IP WDM students by 115cNMe1

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									Agenda

Protocol Layering
Why Simplify?
First Steps: MPS
Emerging Optical Switching Technologies:




                                       Slide 1
Protocol Layering

           Application




                           We know from experience
                         that we can't run applications
                              directly over media
                          Solution: Protocol Layering




             FIBER


                                                   Slide 2
Protocol Layering

              Application

                            Applications include…
                            • Leased lines
                            • National telephone services



     SDH / SONET




                   Fiber


                                                   Slide 3
Protocol Layering

              Application

                            IP




                                 Internet services emerge
     SDH / SONET




                   Fiber


                                                     Slide 4
Protocol Layering

                          Application

                                        IP
                      PoA        PoS
              ATM
                                         ATM is introduced as…
         SDH / SONET                     • Traffic Engineering layer in
                                           the Internet
                                         • Native service


                             Fiber

  PoA - Packet over ATM     PoW - Packet over WDM
  GE - Gigabit Ethernet     PoS - Packet over SDH
                                                                 Slide 5
Protocol Layering

              Application

                            IP
              PoA
        ATM                       Wavelength Division
                                 Multiplexing appears as a
                                  mechanism to increase
     SDH / SONET                    capacity on a fibre



                             WDM

                    Fiber


                                                     Slide 6
                                   Native Ethernet services
Protocol Layering                     appear to be a cost-
                                    effective alternative, but
                                   need SONET/SDH framing


              Application

                              IP
              PoA       PoS
        ATM                                      GE

     SDH / SONET


                               WDM

                    Fiber


                                                        Slide 7
  Protocol Layering
  MultiProtocol Label
  Switching appears as         Application
alternative to ATM Traffic
       Engineering
                                               IP
                               PoA
                         ATM                 MPLS     GE
                                         PoS                PoS
                   SDH / SONET


                                                WDM

                                     Fiber


                                                           Slide 8
    Protocol Layering
Digital Wrapper appears as
    an early "SONET-lite"      Application
     technology for direct
 Packet-over-Wavelengths
                                                   IP
                               PoA
                         ATM                 MPLS               GE
                                             PoS
                   SDH / SONET                            PoW

                                              Digital Wrapper
                                                    WDM

                                     Fiber


                                                                     Slide 9
Data Transfer Over Frame-
based Networks

File


TCP


IP


Frame
(Ethernet,
 FR, PPP)
                            Slide 10
  Data Transfer Over Cell-
  based Networks

   File

   TCP

   IP


Adaptation


  ATM Cells

                             Slide 11
Agenda

 Protocol Layering
 Why Simplify?
 First Steps: MPS
 Emerging Optical Switching Technologies:
     Optical Packet Switching
     Optical Burst Switching




                                             Slide 12
What do these layers do?

 IP   is the service                     IP
   Addressing
   Routing
                                        Over
 ATM provides Traffic                  ATM
 Engineering

 SONET/SDH       provides…              Over
   Provisioning control      SONET   SONET/SDH
   Service restoration        SDH
   OAM statistics
   Low error rate
                                         Over
                               WDM      DWDM
 WDM     provides capacity
                                         Slide 13
    Control Plane v Data Plane

The data plane actually carries the
information while the control plane
sets up pathways through the data
plane

MPLS LSRs and MPS OXCs both
solve performance scalability
problem by decoupling control and
data planes
                                  Slide 14
  An IP Router:
  The Data Plane



                     Control Processor

                                         OUTPUTS

            INPUT                                  Outbound Packet

Inbound Packet      Packet Backplane




                                                        Slide 15
An IP Router:
The Control Plane
      Routing Table


                      Router Applications
                                            eg. OSPF, ISIS, BGP


                       Control Processor




                      Packet Backplane




                        Routing Updates

                                                         Slide 16
Bandwidth Bottlenecks

   Routing Protocols Create A Single "Shortest Path"


         C1


                                                        C3

         C2
                                              "Longer" paths
                                              become under-
                                                 utilised
                          Path for C1 <> C3

                          Path for C2 <> C3
                                                             Slide 17
Engineering-Out     The Bottlenecks

   ATM Switches Enable Traffic Engineering

       C1


                                      C3

       C2




                   PVC C1 <> C3

                   PVC C2 <> C3
                                           Slide 18
What Is MPLS?
A Software Upgrade To Existing Routers

 MPLS…a   software upgrade?




