Transcript RingBuilder™ Evolution: New Capabilities, Tech Transfers

E E 681 - Lecture 1
Kick-off Lecture: Introduction to
Survivable Transport Networks
Wayne D. Grover
TRLabs & University of Alberta
© Wayne D. Grover 2002, 2003
(version for book website)
Outline
• Intro to author: Dr. Wayne Grover
• Educational Objective of course
• Walk-through of course outline and logistics
• Importance and impact of outages - reading assignment
• Concept of a “transport network”
• Restorability, redundancy,
• Reliability and availability
• Relationship of restorability to availability
• First look at all architectures for restoration
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The author: Dr. Wayne Grover
• B.Sc. - Carleton U, Ottawa
• M.Sc. - U. Essex, U.K.
• 10 years BNR (Nortel Networks) Research & Development
• In start-up of TRLabs consortium, 1986 (Founding VP Research)
• Ph.D. - U. Alberta (‘89) - “Self-healing Networks”
• Research and management roles at TRLabs, 1986- present
• 1992 on Faculty U of Alberta (ECE)
• 2001-2002 NSERC E.W.R Steacie Fellow
• 2002 IEEE Fellow
• web site: http://www.ee.ualberta.ca/~grover/
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E E 681: Educational Objective
• Graduates of E E 681 will have a basic preparation and
awareness of current and emerging transport networking
alternatives, mechanisms, issues, and design theory,
enabling them to continue in:
– research: will be equipped to pursue a thesis project and participate
in ongoing graduate research in these areas
– R&D: will be able to contribute to transport networking equipment
design and product strategies
– operations: will be able to contribute to network planning and
network evolution strategy
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E E 681 : Some specific key objectives
• Graduates of EE 681 will understand the following systemlevel technology, networking concepts, design and
operational issues :
– APS systems, ring-based networking, mesh-restorable networks,
ATM backup-VP networks, design theory for ring, mesh and ATM
networks,
– rudimentary availability analysis of survivable networks,
– distributed mesh restoration and self-organizational principles in
mesh networking
– appreciation of recent research topics such as p-cycles, hybrid
networks, ring-to-mesh evolution, others
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Concept of a “transport network”
SITE i traffic sources to: SITE j
Telephony:
500 DS1s
Internet:
5 STS3c
End-users
ATM:
5 STS3c
Video:
8 DS3s
(18)
(30)
(15)
(8)
M
U
L
T
I
P
L
E
X
Bulk
equivalent= 76
STS-1s
Private networks:
100 DS1
Service layer
(5)
Frame-relay
services:
36 DS1
SERVICES
TRANSPORT
di,j = 76
Logical layer
system
Physical layer
geographical
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Concept of a “transport network”
• Voice-band switching, Internet, private lines, corporate
networks, ATM networks, etc. are all ‘virtual’, logical
abstractions implemented within the transport network.
• The transport network sits “just above” the physical
transmission systems in a layering sense.
• Individual switched connections, leased lines, pipes
between IP routers, etc. do not “make their own way
directly” over the fiber systems..
• Rather, traffic of all sorts is “groomed” to fill standard rate
“containers” created in the transport network.
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Concept of a “transport network” (2)
• “grooming” at or near clusters of sources (the edge or
access network) tries to efficiently fill these containers so
they won’t need to be opened again (i.e., processed at a call,
cell or packet level), until at or near their destinations.
• Transport network thus sees a composite “demand pattern”
(in STS-n units typically) that is the resultant totals of pointto-point container requirements arising from all client
network / service layer requirements, e.g., trunk groups, IP
pipes, leased lines, private networks, etc.
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Concept of a “transport network”
End-users
Service layer
Logical layer
Physical layer
system
geographical
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“Geographical” or facility routes level
• “node”:
– buildings, equipment huts, man-holes, (co-location space)
• generic “link” resource:
– conduits, rights-of-way, leased lambda(s)
• main survivability principles:
– spatial / physical diversity and high connectivity
• “performance” measure:
– network average nodal degree, miles of duct, buried, aerial
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Transmission “System” level
• “node”:
– transmission termination and multiplex equipment
• generic “link” resource:
– fibers, wavelengths, radio, copper, coax, satellite
• main survivability principles:
– 1+1 or 1:N protection-switching for high system availability
• “performance” measure:
– system availability (e,g. 99.99.. per regen. section),
– protection switching time (e.g., ~ 50 ms)
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“Logical” (capacity management) level
• “node”:
– digital (Sonet) and / or optical (wavelength) cross-connects
• generic “link” resource:
– standardized logical bandwidth units such as DS1, DS3, STS-n,
ATM VP, wavelengths, wavebands
• main survivability principles:
– ring, mesh, backup-VP or p-cycle based real-time restoration rerouting.
• “performance” measures:
–
–
–
–
–
restorability (of spans, nodes)
restoration time (e.g., 150 ms - 2 sec)
end-to-end path availability (e.g., 99.996 on 4,000 km HRDP)
best efforts and / or assured restoration classes
path provisioning time (seconds or days ?)
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Concept of logical capacity management
K
B
C
D
A
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Access Metro and Longhaul transport
Partitioned view of a transport network.
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“Service” level
• “node”:
– routers / packet switches, circuit-switches, ATM switches, DS1/0
private networking devices
• generic “link” resource:
– IP “pipes”, ATM VCs, trunk groups, private line circuits
• main survivability principles:
– routing table updates, dynamic routing, dual homing, limits to switch
size, “they’ll dial again”.
• “performance” measure(s):
– cell or packet loss probabilities / denial of service
– call blocking, voice echo-delay
– call set-up / dial-tone delays - packet jitter, delay time variance
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Concept of a “transport network” (3)
• Airline inter-hub analogy:
– a business person from Billings, Montana needs to fly to Kyoto,
Japan.
