E E 681 - Module 10 © Wayne D. Grover 2002, 2003 1 Introductory Briefing on RingBuilder™ Research prototype ring-network design system developed 1997-2001

E E 681 - Module 10 © Wayne D. Grover 2002, 2003 1

Introductory Briefing on RingBuilder™

Research prototype ring-network design system developed 1997-2001 at TRLabs

byW. D. Grover,

D. Morley, (PhD candidate) J. Slevinsky, (Telus Industrial rep., MSc candidate)

M. Jeremiah (U of A coop student)J. Hopkins, Nortel (lead user / advisor)

W. D. Grover

TRLabs & University of Alberta© Wayne D. Grover 2002, 2003

E E 681 - Module 10


Multi-Ring Network Design Problem(RingBuilder view)

RingBuilder(or any other

design method )

RingBuilder(or any other

design method )

Given• Network topology• Demand pattern• Ring technologies• Cost models

~ Min-cost Design• Ring System decisions

Type OC-n size Topological layout Glass-through locations

• Routing plan

Ring assignment Inter-ring transit locations

Subject to:

• All demands served• Ring capacity constraints• Max. ADMs per ring• Limited Inter-ring transit locations• Partial add/drop constraints• ( Matched-nodes requirements, etc.)


RingBuilder....

• RingBuilder has a high degree of “fidelity” (realism in modeling the actual problem in all its details) but is a sub-optimal (heuristic-based) design system.

• Output designs are fully specified, feasible to construct directly.

•Based on a central “greedy” hypothesis: - that a good network design is comprised of good individual rings

- that a complete network design can be developed by choosing “good” rings one after another until all demands are served.

• As RingBuilder developed, it includes an increasing number of tactics to “overcome” this greediness in terms of solution quality, while retaining the basic iterative - synthesis framework.


RingBuilder....(ver. 3) •Basic Method:

- Phase 1 pre-processing steps (i) Candidate Generation: Depth-first search algorithm used to enumerate all distinct simple cycles. (ii) Demand Routing:

Route point-to-point demands via shortest path over basic graph topology. Split flows over equal shortest routes if they exist.

- Phase 2 Iterative Design synthesis (i) Solve loading problem for each distinct cycle in each ring technology in current environment of un-served demand segments. (optimal or heuristic). (ii) Choose and place ring candidate with highest measure of transport utility, (iii) Demand packing: exploit the rings just (or so far) placed to convey any un-served demand segments. (iv) Update un-served segments of remaining routes. - Phase 3 (optional) Improvement heuristics or repeat Phase 2 with random variation


… (428 cycles in total)

20 nodes, 31 spans

• Phase 1: Candidate Generation– Each combination of network cycle and ring technology (i.e., ring

type and line rate) represents a ring candidate.

RingBuilder....Design Methodolgy

Example:


• Phase 1: Initial Demand Routing– Point-to-point demands are routed across the network topology

before any rings are placed using shortest path algorithm (min-hop or min-distance).


Example:

1

42

5

3

6

Node 1 2 3 4 5 6

1 - 0 0 0 8 02 - 5 3 4 23 - 0 0 04 - 6 15 - 0

Min-hop routing Possible min-distance (cost)routing may differ

1

42

5

3

6

Point-to-point demand matrix

need: algorithms for shortest path routing (Dijkstra)


• Phase 2: Candidate Ring Loading (heuristic method)– Where the route of a demand flow intersects a ring candidate the relevant

demand segments are loaded onto each candidate ring in decreasing order of length served (or capture achieved) until

all segments are loaded or capacity is exhausted.


Example (by segment length priority):

Working capacity

Spare (unused)

Protection capacityADM

Glass-through

Node

Self-healing Ring

2nd demand loaded

3rd demand loaded4th & 5th demands loaded

1st demand loaded


• Phase 3: Ring Selection (and placement).


, , ,ˆ ˆ, : ( )

,

"transport efficiency of ring candidate , "

such that ( )

cost of ADMs, fibers, regens, add/drop IFsj j

i j m i m ii m s s i

j k

j k

l d d k s

R R

Z

where :

is a distinct simple cycle of the network graph

is a specific ring technology being considered (capacity is ( ))

ˆ is the set of all route-segments that have an intersection with cyj

j

k kZ

R

,

,

cle .

