Hybrid Swtiching dyk04

March-2004 1

HTM Switching Architecture

Dae Young Kim(http://cnu.ac.kr/~dykim)

Chungnam Nat’l Univ.

March-2004 2

Learned in Kindergarten Circuit Switching is:

Guaranteeing QoSExpensiveWasting the bandwidthGood for CO operationFor Telco believers

Packet Switching is:Not for serious QoSCheapExploiting the bandwidthGood for CL operationFor Computer-manias

March-2004 3

Why Is Circuit Switching So Expensive?Due to:

Over-specification; five-9 in OAM&P, MTBF, ...Network is too smart Telco Monopoly

Can be made drastically cheaper:Loosened specs

Data is over 90% of allPacket back-up is available

TDM chips are cheapOpen-ended competition among network/service providers

March-2004 4

Two DiversionsVirtual Circuit

Fake circuitCO-operated packetsPacket but with QoSX.25, FR, ATM

QoS over CL PacketsIP IntServ/DiffServDaydream...?Not quite QoS, but CoS

March-2004 5

QoS over Packets?VC

X.25 ended up with few Kbps.FR ended up with sub-Megs.ATM's yet to be proved in large scale.

IPWill never succeed in QoSOver-provisioning has a better chance.Thank God! Most data don't need QoS.Over-provisioned BE is enough, at most CoS.

March-2004 6

Now What? Ultimately, people'll expect you to deliver uncompromised HDTV in the same pipe as you do IP packets.Until then, they'll never be happy, you'll never be dismissed.Sorry, the world is divided into two, and you have to take a side:

either Packet or CircuitOr you're just a believer in the theory:

They'll eternally go in parallel, like railways;Always two pipes to your home and office.

March-2004 7

Circuit over Packet Circuit(QoS) emulation is not end-to-end scalable.

Too many states to manageConsumes too much computing resource.

Can be close to a circuit, but never really is one.Not enough for uncompromised DTV quality for military/medical/physics applications

March-2004 8

Advantages of Packets over Circuits

QoS comes as default.Less states needed for circuitsStates not too dynamic, just static to quasi-static

March-2004 9

Synchronous Hybrid Switched Network

Using synchronous slots based on Circuit-oriented networkHybrid Switch : Using both Connection-orient(CO) and Connectionless-orient(CL) slotHybrid type switch networks; Circuit switch based + packet switch based mechanism

semi-packet switching

March-2004 10

Principle of HTM

A

D

C

B

Usert0

Buffer

To Remote

A B B D B B C BCycle1 Cycle2

Header

CL slot

CO slot

A B B B B B C BCycle3 Cycle4

Idle slot

t1 t2 t3

March-2004 11

Slot format10 9 8 7 6 5 4 3 2 1

Header Payload

01 Payload1 10 Payload2

Slot format

11 Payload3 01 Payload1 00 Payload2

CL traffic CO traffic

00; Idle slot, 01;Start of CL type, 10; Continuance Measage of CL Type 11; CO type

CL traffic Idle traffic

March-2004 12

Hybrid Switching block diagram

Buffer

RouterModule

HeaderInsertion

OutputSlot

Inserter

Packetreassembler

HeaderExtracter

CO/CLClassifier

Switch Module

InterfaceSerial

Cut-through

table lookup

CL

CO

Low PriorityHigh Priority

March-2004 13

HTM Switch Structure

Admission Control/Control Signaling Processing

TDM SwitchControl

Data

Routing Module

Coordinator

March-2004 14

Host Structure

SAR Signaling Management

RX TX Logic

CO CLCO

PHY

HighPriority

LowPriority

High Level

March-2004 15

Flow Chart of Hybrid SwitchSTART

END

Demultiplexing

CO Traffic?

Switch Module

Packet reassemble

Router Module

Is there ouput idletime-slot?

BufferingOutput Slot Inserter

Multiplexing

No

No

Yes

Yes

March-2004 16

Dynamic Slot Allocation

Host Switch

Time Slot Request(number of slots)

Time SlotResponse(Reason)

March-2004 17

Following ConnectionSender

AccessSwitch

BackboneSwitch

AccessSwitch Receiver

CRSet-up

Time Data

Data

CONNECT CONN ACK

CRCR

CRCC

CCCC

CCData

DataData

CONN ACKCONN ACKCONN ACK

March-2004 18

Simulation Topology

HTM Network

HTM Ingress Border SW

Packet Node A

HTM Egress Boder SW

Circuit Node A

Packet Node B

Circuit Node B

March-2004 19

Simulation

March-2004 20

Conclusion(I)Circuit QoS over Packet

SAND

MM

QoS

PKT

March-2004 21

Conclusion(II)Dumb Packet over Circuit

Seamless Packet over Circuit

Need New Switching Paradigm!