1、 AMERICAN NATIONAL STANDARD FOR TELECOMMUNICATIONS ATIS-0100524.2004(R2013) Terminology for Network Elements in Evolving Communication Networks As a leading technology and solutions development organization, ATIS brings together the top global ICT companies to advance the industrys most-pressing bus
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11、er-NE (between NEs), such as dual-homed network elements. A reliability-related objective - such as total system downtime - when applied to a network element, specifies only intra-NE fault-tolerant design strategy. This design is not always the most optimal in providing reliability. In some network
12、scenarios, redundant network elements without internal redundancy can provide equivalent or higher levels of service reliability. For the next generation network a multi-service packet-based network design flexibility is a necessity to satisfy the broad range of service reliability expectations. For
13、 this reason, reliability-related objectives should be applied to functional elements as well. The following is an example to illustrate the application functional elements to define different fault-tolerant design options. Let us assume that there are two NE types that the network designer can use
14、to implement the functional element: 1. the FFT NE (fully fault-tolerant network element), which has a total system downtime of 2 minutes per year; and 2. the PFT NE (partially fault-tolerant network element), which has a total system downtime of 10 minutes per year. As Figure 2 illustrates, Option
15、A uses two independent PFT NEs networked together to achieve a total FE downtime of less than 0.001 minutes per year. This option has the benefit of protecting the customers service from site outages. Option B uses one FFT NE to achieve a FE downtime of 2 minutes ATIS-0100524.2004 5 per year. And Op
16、tion C employs one PFT NE to achieve a FE downtime of 10 minutes per year. The latter option is applicable where the service is considered non-critical. NOTE - For successful failure recovery in Option A, the network recovery mechanism requires signaling between the network elements so that they can
17、 co-operate in the recovery. Configuration Functional Element FE Total System Downtime= z minutes unit of time during a set measurement period, where t0is the criterion for service outage/unavailability. Customer Service Failure Frequency: The FE shall ensure that the service failure rate, as experi
18、enced by the Service Customer, shall not average greater than fo occurrences per unit of time where a service failure results in the end-user or end-device having to re-try to establish service or to re-try a service transaction. Total FE Outage downtime: The entire FE bandwidth shall not be complet
19、ely out of service or degrade below a service availability performance threshold for durations longer than t0seconds for a long term average of z minutes unit of time of a set measurement period, where t0is the criterion for service outage/unavailability. Total FE Outage Frequency: The average frequ
20、ency of occurrence of the entire FEs bandwidth degrading below a service availability performance threshold for durations longer than t0seconds shall not exceed fo occurrences per unit of time. Partial FE Outage Downtime: No more than p% of FE bandwidth shall be out of service or degrade below a ser
21、vice availability performance threshold for a duration longer than t0seconds for a long term average u minutes of a set measurement period, where t0is the criterion for service outage/unavailability. Partial FE Outage Frequency: The average frequency occurrence of p% of FEs bandwidth degrading below
22、 a service availability performance threshold for durations longer than t0seconds shall not exceed fpo occurrences per unit of time. FE Management Control Downtime: The FEs management control functionality shall not be unavailable for durations longer than tcseconds for a long term average w minutes
23、 per ATIS-0100524.2004 8 unit of time of any measurement period, where tcis the criterion for FE management control outage. Weighted Bandwidth Unavailability: The ratio of total bandwidth-weighted unavailable seconds of FE ports by total bandwidth-weighted available seconds during a set measurement
24、period (hour, day, month, etc.) shall be less than b%, where unavailability of a port means that the port is out of service or below a service performance threshold for durations longer than t0seconds. FRU Total Mean-time-to Repair: FRUs shall be less than r minutes measured from the time of FRU fai
25、lure to when a replacement unit has been successfully placed back into service. This metric includes travel and administrative time. FRU Intrinsic Mean-time-to Repair: FRUs shall average over a specified period less than r minutes measured from the start of the repair action to when a replacement un
26、it has been successfully placed back into service. This metric excludes travel time, administrative time, and the assumption that spares are available. This metric measures the effectiveness of the NEs diagnostics. Objectives should be set based on type or criticality of the FRU. FE Maintenance Acti
27、ons: The frequency of FE maintenance actions per unit of time. This attribute can also be normalized to such metrics as the number of service-users, the number of ports, the amount of bandwidth, etc. The objectives must be set for a defined configuration, size and engineered values. Total FE FRU Ret
28、urn Rate: The frequency of FRU returns per unit of time. This attribute can also be normalized to such metrics as the number of service-users, the number of ports, the amount of bandwidth, etc. The objectives must be set for a defined configuration, size, and engineered values. Individual FRU Return
29、 Rate: The NE shall package the hardware into FRUs at a size and return rate that minimizes repair and inventory costs without adversely degrading system complexity and cost. The objective average FRU return rate shall be less than v% per year. 3 RELIABILITY-RELATED INTERNAL FEATURES AND METRICS The
