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
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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
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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
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7. OTN aim
• Combine the
– Benefits of SONET/SDH (OAM&P) and
– Bandwidth expandability of DWDM
• Includes FEC
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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
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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.
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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
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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!
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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
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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)
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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
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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
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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
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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.
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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
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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).
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