                    +                =
     Router                    S/W       LSR

                                          Slide 19
What Is MPLS?
A Software Upgrade To ATM Switches

MPLS…a   software upgrade?



              +               =
      ATM                         ATM
                     S/W
     Switch                       LSR
                                     Slide 20
       ROUTE AT EDGE, SWITCH IN
       CORE



IP              IP   #L1       IP   #L2      IP   #L3         IP




     IP Forwarding         LABEL SWITCHING        IP Forwarding



                                                             Slide 21
       MPLS: HOW DOES IT
       WORK
TIME              UDP-Hello




                  UDP-Hello


                  TCP-open



                Initialization(s)

                 Label request
           IP


                               #L2
                Label mapping
TIME
                                     Slide 22
         Forwarding Equivalence Classes

                               LSR                LSR
         LER                                                           LER

                  LSP

IP1                                                                                IP1
                IP1    #L1            IP1   #L2          IP1    #L3
                IP2    #L1            IP2   #L2          IP2    #L3
IP2                                                                                IP2

         Packets are destined for different address prefixes, but can be
         mapped to common path


  • FEC = “A subset of packets that are all treated the same way by a router”
  • The concept of FECs provides for a great deal of flexibility and scalability
  • In conventional routing, a packet is assigned to a FEC at each hop (i.e. L3
    look-up), in MPLS it is only done once at the network ingress
                                                                               Slide 23
      MPLS BUILT ON STANDARD IP
                              Dest   Out            Dest   Out
                              47.1   1              47.1   1
                              47.2   2              47.2   2
                              47.3   3              47.3   3


                                                                 1 47.1
         Dest   Out
                                                3
         47.1   1                          1                     2
         47.2   2         3
         47.3   3                          2


                      1
     47.3 3                                                                 47.2

                      2




• Destination based forwarding tables as built by OSPF, IS-IS, RIP, etc.

                                                                          Slide 24
MPLS Takes Over

 MPLS   LSRs Enable Traffic Engineering


     C1


                                           C3

     C2




                        LSP C1 <> C3

                        LSP C2 <> C3
                                                Slide 25
MPLS Path Creation:
Quality of Service Refinements

   Source device (S) determines the type of path on the basis of the data




           S
                                                                       D




                      Low delay (preferred for VoIP traffic)

                      High bandwidth (preferred for FTP)
                                                                             Slide 26
Typical IP Backbone (Late
1990’s)
         Core                                                       Core
        Router                                                     Router

                  ATM                                          ATM
                 Switch                                       Switch

                          MUX                           MUX


          SONET/SDH             SONET/SDH                     SONET/SDH
             ADM                   DCS                           ADM



          SONET/SDH                         SONET/SDH         SONET/SDH
             ADM                               DCS               ADM


                          MUX                           MUX


                  ATM                                          ATM
                 Switch                                       Switch

         Core                                                       Core
        Router                                                     Router




   Data piggybacked over traditional voice/TDM transport

                                                                            Slide 27
  IP/PPP/HDLC packet
   mappings to SONET      IP routing protocols
                              (OSPF, BGP)
frames (OC-48, OC-192)


Gigabit IP Router

                         Mux                     Demux




                                                            SONET
               SONET




                               Point-to-point
                                DWDM links
                               (Linear or ring
                                   SONET
                                 topologies)



