A Survey of Media Access Protocols for Optical Networks

1
A Survey of Media Access Protocolsfor Optical
Networks
In Part fulfillment of Interconnection Networks

• By
• Yasir Drabu

2
Overview

• Introduction
• Current Scenario, Why optical access networks
• Optical Networking Architectures
• WDM Links, Wavelength routing networks,
  Broadcast-and-select networks and Passive Optical
  Networks
• Optical Components
• Transmitters and Receivers
• Medium Access Protocols
• Issues, Classification, comparison and
  description
• Conclusion
• References

3
Introduction - Current Market Scenario
Metropolitan Networks
Access Networks
Long Haul Networks
4
Introduction - Current Market Scenario (Cont.)
5
Introduction - Why Optical LANs

• Immune to EMI (Electromagnetic Interference)
• Extreme High Bandwidth
• Secure transmissions
• Reduced Cross Talk
• Broadband service applications
• Evolution-proof capabilities
• Low Power Requirements

6
Optical Network Architecture - Classification

• Two major Issues with high speed networks
  Bandwidth and Latency
• WDM makes maximum use of bandwidth by taking into
  consideration the limitation posed by the
  electronic control circuitry.

7
Optical Network Architecture -
Broadcast-and-Select Networks

• Broadcast and select networks are based on a
  passive star coupler device, connected to several
  stations in a star topology.
• These networks are simple as the coupler is a
  passive element and these n/w have a natural
  broadcasting and multicasting capability.

8
Key Components- For a Optical Terminal

• Optical Terminals (Nodes)
• An optical terminal basically has a optical
  transmitter and an optical receiver.
• The primary factor is cost. As optical technology
  evolves, optical network interface units will
  cost less.
• We can have
• Fixed Receivers (FR)
• Tunable Receiver (TR)
• Fixed Transmitters (FT)
• Tunable Transmitters (TT)

iolon Tunable Receiver
9
MAC Layer and Protocols - In Prospective

• The data link layer is divided into two sub
  layers
• LLC This sub layer takes care of error and
• flow control. Manages link control and
  defines
• SAP (HDLC)
• MAC Decides channel arbitration, essentially
• controls the media being used. (Ethernet,
  Token Ring)
• ISSUES
• MAC protocols are designed - depending on the
  needs of the application, the hardware
  capabilities at the nodes and the level of
  performance required.
• CSMA/CD is not efficient because of the delay to
  transmission ratio is low in optical networks.
• The Key issue is complexity and not bandwidth.
• There is always a trade off between throughput
  and implementation complexity of MAC protocols.

10
Broadcast and Select MAC Protocols -
Classification

• In a broadcast and select network the key issues
  become
• When to broadcast ?
• What to select ?
• Pretransmission protocols use a simple tell and
  go technique to arbitrate the channel.
• Reservation protocols are more complex but
  require less processing.

11
Broadcast and Select MAC Protocols-Basic
Protocol (Slotted Aloha/Slotted Aloha)

• The Aloha and Slotted Aloha were the earliest
  protocols developed of a single broadcast
  channel.
• To extend this protocol to multiple channels, let
  us assume that there are W wavelengths and n
  nodes. Also there is a (W1)st channel called
  the control channel.
• On the data channel we transmit data packets and
  on the control channel we transmit the control
  packets. The data packet size is L times that of
  the control packet, as the control packet is
  assumed to be smaller.
• Whenever a node, say , x, has a data packet to
  send
• It first sends a control packet in a control slot
• Then the data packet is send immediately in the
  following slot.
• The control packet carries the identity of the
  wavelength on which the data packet will be
  transmitted,say, ?k , and the identity of the
  node say y.
• Provided no other node transmits a control
  packet in the same slot, node y will receive the
  control packet sent by node x in the interval
  dprop , dprop1 and know that in the next data
  slot, a data packet intended for it has been
  transmitted on wavelength ?k . Node y tunes its
  receiver to ?k and receives data.

