ESS/GSS/mediation system for charging and/or analysis.
The file naming convention for created xDRs (EDR/UDR/FDRs) are described in the Impact on xDR File Naming section.
ECS provides off-line content filtering support and in-line static and dynamic content filtering support to control static and dynamic data flow and content requests.
ECS supports external Content Filtering servers through Internet Content Adaptation Protocol (ICAP) implementation between ICAP client and Active Content Filter (ACF) server (ICAP server).
ICAP is a protocol designed to support dynamic content filtering and/or content insertion and/or modification of Web pages. Designed for flexibility, ICAP allows bearer plane nodes such as firewalls, routers, or systems running ECS to interface with external content servers such as parental control (content filtering) servers to provide content filtering service support.
Content Filtering is a fully integrated, subscriber-aware in-line service available for 3GPP and 3GPP2 networks to filter HTTP and WAP requests from mobile subscribers based on the URLs in the requests. This enables operators to filter and control the content that an individual subscriber can access, so that subscribers are inadvertently not exposed to universally unacceptable content and/or content inappropriate as per the subscribers’ preferences. Content Filtering uses Deep Packet Inspection (DPI) capabilities of ECS to discern HTTP and WAP requests.
IMPORTANT: For more information on Content Filtering support, refer to the Content Filtering Services Administration Guide.Readdressing of packets based on the destination IP address of the packets enables redirecting unknown gateway traffic to known/trusted gateways.
IP Readdressing is configured in the flow action defined in a charging action. IP readdressing works for traffic that matches particular ruledef, and hence the charging action. IP readdressing is applicable to both uplink and downlink traffic. In the Enhanced Charging Subsystem, uplink packets are modified after packet inspection, rule matching, etc., where the destination IP/port is determined, and replaced with the readdress IP/port just before they are sent out. Downlink packets (containing the readdressed IP/port) are modified as soon as they are received, before the packet inspection, where the source IP/port is replaced with the original server IP/port number.
For one flow from an MS, if one packet is re-addressed, then all the packets in that flow will be re-addressed to the same server. Features like DPI, rule-matching, etc. remain unaffected. Each IP address + port combination will be defined as a ruledef.
In case of IP fragmentation, packets with successful IP re-assembly will be re-addressed. However, IP fragmentation failure packets will not be re-addressed.
ACS supports the ability to set the next hop default gateway IP address as a charging action associated with any ruledef in a rulebase. This functionality provides more flexibility for service based routing allowing the next hop default gateway to be set after initial ACL processing. This removes need for AAA to send the next hop default gateway IP address for CC opted in subscribers.
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When the packet matches a rule and the appropriate charging action is applied, the next-hop address is picked from the charging action and stored in the CALL line.
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IMPORTANT: This is a customer-specific feature. Please contact your sales representative for more information.Extension header (x-header) fields are the fields not defined in RFCs or standards but can be added to headers of protocol for specific purposes. HTTP 1.1 allows use of x-headers in entity-header. The x-header mechanism allows additional entity-header fields to be defined without changing the protocol, but these fields cannot be assumed to be recognizable by the recipient. Unrecognized header fields are ignored by the recipient and are forwarded by transparent proxies.
The x-header Insertion feature enables inserting x-headers in HTTP GET and POST request packets. Operators wanting to insert x-headers in HTTP GET and POST request packets, can configure rules for it. The charging-action associated with the rules will contain the list of x-headers to be inserted in the packets.
For example, if an operator wants to insert header field X-Test-Url in the HTTP header with its value being http url, i.e. the header inserted should be:
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Creating/configuring a rulebase and configuring the charging-action, which will insert the x-header fields into the HTTP packets.
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The packet size is assumed to be less than “Internal MED MTU size, the size of header fields inserted”. Header insertion does not occur after the addition of the fields, if the total length of packet exceeds the internal MTU size.
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Header insertion occurs for both HTTP GET and POST requests. However, for POST requests, the resulting packet size will likely be larger than for GET requests due to the message body contained in the request. If the previous limitation applies, then POST request will suffer a bigger limit due to this.
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Window size scaling is not handled in the case of header insertion. Header insertion does not occur if the resulting packet after header insertion exceeds the advertised TCP window size of the server.
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The Post Processing feature enables processing of packets even if the rule matching for them has been disabled. This enables all the IP/TCP packets including TCP handshaking to be accounted and charged for in the same bucket as the application flow. For example, delay-charged packets for IP Readdressing and Next Hop features.
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DCCA: Taking appropriate action on retransmitted packets in case the quota was exhausted for the previous packet and a redirect request was sent.
