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
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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
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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
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Edge Edge Control Plane
OXC
Transit
λx
λy
Date Plane
OXC: optical cross connect Co-routed bidirectional lightpath
WSON
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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
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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
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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)
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• 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
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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”
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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
pro
ba
bil
ity
10- 6
10- 5
10- 4
10- 3
10- 2
10- 1
100
Current standard’s 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
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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
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Terminator
Initiator Colored edge Colorless edge
Colored edge Same wavelength use Same wavelength use
Colorless edge Same wavelength use Different wavelengths use
λ1
λ1 λ1
λ2
Scenarios and corresponding Signaling candidate schemes • Same wavelength use scenario
• UL, ULS, TU, LS • Different wavelengths use scenario
• UL, ULS, TU
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Upstream Label Approach (UL) RFC 3473 ’s Behavior - Needs 2nd Time Signaling (Crank-back) (Same Wavelength Use)
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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
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Upstream Label Approach (UL) RFC 3473 ’s Behavior - Needs 2nd Time Signaling (Crank-back) (Diff Wavelength User)
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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
Different blocking situations in 1st time signaling result in different blocking probability in 2nd time signaling
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Upstream Label Set Approach (ULS)’s Behavior (Same Wavelength Use) cf) E. Oki et al., vol.E87-B, no.6, June 2004.
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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.
Different blocking situations in 1st time signaling result in different blocking probability in 2nd time signaling
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Upstream Label Set Approach (ULS)’s Behavior (Diff Wavelength Use) cf) E. Oki et al., vol.E87-B, no.6, June 2004.
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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.
Different blocking situations in 1st time signaling result in different blocking probability in 2nd time signaling
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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
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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”
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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.
Different blocking situations in 1st time signaling result in different blocking probability in 2nd time signaling
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Network Model
Initiator Terminator H hops
W
For each wavelength λi in one fiber - Average utilization rate (the cause of forward blocking): p - Competition rate (the cause of backward blocking): b
λ
W
F pairs of fibers
s d i j
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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 Analysis—Blocking 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
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Blocking Probabilities after the 1st and 2nd Signaling
UL(1st) ULS/LS/TU(1st)
UL(2nd) ULS/LS/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
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)
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UL UL
ULS/LS/TU ULS/TU
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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
(a) Same-wavelength-use (b) Different-wavelength-use
(F=1, W=64, b=0, p=0.2, 0.4 and 0.6)
WTC2012 Miyazaki 17
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Blocking Probability in the Restoration Scenarios
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(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
(a) Same-wavelength-use (b) Different-wavelength-use
(F=1, W=64, H=4, b=0.001)
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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.
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UL(2nd)F1 UL(2nd)F6
ULS/TU(2nd)pF1 ULS/TU(2nd)F6
Pbwave(2nd)F1 Pbwave(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
(a) Same-wavelength-use (b) Different-wavelength-use
(H=4, p=0.8, b=0.001, F=1 and 6)
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-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)
UL’s gain, F=1 ~6
All, F=1
F=6
Remarkable gain of ULS/TU’s upgrading to F6, p=0.8
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
pro
ba
bil
ity
10- 6
10- 5
10- 4
10- 3
10- 2
10- 1
100
UL’s gain, F=1 ~6
All, F=1
F=6
Remarkable gain of ULS/LS/TU’s upgrading to F6
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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
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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)
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ULS independently operates two Label Sets
LS operates only one Label Set
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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)
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Thank you !
WTC2012 Miyazaki 23