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Research Methodology

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Doctor of Technology Thesis

A Multi-Channel Network Architecture Based on Fast

Circuit Switching

by Per Lindgren

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At the end you should have heard …At the end you should have heard …

Optical Multi-Channel Networks;Packet switched or circuit switched

networksUnderstand about DTM; New Interface design to cater for

High bandwidth networks;

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About Per Lindgren

      

        

Per LindgrenVP Business Development (founder) Net Insight. Born 1967. Ph.D. in Teleinformatics (KTH 1996). Per was previously Assistant Professor at KTH, where he was involved in the DTM project, among other things. He has also been involved in the DIM project.

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Rationale for this study

Evolution of Fiber and Optical networks; Increase of link Capacities Broadband networks vs Integration of

Video, VoIP, and other distributed multimedia applications

Integration of communication, computing and media

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Issues addressed by this thesis

Bottlenecks in processing and buffering in switch points;

Bottlenecks in network links (fiber), protocols and host interfaces

Consequences of a communication bottleneck change ( I.e., circuit-switched versus packet-switched networks)

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New Proposal

New network architecture based on DTM

New Host Interface

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The thesis examines

Optical multi-channel networks, eg. Based on WDM

Believe that parallel channel structure in such networks is more cost effective solution than increasing the bit rate of a single bit stream.

The interface between the network and the host interface and the host interface design

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What technology at the time this thesis was written

ATMFDDIFast Ethernet was springing

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End to end communication

A

Switching

Device

B

Network ANetwork B

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End to End Communication

Protocol

Protocol

Interface design Communication

media

Communication media

Interface design

Protocol Design

Switch pointRouting protocol

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Domain = Scope of the Thesis

Two different aspects of end-to-end communication:

•Service requirements and Performance aspects, within two different areas:

–Network Architecture

–Host Interface Design

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Contents of the thesis (179 pages)

Introduction …………………………………………………………………8 pages

Architecture for high Capacity Communications:• Background ………………………………………………………..3 • Existing Network Architectures ……………………………. 10• Multichannel Network Systems …………………………….. 6• Host Interface Design …………………………………………. 10

DTM –Circuit Switching Enhanced for Future Integrated Services:• Basic Principles of DTM ………………………………………… 7• DTM Protocol Suite ………………………………………………. 30 • DTM Enhancements ………………………………………….. 6• DTM Prototype Network …………………………………….. 8

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Contents of the thesis DTM Using Parallel Bitstreams: ………………………………………… 35 pages

• Parallel DTM Protocol Aspects……………………………….• Parallel DTM Hardware aspects …………………………….• Parallel DTM Synchronization Aspects……………………..• Prototype Implementation………………………………………• Distributed Switching…………………………………………….• Simulation of Parallel DTM…………………………………….• Simulation Results………………………………………………..

DTM Host Interface………………………………………………………….. 20 pages• The DTM Shared Memory Host Interface………………..• A Low-Cost Interface to the DTM Network……………….• Hardware Aspects of the Prototype Interface……………• Performance Measurements …………………………………..

Conclusion and Future Work ……………………………………………..3+3 Pages References …………………………………………………………………….. 16 pages

with 205 ref

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Packet Switching

Internet Network

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Circuit Switching

Telephone Network

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Competing Technologies

ATM – Asynchronous Transfer ModeGigabit EthernetFDDI – Fiber Distributed Data InterfaceDPT – Dynamic Packet TransportDTM – Dynamic Synchronous Transfer

Mode

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Competing Technologies

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ATM – What is it? Pros? And Cons?

Asynchronous Transfer Mode (ATM) is a packet switching and multiplexing technology designed as a general-purpose connection oriented (virtually circuit switched) transport mechanism for a wide range of services.

Benefits– Supports different types of data– High transmission rates– Good support for real-time traffic– Scales easily – Well suitable for long distances

Drawbacks– Complex technology– Expensive– Does not interoperate well with

Ethernet– No support for broadcast or

multicast– Only QoS for some ATM traffic

classes – Large amount of overhead

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FDDI – What is it? Pros? and Cons? FDDI uses a dual ring

topology. During normal operation,

the primary ring is used for data transmission, and the secondary ring remains idle.

The primary purpose of the dual rings is to provide superior reliability and robustness.

Benefits• Reliable• Built in redundancy• Large MTU size• Well tested

Drawbacks• Limited traffic

capacity (100 Mbps)• More expensive• Lacks multicast

support• No future potential

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Gigabit Ethernet- What is? Pros and Cons

Ethernet standard 802.3 started in the 1973

Improved to fast ethernet – 100Mbps

1995 Began the Gigabit Ethernet standard 802.3z

10Gbps Standard 802.3ae on the way

Benefits• Cheap• Well known• Commonly used• Simple to manage• Support for multicast and

broadcast• Low overhead

Drawbacks• No Bandwidth guarantees• Best effort – Problems for

applications such as VoIP, VC or any Real time application

• Small MTU size• Limited management capability

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DTM – What is it? Pros? And Cons? Developed at KTH Built in circuit switching techn

ology But utilizes the best features

of Circuit and packet switching technologies

It enables the user to set up and tear down the circuits instantly (like in a packet

switched system) while getting reservation of

bandwidth (which all circuit

switched systems offer)

Benefits– Offers true QoS– Dynamic increase/decrease of

bandwidth (DTM channels)– Fixed overhead size (depending on

number of nodes), i.e. not proportional to link data speed. Small total overhead

– Fast set-up and tear-down of channels compared to other circuit switched technologies

– Simple and good support for multicast– Compatible with other technologies,

support for IP-routing, Ethernet bridging, VLAN and E1/T1 tunneling. Can be run on dark fiber, DWDM and SDH/SONET (not all DTM versions)

– Deterministic delay – High capacity

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DTM – What is it? Pros? And Cons? … Drawbacks

• Circuit switched. Setting up a connection takes time (even though it is faster than other circuit switched alternatives), which is negative for short transfers

• New technology with an uncertain future• Dynarc and Net Insight develop different

protocols that are incompatible• Minimum channel speed is 512 kbps, which

might be unnecessary high for small transfers• Complex, with unnecessarily many parameters• Expensive,

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DPT – What is it? Pros? and Cons? Developed by CISCO

Official name is Resilient Packet Ring - IEEE 802.17

DPT is designed to be an IP packet optimized transport solution.