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DCCA with buffering enabled: Match CCA rules, charging-action will decide action—terminate flow/redirect
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Content ID based ruledefs: On rule match, if content ID based ruledef and charging action are present, the rule is matched, and the new charging action will decide the action
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A ruledef can be configured as a post-processing rule in the ruledef itself using rule-application of the ruledef. A rule can be charging, routing, or a post-processing rule. If the same ruledef is required to be a charging rule in one rulebase and a post-processing rule in another one, then two separate identical ruledefs must be defined.
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If the disposition action is to either buffer or discard the packets, or if it is set by the ACF, or if there are no post-processing rules, the packets are not post processed. The disposition action is applied directly on the packets. Only if none of the above conditions is true, post processing is initiated.
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Post-processing rules are matched and the associated charging-action and then the disposition-action obtained through control-charge.
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If both match-rule and control-charge for post processing succeed, the disposition-action obtained from post-processing is applied. Otherwise, the disposition-action obtained from charging rule-matching is used.
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If no disposition action is obtained by matching post-processing rules, the one obtained by matching charging-rules will be applied.
Irrespective of whether post processing is required or not, even if a single post-processing rule is configured in the rulebase, post processing will be done.
The following points should be considered while configuring post-processing rules for next-hop/readdressing.
For xheader-insertion, there should either be a post-processing rule whose charging-action gives no disposition-action or the packet should not match any of the post-processing rules so that the disposition action obtained from charging-rule matching is applied.
Within a rulebase, ruledefs/groups-of-ruledefs are assigned priorities. When packets start arriving, as per the priority order, every rule/group-of-ruledefs in the rulebase is eligible for matching regardless of the packet arrival time. By default, the ruledefs/groups-of-ruledefs are active all the time.
The Time-of-Day Activation/Deactivation of Rules feature uses time definitions (timedefs) to activate/deactivate static ruledefs/groups-of-ruledefs such that they are available for rule matching only when they are active.
The following steps describe how the Time-of-Day Activation/Deactivation of Rules feature enables charging according to the time of the day/time:
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Timedefs are configured in the Timedef Configuration Mode. Within a timedef, timeslots specifying the day/time for activation/deactivation of rules are configured.
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In the Rulebase Configuration Mode, timedefs are associated with ruledefs /groups-of-ruledefs along with the charging action.
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One timedef can be used with several ruledefs/group-of-ruledefs. If a ruledef/group-of-ruledefs does not have a timedef associated with it, it will always be considered as active.
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When a packet is received, and a ruledef/group-of-ruledefs is eligible for rule matching, if a timedef is associated with the ruledef/group-of-ruledefs, before rule matching, the packet-arrival time is compared with the timeslots configured in the timedef. If the packet arrived in any of the timeslots configured in the associated timedef, rule matching is undertaken, else the next ruledef/group-of-ruledefs is considered.
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If for a timeslot, “start time” > “end time”, that rule will span the midnight. I.e. that rule is considered to be active from the current day till the next day.
If for a timeslot, “start day” > “end day”, that rule will span over the current week till the end day in the next week.
ruledef HTTP://AB-WAP.YZ
The HTTP request for the URL “http://ab-wap.yz” is first sent to a proxy “http://cdab-subs.opera-mini.net/”.
The URL “http://cdab-subs.opera-mini.net/” will be configured as a prefixed URL.
Prefixed URLs are URLs of the proxies. A packet can have a URL of the proxy and the actual URL contiguously. First a packet is searched for the presence of proxy URL. If the proxy URL is found, it is truncated from the parsed information and only the actual URL (that immediately follows it) is used for rule matching and EDR generation.
The group-of-ruledefs can have rules for URLs that need to be actually searched (URLs that immediately follow the proxy URLs). I.e., the group-of-prefixed-URLs will have URLs that need to be truncated from the packet information for further ACS processing, whereas, the group-of-ruledefs will have rules that need to be actually searched for in the packet.
URLs that you expect to be prefixed to the actual URL can be grouped together in a group-of-prefixed-URLs. A maximum of 64 such groups can be configured. In each such group, URLs that need to be truncated from the URL contained in the packet are specified. Each group can have a maximum of 10 such prefixed URLs. By default, all group-of-prefixed-URLs are disabled.
IMPORTANT: A prefixed URL can be detected and stripped if it is of the type “http://www.xyz.com/http://www.abc.com”. Here, “http://www.xyz.com” will be stripped off. But in “http://www.xyz.com/www.abc.com”, it cannot detect and strip off “http://www.xyz.com” as it looks for occurrence of “http” or “https” within the URL.
ECS supports different accounting and charging interfaces for prepaid and postpaid charging and record generation.
