1AC_055_2000 © 2000, Cisco Systems, Inc. Fast IP Routing Axel Clauberg Consulting Engineer Cisco...

1AC_055_2000 © 2000, Cisco Systems, Inc.

Fast IP RoutingFast IP Routing

Axel ClaubergConsulting Engineer

Cisco Systems [email protected]

Axel ClaubergConsulting Engineer

Cisco Systems [email protected]


AgendaAgenda

• The Evolution of IP Routing

• Transmission Update: 10GE

• Router Architectures

• So, it‘s all just speed ?


The Evolution of IP RoutingThe Evolution of IP Routing


Heard around the corner ?Heard around the corner ?

• IP Routers are slow, sw-based

• IP Routers cause high latency

• IP Routers are undeterministic

• IP Routers do not support QoS


WAN Customer Access Speed WAN Customer Access Speed EvolutionEvolution

• Late 1980s: 9.6 Kb/s .. 64 Kb/s

• Early 1990s: 64 Kb/s .. 2 Mb/s

• Late 1990s: 2 Mb/s .. 155 Mb/s

• Early 2000s: 155 Mb/s .. 10 Gb/s


Backbone EvolutionBackbone Evolution

• Late 1980s: 56/64 Kb/s

• Early 1990s: 1.5/2 Mb/s

• Mid 1990s: 34 Mb/s, 155 Mb/s

• Late 1990s: 622 Mb/s, 2,5 Gb/s

• Early 2000s: 10 Gb/s, 40 Gb/s

• Late 1980s: 10 Mb/s

• Early 1990s: 100 Mb/s (FDDI)

• Mid 1990s: 155 Mb/s (ATM)

• Late 1990s: nx FE, 155 Mb/s, 622 Mb/s, GE

• Early 2000s: 10 Gb/s, n x 10 Gb/s

WAN Campus


Transmission Update: 10GETransmission Update: 10GE


Lower Cost and OverheadLower Cost and OverheadLower Cost and OverheadLower Cost and Overhead

MAN/WAN IP Transport MAN/WAN IP Transport Alternatives Alternatives

IPIP

ATMATM

OpticalOptical

B-ISDN

IPIP

OpticalOptical

IPIP

SONET/SDHSONET/SDH

OpticalOptical

ATMATM

SONET/SDHSONET/SDH

IPIP

OpticalOptical

Multiplexing, Protection and Management at every LayerMultiplexing, Protection and Management at every Layer

IP over ATM

IP over SDH IP over Optical

IPIP

EthernetEthernet

OpticalOptical

IP over Ethernet

GE

10GE


Ethernet Scaling HistoryEthernet Scaling History

• 1981: Shared 10 Mbit 1x

• 1992: Switched 10 Mbit 10x

• 1995: Switched 100 Mbit 100X

• 1998: Switched 1 Gigabit 1000X

• 200x: Switched 10 Gigabit 10000X


Moving the Decimal Point: 10 GbE PerformanceMoving the Decimal Point: 10 GbE Performanceand Scalabilityand Scalability

1996 1997 1998 1999 2000

1 Gbps

100 Mbps

10 Gbps 10 GbpsEthernet

Gigabit Ethernet

Fast Ethernet

Fast EtherChannel

Gigabit EtherChannel

STM-64

2001 2002

10 GbE IEEE 10 GbE IEEE 802.3ae 802.3ae StandardStandard

• LAN applications

• Metro applications

• WAN applications


Why 10 Gigabit EthernetWhy 10 Gigabit Ethernet

• Aggregates Gigabit Ethernet segments

• Scales Enterprise and Service Provider LAN backbones

• Leverages installed base of 250 million Ethernet switch ports

• Supports all services (packetized voice and video, data)

• Supports metropolitan and wide area networks

• Faster and simpler than other alternatives


IEEE Goals for 10 GbEIEEE Goals for 10 GbE(Partial List) (Partial List)

• Preserve 802.3 Ethernet frame format

• Preserve minimum and maximum frame size of current 802.3 Ethernet

• Support only full duplex operation

• Support 10,000 Mbps at MAC interface

• Define two families of PHYs

LAN PHY operating at 10 Gbps

Optional WAN PHY operating at a data rate compatible with the payload rate of OC-192c/SDH VC-4-64c