12
Medium Access Protocols - Another Protocol
(DT-WDMA)

• This protocol assume that the
• Number of nodes n is equal to the number of
  wavelengths W.
• Each node has a 1 FT, 1 TR and 1 FR for the
  control channel
• The size of the data slots is n times the control
  slots.
• The data slots do not overlap in time.
• When ever a node, say xi, has a data packet to
  send, it sends a control packet in a control slot
  and the data packet in the data slot immediately
  following it.
• The control packet is sent on the control
  wavelength (W1) and the data packet on the
  wavelength assigned to node is fixed tuned
  transmitter, namely, wavelength ?i , The control
  packet carries the identity of the intended
  receiving node, say node, xj ,and the control
  slot in which this packet is transmitted
  implicitly identifies the wavelength on which the
  data packet will be transmitted, namely, ?i .
• Each node continuously monitors the control
  channel. Thus when node xj , receives a control
  packet send by node xi it knows that the next
  data slot has a packet intended for it being
  transmitted on wavelength ?I so it tunes its TR
  to that wavelength.
• Features Data packets never collide also
  control packet never collide.

13
Medium Access Protocols - Comparison Of
Pretransmission Coordination based Protocols
14
Medium Access Protocols - Comparison Of
Reservation based Protocols
15
Optical Companies in Context
16
Conclusions

• MAC protocols that provide high throughput, low
  delay, simplicity, robustness, and support for
  priorities and different traffic classes are good
  candidates for future research.
• Continued development of fast tunable, wide range
  lasers and filters is needed to implement the
  tunable transmitters and receivers required for
  these protocols.
• Another key to the widespread deployment of
  all-optical networks is cost reduction for
  optical components.
• A final important issue is the development of an
  efficient protocol stack that supports current
  and future heterogeneous network traffic. As
  research in optical technology progresses,
  decisions will have to be made on the optimal
  protocol layering for high-speed WDM networks.

17
References
Books 1. Optical Networks A Practical
Perspective By Ramaswami and Sivarajan. 2.
Multiple Access Communications - Foundations for
Emerging Technologies. IEEE Press,
1992.   Papers 1 Eytan Modiano,Richard Barry -
" A Novel Medium Access Control Protocol for
WDM-Based LANs and Access Networks Using a
Master/Slave Scheduler"- IEEE JOURNAL OF
LIGHTWAVE TECHNOLOGY, VOL. 18, NO. 4, APRIL 2000
  2 P. Dowd, Random access protocols for high
speed interprocess communications based on a
passive optical star topology, J. Lightwave
Technology., June 1991.   3 T. P. Lee and C. E.
Zah, Wavelength-tunable and single frequency
semiconductor lasers for photonic communications
networks IEEE Communication. Mag., pp. 42 52,
Oct. 1989.   4 Ori Gerstel. On the future of
wavelength routing networks. IEEE Network, pages
14-20, Nov. 1996   5 David A. Levine and Ian F.
Akyildiz, "PROTON A media access control
protocol for optical networks with star
topology", IEEE/ACM Transactions on Networking,
Volume 3,Number 2,pp.158-168, April 1995.   6
K. M. Sivalingam, K. Bogineni, and P. W. Dowd,
Pre-allocation media access control protocols
for multiple access WDM photonic networks", Proc.
ACM SIGCOMM '92 in Computer Communication Review,
vol. 22, no. 4, pp. 235-246, Oct. 1992.   7
Patrick W Dowd, "Random Access Protocols for High
Speed Interprocessor communication Based on an
Optical passive Star Topology", IEEE JOURNAL OF
LIGHTWAVE TECHNOLOGY, VOL. 9, pp 799-808, June
1991.   8 Michael Montgomery, " A Review of MAC
Protocols for All-Optical Networks" Tech. Rep.
PDS-95-011, ECE Dept., UT-Austin, 1994