IMPORTANT: Some feature supports described in this section are license enabled. If you have not previously purchased licenses for these services, contact your sales representative for more information.GTTP accounting in ECS allows the collection of counters for different types of data traffic, and including that data in a G-CDR that is sent to a Charging Gateway Function (CGF).
Standard G-CDRs do not have an attribute which defines traffic counters depending upon the traffic type but they do have a field named “Record Extensions” where all vendor-specific information can be included. ECS includes the counters for different types of data traffic in this field when sending a G-CDR.
The Remote Authentication Dial-In User Service (RADIUS) interface in ECS is used for the following purposes:
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Subscriber Category Request: ECS obtains the subscriber category from the AAA server (either prepaid or postpaid) when a new data session is detected. The AAA server used for the subscriber category request can be different from the AAA server used for service authorization and accounting.
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Service Access Authorization: ECS requests access authorization for a specific subscriber and a newly detected data session. The AAA server is the access Policy Decision Point and the ECS the Policy Enforcement Point.
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On-line Service Accounting (Prepaid): ECS reports service usage to the AAA server. The AAA server acts as a prepaid control point and the ECS as the client. Accounting can be applied to a full prepaid implementation or just to keep ECS updated of the balance level and trigger a redirection if the subscriber balance reaches a low level.
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The Diameter Credit Control Application (DCCA) is used to implement real-time online and/or offline charging and credit control for a variety of services, such as network access, messaging services, and download services.
In addition to being a general solution for real-time cost and credit control, DCCA includes these features:
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Real-time Rate Service Information: DCCA can verify when end subscribers' accounts are exhausted or expired; or deny additional chargeable events.
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Support for Multiple Services: DCCA supports the usage of multiple services within one subscriber session. Multiple Service support includes:
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The ability to identify and process the service or group of services that are subject to different cost structures.
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The Gx interface is used in IMS deployment in GPRS/UMTS networks. Gx interface support on the system enables wireless operators to intelligently charge the services accessed depending on the service type and parameters with rules. It also provides support for IP Multimedia Subsystem (IMS) authorization in a GGSN service. The goal of the Gx interface is to provide network-based QoS control as well as dynamic charging rules on a per bearer basis for an individual subscriber. The Gx interface is in particular needed to control and charge multimedia applications.
Rel 6. Gx Interface: The provisioning of charging rules that are based on the dynamic analysis of flows used for the IMS session is carried out over the Gx interface. The Rel. 6 Gx interface is located between the Access Gateway functioning as Traffic Plane Function (TPF), and the Charging Rule Function (CRF). The GGSN/TPF acts as the client where as the CRF contains the Diameter server functionality. Rel. 6 Gx interface is based on the Diameter base protocol (DIABASE) and the Diameter Credit Control Application (DCCA) standard.
Rel. 7 Gx Interface: The Rel. 7 Gx interface enables policy-based admission control support (enforcing policy control features like gating, bandwidth limiting, etc.,) and Flow-based Charging (FBC). This is accomplished via dynamically provisioned Policy Control and Charging (PCC) rules. These PCC rules are used to identify service data flows and do charging. Other parameters associated with the rules are used to enforce policy control.
The PCC architecture allows operators to perform service-based QoS policy, and flow-based charging control. In the PCC architecture, this is accomplished mainly by the Policy and Charging Enforcement Function (PCEF)/Starent Networks GGSN and the Policy and Charging Rules Function (PCRF).
The Rel. 7 Gx interface is located between the PCEF and the PCRF. Rel. 7 Gx interface is a Diameter-based interface that combines the functions provided earlier by the Rel. 6 Gx and Go interfaces.
IMPORTANT: For more information on Gx interface support, see Gx Interface Support chapter of the System Enhanced Feature Configuration Guide.The Gy interface provides a standardized Diameter interface for real-time content-based charging of data services. It is based on the 3GPP standards and relies on quota allocation.
It provides an online charging interface that works with the ECS deep packet inspection feature. With Gy, customer traffic can be gated and billed in an “online” or “prepaid” style. Both time- and volume-based charging models are supported. In all these models, differentiated rates can be applied to different services based on shallow or deep packet inspection.
Gy is a Diameter interface. As such, it is implemented atop, and inherits features from, the Diameter Base Protocol. The system supports the applicable base network and application features, including directly connected, relayed or proxied DCCA servers using TLS or plaintext TCP.
In the simplest possible installation, the system will exchange Gy Diameter messages over Diameter TCP links between itself and one “prepay” server. For a more robust installation, multiple servers would be used. These servers may optionally share or mirror a single quota database so as to support Gy session failover from one server to the other. For a more scalable installation, a layer of proxies or other Diameter agents can be introduced to provide features such as multi-path message routing or message and session redirection features.
