Framework for GMPLS and PCE Control of Wavelength Switched Optical Networks (WSON)

Analysis of Signaling in GMPLS-Based WSONs: Distributed Wavelength Assignment in

Bidirectional Lightpath Provisioning

Sugang Xu and Hiroaki Harai

Photonic Network Research Institute

National Institite of Information and Communications Technology

WTC2012 Miyazaki 1

National Institute of Information and Communications Technology

Outlines

Introduction

Requirement for enhancing distributed wavelength assignment (WA) support with signaling

Performance measures and selected Findings

Some constraints in consideration

Candidates of distributed WA approaches

Numerical results

Summary

WTC2012 Miyazaki 2


Introduction Lightpath services in wavelength switched optical network (WSON)

Unidirectional lightpath

Bi-directional lightpath

Current topics in IETF: extensions of GMPLS for better WSON support

Focus of this talk:

Efficient Signaling support for distributed wavelength assignment (WA) in the GMPLS-based control plane of WSON

Co-routed bi-directional LSP provisioning support, per RFC 3945, RFC 3473

Is the current standard RSVP-TE per RFC 3473 enough?

What perspective can be improved further?

Any other cost-efficient signaling schemes?

Conduct protocol analysis and share

the findings

Out of the scope of this talk (other perspectives)

Physical impairment concern

3R concern

Wavelength conversion concern

WTC2012 Miyazaki

3

Edge Edge Control Plane

OXC

Transit

x

y

Date Plane

OXC: optical cross connect Co-routed bidirectional lightpath

WSON


Architectures for Co-Routed Bi-directional Lightpath Provisioning

Three phases in R&WA and R+WA architectures

Routing (or NMS) collects the up-to-date wavelength availability information

PCE, or C-SPF performs RWA calculation

A simple signaling performs the wavelength allocation which is specified by RWA optimization

WTC2012 Miyazaki 4

Current standard RSVP-TE is applicable in R&WA, R+WA modes (Single RWA solution: specify one wavelength in the Upstream Label obj, per RFC 3471, RFC 3473)

Architecture Categories: 1. Combined RWA (R&WA) computation + Signaling 2. Separated RWA (R+WA) computation + Signaling 3. Routing + Signaling-based distributed wavelength assignment (R+DWA)

cf) RFC 6163

R&WA, R+WA Wavelength assignment is strictly dependent on up-to-date network Info

TED

GMPLS GMPLS

Wavelength availability info (by NMS or routing)

Specify RWA for signaling

GMPLS


R&WA and R+WA WSONs Also Needs Robust Distributed WA Support with Signaling

Needs robust Distributed WA support with Signaling (not highly relying on up-to-date info)

WTC2012 Miyazaki 5

RSVP-TE only supports single RWA solution specification

feasible WA solution highly depends on the up-to-date info

acquiring the up-to-date info leads to the increased information dissemination, resulting in heavy load in control plane

Restrict the scalability of WSON

Limit the possibility for dynamic lightpath service in WSON

Already standardized novel DWA mechanisms in RFC 3471, 3473 Unidirectional lightpath

Label Set obj CAN convey the multiple wavelengths (labels) assignment solutions in the downstream direction (Increasing the possibility of successful lightpath provisioning)

Bidirectional lightpath with Upstream Label (UL) ? Upstream Label obj conveys only one specified wavelength in the upstream direction Acceptable Label Set conveys the available wavelengths in case the upstream label in

the Upstream Label obj is blocked Relies on crank-back (a second time signaling)

Any other possibilities to provide more cost-efficient bidirectional lightpath provisioning?

R&WA, R+WA Wavelength assignment is strictly dependent on up-to-date network Info

TED

GMPLS GMPLS

Wavelength availability info (by NMS or routing)

Specify RWA for signaling

GMPLS


Performance Measures and Selected Findings Highlight

What measures do we use in signaling evaluation?

Blocking performance (efficiency measure)

Single lightpath

Multiple lightpaths Restoration

Number of the successfully re-established lightpaths by signaling (with evenly distributed re-routing)

Long-term view of performance potential (future-proof signaling solution)

Upgrade WSON with more wavelengths, fibers

Protocol cost (cost measure)

Total number of traversed Hops in one set of signaling

Accumulated label-processing times

WTC2012 Miyazaki 6

UL(1st) ULS/LS/TU(1st)

UL(2nd) ULS/LS/TU(2nd)