– A regional “commuter” jet brings him/her to Denver.
– at Denver, people from all over the region, board a well-filled 747
non-stop to Tokyo
– from Tokyo, a regional jet takes him/her to Kyoto
• The pattern is: access - transport - access
• An STS-n, or soon, a DWDM wavelength, is the “747”
• multiplexing and grooming in the access (switches, routers,
ATM service nodes) are the regional airlines.
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Concept of a “transport network” (4)
• This is why fully router-based “IP over light” (just as prior
“ATM on glass”) is improbable when the short-term hype is
replaced by longer term performance, complexity, cost,
maintenance and operational assessments.
• The single biggest factor in IP QoS in particular is the
average number of router hops in a ‘connection’...
• All other transport industries find an optimum combination
of access grooming/muxing and backbone transport; pure
“IP over light” implies unpacking and reloading the moving
van in every city en-route.
• Or, “would you move a house brick by brick?”
• More likely structure is to stat mux and groom in one or two
access stages, then launch into near mesh of nonstochastic high OCn or ?-based transport paths.
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Concept of a “transport network” (5)
• Another layering view:
ATM (VC)
ATM (VP)
SONET
DWDM
IP
fiber
• For various applications, DWDM, SONET, ATM, even IP (with
extensions), can all act as a transport network to higher
layers.
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Each layer has a native form of “demand units” that are
aggregated into capacity units of the next lower layer
Erlangs, packets, private lines, VCs
End-users
Service layer
#s of: DS-0, DS-1, VPs, STS-n(PL), STSn(IP)
Logical layer
#s of: OC-48, OC-192, wavelengths
“the transport
network”
system
Physical layer
#s of fibers, wavelength regens, add-drop
geographical
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#s of cables, ducts, transponders,
spectral allocations
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Example of how various services map into transport “demands”
Type
Bandwidth
Type
Bandwidth
PL-DS1
0.036
IP-OC12
1.528
PL-DS3
1.0
IP-OC48
6.112
PL-OC3
3.0
IP-100T0.283
PL-OC12
12.0
IP-GIGE
2.830
PL-OC48
48.0
WL-2.5MUX
96.000
IP-DS1
0.005
WL_10
192.000
IP-DS3
0.127
SS
1.000
IP-OC3
0.382
Typical service types and corresponding STS1 bandwidth requirements for the transport network
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some terminology (1)
•
DCS: digital cross-connect
system
•
ADM: add/drop multiplexer
•
Link (or “channel”): single unit
of bandwidth at the respective
level of transport management,
e.g., STS1, STS3, DS3, etc.
•
•
Path: a concatenation of crossconnected links forming a unitcapacity digital connection
between its end points
Span: set of all (working and
spare) links between nodes that
are adjacent in the physical
graph
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Route: set of span designations
that are contiguous on the
physical graph
•
Pathset: set of link-disjoint
paths sharing the same endnodes
•
Working link (or “worker”):
link that is in-service, as part of
a traffic-bearing ‘working path’.
•
spare link (or “spare”):
equipped but idle link available
for restoration
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some terminology (2)
•
Reserve network: the
capacitated graph formed from
the set of all spare links
•
Adjacent: nodes directly
connected by a 1-hop route in
the physical graph.
•
Logically adjacent: nodes
directly connected by an edge in
the transport graph.
•
simple graph: a network graph
where there is at most one edge
between adjacent nodes
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Multi-graph: a network graph
where there can be many links
in parallel between adjacent
nodes
•
Capacitated graph: a graph
where all edges have a finite
capacity
© Wayne D. Grover 2002, 2003
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Example: use of terms route, span, path, link...
• Span AZ has lost 35
working links
• The restoration pathset is
comprised of routes ABCZ,
ABDEZ, ABDECZ,
AFZ,AFGZ,AFGHZ
• The route ABDEZ supports
5 restoration paths
• 20 spare links on span AB
are used in the restoration
pathset
• The restorability of span AZ
is (20+15)/35 = 100%
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Additional initial concepts / terms *
• Restorability: the fraction of working demand flows affected
by a failure that are restored or for which a restoration path
set solution is feasible.
• Redundancy: the ratio of spare capacity required in a
network to meet restorability goals to working capacity
required only to route demands without survivability
concerns.
* we will return to all these concepts in greater depth. The aim today is just to create an
initial orientation.
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Additional initial concepts / terms
• Reliability: the probability that a system operates without a
service-affecting failure for a given amount of time. R(t) can
be thought of as the probability distribution function of timeto-first-failure from a known-good starting state.
• Availability: the probability that a continuously operating
system undergoing repair after each failure is found in the
“up” state at any random time in the future.
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Relationship of restorability to availability
• Does a “fully restorable” network have 100% availability ?
– No. If the network restorability design is for 100% restorability to all
n-failure scenarios, “(n+1) failure” scenarios may be outage-causing.
– In practice commercial / public networks used to have n = 0 (in the
sense that no cable cuts would be 100% restorable). In which case
addition of redundancy to get to n=1 (full restorability against any
single cable cut) gives a massive boost in availability.
– But availability does not reach unity because then dual failure
scenarios can then cause outage.
– --> leads to usual economic practice of : design for 100% singlefailure restorability, and analyze for the dual failure (un)availability.
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Basic approaches to restoration or…
“the whole course in 2 slides”
•
APS systems
– 1+1
– 1:1
– 1:N
•
rings
–
UPSR: unidirectional path
switched rings
– BLSR: bi-directional lineswitched rings
•
•
p-cycles
•
ring-mesh hybrids
– based on access / core
principles
– based on forcer clipping
principle
mesh
– span - restorable
– path - restorable
•
shared 1:1 backup path
protection
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