Gy interface is the reference point between Diameter server and GGSN for online accounting and charging through Diameter based protocol. The Diameter server functions as Online Charging Service (OCS) and provides the online charging data to the GGSN, which acts as a Charging Data Function (CDF). Connection bewteen Diameter Client (Diabase) and OCS is maintained by underlaying TCP connection of Diameter based protocol and exchanges a series of messages to check the status of the connection and capabilities.
The Diameter Credit Control Application (DCCA) which resides as part of the ACS manages the credit and quota for a subscriber.
The following figure depicts a typical Gy interface implementation between GGSN (CDF) and Diameter server (OCS) with ECS.
ECS provides for the generation of charging data files, which can be periodically retrieved from the system and used as input to a billing system for post-processing.
The results of traffic analyzer are used to generate Session usage data. The generated usage data are in a standard format, so that the impact on the existing billing system is minimal and at the same time, these records contain all the information required for billing based on the content.
The accounting records also contain the information to identify the user, with Dynamic address assignment and information to obtain the URL for HTTP content request or a file-name or path from FTP request, the type of service from the first packet of the connection, and transaction termination information so that the billing system can decide transaction success or failure.
Charging records support details of the termination, such as which end initiated the termination, termination type, for example RST, FIN, etc. And, in case of HTTP 1.1, whether or not the connection is still open.
ECS supports pipelining of up to 32 HTTP requests on the same TCP connection. Pipeline overflow requests are not analyzed. Such overflow requests are treated as http-error. The billing system, based on this information, decides to charge or not charge, or refund the subscriber accordingly.
To cover the requirements of standard solutions and at the same time, provide flexible and detailed information on service usage, ECS provides following type of usage records:
IMPORTANT: G-CDRs are only available in GGSN networks.IMPORTANT: For more information on G-CDR fields, refer to the AAA Interface Administration and Reference Guide.IMPORTANT: eG-CDRs are only available in GGSN networks.The ECS also supports enhanced G-CDRs, which is an enhanced format of standard G-CDRs to provide greater portability of charging information.
eG-CDRs are compliant with 3GPP TS 32.298 v6.5.0 for Rel. 6 based dictionaries, and with 3GPP TS 32.298 v7.4.0 for Rel. 7 based dictionaries.
By default, the G-CDR does not support the traffic and vendor specific records. To support a traffic and vendor specific record, the ECS must be configured to generate eG-CDRs. eG-CDRs are useful to implement TBC and FBC to ECS.
eG-CDR supports customer specific formats configured in Ga context in a GGSN service with standard or custom specific GTPP dictionaries.
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When a change of PDP context conditions (QoS change, SGSN change, PLMN Id change, RAT change) occurs a set of List of Service Data (LOSDV) and List of Traffic Volume (LOTV) containers, i.e. all active service data flow containers, will be added to eG-CDR.
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When a change of tariff time occurs a set of List of Service Data (LOSDV) and List of Traffic Volume (LOTV) containers, i.e. all active service data flow containers, will be added to eG-CDR.
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Failure handling procedure triggering
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When the failure handling mechanism is triggered and the failure action is set to “continue” a set of List of Service Data (LOSDV) and List of Traffic Volume (LOTV) containers, i.e. all active service data flow containers, will be added to eG-CDR.
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When an expiry of time limit, volume limit or termination is detected for a service data flow a set of List of Service Data (LOSDV) container is added to eG-CDR.
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When a CDR closure occurs all active List of Service Data (LOSDV) container is added to eG-CDR.
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De-activation of the PDP context in the GGSN closes the eG-CDR. The trigger condition covers:
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IMPORTANT: For more information on eG-CDR fields, refer to the AAA Interface Administration and Reference Guide.Event Detail Records (EDRs) are usage records with support to configure content information, format, and generation triggers by the system administrative user.
EDRs are generated according to explicit action statements in rule commands. Several different EDR schema types, each composed of a series of analyzer parameter names, are specified in EDR. EDRs are written at the time of each event in CSV format. EDRs are stored in timestamped files that can be downloaded via SFTP from the configured context.
EDRs are generated on per flow basis, and as such they catch whatever bytes get transmitted over that flow including retransmitted.
The EDRs can be generated in comma separated values (CSV) format as defined in the traffic analysis rules.
IMPORTANT: In EDRs, the maximum field length for normal and escaped strings is 127 characters. If a field’s value is greater than 127 characters, in the EDR it is truncated to 127 characters.Flow-overflow EDR or Summary FDR is a feature to count the data bytes from the subscriber that are missed due to various reasons in ACS.