ˆ is an individual route-segment in set

is the length (distance or hops) of the intersection of route-segment

and cycle .

is an amount of un-served demand for orig

j

i j

m i

j

i

l i

j

d

R

in-destination pair routed

partly or entirely over route segment

m

i

max feasible loading

total detailed cost ofconstructing the correspondingring of type k on cycle j.

i.e.,

Note that choice of demand segments in numerator,

determines wherethe glass-through nodes

are and all low-speed add / drop circuit pack costs

that are incurred


RingBuilder....Simple example (1)

Point-to-point demand matrix

1

32

4 5 6

Node 1 2 3 4 5 6

1 - 0 2 4 1 02 - 10 5 0 33 - 2 3 14 - 10 75 - 1

Network Topology1

32

4 5 6

5 2

11

17

4 4

11

12

Min-Hop Demand Routing

• This example based on assuming

4 fiber OC-12 or 2 fiber OC-24 rings

• Ring selection based on:

min( ,12) covered by the ring

12 (no. of spans on ring)iw

revised Oct 24, 2000



1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

Cycle Finding

1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

Ring Loading1st Iteration

12 4 11 min(17,12) 110.833

5 12

1

32

4 5 6

5 2

11

17

4 4

11

12

*Assume BLSR/4 OC-12

Ring #1




Remove covered route segments

1

32

4 5 6

11/12

12/12

4/12

11/12

12/12

1

32

4 5 6

5 2

0

5

4 0

0

0

Remaining un-served demand segmentsRing #1

1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

4 50.25

3 12

1

32

4 5 6

5 2

0

5

4 0

0

0

Ring #2

Ring Loading2nd Iteration





1

32

4 5 6

0/0

5/12

1

32

4 5 6

5 2

0

0

0 0

0

0


1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

1

32

4 5 6

5 2

0

0

0 0

0

0

4/12

Ring Loading3rd Iteration

5 20.19

3 12

Ring #3





1

32

4 5 6

5/12 2/12

1

32

4 5 6

0 0

0

0

0 0

0

0


0/12

1

32

4 5 6

11/11

12/12

4/12

11/12

12/12

1

32

4 5 6

5/12 2/12

0/12

1

32

4 5 6

0/12

5/12

4/12

Final Ring-cover Network Design (and resultant loadings)


RingBuilder .... Main User Interface


RingBuilder .... “Advisor” Mode


Summary: State of the art and Research Directions in Multi-Ring Network Design

SolutionQuality

Model Accuracy

Eulerian Ring Covers(Gardner et al., ‘94).

Ring Coverage IP(Kennington, ‘97).

RingBuilder™ (Slevinsky,Grover, ‘93)

Net-Solver (Gardner et al., ‘95)

Simulated Annealing(Roberts, ‘94).

Hierarchical Rings (Shi,Fonseka, ‘96).

Strategic Options (Wasem,Wu ‘91)

Researc

h Goals

RingBuilder™ (Slevinsky,Grover, ‘95)

Capacitated Multi-technology Multi-period • Probabilistic• Topology


Other approaches to Multi-Ring Network Design

•Preliminary: Concept of “ideal” or “topological” rings

• An idealized or purely topological ring has architectural properties or other figures of merit relative to some problem, but is not modularlike a real ring and in fact has no assumed capacity limit.

Examples: idealized ring may still have attributes of:

- spans covered

- working capacity balance

- capture efficiency

- total mileage

Purpose is usually to permit problem simplification while still identifying high merit (low redundancy) ring-layouts or efficient span cover solutions, etc.


Other approaches: RingBuilder versions 1, 2 • ver 1. sought to minimize redundancy of an ideal ring span cover of the graph

• demands are shortest-path routed beforehand, cycle set enumerated beforehand

• greedy-iterative buildup of a ring cover based on choosing ring with best balance efficiency at each iteration.

• ver. 2, also assessed each ring candidate for demand capture efficiency- balance and capture efficiency measures were ‘blended’ into a single combined figure of merit.

- expressions for balance & capture efficiency are those already given.

- ver 2. also extended into modular ring case:

- loading algorithms would select demands to try to maximize balance or capture

- hypothesis was that a cost-optimal design had to represent the best trade-off of capture versus balance effects.

- hence tactic of a “sweep” of alpha from 0 to 1 to identify a near min cost design

- select rings on bal-capture merit, but measure design by detailed costing including glass-through details etc.

(1 )bal cap bal cap


Other approaches:

• results show hypothesis is basically sound, but overall method had following drawbacks :

- inherently a “single technology” design approach

- alpha sweep onerous, and only a surrogate-based search for cost minimum

BalanceCapture0.00 0.25 0.50 0.75 1.00

1400

1800

2200

2600

3000

1.5

2.0

2.5

3.0

3.5

Transitions

Redundancy

Tota

l Tra

nsiti

ons,

T

Net

wor

k R

edun

danc

y, r

RingBuilder version 2

actual designcost

low alpha min-cost for metro

high alpha min-cost for metro


Pure“Balance-optimized” Design

= 1.0Total transitions = 2970Avg. balance efficiency = 0.47

Example from RingBuilder 2:

9 rings



Pure“Capture-optimized” Design


11 rings



Compromise Designnear min cost foundempirically at ~0.4


fewest rings of all:

8 rings

Documents

E E 681 - Module 10 © Wayne D. Grover 2002, 2003 1 Introductory Briefing on RingBuilder™ Research prototype ring-network design system developed 1997-2001