Smart IP Switching A Hybrid System for Fast IP-based Network Backbones David Lloyd Donal O’Mahony

Smart IP Switching A Hybrid System for Fast IP-based Network

Backbones

David Lloyd

Donal O’Mahony

IP over ATM

Conventional IP routers have become a bandwidth bottleneck

ATM technology offers high bandwidth capability

IP over ATM schemes have been developed to support IP over and ATM Network

•Classical IP over ATM•Next Hop Resolution Protocol (NHRP)•LAN Emulation (LANE)•Multi-Protocol Over ATM (MPOA)

Heavyweight Nature of Emulation Techniques

ATM Network

Emulation Scheme

IP Network

Overlay Model

IP on ATM Hardware

IP implemented directly on ATM hardware

Schemes may be categorised by the approach they employ for setting upswitched paths through a network

Principal Approaches are:

•Traffic-Driven- Nature of traffic drives switch path establishment- (Ipsilon’s IP Switching and Toshiba’s CSR)

•Control-Driven

- Switched paths set up before data traffic flows- (Cisco’s Tag Switching and IBM’s ARIS)

Traffic-Driven ApproachesAdvantages

Switched paths are only set up for long-lived flows

Schemes are non-complex

Resilient in event of failure

Scalable

Disadvantages

Flow aggregation is not an inherent property of the scheme

Short-lived Flows that recur consistently can cause excessive control traffic

Flow Merging in Control-driven Schemes

VC Merge

The merging of one or more incoming VCs into the same outgoing VC

Requires special VC merge-capable ATM hardware

VP Merge

The merging of one or more incoming Virtual Paths (VPs) onto the same outgoing VP

It is imperative to ensure that active VCs are not merged

Block allocation of VCIs Required

AAL-5 Cell Interleave

Node 1

Node 2

Node 3 Node 4

AAL-5 PDU A

AAL-5 PDU B

Virtual Channel

Virtual Channel

Virtual Channel

ATM Cells

ATM Cells

ATM Cells

Control-Driven Approaches

Advantages

No delay in setting up a dedicated VC on a flow by flow basis

All IP packets are switched at layer 2

Disadvantages

Dedicated-VCs are established for all routes

Schemes are Complex

Multi-Protocol Label Switching

In early 1997 the IETF Multi-Protocol Label Switching (MPLS) working group was established.

The group issued a framework document, which attempts to:

Provide a coherent description of the major approaches

Discuss the technical issues involved

Lay the way forward for standardisation

Introduction to Smart IP Switching

Smart IP Switching is a new traffic-driven scheme that exhibits advantages of both the traffic-driven and control-driven approaches.

The main benefits of Smart IP Switching are:

The Introduction of flow aggregation into a traffic-driven scheme

The definition of short-term and long-term VCs

Increasing the proportion of IP packets switched at layer 2

Smart IP Switching Concepts

The key concepts that define Smart IP Switching are:

Unique Flow Identifier - Flow Identification

Flow aggregation - Based on CIDR prefixes

Ingress-piping - Merging flows at an ingress node

Virtual Merge - Merging flows at intermediate nodes

Longevity of VCs - short-term and long term VCs

Flow Identification

Unique Flow Identifier (UFI)

flow type flow identifier prefix mask

The Unique Flow Identifier identifies Ipsilon flow types plus a new flow type (flow type 3)

Flow type 3 is specifically defined to represent aggregate flows

Smart IP Switch Representation

Pseudo IPModule

Smart IP Switch Controller

routingtable

forwardingengine

FlowInformationBase (FIB)

Residual FIB(RFIB)

ControllerFunctions

switch fabric

ipswitch port ipswitch portipswitch portipswitch port

write-down operationsand control of switch

fabric

write-up operations

Smart IP Switch Operation (1)

SIPS Operation (First Packet)

SIPS Operation (Dedicated VCs)

VPI=0 VPI=0VPI=0

VCI=32 VCI=32VCI=32

Default VC

Default VC

Default VC

Default VC

SIPS1

SIPS1

SIPS3

SIPS3

SIPS2

SIPS2

LAN1

LAN1

Default VC

first packet first packet first packet

IFMP REDIRECT IFMP REDIRECT IFMP REDIRECT

first packetP1

P2 P2P2 P1P1P1

P2P1P1 P2P2

P1=port 1P2=port 2

Default VC

Ingress-pipeIngress-pipe

Smart IP Switch Operation (2)

SIPS Operation (Second packet)

SIPS Operation (First Cut-through)

VPI=0

VPI=0

VPI=0

VPI=0

VPI=0

VPI=0

VCI=32

VCI=32

VCI=32

VCI=32

VCI=32

VCI=32

Default VC

Default VC

Default VC

Default VC

SIPS1

SIPS1

SIPS3

SIPS3

SIPS2

SIPS2

LAN1

LAN1

second packet

second packet P2

P2

P2

P2

P2

P2

P1

P1

P1

P1

P1

P1

second packet

Ingress-pipe

Ingress-pipe

Cut-through

Default VC

Down-piping

Smart IP Switching Operation (3)

