1. 1
OPTICAL BURST SWITCHING
Under the guidance of
Mr. Ejaz Aslam Lodhi
Indian Institute of Technology Kanpur (IITK)
Submitted By
Jigyasa Singh
M.TECH(ECE)
4. 4
Optical Circuit Switching
⢠Long circuit set-up (a 2-way process with
Req and Ack).
⢠Good for smooth traffic and QoS guarantee
due to fixed BW reservation.
⢠Either wasted BW during off/low-traffic
periods & too much overhead (e.g., delay)
due to frequent set-up/release (for every
burst).
5. 5
Optical Packet Switching
⢠Problem is lack of optical buffer (RAM).
⢠Fiber delay lines (FDLs) are bulky and
provide only limited & deterministic delays.
â store-n-forward (with feed-back FDLs) leads to
fixed packet length and synchronous switching.
⢠Tight coupling of header and payload.
â requires stringent synchronization, and fast
processing and switching (ns or less).
6. 6
Optical Burst Switching (OBS)
⢠Combines advantage of circuit & packet
switching.
⢠A burst has a long, variable length payload.
⢠It is assembled at an ingress router by
aggregating a no. of IP packets which may
be received from single host or multiple
host from same or different access network.
8. Objectives
⢠Study of architecture of OBS.
⢠Study of burst assembly schemes.
⢠Study of burst scheduling algorithm.
⢠Study of contention resolution techniques.
⢠Study of QoS.
⢠Implementation.
⢠Analysis.
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10. Architecture of OBS
routed through OBS network
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OBS NETWORK
EDGE
NODE
CORE
NODE
Optical
switching
matrix +
Switch control
Matrix
Responsible to
forward data
burst
Optical
switching
matrix +
Switch control
Matrix
Responsible to
forward data
burst
Ingress
Node
Egress
Node
11. Burst Assembly schemes
TIME BASED SCHEME THRESHOLD BASED SCHEME
A timer is started at the initialization of
the burst assembly. A data burst
containing all the packets in the buffer
are generated when timer exceeds the
burst assembly period.
A burst is created & sent into the OBS
network when total size of the packets
in the queue reaches the threshold
value.
Suitable for real time/ time constrained
application.
Suitable for time insensititive
application.
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12. Wavelength reservation schemes
Tell-and-Go (TAG) Just-in-Time (JIT) Just-enough-Time (JET)
Immediate reservation
scheme.
Immediate reservation
scheme.
Delayed reservation
scheme.
Control packet is txd on
control channel followed
by payload on data
channel with zero or
negligible offset.
The buffering of payload
at each node is eliminated
by inserting a time slot
between control packet &
payload.
Control packet reserves
wavelength for upcoming
burst for a fixed duration
of time.
Source send control
packet after payload.
Nodes reserve the
resources as soon as
control packet is
processed.
Size of the data burst is
decided before the control
packet is txd by the
source.
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13. Burst scheduling algorithms
WITHOUT VOID FILLING WITH VOID FILLING
FFUC ( First fit unscheduled channel)
LAUC ( Latest available unscheduled
channel)
FFUC-VF
Min-EV (Minimum end-void)
LAUC-VF
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15. QoS
RELATIVE QoS ABSOLUTE QoS
The performance of each class is not
defined quantitatively in absolute terms.
It provides a bound for loss probability
of guaranteed traffic.
The QoS of one class is defined
relatively in comparison to other
classes.
It is preferred to ensure that each user
recieves an expected level of
performance.
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