IEEE 802.3ae Task Force MilestonesIEEE 802.3ae Task Force Milestones

19991999 20012001 2002200220002000

PARPARDraftedDrafted

PARPARApprovedApproved

802.3ae802.3aeFormedFormed

First First DraftDraft

WorkingWorkingGroupGroupBallotBallot

LMSCLMSCBallotBallot

StandardStandard

HSSG= Higher Speed Study Group

PAR= project authorization request

802.3ae= the name of the project and the name of the sub-committee of IEEE 802.3 chartered with writing the 10GbE Standard

Working group ballot= task force submits complete draft to larger 802.3 committee for technical review and ballot

LMSC: LAN/MAN Standards Committee ballot. Any member of the superset of 802 committees may vote and comment on draft

HSSGHSSGFormedFormed

First 10GE First 10GE deliveriesdeliveries


10 Gigabit Ethernet Media Goals10 Gigabit Ethernet Media Goals

1300 nm Laser1300 nm LaserCDWM (4x2.5)CDWM (4x2.5)

1300 nm Laser1300 nm Laserstandard reachstandard reach

Media TypeMedia TypeTypeType

1550 nm Laser1550 nm Laserextended reachextended reach

40-100 km 40-100 km std/dispersion free fiberstd/dispersion free fiber

single mode fibersingle mode fiber 2-10 km 2-10 km

multimode fibermultimode fiber 300 m 300 m

200 m 200 m ribbon multimode fiberribbon multimode fiber

Max DistanceMax Distance

780 nm VCSEL780 nm VCSELmultichannelmultichannel


IEEE StatusIEEE Status

• 802.3ae Meeting 10.-14. Juli 2000

• 75% Consensus

1550nm Transceiver 40 Km @ SMF

1300nm Transceiver 10 Km @ SMF

• No Consensus yet

Multimode Support

300m mit 62.5µ 160/500 Mhz*Km MM

50µ 2000/500 MHz*Km MM


Router ArchitecturesRouter Architectures


ComponentsComponents

• Memory Architecture

• Interconnect

• Forwarding Engine

• Scalability

• Stability

• Queueing / QoS


Basic DesignBasic Design

• Data are of random sizes

• Arrival is async, unpredictable, independantly on i/f

• Data have to be buffered

• TCP/IP traffic is bursty, but short-term congestion only

Router... ...Inputs Outputs

ForwardingEngine

RouteProcessor

BufferMemory

Interfaces


How much buffers ?How much buffers ?

• Rule of Thumb: RTT x BW(Villamizer & Song, High Performance TCP in ANSNET,

1994)

• STM-16 @ 200 ms: ~ 60 MB buffering capacity


How to Buffer ?How to Buffer ?

• SRAM

Fast, Power-hungry, Density 8 Mb -> 16 Mb, Simple Controller Design

• DRAM / SDRAM

Slower, Less Power, Density 64 Mb -> 256 Mb, Complex Controller Design


InterconnectInterconnect

• Switch Fabric / Crossbar

• Shared Memory

• Variations


Switch Fabric / CrossbarSwitch Fabric / Crossbar

• Packet forwarding decision done on each linecard

• Ingress and Egress Buffering on Linecards

• Possible Problem: Head of Line Blocking

• Solution: VOQ

LineCard 0Line

Card 0

SwitchFabricSwitchFabric

SchedulerScheduler

LineCard 1Line

Card 1

LineCard N

LineCard N

LineCard 0Line

Card 0

LineCard 1Line

Card 1

LineCard N

LineCard N

RPRP RPRP

Ingress Line Cards Egress Line Cards


Linecard in DetailLinecard in Detail

Physical Layer

(Optics)

Physical Layer

(Optics)

Layer 3 Engine

Layer 3 Engine

Fabric InterfaceFabric

Interface

RXRX

TXTX

CPUCPU

To FabricTo Fabric

From FabricFrom Fabric

SwitchFabricSwitchFabric

SchedulerScheduler

• HOL Blocking can occur when packet cannot flow off transmit linecard• Packet will be buffered on receiving linecard• Packet blocks other packets to other linecards• Solution: Virtual Output Queues, one per egress linecard