# of affected paths

p

0 0.2 0.4 0.6 0.8 1

0

5

10

15

20

25

UL(2nd)F1 UL(2nd)F6

ULS/LS/TU(2nd)pF1 ULS/LS/TU(2nd)F6

Pbwave(2nd)F1 Pbwave(2nd)F6

W

20 40 60 80 100 120

Blo

ck

ing

pr

ob

ab

ilit

y

10- 6

10- 5

10- 4

10- 3

10- 2

10- 1

100

Current standards gain

F=1

F=6

Remarkable gain of extensions

Significant improvement brought by extensions of the current standard 1st and 2nd time signaling

After restoration

After upgrading

High utilization rate p=0.8

Utilization rate

F=1

# of Restored

Blocking

# of Wavelengths


Constraint Concerns in Protocol Behavior Analysis

CI-Incapable

Co-routed bi-directional lightpath

Is it necessary to use the same wavelength in both directions?

Yes. Either initiator or terminator are the colored edge

(with the port/wavelength restriction at edges)

No. Both initiator and terminator are the colorless edge

WTC2012 Miyazaki 7

Terminator

Initiator Colored edge Colorless edge

Colored edge Same wavelength use Same wavelength use

Colorless edge Same wavelength use Different wavelengths use

1

1 1

2

Scenarios and corresponding Signaling candidate schemes Same wavelength use scenario

UL, ULS, TU, LS Different wavelengths use scenario

UL, ULS, TU


Upstream Label Approach (UL) RFC 3473 s Behavior - Needs 2nd Time Signaling (Crank-back) (Same Wavelength Use)

WTC2012 Miyazaki 8

Blocking situations in UL (1st time signaling) Forward blocking A: The specified upstream label has been occupied by other lightpath B: The specified upstream label is not appeared in final Label Set (cannot use the same wavelength) C: Initiator receives an empty Acceptable Label Set, indicating that no wavelength is available along this path, resulting in rerouting

a b c

Label Set

Path Upstream Label

Label Set

Upstream Label

Path

PathErr PathErr

Acceptable Label Set Acceptable Label Set

Label Set

Upstream Label

Label Set

Upstream Label

Label Label

1st time signaling

A

B

D, E

C

Backward blocking D: Upstream label is successfully reserved in the upstream direction, and is in Label Set (available in downstream), however, the label is firstly reserved by other concurrent competitive lightpath request. This label happens to be the last available wavelength. No support in RSVP-TE per RFC 3473 can indicate this situation, resulting in useless crank-back E: Similar to D, but there still are other available wavelengths

PA

PB

PA~PE: Probabilities of individual cases PA+PB+PC+PD+PE=P P: total blocking probability PC

PD, PE

Different blocking situations in 1st time signaling result in different blocking probability in 2nd time signaling


Upstream Label Approach (UL) RFC 3473 s Behavior - Needs 2nd Time Signaling (Crank-back) (Diff Wavelength User)

WTC2012 Miyazaki 9

Blocking situations in UL (1st time signaling) Forward blocking A: The specified upstream label has been occupied by other lightpath B: Initiator receives an empty Acceptable Label Set, indicating that no wavelength is available along this path, resulting in rerouting

a b c

Label Set

Path Upstream Label

Label Set

Upstream Label

Path

PathErr PathErr

Acceptable Label Set Acceptable Label Set

Label Set

Upstream Label

Label Set

Upstream Label

Label Label

1st time signaling

A

C, D

B

Backward blocking C: upstream label is successfully reserved in the upstream direction, and Label Set (available in downstream) is not empty, however, the label (downstream) is firstly reserved by other concurrent competitive lightpath request This label happens to be the last available wavelength (a rare case) D: Similar to C, but there still are other available wavelengths

PA

PB

PA~PD: Probabilities of individual cases PA+PB+PC+PD=P

PC

PD, PE



Upstream Label Set Approach (ULS)s Behavior (Same Wavelength Use) cf) E. Oki et al., vol.E87-B, no.6, June 2004.

WTC2012 Miyazaki 10

Blocking situations in ULS (1st time signaling) Forward blocking A: There is not any common wavelength in Upstream Label Set and Label Set at terminator. This includes the situation which either Label Set obj is empty during the Path message processing

Backward blocking B: Upstream label (upstream) or label (downstream) is firstly reserved by other concurrent competitive lightpath request. This label happens to be the last available wavelength (a rare case) C: Similar to B, but there still are other available wavelengths

a b c

Label Set

Path

Upstream Label Set

Label Set

Upstream Label Set

Path

Resv Resv

Label Label

Upstream Label

Upstream Label Upstream Label

1st time signaling

B, C

A

PA~PC: Probabilities of individual cases PA+PB+PC=P

PA

PB, PC

We can extend ULS by adding a new object to inform the initiator the number of available wavelengths. Initiator can correctly decide if a new route should be employed, in case no wavelength is available.



