E E 681 — Lecture 1 Kick-off Lecture

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 E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 2

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/ E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 3

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 E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 4

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 E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 5

Concept of a “transport network” End-users Service layer Logical layer system Physical layer geographical E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 6

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. E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 7

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. E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 8

Concept of a “transport network” End-users Service layer Logical layer Physical layer E E 681 Lecture #1 system geographical © Wayne D. Grover 2002, 2003 9

“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 E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 10

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. . per regen. section), – protection switching time (e. g. , ~ 50 ms) E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 11

“Logical” (capacity management) level • “node”: – digital (Sonet) and / or optical (wavelength) cross-connects • generic “link” resource: – standardized logical bandwidth units such as DS 1, DS 3, 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 ? ) E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 12

Concept of logical capacity management E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 13

Access Metro and Longhaul transport E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 14

“Service” level • “node”: – routers / packet switches, circuit-switches, ATM switches, DS 1/0 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 E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 15

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. E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 16

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 Qo. S 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. E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 17

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. E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 18

Each layer has a native form of “demand units” that are aggregated into capacity units of the next lower layer End-users Erlangs, packets, private lines, VCs 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 E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 #s of cables, ducts, transponders, spectral allocations 19

Example of how various services map into transport “demands” Type Bandwidth PL-DS 1 0. 036 IP-OC 12 1. 528 PL-DS 3 1. 0 IP-OC 48 6. 112 PL-OC 3 3. 0 IP-100 T 0. 283 PL-OC 12 12. 0 IP-GIGE 2. 830 PL-OC 48 48. 0 WL-2. 5 MUX 96. 000 IP-DS 1 0. 005 WL_10 192. 000 IP-DS 3 0. 127 SS 1. 000 IP-OC 3 0. 382 Typical service types and corresponding STS 1 bandwidth requirements for the transport network E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 20

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. , STS 1, STS 3, DS 3, etc. • • Path: a concatenation of crossconnected links forming a unitcapacity digital connection between its end points • Route: set of span designations that are contiguous on the physical graph • Pathset: set of link-disjoint paths sharing the same end-nodes • 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 Span: set of all (working and spare) links between nodes that are adjacent in the physical graph E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 21

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. • • 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 simple graph: a network graph where there is at most one edge between adjacent nodes E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 22

Example: use of terms route, span, path, link. . . • Span AZ has lost 35 working links • The restoration pathset is comprised of routes ABCZ, ABDECZ, 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% E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 23

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. E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 24

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. E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 25

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. E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 26

Basic approaches to restoration or… “the whole course in 2 slides” • • – 1+1 – 1: N • rings – UPSR: unidirectional path switched rings – BLSR: bi-directional lineswitched rings • p-cycles • APS systems ring-mesh hybrids – based on access / core principles – based on forcer clipping principle mesh – span - restorable – path - restorable • shared 1: 1 backup path protection E E 681 Lecture #1 © Wayne D. Grover 2002, 2003 27