“Optical Transport Network (?)”

      A technology walkthrough




             (c) Anuradha Udunuwara   1
What is “OTN”?
• As per ITU-T, it’s G.709 standard
  – a.k.a Digital Wrapper (DW)
  – a.k.a Optical Transport Hierarchy (O...
Why OTN?
• IP/MPLS core/backbone networks were originally designed
  and meant for IP services (ex: L3 VPN)
• They are not...
Main functionality provided by an
                OTN
• Transparent transport of different optical
  clients
• Interconnec...
DWDM
• Increase fiber bandwidth
• Lacks protection and management capabilities
• strict network-design limitations imposed...
SONET/SDH
• protection and management capabilities are
  inherent




                  (c) Anuradha Udunuwara       6
OTN aim
• Combine the
  – Benefits of SONET/SDH (OAM&P) and
  – Bandwidth expandability of DWDM
• Includes FEC




       ...
Pre-OTN WDM Vs. OTN
Pre-OTN WDM                       OTN
• simple transport                • networking – solution
• Band...
Following technologies/standards have nothing
    to do with OTN but are mostly confused.
• IP/MPLS
• PBB/PBT
• MPLS-TP


...
Non-IP network layer control

• ASON (Automatic Switched Optical Network)
• GMPLS (Generalized Multi-Protocol Label Switch...
ASON auto provisions the required BW(ex:
  another λ) (o.w manual provisioning)

Without ASON                             ...
ASON (ITU-T)
• Alternative/supplement for/to NMS based
  connection management
• ASON does not change transport plane
  fu...
The Optical Layer As the Transmission Medium


• The optical layer is connection oriented (circuit
  switched), Lightpaths...
GMPLS (IETF)
• Extends MPLS to provide the control plane
  (signaling and routing) for devises that switch
  in any of the...
Related / associated
equipment/standards/technologies
Equipment
• OADM (optical add-drop multiplexer)
• ROADM (Reconfigura...
OADM
• is a device used in WDM systems for
  multiplexing and routing different channels
  of light into or out of a singl...
ADM vs. OADM
ADM                                    OADM
• function in the                      • function in the photonic...
ROADM
• ability to remotely switch traffic from a WDM system at
  the wavelength layer.
• planning of entire bandwidth ass...
Optical Transport
                     Networks - evolution scenarios


      short term              medium term         ...
So…..what OTN means in “simple”
            terms
• An OTN consists of ROADMs with DWDM,
  which can provide transport for...
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Optical Transport Network