Upstream Label Set Approach (ULS)s Behavior (Diff Wavelength Use) cf) E. Oki et al., vol.E87-B, no.6, June 2004.

WTC2012 Miyazaki 11

Blocking situations in ULS (1st time signaling) Forward blocking A: There is not any wavelength in either Upstream Label Set or Label Set

Backward blocking B: Either upstream label (upstream) or label (downstream) is firstly reserved by other concurrent competitive lightpath request. This label happens to be the last available wavelength (a rare case) C: Both upstream label (upstream) and label (downstream) are blocked by other concurrent competitive lightpath request(s), but there are other available wavelengths left to use D: One direction is blocked, the other direction is not blocked, but there are other available wavelength to use

a b c

Label Set

Path

Upstream Label Set

Label Set

Upstream Label Set

Path

Resv Resv

Label Label

Upstream Label

Upstream Label Upstream Label

1st time signaling

A

B, C, D

PA~PD: Probabilities of individual cases PA+PB+PC+PD=P

PA

PB, PC, PD

We can extend ULS by adding a new object to inform the initiator the number of available wavelengths. Initiator can correctly decide if a new route should be tried, in case no wavelength is available.



Two Unidirectional Lightpaths Approach (TU) s Behavior (One set signaling for two directions) Different Implementation Different Performance !!

WTC2012 Miyazaki 12

Because TU is of the most flexibility in implementation, in principle, in both Same Wavelength Use and Different Wavelength Use scenarios, TU may reach the same blocking level as that of ULS

a b c

Label Set

Path

Label Set

Path

Resv Resv

Label Label

Label Set

Label Label

Label Set

Association Association

Bi-dir Flag Bi-dir Flag

Label Set Label Set

Resv Resv

Label Label

Example


Label Set + LSP_ATTRIBUTES Approach (LS)s Behavior (Same Wavelength Use Only)

a b c

Label Set

Path

LSP_ATTRIBUTES

Label Set

LSP_ATTRIBUTES

Path

Resv Resv

Label Label

cf) G. Bernstein et al., draft-ietf-ccamp-wson-signaling-01.txt

WTC2012 Miyazaki 13

A

B, C

PA

PB, PC

1st time signaling

PA~PC: Probabilities of individual cases PA+PB+PC=P

Blocking situations in LS (1st time signaling) Forward blocking A: There is not any wavelength in Label Set

Backward blocking B: Upstream label (upstream) or label (downstream) is firstly reserved by other concurrent competitive lightpath request. This label happens to be the last available wavelength (a rare case) C: Similar to B, but there still are other available wavelengths

We can extend LS by adding a new object to inform the initiator the number of available wavelengths. Initiator can correctly decide if a new route should be tried, in case no wavelength is available.



Network Model

Initiator Terminator H hops

W

For each wavelength i in one fiber - Average utilization rate (the cause of forward blocking): p - Competition rate (the cause of backward blocking): b

W

F pairs of fibers

s d i j

WTC2012 Miyazaki 14

Blocking probability P is the function of p, b, H, F, W. P(p, b, H, F, W)

Exist available disjoined route in case of rerouting

Scenarios

Approaches Same Wavelength Use Different Wavelength Use

1) UL

Upstream Label

+ Acceptable Label Set

2) TU

Associated two uni-LSPs

3) ULS

Upstream Label Set

+ Label Set

4) LS

Label Set

+LSP_ATTRIBUTES

not support

Probabilistic AnalysisBlocking Probability (1st Time Signaling) 2nd Time Signaling (crank-back) Analysis is not shown here, due to time limitation. Please refer to Proc.

H : number of hops W : number of wavelengths F: number of fibers p: wavelength utilization rate per fiber link b: competition rate


Blocking Probabilities after the 1st and 2nd Signaling



Pbwave(1st) Pbwave(2nd)

p

0 0.2 0.4 0.6 0.8 1

Blo

ck

ing

pro

ba

bil

ity

10- 4

10- 3

10- 2

10- 1

100

UL(1st) ULS/TU(1st)

UL(2nd) ULS/TU(2nd)

Pbwave(1st) Pbwave(2nd)

p

0 0.2 0.4 0.6 0.8 1

Blo

ck

ing

pro

ba

bil

ity

10- 4

10- 3

10- 2

10- 1

100

(a) Same-wavelength-use (b) Different-wavelength-use

(F=1, W=64, H=4, b=0.001)