                                                  Wavelength laser
                                                   transponders
                                                                     Slide 28
Slide 29
    Why So Many Layers?
   Router                            MUX
    Packet switching                  Speed match router/ switch
    Multiplexing and statistical       interfaces to transmission
     gain                               network
    Any-to-any connections         SONET/SDH
    Restoration (several seconds)     Time division multiplexing
 ATM/Frame switches                    (TDM)
    Hardware forwarding               Fault isolation

    Traffic engineering               Restoration (50mSeconds)

       Restoration (sub-second)      DWDM
                                        Raw bandwidth
                                        Defer new construction
   Result
      More vendor integration
      Multiple NM Systems
      Increased capital and operational costs
                                                              Slide 30
IP Backbone Evolution
   Core
   Router                                    Core
   (IP/MPLS)                                 Router
                                             (IP/MPLS)
                MUX   becomes redundant
    FR/ATM
    Switch          IP trunk requirements
                     reach SDH aggregate
                     levels
   MUX
                    Next generation         SONET/
                     routers include high    SDH
   SONET/SDH
                     speed SONET/SDH
                                             DWDM
                     interfaces
   DWDM
   (Maybe)



                                               Slide 31
    Collapsing Into Two Layers
IP Service (Routers)




                       Optical Core
Optical Transport
(OXCs, WDMs,
SONET ?)




                                      Slide 32
                  WDM Network Architecture


         Core Router                                               Core Router



STM-16
STM-64           Transponder                                Transponder
 POS
                       O/EO                                   O/EO

                                           OA

                                 WDM              WDM
                               Mux/demux        Mux/demux




                                                                          Slide 33
IP core routers with optical interfaces will be interconnected to DWDM equipment via a
transponder device.

Transponders perform the function of translating a standard optical signal (normally at
1330 nm) from a router line card to one of several wavelengths on a pre-specified grid
of wavelengths (sometimes called 'colors') as handled by the DWDM equipment.

This could be used to implement an OC-48 or OC-192 circuit between core routers in
an IP backbone.

It is worth pointing out that packet-over-SONET (POS) interfaces are used, so there is
SONET framing in the architecture to provide management capabilities like inline
monitoring, framing and synchronization.

The architecture is still referred to as IP-DWDM as there is no discrete SONET
equipment between the core routers and the optical transmission kit. The optical link
might also include optical amplifiers and, if the distance is large enough, electronic
regeneration equipment.


                                                                             Slide 34
It is very important to differentiate between functional layers and layers
of discrete equipment.

In the diagram, many functional layers can be integrated within a single
equipment layer.

This is emphasized by the multilayer stack on the right hand side, which
involves two discrete layers of equipment, IP routers and DWDM
transmission.

In the case of IP routers, there are actually four distinct functional layers
(IP, MPLS, PPP and SDH).

The notion of collapsed layers is therefore only applicable to the number
of network elements involved, rather than the numeric of functional
layers. It is perhaps more meaningful to refer to increasing integration of
transmission network architectures                                 Slide 35
                 The Problem

 Should carriers control their next-generation
  data-centric networks using only routers, or
  some combination of routers and OXC
  equipment?

 The  debate is really about the efficiency of
   a pure packet-switched network versus a
  hybrid, which packet switches only at the
  access point and circuit switches through
  the network.
                                            Slide 36
Slide 37
Slide 38
Node B: Nodal Degree of 2, 100/fiber
2X2X100 ports to add/drop


                                                        OXC

              OXC                                                                                 OXC
                                                         (IP-aware)
                                                            OXC
                                                        CONTROLLER


               (IP-aware)                                                                          (IP-aware)
                  OXC                                                                                 OXC
              CONTROLLER                  Transponder                 Transponder                 CONTROLLER
                                                         IP/MPLS
                                           Interface                   Interface
                                                          module
                                                        Tx’s Rx’s
Transponder                 Transponder                                             Transponder                 Transponder
              IP/MPLS                                                                             IP/MPLS
 Interface                   Interface                                               Interface                   Interface
               module                                                                              module
              Tx’s Rx’s                             Local Add / Drop                              Tx’s Rx’s


