THE SERVICE RELIABILITY ECOSYSTEM

Transcription

THE SERVICE RELIABILITY
ECOSYSTEM
©M ichael Tor tor ella, Ph. D.
M anaging Dir ector
Assur ed Networ ks, LLC
THEME
SDN/NFV NETWORK RELIABILITY
STANDARDS CAN’T BE SENSIBLY
CONSTRUCTED UNLESS YOU FIRST
KNOW WHAT
SERVICE RELIABILITY TARGETS YOU
ARE TRYING TO MEET
CQR Emerging Technologies
Roundtable
11 May 2015
©2015 M. Tortorella
Slide 2
OVERVIEW
Ser vice examples
Customer s want r eliable ser vices
Ther e is a language for talking about ser vice
r eliability
Ther e is a theor y and a set of engineer ing
pr inciples suppor ting r eliable ser vices
Ser vice r eliability r equir ements come fir st!
Roundtable
11 May 2015
Slide 3
OVERVIEW
Ser vice r eliability r equir ements ar e
abstr acted fr om any r equir ements for
r eliability of ser vice deliver y infr astr uctur e
(SDI) and its elements
The r eliability char acter istics of the SDI
deter mine the how r eliable the ser vice it
suppor ts will be
The or der in which you do things matter s!
Ecosystem diagr am
Roundtable
11 May 2015
Slide 4
TELECOM SERVICE
EXAMPLES
Voice telephony ser vice



POTS networ k
Connectionless networ ks
M obile
Inter net access ser vice


TCP/ IP W AN backbone
Local access var ies
+
+
+
+
Dial-up
DSL
TV Cable
Optical
Roundtable
11 May 2015
Slide 5
TELECOM SERVICE
EXAMPLES
Var ious enter tainment ser vices

M ost mediated by the Inter net
Complex combinations of ser vices



Video teleconfer encing
Point-of-sale cr edit appr oval
M obile banking
Peer -to-peer ser vices
Roundtable
11 May 2015
Slide 6
CUSTOMERS WANT
RELIABLE SERVICES
PC M agazine r eliability r atings of ISPs


Inter net access ser vice “outages”
Upload and download speeds
Customer r eliability complaints about mobile
ser vices



Dr opped calls
Echo
Slow data
Ver izon FiOS adver tising “the fastest and
most r eliable Inter net”
Roundtable
11 May 2015
Slide 7
SERVICE RELIABILITY
LANGUAGE
Tr ansactions
Ser vice failur e classifications accor ding to
tr ansaction phases



Accessibility
Continuity/ Fulfillment
Release
Requir ements for these ar e based on
systems engineer ing under standing of
customer needs and desir es for satisfactor y
tr ansactions in each ser vice
Roundtable
11 May 2015
Slide 8
SERVICE RELIABILITY
ENGINEERING PRINCIPLES
Ser vice failur e modes can be catalogued
Ser vice failur e mechanisms and failur e
causes ar e events or omissions in the SDI
Congestion is always a factor in SDIs


Economically unr easonable to pr ovision an SDI
for ever y possible ser vice demand
W hen SDI elements fail, a level of ser vice
demand that might have been suppor table if
ever ything wer e wor king pr oper ly will lead to
incr eased congestion
Roundtable
11 May 2015
Slide 9
SERVICE RELIABILITY
So if you want to under stand how r eliable
your ser vice is,


M ake a r eliability model to r elate the fr equency
and dur ation of ser vice failur es and outages to
the fr equency and dur ation of events or
omissions in the SDI and/ or
Collect and analyze accessibility,
continuity/ fulfillment, and r elease data
+ DPM appr oach is followed by many ser vice pr ovider s
Roundtable
11 May 2015
Slide 10
SERVICE RELIABILITY
And if you want to know what r eliability
r equir ements you should put on your SDI
and its elements, “wor k the model
backwar ds”
Roundtable
11 May 2015
Slide 11
VOICE TELEPHONY
EXAMPLE
 Voice telephony (VT) is the ability to speak with
another par ty beyond shouting distance
 VT was fir st deliver ed on an analog networ k


Panel, step-by-step, cr ossbar switching
Twisted pair , coax, micr owave tr anspor t
 In the 1 9 6 0 s-1 9 7 0 s, VT began to be pr ovided on a
digital networ k

Seamless tr ansition to
+ Electr onic switching
+ SONET/ SDH, OC-3 -1 2 -4 8 -2 9 2 , and many other digital
tr anspor t systems
Roundtable
11 May 2015
Slide 12
VOICE TELEPHONY
EXAMPLE
Nobody noticed! Customer s don’t know or
car e what technology you ar e using to
pr ovide their ser vice
This impor tant pr inciple means that ser vice
r eliability r equir ements ar e invar iant with
r espect to the natur e of the SDI you use to
deliver the ser vice
Roundtable
11 May 2015
Slide 13
VOICE TELEPHONY
EXAMPLE
 “Car r ier gr ade” ser vice accessibility has always been
claimed to be ≥ 0 .9 9 9 9 9 (“5 nines”)


Does not account for delays
No local – toll distinction
 “Car r ier gr ade” ser vice continuity objective was “no
mor e than 2 5 0 DPM ” (for exponentially-distr ibuted
holding times with a mean of 6 minutes)
 Ser vice r elease failur es wer e so r ar e that no one
car ed
 Some impor tant questions still linger