In case any condition that affects the callline (FLOW end-condition like hagr, handoff) occurs, flow-overflow EDR generation is enabled, an extra EDR is generated. Based on how many bytes/packets were transferred from/to the subscriber for which ACS did not allocate data session. This byte/packet count is reflected in that extra EDR. This extra EDR is nothing but “flow-overflow” EDR or Summary FDR.
The bytes/packet count will be printed as a part of “sn-volume-amt” attribute in the EDR. Hence, this attribute must be configured in the EDR format.
EDR Generation in Flow-end and Transaction Complete Scenarios with sn-volume Fields
“sn-volume-amt” counters will be re-initialized only when the fields are populated in EDRs. For example, consider the following two EDR formats:
“sn-volume-amt counters” will be re-initialized only if these fields are populated in the EDRs. Now if edr2 is generated, these counters will not be re-initialized. These will be re-initialized only when edr1 is generated. Also, note that only those counters will be re-initialized which are populated in EDR. For example, in the following EDR format:
If edr3 is generated, only uplink bytes and downlink bytes counter will be re-initialized and uplink packets and downlink packets will contain the previous values till these fields are populated (say when edr1 is generated).
Usage Detail Records (UDRs) contain accounting information based on usage of service by a specific mobile subscriber. UDRs are generated based on the content-id for the subscriber, which is part of charging action. The fields required as part of usage data records are configurable and stored in the System Configuration Task (SCT).
UDRs are generated on any trigger of time threshold, volume threshold, handoffs, and call termination. If any of the events occur then the UDR subsystem generates UDRs for each content ID and sends to the CDR module for storage.
The UDRs are generated in Comma Separated Values (CSV) format as defined in the traffic analysis rules.
On ST40 chassis, the system allocates 512 MB of memory on the PSC RAM, and on ST16 chassis 256 MB on the PAC RAM to store generated charging detail record files (xDRs). The generated xDRs are stored in CSV format in the /records directory on the PAC/PSC RAM. As this temporary storage space (size configurable) reaches its limits, the system deletes older xDRs to make room for new xDRs. Setting gzip file compression extends the storage capacity approximately 10:1.
Because of the volatile nature of the memory, xDRs can be lost due to overwriting, deletion, or unforeseen events such as power or network failure or unplanned chassis switchover. To avoid loosing charging and network analysis information, configure the CDR subsystem in conjunction with the ESS to offload the xDRs for storage and analysis. Or, configure the system to push records to the ESS.
In the ST40 platform, a hard disk has been introduced for additional storage capability. When storing CDR files on the SMC hard disk, first they are stored on RAMFS before they are moved to the hard disk, then they can be off-loaded via FTP or SFTP to an external server (such as the L-ESS or the GSS) or billing system.
When using the hard disk for EDR/UDR storage, EDR/UDR files are transferred from RAMFS on the PSC card to the hard disk on the SMC card. The hard disk may also be used to store any data that needs to be backed up.
The secondary SMC card also contains a hard disk which serves as a redundant, and becomes active during an SMC failover. The hard disk on the secondary is mirrored to the hard disk on the primary in order to avoid any data loss. Basically, the drives are raid-1 redundant.
The hard disk support is available only on the ST40 platform, so in the case of ST16 platform or an “ST40 without a hard disk”, a card failover results in a loss of CDR files. In the case of card failover on an “ST40 with a hard disk”, the new Active SMC starts pushing the files. Any files that are left in the middle of the transfer will be transferred again.
Prepaid billing operates on a per content-type basis. Individual content-types are marked for prepaid treatment. A match on a traffic analysis rule that has a prepaid-type content triggers prepaid charging management.
In prepaid charging, ECS performs the metering function. Credits are deducted in real time from an account balance or quota. A fixed quota is reserved from the account balance and given to the system by a prepaid rating and charging server, which interfaces with an external billing system platform. The system deducts volume from the quota according to the traffic analysis rules. When the subscriber’s quota gets to the threshold level specified by the prepaid rating and charging server, system sends a new access request message to the server and server updates the subscriber's quota. The charging server is also updated at the end of the call.
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RADIUS Credit Control Application: RADIUS is used as the interface between ECS and the prepaid charging server. The RADIUS Prepaid feature of ECS is separate to the system-level Prepaid Billing Support and that is covered under a different license key.
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Diameter Credit Control Application: The Diameter Credit Control Application (DCCA) is used to implement real-time credit control for a variety of services, such as networks access, messaging services, and download services.
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In addition to being a general solution for real-time cost and credit control, DCCA includes the following features:
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Real-time Rate Service Information: DCCA can verify when end subscribers' accounts are exhausted or expired; or deny additional chargeable events.
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Support for Multiple Services: DCCA supports the usage of multiple services within one subscriber session. Multiple service support includes:
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- The ability to identify and process the service or group of services that are subject to different cost structures.
