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Dynamic Multi-Layer Mesh
© 2009 AT&T Intellectual Property. All rights reserved. AT&T and the AT&T logo are trademarks of AT&T Intellectual Property.
Dynamic Multi-Layer Mesh Networks:
A Provider’s Perspective
Peter MagillExecutive Director, Optical Systems ResearchAT&T Labs
RECONFIGURABLITY Eliminating unnecessary
transponders leads to
Tingye Li, AT&T Bell Labs
March 1994
RECONFIGURABLITYfurther enhances the efficiency of optical add/drops.
transponders leads to
dramatic savings.
TX
The Multiwavelength Optical NETworking VisionMONET: DARPA, AT&T, Lucent, Bellcore, Bell Atlantic , ...
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Saleh, OFC ’96; Wagner, et al, JLT June ’96;Alferness, et al, OFC ’97; Garrett, et al, JSAC Sept ‘98
A.A.M.Saleh, 1998
The ever-increasing demand for increased capacity and level
of service at a lower cost are key drivers fueling the evolution
of core optical networks from statically provisioned optical
links interconnected with electronic switching and
regeneration to more complex and flexible, optically switched
mesh topologies with dynamic provisioning.
Let’s Dissect Abstract of Symposium
mesh topologies with dynamic provisioning.
Page 4
What does this mean?
ECOC 2009 - Symposium 6.7
point-to-point
fixed OADM
2-degree ROADM (static)
multi-degree ROADM (static)
multi-degree ROADM
dynamic (few minutes; via planners)
multi-degree ROADM
dynamic (few sec; via
automated
multi-degree ROADM dynamic
Photonic Networking Timeline
multi-degree dynamic R-ADM (few sec; via automated
process)
multi-degree R-ADM dynamic
( <100 ms )“Optical” Networking
(static) (static) minutes; via planners)
automated process)
dynamic ( <100 ms )
GMPLS
Page 5 ECOC 2009 - Symposium 6.7
mesh
GMPLS?
Feasible
?
NOT feasible with today’s transmission systems
Why Rapidly-Dynamic ROADM Networks
Not Feasible?
A long-haul (L > ~600 km) transport system contains:
• Many optical amplifiers:
• Most with adjustments needed for multiple pump laser powers
• Some with adjustable gain flattening filters (GFF)
• All with control circuits for optical transient control
• Multiple ROADMs:
• Usually with per-channel variable optical attenuator adjustments • Usually with per-channel variable optical attenuator adjustments
• Multiple transponders
• Each with tunable laser
• Many with tunable dispersion compensators (TDC)
• Each with variable optical attenuator (VOA)
• Together, there DOZENS of things which need to be adjusted (“tuned”) and collection of control loops makes some of them get VERY slow [frequently minutes to converge]
Page 6 ECOC 2009 - Symposium 6.7
DWDM Transport - Today
• Longer provisioning cycle than desired– Many manual steps
– Across the country (both ends + maybe middle)
– Mux/demux inflexible
• Static mapping: circuit �� wavelength
Transponders ROADM LayerTransponders cannot be pre-deployed withoutcommitting wavelengths.
ROADM Layer
ROADM
T/R
ROADM
T/R
ROADMROADM
ROADMROADM
ROADM
ROADM
ROADM
Page 7ECOC 2009 - Symposium 6.7
DWDM Transport Evolution – Next Step
• Colorless add/drops
– Currently: transponders are tunable but demux is not.
– Tunable demux will enable transponders to be pre-deployed, and circuits to be turned up rapidly. Transponder at B can be connected to A or C simply by tuning pair of transponders to the same wavelength, and setting demux and ROADMs properly. ROADM Layer ROADMproperly.
– Wavelengthdoes not needto be chosenin advance.