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Optical Transport Network

  1. 1. “Optical Transport Network (?)” A technology walkthrough (c) Anuradha Udunuwara 1
  2. 2. What is “OTN”? • As per ITU-T, it’s G.709 standard – a.k.a Digital Wrapper (DW) – a.k.a Optical Transport Hierarchy (OTH) standard • In the industry/telco field? – OTN – POT (Packet Optical Transport) • packet (MPLS-TP?)+ TDM (SDH/PDH) + WDM + ROADM – Optical Packet Transport layer (c) Anuradha Udunuwara 2
  3. 3. Why OTN? • IP/MPLS core/backbone networks were originally designed and meant for IP services (ex: L3 VPN) • They are not designed for bulk transports (ex: wholesale L2 pipes) • It’s complex and inefficient to use IP, IGP, LDP, LSP etc. to transport L1 and L2 bulk data • Therefore, an OTN is required to address; – L1, L2 bulk transport and Optical Virtual Private Network (OVPN) – To make IP/MPLS backbone an overlay network with OTN addressing the resiliency and network high availability requirements • However, today’s industry practice is to move to OTN if the bandwidth requirements are 40Gbps and above (c) Anuradha Udunuwara 3
  4. 4. Main functionality provided by an OTN • Transparent transport of different optical clients • Interconnection of different administrative domains • Optical channel networking and protection • Performance monitoring and alarm supervision • Network management (c) Anuradha Udunuwara 4
  5. 5. DWDM • Increase fiber bandwidth • Lacks protection and management capabilities • strict network-design limitations imposed (c) Anuradha Udunuwara 5
  6. 6. SONET/SDH • protection and management capabilities are inherent (c) Anuradha Udunuwara 6
  7. 7. OTN aim • Combine the – Benefits of SONET/SDH (OAM&P) and – Bandwidth expandability of DWDM • Includes FEC (c) Anuradha Udunuwara 7
  8. 8. Pre-OTN WDM Vs. OTN Pre-OTN WDM OTN • simple transport • networking – solution • Bandwidth • Management enabler of multiplication by means WDM network of WDM transport • First transmission • Point-to-point technology in which application that can each stakeholder gets transport STM-N/OC-N its own (ODUk) as a service connection monitoring (c) Anuradha Udunuwara 8
  9. 9. Following technologies/standards have nothing to do with OTN but are mostly confused. • IP/MPLS • PBB/PBT • MPLS-TP Actually the above technologies address the same thing. (c) Anuradha Udunuwara 9
  10. 10. Non-IP network layer control • ASON (Automatic Switched Optical Network) • GMPLS (Generalized Multi-Protocol Label Switching) • GMPLS ‘ starting point is based on the IP view of the transport plane: one physical layer – Fibers are the reference points – Equipment are black boxes identified by switching capabilities – Topology and link state information distributed to all equipment independent of network layer the equipment operates on (“peering”) • GMPLS is a tool box which can be used to support ASON’s view of the transport plane (c) Anuradha Udunuwara 10
  11. 11. ASON auto provisions the required BW(ex: another λ) (o.w manual provisioning) Without ASON With ASON • traffic grows • The client equipment • the customer analyses traffic request the establishment reports of a new connection and • he contacts the network sends a connection setup provider request • the job order moves on • the operator looks for a route • setup request is • the route is found and the acknowledged network is re-configured • the new connection is • the new connection is established! operational! (c) Anuradha Udunuwara 11
  12. 12. ASON (ITU-T) • Alternative/supplement for/to NMS based connection management • ASON does not change transport plane functionality • Signaling between transport equipment for network discovery • Each network element knows the network topology (c) Anuradha Udunuwara 12
  13. 13. The Optical Layer As the Transmission Medium • The optical layer is connection oriented (circuit switched), Lightpaths are easy to be established. • Lightpaths can be seen as LSPs between ingress and egress OXCs. • Multiprotocol Lambda Switching (MPλS) was defined as a control plane for optical networks. • MPLS and MPλS were then unified and called Generalized MPLS (GMPLS, RFC 3945) (c) Anuradha Udunuwara 13
  14. 14. GMPLS (IETF) • Extends MPLS to provide the control plane (signaling and routing) for devises that switch in any of these domains: packet, time, wavelength and fiber. • This common control plane simplify network OAM & automatic e2e Provisioning (c) Anuradha Udunuwara 14
  15. 15. Related / associated equipment/standards/technologies Equipment • OADM (optical add-drop multiplexer) • ROADM (Reconfigurable OADM) Standards/technologies • xWDM (photonics layer) • NG-SONET/SDH (EoSDH) (c) Anuradha Udunuwara 15
  16. 16. OADM • is a device used in WDM systems for multiplexing and routing different channels of light into or out of a single mode fiber • An OADM with remotely reconfigurable optical switches in the middle stage is called a ROADM (c) Anuradha Udunuwara 16
  17. 17. ADM vs. OADM ADM OADM • function in the • function in the photonic traditional SONET/SDH domain under WDM networks • Used by conventional DWDM networks (c) Anuradha Udunuwara 17
  18. 18. ROADM • ability to remotely switch traffic from a WDM system at the wavelength layer. • planning of entire bandwidth assignment need not be carried out during initial deployment of a system. The configuration can be done as and when required without affecting traffic already passing the ROADM. • ROADM allows for remote configuration and reconfiguration. • Included in most of the xWDM equipment • Improves xWDM • migration to mesh architectures is a secondary driver for ROADM architectures. (c) Anuradha Udunuwara 18
  19. 19. Optical Transport Networks - evolution scenarios short term medium term long term Introduction of GFP, enhanced addition of a reconfigurable WDM SDH/SONET control plane, either networks (ROADM) technologies and ASON or GMPLS based. OTN (c) Anuradha Udunuwara 19
  20. 20. So…..what OTN means in “simple” terms • An OTN consists of ROADMs with DWDM, which can provide transport for NG-SDH, IP/MPLS, PBB/PBT, MPLS-TP, Ethernet and ATM. The control plane of this network(ROADMs) is GMPLS or/and ASON based (EMS based). (c) Anuradha Udunuwara 20

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