SIPS Operation (Second Cut-through)

VPI=0 VPI=0VPI=0

VCI=32 VCI=32VCI=32

Default VC Default VCSIPS1 SIPS3SIPS2

LAN1

P2 P2P2 P1P1P1

second packet

VCI=33 VCI=33

Ingress-pipe Ingress-pipe

Cut-throughCut-through

Ingress-pipe at Intermediate Node

SIPS Operation (Intermediate Ingress-Pipe)

VPI=0 VPI=0VPI=0

VCI=32 VCI=32VCI=32


LAN1

P2 P2P2 P1P1P1

VCI=33 VCI=33

FDDI : LAN

VCI=35

Ingress-pipe

P1=port 1P2=port 2

Cut-through

Virtual Merge

SIPS Operation (Virtual Merge)

SIPS1 SIPS3SIPS2

LAN1

P1P2P1P1 P2P2

P1=port 1P2=port 2

egress node

Dedicated VC next available VC

ingress node

ingress-pipe

SIPS4 P2P1

LAN2

virtual mergeingress-pipe

Dedicated VC

default VCs omittedfor clarity

Ingress-Piping

SIPS1

10/100 Mb Ethernetlinks

10 Mb Ethernet LAN

network :172.16.0.0SIPS3

SIPS4

SIPS2

LAN3

LAN1

LAN2

Flow Management

Flow Information Base (FIB) used to manage flows

Ipsilon flow types are created and refreshed as normal

Detection of a potential aggregate flow is based existence of a CIDR prefix

Flow type 3 is refreshed by sending an REDIRECT message with a redirect message element attached for every upstream ingress-pipe that remains active

Referesh of VCs is managed on a localised scope

Longevity of VCs

The first time a flow is detected, it is set up as short-term

A VC used by many flows is transitioned to long-term

VCs for flows that recur are set up as long-term

Long-term VCs do not have to be refreshed as often as short-term VCs

VC Pool

The use of a VC pool eliminates the delay incurred in setting up a VC

A suitable strategy to manage VC pool size must be employed

VCs may be expensive

Packets arriving on an unassigned VC must be associated with the relevant flow type 3

The use of a VC pool has been discussed in the literature

CIDR Fall-back

VPI=0VPI=0

VCI=32VCI=32


LAN1

P2 P2P2 P1P1P1

Host:172.16.3.1

Network: 172.16.3.0

Routing table entry172.16.3.0



Based on UFI prefix172.16.0.0


CIDR-Fall-back (2)

VPI=0VPI=0

VCI=32VCI=32


LAN1

P2 P2P2 P1P1P1

Host:172.16.3.1

Network: 172.16.3.0




VCI=33



Simulated Network

heuston.hea.ie

connolly.hea.ie

cisco.tcd.ie

Boston.mci.net

SanFrancisco.mci.net

TCD

UCG

UL

DCU

UCD

disney.com www.cise.nfs..gov

www-vbns.reston.mci.net.net

mit.edu

ieee.org

altavista.com

webcrawler.com

pointcast.com

microsoft.com

netscape.com

QUB

ebone.london

man.ja.net

SIPS, or Router (Not Implemented)SIPS(Implemented)

Simulated ATM Link(Implemented)Simulated ATM Link(Not Implemented)

Non-existent or Sink Port

192.121.154.230

198.3.101.102

193.1.194.26

193.1.194.18

134.226.0.0

193.1.195.30

193.1.195.250

204.189.128.178

193.1.195.90

141.142.3.16206.235.18.81

206.235.18.84

204.70.133.152

vvv.nsf.gov

204.189.128.177

199.172.136.1

18.69.0.27

208.218.3.1

204.123.2.69

205.228.184.6

207.200.71..20

207.68.137.64

ncsa.uiuc.edu

204.189.216.152

204.189.216.153

193.1.195.249193.1.195.29

193.1.194.110

137.43.0.0136.206.0.0

193.1.194.18136.201.0.0

140.203.0.0

IP PacketMonitoring Device

Simulation Results

IP Switching Smart IP Switching

TEST-SET1Percentage IP Packets Switched at Layer 2 54.0% 99.2%Percentage of control traffic overhead 7.1% 1.4%

TEST-SET2Percentage IP Packets Switched at Layer 2 50.6% 95.1%Percentage of control traffic overhead 2.5% 9.5%

SummarySmart IP Switching:

Is a new traffic-driven IP on ATM hardware scheme modelled on Ipsilon’s IP Switching

Introduces Flow Aggregation into the traffic driven-scheme

Introduces the concept of short-term and long-term VCs

Significantly increases the proportion of IP Packet that are diverted from being forwarded (layer 3) to being switched (layer 2)

- A performance level that is comparable to that of the control-driven approaches, while retaining the simplicity, scalability and reliability of the traffic-driven approach

Documents

Smart IP Switching A Hybrid System for Fast IP-based Network Backbones David Lloyd Donal O’Mahony