ROADM Layer
ROADM A
T/R
ROADMB
ROADMC
T/R
T/R
Page 8ECOC 2009 - Symposium 6.7
When Discussing Alternate Network
Architectures …
• What some call “IP/WDM”
– Proposal to have ‘colored’ (long-haul wavelength) interfaces directly on IP routers
– Or integrate long-haul optics in IP routers
• Others call this an “alien wavelength” architecture
• In AT&T’s inter-city network:
Page 9 ECOC 2009 - Symposium 6.7
• In AT&T’s inter-city network:
– AT&T will require 100G (OTU4) ‘gray’ (non-WDM) optics on routers
– AT&T will have NO colored optics in routers
– AT&T will consider multiple vendors for routers and for transport
– While IP routers are a big source of traffic, they are not the only one
– We also have other network layers and private line traffic which use long-haul transport – not through core routers
Project GRIPhoN
Globally Reconfigurable Intelligent Photonic Network
An AT&T Labs Research project to study:
• feasibility of a dynamic wavelength layer
• cross-layer control and timing issues
• control and management software requirements
Collaborators:
Martin Birk, Angela Chiu, Bob Doverspike, Mark Feuer, Pete Magill, Emmanuil Mavrogiorgis, Jorge Pastor, Sheri Woodward, Jennifer Yates, Joy Zhang
Page 10 ECOC 2009 - Symposium 6.7
Fiber Cross-Connect (FXC)
A-ports and B-ports: each N in number
Connections established between any pair of an A-port and a B-port
Connections don’t care about direction or wavelength of light
A B
demux mux
Recent developments:• Low optical loss (< 3dB)• Very low cost
FXC
A B
Subsequent slides don’t showA & B separately, and connectionlines represent fiber PAIRS.
T/R
T/R
T/Rtransponders
Page 11 ECOC 2009 - Symposium 6.7
Dynamic Wavelengths in Transport
• Purpose of a transport system:
• convey a bit stream from one client to another
• over a long distance (> 2 km)
• with an error rate < ~10-14
• “Client” could be:
• IP Router, OTN switch, Ethernet switch, SONET/SDH ADM
• Other electronic switches or cross connects• Other electronic switches or cross connects
Page 12 ECOC 2009 - Symposium 6.7
λ1
λ2
λ3
λN
R
R
R
R
λ1
λ2
λ3
λN
C
C
C
C
C
C
C
C
Proposed ROADM Architecture: Overall
• ROADM = Reconfigurable Optical Add/Drop Multiplexer
West East
South
ROADM
Wavelength-Selective
Cross-Connect
(WSXC)
Line-side
Page 13 ECOC 2009 - Symposium 6.7
T/R T/R T/R T/R
Line-sideFiber Cross-Connect
CLIENT
Client-sideFiber Cross-Connect
CLIENTCLIENT
L-FXC
C-FXC
T/R
Any client can use any transponder to access any unused optical channel, routed in any direction.
ROADM Architecture:
Colorless Add/Drop• Today the “R” in ROADM is misleading
• Reconfiguration of commercially available ROADMs includes manual steps of cabling fiber pair from the line side of each transponder to wavelength MUX/DMUX
• CANNOT be done remotely
• Instead, East
ROADM
Page 14
• Instead, insert low-loss FXC between transponderand mux/ dmux
East
T/R
Wavelength-Selective
Cross-Connect
(WSXC)
Line-sideFiber Cross-Connect
L-FXC
T/R
ECOC 2009 - Symposium 6.7
ROADM Architecture:
Steerable Transponders• For multi-degree ROADM (e.g., with fiber routes to North, South, East and West)
• Transponders should be grouped into “banks” – One (or two for redundancy)
• But then any transponder from any bank should be able to be used for any fiber direction (N, E, S or W)
– Gives carrier flexibility since changes in traffic are notoriously hard to predict
ROADM
Page 15 ECOC 2009 - Symposium 6.7
West East
South
T/R T/R T/R T/R
ROADM
Wavelength-Selective
Cross-Connect
(WSXC)
Line-sideFiber Cross-Connect
L-FXC
T/R
ROADM Architecture:
Client-Side FXC
• For full flexibility, each transponder should not be permanently “wed” to a given client
• Connections between clients and transport system should also be remotely reconfigurable
• Any transponder should be able to connect to any client
Page 16 ECOC 2009 - Symposium 6.7
T/R T/R T/R T/R
CLIENT
Client-sideFiber Cross-Connect
CLIENTCLIENT
C-FXC
T/R
Reprise: Full Node Architecture
- One Option
West East
South
ROADM
Wavelength-Selective
Cross-Connect
(WSXC)
Line-sideFiber Cross-Connect
T/R T/R T/R T/R
Line-sideFiber Cross-Connect
CLIENT
Client-sideFiber Cross-Connect
CLIENTCLIENT
L-FXC
C-FXC
T/R
• Now any client can use any transponder to access anyunused optical channel, connected in any direction.