In a postpaid environment, the subscribers pay after use of the service. AAA/RADIUS server is responsible for authorizing network nodes (GGSNs, PDSNs, or HAs) to grant access to the user, and the CDR system generates G-CDRs/eG-CDRs/EDRs/UDRs for billing information on pre-defined intervals of volume or per time.
ECS also supports FBC and TBC methods for postpaid billing. For more information on FBC and TBC in ECS, see the Enhanced Services in ECS section.
In a prepaid environment, the subscribers pay for service prior to use. While the subscriber is using the service, credit is deducted from subscriber’s account until it is exhausted or call ends. The prepaid charging server is responsible for authorizing network nodes (PDSNs and HAs, or GGSNs) to grant access to the user, as well as grant quotas for either time connected or volume used. It is up to the network node to track the quota use, and when these use quotas run low, the network node sends a request to the prepaid server for more quota.
If the user has not used up the purchased credit, the server grants quota and if no credit is available to the subscriber the call will be disconnected. ECS and DCCA manage this functionality by providing the ability to set up quotas for different services.
The following figure illustrates a typical prepaid billing environment with system running with ECS.
This section describes the credit control application that is used to implement real-time credit-control for a variety of end user services such as network access, Session Initiation Protocol (SIP) services, messaging services, download services, etc. It provides a general solution to the real-time cost and credit control.
CCA with RADIUS or Diameter interface uses a mechanism to allow the user to be informed of the charges to be levied for a requested service. In addition, there are services such as gaming and advertising that may debit from a user account.
The following figure and steps describe how CCA works with in a GPRS/UMTS or CDMA-2000 network for prepaid billing.
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Credit Database in DW sends pre-configured amount of usage limit from subscriber’s quota to CCA. To reduce the need for multiple requests during subscriber’s session configured amount of usage limit a major part of available credit quota for subscriber is set.
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When the initial amount of quota runs out, system sends another request to the CCA and the CCA sends another portion of available credit quota.
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EDRs and/or UDRs are periodically SFTPd from system memory to the ESS, if deployed or to billing system directly as they are generated. Or, if configured, pushed to the ESS at user-configurable intervals.
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IMPORTANT: External Storage System (ESS) is an optional and separately licensed feature which can be used with or without a billing/mediation system. For more information on the ESS, see the External Storage System section.This section describes the postpaid billing that is used to implement off-line billing processing for a variety of end user services.
The following figure and steps describe how ECS works within a GPRS/UMTS network for postpaid billing.
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System generates G-CDRs/eG-CDRs and sends them to GSS, if deployed or to billing system directly as they are generated.
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EDRs/UDRs are periodically SFTPd from system memory to ESS, if deployed, or to billing system directly as they are generated.
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The system stores the last of the xDRs to the system memory and final xDRs are SFTPd from system memory to ESS, if deployed or to billing system directly.
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File generation utility, FileGen in GSS periodically runs to generate G-CDRs/eG-CDRs files for billing system and send them to the billing system
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The following figure and steps describe how ECS works within a CDMA-2000 network for postpaid billing.
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EDRs/UDRs are periodically SFTPd from system memory to ESS, if deployed or to billing system directly as they are generated.
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The system stores the last of the xDRs to the system memory and final xDRs are SFTPd from system memory to the ESS system, if deployed or to billing system directly.
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External Storage System (ESS) is a high availability, fault tolerant, redundant solution for short-term/long-term storage of files containing detail records (UDRs/EDRs/FDRs (xDRs)). To avoid loss of xDRs on the chassis due to overwriting, deletion, or unforeseen events such as power or network failure or unplanned chassis switchover, xDRs are off-loaded to ESS for storage and analysis to avoid loss of charging and network analysis information contained in the xDRs.
The xDR files can be pulled by the L-ESS from the chassis, or the chassis can push the xDR files to the L-ESS using SFTP protocol. In the Push mode, the L-ESS URL to which the CDR files need to be transferred to is specified. The configuration allows a primary and a secondary server to be configured. Configuring the secondary server is optional. Whenever a file transfer to the primary server fails for four consecutive times, the files will be transferred to the secondary server. The transfer will switch back to the original primary server when:
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Transfer interval: A time interval, in seconds, after which the CDRs are pushed to the configured IP periodically. All the files that are completed before the PUSH timer expires are pushed.
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Remove file after transfer: An option to keep or remove the CDR files on the hard disk after they are transferred to the L-ESS successfully.
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For reliability, ESS incorporates two external components: Local (short-term) external storage component (L-ESS) and Remote (long-term) external storage components:
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L-ESS storage server connects logically to the chassis system and operates as an integrated element of the network system.