          Local Add / Drop                              Node B                                Local Add / Drop


              Node A                                                                              Node C
                                                                                                                Slide 39
IP over Optical Network
  Architectural Models


                          Slide 40
We Need Optical Traffic
Engineering
Classically   the OXC "control plane" is based on
 the NMS

   Relatively slow convergence after failure
    (from minutes to hours)
   Complicates multi-vendor interworking
Traffic Engineering is achieved via a
 sophisticated control plane…

   Dynamic or automated routing become
    proprietary
   Complicates inter-SP provisioning
                                                Slide 41
Solution: Optical Switching
 All-opticalData Plane products are widely available today
    Typically DWDM OADMs and OXCs
 Some of these devices have dynamic reconfiguration
  capabilities
    Generally via NMS or proprietary distributed routing
     protocols
 The Control Plane of these devices remains electronic
    So control messages must be sent over a lower
     speed channel
    There are several ways to achieve this
 Typical DWDM is "service transparent"
    The data plane does not try to interpret the bitstreams
    Implies amplification, not regeneration
    Also implies that signal bit error rate is not monitored
                                                         Slide 42
Lambda Switching Objectives
Fosterthe expedited development and
 deployment of a new class of versatile
 OXCs, and existing OADMs

Allow the use of uniform semantics for
 network management and operations
 control in hybrid networks

Provide  a framework for real-time
 provisioning of optical channels in
 automatically-switched optical networks

                                           Slide 43
How Do We Label a Lambda?

Remember    that the OXC is "service transparent"
  Will not interpret the bitstream
  May not even be able to digitally decode bits
   at this speed

Theobvious property available is the value of the
 wavelength
  This is why we call it "Lambda Switching"




                                               Slide 44
Concepts in Lambda
Switching
 Involvesthe idea of space-switching channels from an
  inbound port to an outbound port
       Variety of space-switching technologies are appropriate

 May involve wavelength translation          at the outbound port
   Wavelength translation is expensive


 If   data channels are "service transparent", how do we…
       Exchange routing protocols?
       Exchange signalling protocols?
       Send network management and other messages that must
        terminate in the lambda switch?



                                                                  Slide 45
Recap: MP Label S
A technique that uses IP as the control plane for
 a connection-oriented, switched data plane
Initial application (focussed on reducing costs)
   Traffic Engineering (put the traffic where the
     bandwidth is)
Emerging Applications (focussed on additional
 revenues)
   VPNs
   Voice over MPLS
   ”Video over MPLS"
Future Applications
   Universal Control Plane
                                               Slide 46
The Label Information Base
                                           Connection Table
                                          In                  Out
                                     (port,Label)   (port, Label, Operation)
5      Port 1     Port 3
                                      (1, 5)          (4, 7, Swap)
                                      (1, 3)          (4, 27, Swap)
                                     (1, 17)         (4, 123, Swap)
       Port 2     Port 4       7
                                      (2, 3)          (3, 17, Push)



 Labelled  packet arrives at Port 1, with Label value "5"
 LIB entry indicates switch to Port 4, and swap label to
  value "7"



                                                                      Slide 47
The Optical Connection Table
Case 1a: No wavelength translation
                                               Connection Table
                                               In              Out
                                         (port,Lambda)   (port, Lambda)
2     Port 1     Port 3
                                          (1, 2)          (4, 2)
                                          (1, 3)          (4, 3)
                                          (1, 1)          (4, 2)
       Port 2     Port 4     2           (2, 1)          (3, 1)



  Channel  arrives on Port 1 on 2, the "green" lambda
  Connection table indicates that this channel should be
   space-switched to Port 4
  At Port 4, 2 is available for onward transmission


                                                                 Slide 48
The Optical Connection Table
Case 1b: No wavelength translation
                                               Connection Table
                                               In              Out
                                         (port,Lambda)   (port, Lambda)
3     Port 1     Port 3
                                          (1, 2)          (4, 2)
                                          (1, 3)          (4, 3)
                                          (2, 3)          (4, 1)
       Port 2     Port 4     3           (2, 1)          (3, 1)