Page 17 ECOC 2009 - Symposium 6.7
Alternative ROADM Design: Serve Banks of
Transponders Directly From ROADM Core
West East
South
Wavelength-Selective
Cross-Connect
(WSXC)
transponder
banktransponderWSS
WSS
• Transponder bank served by another fiber-degree of WSXC• Enables transponder steering without line-side FXC • Scales gracefully over entire lifetime
CLIENT CLIENTCLIENT
T/RT/RT/R
transponder
bankT/R
C-FXC
T/RT/R
Page 18 ECOC 2009 - Symposium 6.7
Another Possible Implementation
Node A’s WSXC
• This ROADM also supports growth of degree (in service)
fixedjumpers
Page 19ECOC 2009 - Symposium 6.7
Desirable Node Attributes
• Full flexibility
– Transponders also not dedicated to a particular color or direction
– Called “colorless” and “steerable”
• Scaleable architecture
– Low first cost, yet able to grow as traffic grows
• Graceful growth
– Ability to add new routes and more transponders while node remains in service
direction-less
while node remains in service
• Hitless operation
• Directional separability
– Single failure should not affect all add-drops or all routes
• Minimize loss/OSNR degradation to maximize reach
• Explicitly test/verify correct lightpath routing
• Low cost
Page 20ECOC 2009 - Symposium 6.7
Possible Applications for GRIPhoN
Network efficiency
• Wavelength Re-grooming
Faster, Easier Provisioning
• Dynamic Wavelength Service
Maintenance and Restoration
• At Layer 1: for Planned Cable Intrusions
• At Layer 1: for un-planned cable intrusions
• At Layer 3: Backbone router maintenance
Page 21 ECOC 2009 - Symposium 6.7
Application
Wavelength Re-grooming
Today, circuit-to-wavelength mapping: static
Over years, choice of wavelength and route for many circuits become sub-optimal (because of blocking, optical “reach” constraints)
Ability to change wavelength for:
• given circuit over • given circuit over
• given route
is quite valuable
Imperative to have no service disruption
Page 22 ECOC 2009 - Symposium 6.7
Present Mode of Operation (Manual)change wavelength : λλλλ1���� λλλλ4
Node AROADM
core
Node BROADM
coreCDE
λ1 λ4 λ1 λ4 λ1 λ4 λ1 λ4
0. 1A, 1B active at λ1, connected to λ1 ports
1. Take service down!2. MANUALLY insert 2A, 2B1A
2A
1B
2B
Client Client
•Need technicians at all sites (2; more if regenerated)•Traffic affecting – perceptible outage
2. MANUALLY insert 2A, 2B3. MANUALLY connect to λ4 ports 4. MANUALLY tune 2A, 2B to λ4 and
activate 5. MANUALLY move client fibers at
A, B6. Restore service7. Release 1A, 1B for other uses
1A 1B
Page 23ECOC 2009 - Symposium 6.7
Step 0
Bridge-and-Roll
OT OT
Step-by-step operation to change wavelength
Utilizes:
• optical splitter on each client transmitter and
• additional pair of optical transponders (OT)
Step 1Client a Client bOT OT
Step 2
Step 3
GRIPhoN goal:• < 50-100 millisecond interruption to circuit• Will not trigger higher-layer interactions
original transponder pair now available for other operations
Page 24 ECOC 2009 - Symposium 6.7
Application
Rapid Provisioning: Dynamic Wavelength
Service
For photonic layer to be dynamic• need spare resources (transponders, lightpaths, etc.)
