Reliability and Recovery
256 Avaya Application Solutions IP Telephony Deployment Guide
Assessment Methodology and Criteria
The availability of a subsystem is described by the following equation:
where MTBF represents Mean Time Between Failures and MTTR represents Mean Time to
Recover/Repair. MTTR is the time to diagnose, respond, and resume service.
This equation is also sometimes presented in industry literature as the following:
where MTTF is defined as Mean Time to Failure, and equates to (MTBF - MTTR).
Using the above equation, the estimated average annual minutes of downtime experienced due
to a subsystem failure can be expressed as:
(Based on assuming 365.25 days in a year, There are 365.25
×
24
×
60 = 525960 minutes in a
year).
For projecting a enterprise’s total system availability, the sum of annual downtime contributed
from all subsystems is calculated, and then the system availability is estimated by using this
sum.
Note that this formula will result in a crude approximation of availability, as it does not account
for the groups of subsystems whose downtimes overlap.
Definition of Critical Outages and Downtime
The industry recognized criteria used for defining failure, outages and the downtime minutes
experienced is based on the Telecordia (Bellcore) GR-512 Reliability Model requirements for
telecommunications equipment.
Availability
MTBF
MTTR
–
(
)
MTBF
----------------------------------------------
=
Availability
MTTF
(
)
MTTF
MTTR
+
(
)
----------------------------------------------
=
AnnualDowntimeMinutes
1
Availability
–
(
)
525960minutes / year
(
)
×
=
TotalSystemAvailability
1
i
th
SubsystemContributedMinuteDowntime
[
]
i
∑
525960Minutes / Year
------------------------------------------------------------------------------------------------------------------------------------
–
=
Содержание Application Solutions
Страница 1: ...Avaya Application Solutions IP Telephony Deployment Guide 555 245 600 Issue 3 4 1 June 2005 ...
Страница 20: ...About This Book 20 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 21: ...Issue 3 4 1 June 2005 21 Section 1 Avaya Application Solutions product guide ...
Страница 22: ...22 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 74: ...Avaya Application Solutions platforms 74 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 106: ...Call processing 106 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 124: ...Avaya LAN switching products 124 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 139: ...Issue 3 4 1 June 2005 139 Section 2 Deploying IP Telephony ...
Страница 140: ...140 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 186: ...Traffic engineering 186 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 204: ...Security 204 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 214: ...Voice quality network requirements 214 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 228: ...Avaya Integrated Management 228 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 239: ...Reliability Issue 3 4 1 June 2005 239 Figure 69 S8700 Media Server in a high reliability configuration ...
Страница 274: ...Reliability and Recovery 274 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 275: ...Issue 3 4 1 June 2005 275 Section 3 Getting the IP network ready for telephony ...
Страница 276: ...276 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 350: ...Implementing Communication Manager on a data network 350 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 356: ...Network recovery 356 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 366: ...Network assessment offer 366 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 367: ...Issue 3 4 1 June 2005 367 Appendixes ...
Страница 368: ...Appendixes 368 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 394: ...Access list 394 Avaya Application Solutions IP Telephony Deployment Guide ...
Страница 414: ...DHCP TFTP 414 Avaya Application Solutions IP Telephony Deployment Guide ...