  Channel  arrives on Port 1 on 3, the "blue" lambda
  Connection table indicates that this channel should be
   space-switched to Port 4
  At Port 4, 3 is available for onward transmission


                                                                 Slide 49
The Optical Connection Table
Case 2: Wavelength translation
                                                Connection Table
                                                In              Out
                                          (port,Lambda)   (port, Lambda)
       Port 1     Port 3
                                           (1, 2)          (4, 2)
                                           (1, 3)          (4, 3)
                                           (2, 3)          (4, 1)
3     Port 2     Port 4      1           (2, 1)          (3, 1)



  Channel   arrives on Port 2 on 3, the "blue" lambda
  Connection table indicates that this channel should be
   space-switched to Port 4
  At Port 4, 3 is already in use, so lambda is translated to
   1, the "red" lambda
                                                                  Slide 50
New Concept: MP Lambda S
Today: NMS Configuration
 Each   optical trail is set up in Service Provider NOC


                                  NMS




         OADM                                      OADM

                          OXC             OXC


                  OXC             OXC



                                                           Slide 51
New Concept: MP Lambda S
Today: NMS Configuration
 Each   optical trail is set up in Service Provider NOC


                                  NMS




         OADM                                      OADM

                          OXC             OXC


                  OXC             OXC



                                                           Slide 52
New Concept: MP Lambda S
Today: NMS Configuration
 Each   optical trail is set up in Service Provider NOC


                                  NMS




         OADM                                      OADM

                          OXC             OXC


                  OXC             OXC



                                                           Slide 53
New Concept: MP Lambda S
Today: NMS Configuration
 Each   optical trail is set up in Service Provider NOC


                                  NMS




         OADM                                      OADM

                          OXC             OXC


                  OXC             OXC



                                                           Slide 54
New Concept: MP Lambda S
Today: NMS Configuration
 Final stage is to enable connection in CPE        devices
    eg. Manual Traffic Engineering of LSP to OCT


                                   NMS




        OADM                                          OADM

                          OXC               OXC


                  OXC              OXC



                                                              Slide 55
New Concept: MP Lambda S
OXCs take part in routing
 Enhance  OSPF-TE and ISIS-TE to include optical-
 specific metrics and parameters

                                    NMS




      OADM                                              OADM

                         OXC                  OXC


               OXC                 OXC


             Optically-enhanced routing protocol exchange
                                                               Slide 56
New Concept: MP Lambda S
CPE uses Optical UNI Signalling
 Must   create an Optical UNI spec.


                                         NMS




         OADM                                           OADM

                              OXC                 OXC


                   OXC                   OXC


                Optical UNI signalling protocol
                                                               Slide 57
New Concept: MP Lambda S
OXCs create optical trail
 May be based on signalled constraints, and may include
 policy-driven permission

                                       NMS




        OADM                                                OADM

                             OXC                 OXC


                   OXC                 OXC


               NMS notification, and/or policy exchange process
                                                                   Slide 58
 LSP to OCT Mapping
 Granularity Issues

                                      OCT #1
LSP #1                                                    LSP #1
                                        OCT #2
LSP #2                                                    LSP #2

                  Lambda    W            W     Lambda
                            D            D
                   Switch   M            M      Switch
   LSR                                                   LSR



 LSP#1 and LSP #2 are 64kbps IP "telephone calls"
 OCT #1 and OCT #2 are 10Gbps wavelengths
        Utilisation of each OCT would be 0.00064%


                                                           Slide 59
 LSP to OCT Mapping
 Solution: LSP aggregation at LSR

                                  OCT #1
LSP #1                                                LSP #1
  ...                                                   ...
LSP #n                                                LSP #n

               Lambda    W           W     Lambda
                         D           D
                Switch   M           M      Switch
    LSR                                              LSR



 LSR includes path merge function ( )
    LSP constraints are observed
    Optimum OCT utilisation can be maintained

 Constitutes a set of "nested LSPs"
    Outermost label becomes the wavelength
                                                       Slide 60
             Operational Approaches:
             Overlay and Peer Models
   Overlay model
       Two independent control planes
          IP/MPLS routing


    
          Optical domain routing
        Router is client of optical domain
                                                   ?
       Optical topology invisible to routers
       Routing protocol stress – scaling issues
       Does this look familiar?