Receive Line CardTransmitLine Card

Group of 8 CoS Queues Per Interface (M-DRR)

InputPorts

OutputPorts

Cro

ssb

ar S

wit

ch F

abri

cW-RED

CAR

CEF

VirtualOutputQueues

DRR

GSR Queuing ArchitectureGSR Queuing Architecture


Shared Memory ArchitectureShared Memory ArchitecturePhysically CentralizedPhysically Centralized

• One large memory system, data passing through it

• Simple memory management

• High speed memory

• Simple Linecards

• Needs SRAM for high speeds

Interconnects&

ForwardingEngine

Interconnects&

ForwardingEngine

2.5Gbps

2.5Gbps

2.5Gbps

2.5Gbps

Line Cards 1-8

Mem

ory

Con

trol

ler

40G


Shared Memory ArchitectureShared Memory ArchitectureDistributedDistributed

• Memory distributed over linecards

• Memory controller treats sum of pieces as shared memory

• Packet forwarding decision in central engine(s)

• Difficult to maximize interconnect efficiency

Egress line cards simply request packets from shared memory

Causes Head of Line (HOL) blocking and high latency, worsening under moderate-to-heavy system load or with multicast traffic

MemoryController

& ForwardingEngine(s)

MemoryController

& ForwardingEngine(s)

MemorySystem

2.5Gbps

2.5Gbps

MemorySystem

2.5Gbps

2.5Gbps

Line Cards 1-8


Switch Fabric vs. Shared MemorySwitch Fabric vs. Shared Memory

• Shared Memory requires only half the buffer space

• HOL Blocking in Shared Memory, especially for Multicast

• Involvement of distributed shared memory causes more points of failure


Forwarding EngineForwarding Engine

• Classifying the packet

IPv4, IPv6, MPLS, ...

• Packet validity (TTL, length, ...)

• Next Hop

• Basic Statistics

• Optional:

• Policing, Extended Statistics, RPF check (security, Multicast), QoS, Tunnel, ...

• Distributed vs. Central


Central Forwarding ?Central Forwarding ?

• IP Longest match

Hash vs. TCAM vs. Tree Lookup

• Tree Lookup requires high number of routing table lookups

Need SRAM

Danger to run out of SRAM

Forwarding speed dependant on depth of routing table


Distributed ForwardingDistributed Forwarding

• One copy of forwarding info per linecard

• Parallel processing without sync or communication between linecards

• Able to use TCAMs and SDRAMs


So, it’s all just speed ?So, it’s all just speed ?


So, it’s just So, it’s just speed ?speed ?

• Services

IP Multicast

IP QoS

Security

• IPv6

• MPLS

• Manageability

• Availability

• Investment protection


Interdomain MulticastInterdomain MulticastCampus MulticastCampus Multicast

Multicast SolutionsMulticast SolutionsEnd-to-End ArchitectureEnd-to-End Architecture

• End Stations (hosts-to-routers):IGMP

• Switches (Layer 2 Optimization):IGMP Snooping

• Routers (Multicast Forwarding Protocol):

PIM Sparse Mode

• Multicast routing across domainsMBGP

• Multicast Source DiscoveryMSDP with PIM-SM

ISP B

Multicast SourceY

ISP A

Multicast SourceX

ISP B

DRRP

RP

DRDRIGMP PIM-SM

CGMPMBGP

MSDP

ISP A


SummarySummary

• IP Routers have evolved during the past years

• Line rate up to 10 Gb/s

• Crossbar architectures with distributed forwarding seem to scale better than shared memory architectures

• Services remain the most decisive factor


OutlookOutlook

• 10 Gb/s Interfaces supported in 2000

10GE, STM-64/OC-192

• High density of 10 Gb/s interfaces soon in a PoP

• Next step will be STM-256/OC-768 = 40 Gb/s

• Will these routers be „Palm-Size“ ?

Probably not...

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