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8/7/2019 3..Optical Packet Switching Network
http://slidepdf.com/reader/full/3optical-packet-switching-network 1/28
OPTICAL PACKET SWITCHING
NETWORK
8/7/2019 3..Optical Packet Switching Network
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WHAT IS A SWITCH ??
y Device that channels incoming data from any of the
multiple input ports to any of the output ports.y SWITCHING TYPES:
1..CIRCUIT SWITCHING
2..PACKET SWITCHING
y
In circuit switching a dedicated path is established fory communication. EX..telephone networks
y In packet switching, the messages to be transmitted isbroken to small PACKETS.
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Todays switching networks:
y ROUTING and TRANSMISSION are the two functionsrequired to move packets through networks
y The router uses the information in the packet-(IPheader, Type, Priority) to route the packets from inputto output with minimal packet loss..
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Optic fibers
y A medium for transmitting information in the form of light pulses along a glass/fiber
y Also known as LIGHT PIPEy 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 singlestrand of optic fiber
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USE:B y the use of thistechnology, optic
fibertransmissionsystem can carry 32-80 wavelengths
modulated @2.5gbps-10gbpsper wavelength
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OPTICAL TRANSMISSION MEDIA
In MAN, links between the nodes are optical fibersHere packets are in the optical formatO-E-O conversion are required at the interface
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LIMITATIONS
LIMITED PACKET PROCESSINGSLOW OPERATIONCOST 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 FA BRIC
Optical signalsOptical signals
OPTICAL SWITCH FA BRIC
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SWITCH
ARCHITECTURE
An OPS node consists of
following components
1. INPUT INTERFACE
2. SWITCHINGMATRIX 3. BUFFER 4. OUTPUT INTERFACE
5. ELECTRONICCONTROL
UNIT
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1.INPUT INTERFACE
Wave length conversion
->conversion of external to internal
y wavelengths->identification of the beginning and end of the
header and payloadProvides synchronization
Header processing
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CONTROL UNIT
Processing routing informationUpdates header informationForwards header to output interface
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SWITCHING MATRIX
Optical switching of the payloads according tothe commands from the control unit
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OUTPUT INTERFACE
Provides 3R(reamplification ,reshaping, retiming)regeneration
Attaches updated header to correspondingoptical payloadConversion of internal to external wavelengthresynchronization
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GENERAL PACKET FORMAT
A generic packet format consists of
y HeaderPayload
Additional GUARD B ANDS before and after payload
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PACKET HEADER
A packet header may comprise of following fields
y Sync - provides synchronization
y Source Label -provides source node addressDestination Label-provides destination nodeaddress
y Type-type and priority of the carried payload
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continued
y Sequence Number :Packet sequence number toreorder packets arriving out of order and guarantee in-
order packet delivery
y OAM: Operation, Administration,Maintenance
y HEC: Head Error Correction
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OPTICAL SWITCHING TECHNIQUES
Two types of optical switching techniques
1.ALL OPTICAL LA BEL SWAPPING (AOLS)
2.LIQUID CRYSTAL SWITCHES
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ALL OPTICAL LABEL SWAPPING
y Consists of Optical Core Networks
1.Edge Router
2.Core Router
y Here Packets can be routed independent of PayloadBit Rate, Coding format ,length etc
y Can handle IP packets as well as ATM cells
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LABEL
A Lower Bit Rate (LA BEL) is attached to the
front of the packet A LA BEL contains-
1.Error checking information2. Source Information
3. Destination Information4. Framing and timing information
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PROCESS
Packets entered through EDGE nodes (source
side) is encapsulated with the optical labelHeader 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 Erasedback to packet payload
Updated header is encapsulated to the payload
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All tical la l s a i g
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2.LIQUID CRYSTAL SWITCHES
Principle : -when an electric field is applied toliquid crystal, the molecules line up andbecome opaque
The molecules are so thin and straight, will allow light of aparticular orientation to pass through the liquid crystal
It consists of 2 components
4. CELL
5. DISPLACER
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CELL AND DISPLACER
CELL: Formed by placing the liquid crystal between 2plates of glass
Glass is coated with oxide materials that conductselectricity
The function is to REORIENT the polarized lightentering the cell
DISPL A CER:It is a composite crystal that directs the polarized light
leaving the cell
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conclusion
The new technology regarded as ULTIMATE
y SOLUTION to bandwidth needs PROVIDING
-->IMPROVED EFFICIENCY -->LOW COSTS
-->UTILISE DWDM
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DONE BY
SHIKHA SINGH B. Tech(I.T.)- 3rd year
K.N.I.P.S.S., Sultanpur