A Survey of Media Access Protocols for Optical Networks : A Survey of Media Access Protocols for Optical Networks
By
Yasir Drabu In Part fulfillment of
Interconnection Networks
Overview : 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
Introduction - Current Market Scenario : Introduction - Current Market Scenario Long Haul Networks Access Networks Metropolitan Networks
Introduction - Current Market Scenario (Cont.) : Introduction - Current Market Scenario (Cont.)
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
Introduction - Why Optical LANs
Optical Network Architecture - Classification : 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.
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.
Optical Network Architecture - Broadcast-and-Select Networks
Key Components - For a Optical Terminal : 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
MAC Layer and Protocols - In Prospective : 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.
Broadcast and Select MAC Protocols - Classification : 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.
Broadcast and Select MAC Protocols -Basic Protocol (Slotted Aloha/Slotted Aloha) : 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 (W+1)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 , dprop+1] 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.
Medium Access Protocols - Another Protocol (DT-WDMA) : 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 (W+1) and the data packet on the wavelength assigned to node i’s 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.
Medium Access Protocols - Comparison Of Pretransmission Coordination based Protocols : Medium Access Protocols - Comparison Of Pretransmission Coordination based Protocols
Medium Access Protocols - Comparison Of Reservation based Protocols : Medium Access Protocols - Comparison Of Reservation based Protocols
Optical Companies in Context : Optical Companies in Context
Conclusions : 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.
References : 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 LAN’s 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