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Provides the means to archive and compress pulled xDRs for the purpose of extending the storage capacity. (Note: If retrieving gzip compressed xDR files from the chassis, L-ESS compression should not be used.)
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Provides a means of limiting bandwidth usage (in terms of kbps) for file transfer between the chassis and L-ESS.
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R-ESS server handles storage of xDRS files from one or more L-ESSs. R-ESS keeps record files available for long-term planning, network planning, subscriber usage profiling and analysis. Stores copy of records pushed from L-ESS.
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Provides the means to archive and decompress pulled xDRs for the purpose of extending the storage capacity. (Note: If retrieving gzip compressed xDR files from the chassis, L-ESS and R-ESS compression should not be used.)
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Provides a means of limiting bandwidth usage (in terms of kbps) for file transfer between the L-ESS and R-ESS.
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R-ESS Reporting System: R-ESS Reporting System in ESS is comprised of tasks to handle the automatic execution of scheduled xDR data extraction and report generation. It also supports the creation of reports at user’s discretion. It verifies the completeness of xDR data sets, aggregates them, and stores the aggregated data in a database.
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R-ESS report generation tool provides the reports to operator in both tabular and graphical representations for network planning, marketing, etc. of the network-wide traffic distribution on a daily, weekly, monthly basis. It also distributes the report in an efficient and automated manner through a standard PDF format.
Operators can access this report generation tool through a Web-based front-end interface with following functionality:
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Store/archive automatic or manually generated reports for long-term storage at user defined directory location.
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These reports can be used to reflect the subscriber who exceeds the pre-defined threshold limits of a total traffic in bytes/packets.
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The following figure shows a typical organization of ESS including L-ESS, R-ESS, and billing system with chassis having a AAA server.
The system running with ECS stores xDRs on an L-ESS, and the billing system collects the xDRs form the L-ESS and correlates them with the AAA accounting messages using 3GPP2-Correlation-IDs (for PDSN) or Charging IDs (for GGSN).
The L-ESS also provides xDRs to R-ESS for long-term storage of CDRs. Data at R-ESS can be used for post-processing, reporting, subscriber profiling, and trend analysis.
ECS does not require manual resource allocation. The ECS subsystem automatically allocates the resources when ACS is enabled on the chassis. ACS must be enabled on the chassis before configuring services.
This section describes the redundancy support available in ECS to recover user sessions and charging records in the event of software/hardware failure.
CAUTION: Intra-chassis session recovery support is achieved by mirroring the SessMgr and AAAMgr processes. The SessMgrs are paired one-to-one with the AAAMgrs. The SessMgr sends checkpointed session information to the AAAMgr. ACS recovery is accomplished using this checkpointed information.
IMPORTANT: In order for session recovery to work there should be at least four PACs/PSCs, one standby and three active. Per active CPU with active SessMgrs, there is one standby SessMgr, and on the standby CPU, the same number of standby SessMgrs as the active SessMgrs in the active CPU.There are two modes of session recovery, one from task failure and another on failure of CPU or PAC/PSC.
When a SessMgr failure occurs, recovery is performed using the mirrored “standby-mode” SessMgr task running on the active PAC/PSC. The “standby-mode” task is renamed, made active, and is then populated using checkpointed session information from the AAAMgr task. A new “standby-mode” SessMgr is created.
When a PAC/PSC hardware failure occurs, or when a planned PAC/PSC migration fails, the standby PAC/PSC is made active and the “standby-mode” SessMgr and AAAMgr tasks on the newly activated PAC/PSC perform session recovery.
The system supports the simultaneous use of ECS and the Inter-chassis Session Recovery feature. (For more information on the Inter-chassis Session Recovery feature, refer to the System Administration and Configuration Guide.) When both features are enabled, ECS session information is regularly checkpointed from the active chassis to the standby as part of normal Service Redundancy Protocol processes.
In the event of a manual switchover, there is no loss of accounting information. All xDR data from the active chassis is moved to a customer-configured ESS before switching over to the standby. This data can be retrieved at a later time. Upon completion of the switchover, the ECS sessions are maintained and the “now-active” chassis recreates all of the session state information including the generation of new xDRs.
In the event of an unplanned switchover, all accounting data that has not been written to the external storage is lost. (Note that either the ESS can pull the xDR data from the chassis, or the chassis can push the xDR files to a configured ESS at user-configured intervals. For more information, see External Storage System section.) Upon completion of switchover, the ECS sessions are maintained and the “now-active” chassis recreates all of the session state information including the generation of new xDRs.
