OPTICAL PACKET SWITCHING

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OPTICAL PACKET SWITCHING

• Done by
• 
  ARUN JOY
• 
  R7A11

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WHAT IS A SWITCH ??

• Device that channels incoming data from any of
  the multiple input ports to any of the output
  ports.
• SWITCHING TYPES
• CIRCUIT SWITCHING
• PACKET SWITCHING
• In circuit switching a dedicated path is
  established for
• communication. E.g. telephone networks
• In packet switching, the messages to be
  transmitted is broken to small PACKETS.

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Todays switching networks

• ROUTING and TRANSMISSION are the two functions
  required to move packets through networks
• The router uses the information in the packet-(IP
  header, Type, Priority) to
• route the packets from input to output
• with minimal packet loss

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Optic fibers

• A medium for transmitting information in the
  form of light pulses along a glass/fiber
• Also known as LIGHT PIPE
• Provides greater bandwidth

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WAVE LENGTH DIVISION MULTIPLEXING (WDM)

• A technology used to increase the information
  rate
• Here multiple signals can traverse through a
  single strand of optic fiber

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USE

• By the use of this technology, optic fiber
  transmission system can carry 32-80 wavelengths
  modulated _at_ 2.5gbps-10gbps per wavelength

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OPTICAL TRANSMISSION MEDIA

• In MAN, links between the nodes are optical
  fibers
• Here packets are in the optical format
• O-E-O conversion are required at the interface

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LIMITATIONS

• LIMITED PACKET PROCESSING
• SLOW OPERATION
• COST AND COMPLEXITY
• CROSS TALK
• These limitations degrades the performance
  of the system affecting the bandwidth

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SOLUTION!

• The solution is OPTICAL PACKET SWITCHING
• The signals are being processed by means of
  OPTICAL SWITCH FABRIC

OPTICAL SWITCH FABRIC
OPTICAL SIGNALS
OPTICAL SIGNALS
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SWITCH ARCHITECTURE

• An OPS node consists of following components
• INPUT INTERFACE
• SWITCHING MATRIX
• BUFFER
• OUTPUT INTERFACE
• 5. ELECTRONIC CONTROL UNIT
  

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1.INPUT INTERFACE

• Wave length conversion
• -gtconversion of external to internal
  wavelengths
• -gtidentification of the beginning and end of
  the header and payload
• Provides synchronization
• Header processing

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CONTROL UNIT

• Processing routing information
• Updates header information
• Forwards header to output interface

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SWITCHING MATRIX

• Optical switching of the payloads according to
  the commands from the control unit

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OUTPUT INTERFACE

• Provides 3R(reamplification,reshaping,retiming)
  regeneration
• Attaches updated header to corresponding optical
  payload
• Conversion of internal to external wavelength
• resynchronization

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GENERAL PACKET FORMAT

• A generic packet format consists of
• Header
• Payload
• Additional GUARD BANDS before and after payload

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PACKET HEADER

• A packet header may comprise of following fields
• Sync- provides synchronization
• Source Label-provides source node address
• Destination Label-provides destination node
• address
• Type-type and priority of the carried payload

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continued

• Sequence Number Packet sequence number to
  reorder packets arriving out of order
• and guarantee in-order packet delivery
• OAM Operation, Administration, Maintenance
• HEC Head Error Correction

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OPTICAL SWITCHING TECHNIQUES

• Two types of optical switching techniques
• 1.ALL OPTICAL LABEL SWAPPING (AOLS)
• 2.LIQUID CRYSTAL SWITCHES

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ALL OPTICAL LABEL SWAPPING

• Consists of Optical Core Networks
• 1.Edge Router
• 2.Core Router
• Here Packets can be routed independent of Payload
  Bit Rate, Coding format ,length etc
• Can handle IP packets as well as ATM cells

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LABEL

• A Lower Bit Rate (LABEL) is attached to the front
  of the packet
• A LABEL contains-
• 1.Error checking information
• 2. Source Information
• 3. Destination Information
• 4. Framing and timing information
  

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PROCESS

• Packets entered through EDGE nodes (source side)
  is encapsulated with the optical label
• Header is removed.
• At internal CORE nodes, the label is optically
  erased, embedded with a new label
• The payloads with the label gets routed in the
  networks
• At the Edge nodes (destination side) ,the label
  is Erased back to packet payload
• Updated header is encapsulated to the payload

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All optical label swapping
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2.LIQUID CRYSTAL SWITCHES

• Principle -when an electric field is applied to
  liquid crystal, the molecules line up and become
  opaque
• The molecules are so thin and straight, will
  allow light of a particular orientation to pass
  through the liquid crystal
• It consists of 2 components
• CELL
• DISPLACER

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CELL AND DISPLACER

• CELL Formed by placing the liquid crystal
  between 2 plates of glass
• Glass is coated with oxide materials that
  conducts electricity
• The function is to REORIENT the polarized light
  entering the cell
• DISPLACER
• It is a composite crystal that directs the
  polarized light leaving the cell

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conclusion

• The new technology regarded as ULTIMATE SOLUTION
  to bandwidth needs PROVIDING
• -gtIMPROVED EFFICIENCY
• -gtLOW COSTS
• -gtUTILISE DWDM

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THANK YOU!!!

• 
  

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QUESTIONS ????
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DONE BY

• ARUN JOY
• 7TH SEMESTER,DEPARTMENT OF COMPUTER SCIENCE AND
  ENGG,
• SREE NARAYANA GURUKULAM COLLAGE
  OF ENGINEERING,KADAYIRUPPU.