• deployed all over the network
Enterprise customers could use Dynamic Wavelength Service (and the reserve of potential capacity) to turn up a class of wavelength circuits capacity) to turn up a class of wavelength circuits in minutes rather than months [provided the customer has adequate connectivity to core]
Customers could turn capacity up (or down) with seasonal or even time-of-day load shifts
To enable this carrier will need new processes to monitor transport utilization and provide sufficient resources
Page 25 ECOC 2009 - Symposium 6.7
Customer
Dynamic Wavelength Service
- Customer Need
Customer
Site 3
Dynamic – these demands may come and go
Customer
Site 2
OC-48
Customer
Site 1
Router
EthernetSwitch
EthernetSwitch
Customer
Site 4
40 Gb/s
40 Gb/s
Page 26ECOC 2009 - Symposium 6.7
Dynamic Wavelength Service –
ROADM Layer
100Gb/s
FX
C
100
Gb/s
OTN
Customer
Site
100Gb/s
MetroNetwork
Inter-city
Network
ROADM Layer
FX
CF
XC
RO
AD
M
OTN
POP
Page 27ECOC 2009 - Symposium 6.7
OTN Layer
Dynamic Wavelength Service –
Network Layers
100Gb/s
FX
C
100
Gb/s
OTN
Customer
Site
100Gb/s
MetroNetwork
Inter-city
Network
ROADM Layer
FX
CF
XC
RO
AD
M
OTN
POP
Page 28ECOC 2009 - Symposium 6.7
OTN Layer
GRIPhoN
Controller
DWS-Controller
Dynamic Wavelength Service -
Management Plane
100Gb/s
FX
C
100
Gb/s
OTN
Customer
Site
100Gb/s
MetroNetwork
Inter-city
Network
ROADM Layer
Controller
FX
CF
XC
RO
AD
M
OTN
POP
Page 29ECOC 2009 - Symposium 6.7
Dynamic Wavelength Service –
Data Plane
0.6- 2.5Gb/s
circuits
Customer
OTN Layer
Customer
Site 3
100Gb/s
FX
C
100
Gb/s
OTN
Channelized 10 Gb/s
Customer
Site 1
Router
EthernetSwitch
100Gb/s
EthernetSwitch
MetroNetwork
Inter-city
Network
40 Gb/s
40 Gb/s
circuits
Customer
Site 2
Customer
Site 4
ROADM Layer
FX
CF
XC
RO
AD
M
OC-48
OTN
POP
Page 30ECOC 2009 - Symposium 6.7
ApplicationRapid Provisioning: Private Line (PL)
Private Line business could potentially use a Dynamic Wavelength Service internally
Using the same reserve capacity, provision PL circuits via Dynamic Wavelength Service Controller
Page 31 ECOC 2009 - Symposium 6.7
Application
Layer 1 Maintenance:
Planned Cable Intrusions
Geographically large network of fiber routes – all buried
Frequent public works, roadway changes, etc. which require fiber re-routes
Potentially disrupting traffic during few-hour period Potentially disrupting traffic during few-hour period (overnight) for multiple PL customers
Higher layer services (like IP) restore themselves
Page 32 ECOC 2009 - Symposium 6.7
Planned Maintenance Events - 2009
original cable
new route
working path
B
A
EXAMPLE: Dept of Transportation informs carrier that a cable must be moved to make way for a new road project
1) Local alternate route found, and new cable installed
roadproject
hut
hut
1) Local alternate route found, and new cable installed
2) Once the new cable is ready, a network event is scheduled – verify that there are no conflicting events
– notify customers
3) Before the event, conduct a walk-through
4) Network Event:a. Verify that the alternate fiber path is ready
b. Move traffic to alternate fiber path
c. Splice in new cable and check each fiber
d. Move traffic back to working path (over new route & cable)
Page 33 ECOC 2009 - Symposium 6.7