W as the 2 hour s downtime in 4 0 year s switching system
r equir ement r eally necessar y?
Roundtable
11 May 2015
Slide 14
VOICE TELEPHONY
EXAMPLE
 Reliability model for the POTS networ k based on the
5 -level hier ar chy in the toll networ k


Using cut set – path set methods combined with r enewalr ewar d capacity models for networ k elements
Or iginally, this was for the analog networ k (slide 1 6 )
+ But the str uctur e of the digital networ k was similar
+ W ith digital, loss/ noise/ echo wer e no longer issues so
ser vice fulfillment (slide 8 ) became simpler

Later , signaling r an on a separ ate SS7 networ k
+ So signaling networ k failur es need to be incor por ated also
 AFAIK, a complete POTS r eliability model was never
satisfactor ily car r ied to conclusion


Used “r epr esentative connections” appr oach instead
Gener alized to histogr am of connection types
Roundtable
11 May 2015
Slide 15
VOICE TELEPHONY
LL TOLL HIERARCHY
⋅
⋅
⋅
etc.
Roundtable
11 May 2015
Slide 16
VOICE TELEPHONY
EXAMPLE
VT can also be pr ovided on a TCP/ IP
networ k
Then it is called “VoIP” - but it is still a voice
telephony ser vice
Ser vice r eliability r equir ements ar e the
same!
Accessibility ≥ 0 .9 9 9 9 9
 Continuity ≤ 2 5 0 DPM
 Fulfillment?
 Release again negligible

Roundtable
11 May 2015
Slide 17
VOICE TELEPHONY
EXAMPLE
W hat kind of TCP/ IP networ k model do you
need to extr act these voice telephony
ser vice r eliability descr iptor s?
“Repr esentative connections” makes no
sense
Simulation models hold pr omise

The gov’t communication folks use these
Need to gr apple with r outer and tr anspor t
systems r eliability/ capacity cur ves
Roundtable
11 May 2015
Slide 18
INTERNET ACCESS
EXAMPLE
The ser vice is the simple ability to connect
to the inter net
Ser vice accessibility is the pr obability that
you can br ing up your home page when you
want

Requir ement? Any page?
Ser vice continuity is the pr obability that your
br owsing session will be inter r upted by loss
of inter net connectivity

Requir ement?
Roundtable
11 May 2015
Slide 19
INTERNET ACCESS
EXAMPLE
Ser vice fulfillment is the pr obability that
per ceptual aspects (delays, video quality,
etc.) of the exper ience ar e “satisfactor y”

Requir ements?
Ser vice r elease is the pr obability that the
inter net connection goes away when you
dismiss it


M aybe not as simple as it used to be because
malwar e continually intr oduces new wr inkles
Requir ements?
Roundtable
11 May 2015
Slide 20
INTERNET ACCESS
EXAMPLE
 Catalog accessibility, continuity, and r elease failur e
modes
 Catalog associated failur e mechanisms and failur e
causes in the TCP/ IP networ k
 One of the r easons for inconclusive discussions
about inter net access ser vice r eliability is that not
ever yone agr ees on the language


Telephone people
IT people
 Standar dization can help her e
Roundtable
11 May 2015
Slide 21
INTERNET ACCESS
EXAMPLE
Reliability models for TCP/ IP networ ks ar e
consider ably mor e complicated
Analytical appr oaches via limit theor ems for
connectionless networ ks with unr eliable
elements
Simulation appr oaches via OpNET, OmNET,
etc.
W hatever model is used, it needs to be
focused on accessibility, continuity, and
r elease at the ser vice level
Roundtable
11 May 2015
Slide 22
CONSEQUENCES OF
INADEQUATE SERVICE
RELIABILITY ENGINEERING
Over pr ovisioning the SDI

Excess CAPEX
Under pr ovisioning the SDI

M or e ser vice failur es than desir able
+ Excess congestion
Failur es in networ k elements make the
networ k look under pr ovisioned for the per iod
of time the outages per sist
Roundtable
11 May 2015
Slide 23
SERVICE RELIABILITY
ECOSYSTEM DIAGRAM
Start
Here
SERVICE
CUSTOMER
NEEDS/DESIRES
SERVICE
RELIABILITY
REQUIREMENTS
MARKETING
ADVERTISING
Roundtable
11 May 2015
SDI
RELIABILITY
MODEL
SDI ELEMENT
RELIABILITY
REQUIREMENTS
EQUIPMENT
SUPPLIERS
SLAs
Slide 24
SoME BENEFITS OF
STANDARDIZATION
 Pr omote the idea of focusing on the ser vice fir st



Not ever y ser vice pr ovider need offer the same ser vice
r eliability
A ser vice pr ovider can offer differ ent gr ades of ser vice
r eliability
Customer s can make compar isons, analyze SLAs, etc.
 Pr omote a common language acr oss the var ious
stakeholder communities
 Abstr act the ser vice r eliability r equir ements fr om
the SDI element r eliability r equir ements

Rational appr oach to SDI r eliability r equir ements
Roundtable
11 May 2015
Slide 25
Some BENEFITS OF
STANDARDIZATION
Use the ser vice r eliability ecosystem to
establish a pr ocess-based appr oach to SDI
design and pr ovisioning
A clear path for war d for the har d technical
wor k of devising r eliability r equir ements for
SDN/ NFV networ ks and their elements
The next gener ation of telecom engineer s
won’t have to r einvent this wheel

Some “new” “better ” technology will come along
to succeed SDN/ NFV
Roundtable
11 May 2015
Slide 26

THE SERVICE RELIABILITY ECOSYSTEM

Transcription

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