   Peer model
       Single integrated control plane
       Router and optical switches are peers
       Optical topology is visible to routers
       Similar to IP/MPLS model
                                                       Slide 61
            The Hybrid Model
   Hybrid model
       Combines peer & Overlay
         Middle ground of 2
           extremes
         Benefits of both models
       Multi admin domain support
         Derived from overlay
           model
       Multiple technologies within
        domain
                                       Peer

         Derived from peer model      UNI




                                        Slide 62
                       Overlay Model


                               ?
                           Black Box for
                            IP networks



   Two independent control planes isolated from each other
      The IP/ MPLS routing, topology distribution, and signaling
        protocols are independent of the ones at the Optical Layer
   Routers are clients of optical domain
      The Optical Networks provides wavelength path to the
        electronic clients(IP routers, ATM switches)
   Optical topology invisible to routers (Information Hiding)
   Conceptually similar to IP over ATM model
   Standard network interfaces are required such as UNI and NNI

                                                                    Slide 63
Slide 64
                                         Overlay Model

                    IP Border Router



                                   UNI
                                         Border OXC
          IP Border Router    UNI

                                                                 IP Border Router
                        Border OXC        Core OXC
                                                                   UNI
                                                           Border OXC


IP Border Router UNI
                        UNI

                IP Border Router
                                         Client/Server Model


                                                                                    Slide 65
  From   To   Avail. BW                                               IP (Logical) Routing
  A      E    500Mbps
                                           A



                                                  E



Physical (RWA) Routing                  A                               D
2 per fiber, 1Gbps each

                            Router                                            Router
 From    To    Req. BW                                          OXC
 A       E     500Mbps                      OXC


                                                                            OXC
                                                                                             B
                                     OXC

                                                      OXC
                                                                                     Router
                                        C                   E
                               Router
                                                                  Router
                                                                                  Slide 66
  From   To   Avail. BW                                               IP (Logical) Routing
  A      E    500Mbps
  C      D    0                            A                     C


                                                                           D
                                                  E



Physical (RWA) Routing                  A                               D
2 per fiber, 1Gbps each

                            Router                                             Router
 From    To       Req. BW                                       OXC
 A       E        500Mbps                   OXC
 C       D        1Gbps

                                                                            OXC
                                                                                             B
                                     OXC

                                                      OXC
                                                                                     Router
                                        C                   E
                               Router
                                                                  Router
                                                                                  Slide 67
  From   To   Avail. BW                                                   IP (Logical) Routing
  A      E    500Mbps                                 B              C
  C      D    0                            A
  A      B    250Mpbs

                                                                               D
                                                  E



Physical (RWA) Routing                  A                                   D
2 per fiber, 1Gbps each

                            Router                                                 Router
 From    To       Req. BW                                           OXC
 A       E        500Mbps                   OXC
 C       D        1Gbps

 A       B        750Mbps                                                       OXC
                                                                                                 B
                                     OXC

                                                          OXC
                                                                                         Router
                                        C                       E
                               Router
                                                                      Router
                                                                                      Slide 68
  From   To   Avail. BW                                                   IP (Logical) Routing
  A      E    500Mbps                                 B               C
  C      D    0                            A
  A      B    250Mpbs

  B      D    200Mbps                                                          D
                                                  E



Physical (RWA) Routing                  A                                   D
2 per fiber, 1Gbps each

                            Router                                                 Router
 From    To       Req. BW