30、 following is a list of basic reliability-related features and capabilities required to achieve the FE Reliability-related external metrics objectives. They are grouped into the following categories: Hardening: To prevent the occurrence of a failure event. Fault Tolerance: A designs capability to pr
31、event or reduce the impact of failure events on service or OAM&P functionality. Fault Management: To facilitate the containment of a failure and effective repair back to the network systems normal operating state. 3.1 Hardening Features The Solution shall be capable of preventing the following exter
32、nal failure events from causing a functional or equipment failure of the FE as follows: 1. NE Functional Integrity: The NE shall not experience a functional failure or equipment failure within the specified limits of the Service Providers operating environment: climate, operational vibration, earthq
33、uake, EMI/ESD, and supplied power. ATIS-0100524.2004 9 2. Traffic Robustness: Service Customer traffic and control message overloads of x times the specified level shall not cause a service outage. 3. OAM&P Robustness: There shall be no impact on established service from non-service-affecting manage
34、ment commands and queries. All potentially service-affecting OAM&P activities shall require command confirmation to minimize accidental service outage. 4. Human Interface Design Integrity: The physical design and customer operational documentation shall minimize craft person error. The Solution Vend
35、or shall provide test or field data for the Solution to demonstrate that the preceding hardening capabilities are met. 3.2 Fault Tolerance Features The Solution Vendor shall provide both the design specification and the test results for the applicable fault-tolerant features used by the Solution to
36、meet the external reliability-related metric objectives. These features mask or mitigate the impact on service due to specified failure events by using internal and/or network fault tolerance features. They are: Network Protection/Restoration: When configured in a network solution, the NE shall meet
37、 the network solutions network protection/restoration features inter-NE signaling specifications for the complete detection-recovery-repair cycle. Recovery of network services should recover in Trseconds to a predetermined recovery state where the Network Solution is meeting functional and performan
38、ce requirements. The total recovery time (Tr) is the sum of the times to detect, to notify for recovery, and to recover to a pre-determined recovery state. Tr= td+ tt, where: td= Fault detection time tt= Sum of the time interval for processing and transmitting a fault detection signal AND the time t
39、o recover to the original state in case of a transient failure OR the time to recover to a state where the functional requirements are met. Hardware Fault Tolerance: The FE shall automatically detect and recover from c % of the hardware failure rate that impact greater than x % of the customer ports
40、 in trhseconds. The detection time should be tdhseconds. Software Fault Tolerance: The NE shall automatically detect and recover from c % of the system software failure rate to at least a minimal operating configuration of non-failed hardware and a non-corrupted copy of system software in trsseconds
41、 for a specified reference configuration. External Power Protection: The NE shall have the capability to automatically recover from external power outages and survive for a duration x hours without impact on customer service. Internal Power Supply Protection: The NE shall recover from any single int
42、ernal power supply or power distribution failure without impact on service. Manual Recovery: The NE shall have the ability for on-site and remote manual recovery from total outage to at least a minimal operating configuration of non-failed hardware and a non-corrupted copy of system software in less
43、 than x minutes for a specified reference configuration. In-service Software Upgrades: The FE shall be capable of downloading software upgrades without impacting service and installing the software image where the FEs service interruption time shall be less than x seconds for a specified reference c
44、onfiguration. ATIS-0100524.2004 10 In-service Software Upgrade Resiliency: The NE shall have the capability to automatically recover from failed software upgrades and patch applications. It shall recover in less than x seconds for a specified reference configuration. In-service FRU Upgrades: FRU rep
45、lacements shall not require the powering down of the NE. Management Control Fault Tolerance: The NE shall automatically detect and recover from management control hardware failures in less than x1 seconds and shall automatically detect and recover from management control software failures in less th
46、an x2 seconds for a specified reference configuration. Recovery shall not impact customer services. Multiple Control Plane Separation: When the NE supports multiple control planes, failure of one shall not impact the other control plane(s). I/O Port Duplication: The NE shall provide I/O port protect
47、ion based on service criticality, that automatically detects and recovers from x % port hardware and link failures in trlseconds. The detection time should tdlseconds. 3.3 Fault Management Features The Solution Vendors NE shall provide the following fault management features which are used to contai
48、n, isolate, and record failed equipment (locally and remotely) for effective repair and field tracking. Equipment Fault Recording: For all equipment failures, the NE shall record module identification (software and hardware), time of the event, and time of return to service. Link Fault Recording: Fo
49、r all link failures, the NE shall record link identification, time of the event, and time of return to service. Overload Fault Recording: For all service-affecting traffic overload events, the NE should record ports impacted, level of the overload, time of the event, and time of return to service. Fault Record Storage: The NE shall be capable of storing all equipment, link, and overload records for n hours or m records. Fault Record Communication: The NE shall be capable of sending