Combine the bandwidth efficiency and services-rich capabilities of IP routing with the self-healing capabilities of fiber rings.

The key applications for DPT include cable data backbone access rings and regional transport rings.

Benefits

– Fair allocation of bandwidth

– Low overhead

– Effective use of bandwidth (Spatial Reuse)

– Very Reliable and Robust

– Redundancy and large MTU size

– native multicast support and can distinguish between high priority and low priority packets

Drawbacks

– Double ring needed

– Delays caused by buffering in nodes

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Host Interface Design

RAM CPU

Host Interface

System Bus

Transmission Medium

Bottlenecks

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DTM –Circuit Switching Enhanced for Future Integrated Services:

DTM Enhancements

• Fast Channel Creation

• Fast Channel Establishment over several hops

• Dynamic Signaling

• Base Frames consisting of multiple cycles

• Virtual Networks

• Slot Reuse in DTM

• Parallel DTM

• Switch Replication

DTM Prototype Network

                                          

          Fig 1. DTM Prototype Node

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DTM Using Parallel Bit streams

Two ways to increase transmission capacity:•Increase bit rate on the fiber;•Use parallel bit streams

In both we can use•Wavelength division multiplexing (WDM)•Space Division Multiplexing (SDM)

The proposed solution uses parallel bit streams with WDM

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DTM Using Parallel Bitstreams … Prototype Implementation

– The prototype uses replicated hardware to receive data on both wavelengths simultaneously.

– That is possible due to use of two demux, two slot counters and two channel tables on the board.

Distributed Switching– Distributed Switching

scheme between two fibers in parallel DTM is done electrically.

– Is based on the shared medium to avoid switch bottleneck

Simulation of Parallel

• Analyses were performed with regard to Slot Utilization, blocking and access delay for a dual bus with a varying number of parallel bit streams

• The effects of different user requirements, resource management schemes and traffic scenarios were also analysed.

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DTM Using Parallel Bitstreams …

DTM Simulation Results

• It has been shown that Centralized Slot management schemes perform very well specially with partially-equipped nodes;

• Fragmentation of the pool of free slots is normally very modest;

• This scheme simplifies network management;

• Disadvantages setup delay increases; nodes are dependent on the slot server, which makes the system sensitive to failures

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DTM Using Parallel Bitstreams …

DTM Simulation Results• Distributed scheme has several benefits

compared to the centralized. • No risk of bottlenecks caused by a a single

node;• Access delay is shorter, redundancy is higher;• Scales well to longer buses

A Hybrid scheme is however likely to give the best overall performance. For instances distribute slots along nodes. Keep part in several slot servers that share the global state information.

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DTM Host Interface DTM shared memory host interface: Segmentation and reassembly (SAR)

protocol is implemented in hardware in the board

Incoming and outgoing channels operate simultaneously;

Congestion control is not needed as DTM uses circuit switching;

The Interface is based on shared memory in order to reduce the number of transfers over the host systems bus;

The interface uses interrupts for comm state changes with the processor;

The interface is designed to support fast connection establishment. Buffers are allocated to channels without involving CPU

                                          

         Fig 4. DTM Host Interface

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DTM Host Interface …

A Low-Cost Interface to the DTM Network:

• Proposed for equipment that doesn’t need processing capability such as a video terminal.

Hardware Aspects of the Prototype Interface

• The hardware implementation of the host interface was done between a DTM Network and SUN SPARCstation.

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DTM Host Interface

Performance Measurements Performance measurements were done using Sparcstation 2

and 10 and with memory buffers from 4KB to 1MB, in systems using different cache mechanisms

Measurements show that the less System Bus access the better. The faster the system bus the better. Performance will also increase if no no update to the main memory is required when the buffer is flashed.

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Conclusion With evolution of fiber optics, the bottleneck in the

communication infrastructure is moving from capacity in the links to place in the network where processing and storage is needed, for example in switch points.

The main argument is circuit-switched networks have a simple communication architectures with low requirements on processing of data elements that make them well-suited to handle high capacity in fibers.

Convergence of communication, computing and media imposes new requirements on the services the network must provide.

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Research Methodology Used

Introduction•Domain •Problem = purpose•Expected Results

General Background•Framework in time and Technology

Development and Experimentation Conclusions

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What I have learnt through this reading

Nothing that we say today is guaranteed to remain true for tomorrow. Anything we say could be valid within a certain timestamp even if the time stamp is too large for our life

This study was done under some assumptions:•WDM precision diff & not economically

viable•Cost of laser beamers and sensors were

very high to make it viable.

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Contribution to the Knowledge

Knowledge so conceived is not a process that converges toward an ideal view; it is an ever increasing ocean of alternatives, each of them forcing the others into greater articulation, all of them contributing, via this process of competition, to the development of our mental faculties

Prof Naess

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