                                            OXC                 OXC
 A       E        500Mbps

 C       D        1Gbps

 A       B        750Mbps                                                       OXC
                                                                                                 B
 B       D        800Mbps            OXC

                                                          OXC
                                                                                         Router
                                        C                        E
                               Router
                                                                      Router
                                                                                      Slide 69
  From   To   Avail. BW                                                   IP (Logical) Routing
  A      E    500Mbps                                 B               C
  C      D    0                            A
  A      B    250Mpbs

  B      D    200Mbps                                                          D
  A      E    0                                   E



Physical (RWA) Routing                  A                                   D
2 per fiber, 1Gbps each

                            Router                                                 Router
 From    To       Req. BW

                                            OXC                 OXC
 A       E        500Mbps

 C       D        1Gbps

 A       B        750Mbps                                                       OXC
                                                                                                 B
 B       D        800Mbps            OXC
 A       E        500Mbps

                                                          OXC
                                                                                         Router
                                        C                        E
                               Router
                                                                      Router
                                                                                      Slide 70
Slide 71
                               Peer Model


Routers and optical switches
     function as peers
                                             Uniform and Unified
                                                 control plane




                               Integration
                               Continuity




                                                                   Slide 72
           The Peer model (IP-over-WDM)
> The IP and optical network are treated together as a single
  integrated network managed and traffic engineered in a
  unified manner.

 Thus, from a routing and signaling point of view, there is
  no distinction between the UNI, the NNI, and any other
  router-to-router interfaces.

> The OXCs are treated just like any other router as far as
  the control plane is concerned.

> The IP/MPLS layers act as peers of the optical transport
  network, such that a single routing protocol instance runs
  over both the IP/MPLS and optical domains.
                                                         Slide 73
Slide 74
     Which signaling technique for all-optical
     WDM core networks ?
   In-band signaling :
       The header is modulated at a low bit rate and carried on
         channel i
        The payload is modulated at a high bit rate and carried on
         channel i
        The header and the payload transmissions are separated
         by a guard time
        Optical Burst Switching is based on in-band signaling
   Out-of-band signaling :
      The header of each packet is carried on a separate optical
         signaling channel
        This signaling channel may be either unique 0 for all the
         optical data channels (option #1)
        Or specific signaling channels *k are associated to
         subsets of data channels {i} (option #2)
        Out-of-band signaling is well suited to slot synchronized
                                                             Slide 75
            0
Option #1
            i




            *
            0
            i
Option #2   0
            i




                 Slide 76
  How to share the common out-of-band
  signaling channels ?
 Time Division Multiple Access (TDMA)
   Advantage : simple to implement
   Drawbacks :
     Too rigid for bursty traffic
     Not scalable
     Decay in the arrival time of the headers
      associated to parallel data packets
 Code Division Multiple Access (CDMA)
   Advantage : The headers associated to parallel
    packets arrive at the same time
   Drawback:
     Relatively expensive to implement

                                               Slide 77
Sub-carrier modulation (SCM)
  Advantage :
   Cost-effective
   Scalable
   The headers associated to
    parallel packets arrive at the
    same time


                                 Slide 78
           Principle of sub-carrier modulation
           (1)
                                      Optical power




              f0                  
NRZ data
                                                                 Input current

                                                            f0
                                                      "1"
           Microwave oscillator


                                                      "0"




                                                            f0
                                                      "1"




                                                                                 Slide 79
Principle of sub-carrier modulation
(2)
                        Microwav e carriers between 10 MHz and 10 GHz

                                                RF/microwave
                                      f1        bandpass filter
             Header of IP packet #1
                                                   BPF

                             Microwave oscillator                 Optical carriers around 100 THz
                                    f2
                                                                                      
             Header of IP packet #2
                                                  BPF
                           Microwave oscillator                      
                                    f3
           Header of IP packet #2
                                                    BPF
                             Microwave oscillator
                                      f4
             Header of IP packet #4
                                                    BPF

                             Microwave oscillator




                                                                                     Slide 80

								
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