WTC2012 Miyazaki 16

UL UL

ULS/LS/TU ULS/TU


The Signaling Caused Extra Forward Blocking vs. the Number of Hops in UL (after the 2nd signaling)

p0.2 p0.4 p0.6

H2 3 4 5 6 7 8

Sign

alin

g-ca

use

d ex

tra

forw

ard

bloc

king

10- 4

10- 3

10- 2

10- 1

100

p0.2 p0.4 p0.6

H2 3 4 5 6 7 8

Sign

alin

g-ca

used

ext

ra f

orw

ard

bloc

king

10- 4

10- 3

10- 2

10- 1

100


(F=1, W=64, b=0, p=0.2, 0.4 and 0.6)

WTC2012 Miyazaki 17


Blocking Probability in the Restoration Scenarios



# of affected paths

p

0 0.2 0.4 0.6 0.8 1

0

5

10

15

20

25

UL(1st) ULS/TU(1st)

UL(2nd) ULS/TU(2nd)

# of affected paths

p

0 0.2 0.4 0.6 0.8 1

0

10

20

30

40


(F=1, W=64, H=4, b=0.001)

WTC2012 Miyazaki 18

ULS/LS/TU ULS/TU

- ULS/LS/TU can successfully recover most of paths, outperforming UL significantly. - In particular, if recover time needs to be kept short, and reduce the burst control overhead, only 1st time signaling might be preferred.


UL(2nd)F1 UL(2nd)F6

ULS/TU(2nd)pF1 ULS/TU(2nd)F6


W

20 40 60 80 100 120

Blo

ck

ing

pro

ba

bil

ity

10- 6

10- 5

10- 4

10- 3

10- 2

10- 1

100

Blocking Probability in the Upgrade Scenarios


(H=4, p=0.8, b=0.001, F=1 and 6)

WTC2012 Miyazaki 19

-UL cannot effectively take advantage of expended resource (fiber/wavelength)

-Even p=0.8, multifiber WSON has the perfect performance (if ULS/LS/TU is employed)

ULs gain, F=1 ~6

All, F=1

F=6

Remarkable gain of ULS/TUs upgrading to F6, p=0.8

UL(2nd)F1 UL(2nd)F6

ULS/LS/TU(2nd)pF1 ULS/LS/TU(2nd)F6


W

20 40 60 80 100 120

Blo

ck

ing

pro

ba

bil

ity

10- 6

10- 5

10- 4

10- 3

10- 2

10- 1

100

ULs gain, F=1 ~6

All, F=1

F=6

Remarkable gain of ULS/LS/TUs upgrading to F6


Protocol Cost Issue-1: Total Number of Traversed Hops in One Set of Signaling

ULS LS TU

Same-wave-use 3H 3H 11H

Different-wave-use 3H N/A 9H

WTC2012 Miyazaki 20

Cost of TU is implementation dependent


Protocol Cost Issue-2: Accumulated Label-processing Times for ULS and LS (Same Wavelength Use)

ULS-H4 LS-H4 ULS-H8 LS-H8

p

0 0.2 0.4 0.6 0.8 1

Lfo

re

0

200

400

600

800

1000

Lfore stands for the labels amount in singling of forwarding direction (F=1, W=64, b=0.001, H=4 and H=8)

WTC2012 Miyazaki 21

ULS independently operates two Label Sets

LS operates only one Label Set


Major Findings Summary Focused on the signaling- based wavelength assignment needs and performance analysis for co-

routed bi-directional lightpath provisioning

Single RWA solution specification approach in simple current signaling (RSVP-TE per RFC3471, RFC3473 highly relies on the up-to-date info dissemination (resulting in a heavy load of routing on control plane) Needs robust distributed WA support with signaling even in centralized RWA architectures

(relaxing the strict dependency on the up-to-date info and frequent routing)

Review the questions again. How about the capability of Signaling schemes on Distributed WA?: Q: Is the current standard RSVP-TE enough? Finding: Upstream Label (UL) approach is of poor performance in terms of distributed WA capability Q: Are there any possibilities for service providers to provide more cost efficient lightpath service? Finding: Three signaling-based WA approaches are available

Two-Uni has the highest flexibility but the performance depends on implementation ULS extends the idea of Label Set in upstream direction LS reuses the Label Set (optimizes signaling in the same-wavelength-use scenario)

Q: How about the possible gain by employing the extension? Finding: The candidate approaches outperform the UL significantly (blocking performance)

Especially, in restoration scenario and a long-term view (in case of future WSON upgrading)

WTC2012 Miyazaki 22

Thank you !

WTC2012 Miyazaki 23

Documents

Framework for GMPLS and PCE Control of Wavelength Switched Optical Networks (WSON)