Regardless of the type of switchover that occurred, the names of the new xDR files will be different from those stored in the /records directory of PAC/PSC RAM on the “now-standby” chassis. Also, in addition to the file name, the content of many of the fields within the xDR files created by the “now-active” chassis will be different. ECS manages this impact with recovery mechanism. For more information on the differences and how to correlate the two files and other recovery information, see the Impact on xDR File Naming section.
Inter-chassis redundancy in ECS uses Flow Detail Records (FDRs) and UDRs to manage the switchover between Active-Standby system. xDRs are moved between redundant external storage server and Active-Standby systems.
External storage server is responsible for sending records (pulled/pushed from the chassis) to the billing system. A cluster of two L-ESSs is implemented to fulfill the requirements for L-ESS redundancy.
The Active-Standby Inter-chassis Session Recovery architecture consists of two identically configured chassis running ECS service. The active and standby chassis are in constant communication via Service Redundancy Protocol (SRP) link. This SRP link is used to exchange system state information, MIP state information for a seamless recovery of subscriber session after a switchover, and also the basic information of ECS state in order to facilitate the re-creation of a subscriber ECS session on the standby chassis if it is required to be active.
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basename: A global-based configurable text string that is unique per system that uniquely identifies the global location of the system running ECS.
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ChargSvcName: A system context-based configurable text string that uniquely identifies a specific context-based charging service.
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timestamp: Date and time at the instance of file creation. Date and time in the form of “MMDDYYYYHHmmSS” where HH is a 24-hour value from 00-23.
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SeqNumResetIndicator: a one byte counter used to discern the potential for duplicated FileSeqNumber with a range of 0 to 255 which is incremented by a value of 1 for the following conditions:
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Failure of a system such that a second system takes over according to the Inter-chassis Session Recovery feature
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File Sequence Number (FileSeqNumber) rollover from 999999999 to 0
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FileSeqNumber: unique file sequence number for the file with 9 digit integer having range from 000000000 to 999999999. It is unique on each system.
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With inter-chassis session recovery, only the first two fields in the xDR file names remain consistent between the active and standby chassis as these are parameters that are configured locally on the ST16/ST40 platform. Per inter-chassis session recovery implementation requirements, the two chassis systems must be configured identically for all parameters not associated with physical connectivity to the distribution node.
The fields “timestamp”, “SeqNumResetIndicator”, and “FileSeqNumber” are all locally generated by the specific system through CDR subsystem, regardless of whether they are in an Inter-chassis Session Recovery arrangement or not.
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The “timestamp” value is unique to the system generating the actual xDRs and generated at the time the file is opened on the system.
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The SeqNumResetIndicator is a unique counter to determine the number of resets applied to FileSeqNumber. This counter is generated by CDR subsystem and increment the counter in event of resets in FileSeqNumber. This is required as “timestamp” field is not sufficient to distinguish between a unique and a duplicate xDR.
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As such, the “SeqNumResetIndicator” field is used to distinguish between xDR files which have the same “FileSeqNumber” as a previously generated xDR as a result of:
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Normal operation, for example a rollover of the “FileSeqNumber” from maximum limit to 0.
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In any scenario where the “FileSeqNumber” is reset to 0, the value of the “SeqNumResetIndicator” field is incremented by 1.
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The value of the “FileSeqNumber” is directly linked to the ECS process that is generating the specific xDRs. Any failure of this specific ECS process results in resetting of this field to 0.
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On the system startup, xDR files are generated in accordance with the standard processes and formats. If system fails at time given time it results in an inter-chassis session recovery switchover from active to standby and following occurs depending on the state of the call/flow records and xDR file at the time of failure:
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Call/flow records that were in the process of generated and collected in system memory prior to being written out to /records directory on PAC/PSC RAM are not recoverable and therefore are lost.
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Closed xDRs that have been written out to /records directory on PAC/PSC RAM but that have yet to be retrieved by the ESS are recoverable.
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Upon detection of a failure of the original active chassis, the standby chassis transits to the active state and begins serving the subscriber sessions that were being served by the now failed chassis. Any subsequent new subscriber session will be processed by this active chassis and will generate xDRs per the standard processes and procedures.
However, this transition impacts the xDRs for those subscribers that are in-progress at the time of the transition. For in progress subscribers, a subset of the xDR fields and their contents are carried over to the newly active chassis via the SRP link. These fields and their contents, which are carried over after an Inter-chassis Session Recovery switchover, are as follows:
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All remaining fields are populated in accordance with the procedures associated with any new flow with the exceptions that, the field “First Packet Direction” is set to “Unknown” for all in-progress flows that were interrupted by the switchover and the field “FDR Reason” is marked as a PDSN Handoff and therefore is set to a value of “1” and corresponding actions are taken by the billing system to assure a proper and correct accounting of subscriber activities.