EXAMPLE: Dept of Transportation informs carrier that a cable must be moved to make way for a new road project
1) Local alternate route found, and new cable installed
Possible Future Planned Maintenance
Events – with GRIPhoNoriginal cable
new route
working path
B
Aroadproject
1) Local alternate route found, and new cable installed
2) Once the new cable is ready, a network event is scheduled
– verify that there are no conflicting events,
– notify customers
3) Before the event, conduct a walk-through
4) Network Event:
a. Verify that the alternate fiber path is ready
b. Move traffic to alternate fiber path
c. Splice in new cable and check each fiber
d. Move traffic back to working path (over new route & cable)Page 34 ECOC 2009 - Symposium 6.7
Un-Planned Events (Cable Cuts) –
with GRIPhoN
(formerly) working
B
A
EXAMPLE: Joe the Backhoe Operator takes an underground swipe “a little too deep,” severing a buried fiber cable
0) Protection path pre-calculated
Oops!
0) Protection path pre-calculated1) Systems alarm:
– Routers will react, triggering OSPF and/or BGP re-convergence– Transport reacts, triggering GRIPhoN restoration sequence
2) Photonic layer restoration:– GRIPhoN switches move traffic to restoration paths, restoring L1 capacity– For Private Line – out of service for ~1 minute instead of ~6 hours– For Layer 3 – results in more reliable Layer 1 (double failures, etc.)
3) Later (next few days):a. Repair cableb. Use GRIPhoN to move traffic back to working path – no customer impact
Page 35 ECOC 2009 - Symposium 6.7
ApplicationLayer 3 Maintenance:
Backbone Router Upgrades, etc.
IP routers tend to have a lower availability than transmission equipment
IP routers must be brought down regularly for software upgrades
To be very reliable, IP network architecture must To be very reliable, IP network architecture must allow any one router to be down at any time
Use GRIPhoN to provide dynamic transport to off-load routers and divert traffic for L3 maintenance
Solution:
Page 36 ECOC 2009 - Symposium 6.7
Major Challenges
Operations Support Systems (OSSs)
Planning/provisioning process & organizational structure
What should be the ultimate holder of the optical-layer data?• The network (some combination of ROADMs and vendor EMS)?
• Centralized control systems or OSS?
• Some combination of both?
For photonic layer to be dynamic• Need spare resources (transponders, lightpaths, etc.)
• How much? Where? – Strong influence on business case
Page 37 ECOC 2009 - Symposium 6.7
Conclusions
• There are multiple applications for a dynamic wavelength layer
• AT&T Labs Research is studying the feasibility question with a prototype lab implementation
• Results to be published soon
Page 38 ECOC 2009 - Symposium 6.7
BACKUP
Page 39 ECOC 2009 - Symposium 6.7
• Metro (metropolitan area):
– within and around a city
– ~200 km reach
– carry lots of local traffic
– cascade many ROADMs (~16)
• Regional:
– a few states of USA, each region; nationwide overall
– ~1000 km reach, 2-3 ROADMs
AT&T’s Network Covers Many Scales
Page 40 ECOC 2009 - Symposium 6.7
– ~1000 km reach, 2-3 ROADMs
– feeder for ultra-long haul
– recent & older fiber
• Core or Ultra-Long Haul:
– nationwide
– ~1500 km reach
– ~6 ROADMs
– good quality fiber
coherent receiver canhelp with PMD