34k pdf file - High Performance Networking Group - Stanford University

yuba.stanford.edu

34k pdf file - High Performance Networking Group - Stanford University

Real Routing at Gigabit Speeds

The panel

Interop: Sept 9th 1997, Atlanta.

Nick McKeown

Assistant Professor of Electrical Engineering

and Computer Science

nickm@stanford.edu

http://www.stanford.edu/~nickm

1. Nick McKeown, Stanford University

2. Earl Ferguson, Foundry Networks

3. Debbie Deutsch, Prominet

4. Hemant Kanakia, Torrent Networks

5. Steve Haddock, Extreme Networks

6. Questions, Discussion, Flames, and Tomatoes....

Real Routing at Gigabit Speeds Page 2 of 14

The Architecture of

Switches and Routers

Generic Packet Processor:

(e.g. IP Router, ATM Switch, LAN Switch)

1. The Basic Functions of an IP Router

2. The Architecture of Routers

Data

Hdr

Forwarding

Decision

Signaling &

Mgmt

Processor

Interconnect

Output

Scheduler

Real Routing at Gigabit Speeds Page 3 of 14

Real Routing at Gigabit Speeds Page 4 of 14


The Primary Functions

of an IP Router

Performance of IP Routers

MAC frame

1

Extract incoming

IP datagram

DA= SA

ROUTER

FCS

IP Datagram

H DATA

Time

2

Consult IP

routing tables

Destination

IP Subnet Route Via Cost

128.32.0.0 Direct 1

15.255.0.0

192.9.0.0

128.32.136.1

128.32.240.1

4

12

Copy

Time

3

Decrement

Time to Live

0 4 8 16 24

TIME TO LIVE

....

PROTOCOL HEADER CKSUM

....

Forwarding

Decision

Time

Arrival

Time

4

5

Fragmentation

MTU=1500

Recalculate header checksum

MTU=500

MTU=1500

Min back-to-back packet size

Packet size

6

Build outgoing datagram

Real Routing at Gigabit Speeds Page 5 of 14

Real Routing at Gigabit Speeds Page 6 of 14

Performance of IP Routers

Performance of IP Routers

Assuming backplane not congested

and pipelined design

Time

Most routers

do this poorly!

Time

Copy

rate

Header

processing

time

Arrival

rate

Header

processing

time

Arrival

rate

Min back-to-back packet size

Packet size

Min back-to-back packet size

Packet size

Need about

1Mpkt/s per Gb/s

Need about

1Mpkt/s per Gb/s

Real Routing at Gigabit Speeds Page 7 of 14

Real Routing at Gigabit Speeds Page 8 of 14


The Evolution of Routers

The first shared memory routers

1. The Basic Functions of an IP Router

Routing

CPU

Buffer

Memory

2. The Architecture of Routers

DMA DMA DMA

Line

Card

Line

Card

Line

Card

MAC MAC MAC

Real Routing at Gigabit Speeds Page 9 of 14

Real Routing at Gigabit Speeds Page 10 of 14

The Evolution of Routers

The first shared memory routers

The Evolution of Routers

Reducing the number of bus copies

Routing

CPU

Buffer

Memory

Routing

CPU

Buffer

Memory

DMA DMA DMA

Line

Card

Line

Card

Line

Card

MAC MAC MAC

Line

Card

DMA

Route

Cache

Buffer

Memory

DMA

Route

Cache

Buffer

Memory

DMA

Route

Cache

Buffer

Memory

MAC

MAC

MAC

Real Routing at Gigabit Speeds Page 11 of 14

Real Routing at Gigabit Speeds Page 12 of 14


The Evolution of Routers

Reducing the number of bus copies

Caching and “Fastpath-slowpath”

updates Routing Buffer

CPU Memory

The Evolution of Routers

Avoiding bus contention

Memory

Buffer

ROUTE

CPU

DMA

DMA

DMA

MAC

Buffer

Memory

Route

Cache

Route

Cache

Buffer

Memory

MAC

Line

Card

Route

Cache

Buffer

Memory

MAC

Route

Cache

Buffer

Memory

MAC

Route

Cache

Buffer

Memory

MAC

Route

Cache

Buffer

Memory

MAC

Advantage:

Non-blocking backplane—

high throughput

Disadvantage:

Difficult to provide QoS

Real Routing at Gigabit Speeds Page 13 of 14

Real Routing at Gigabit Speeds Page 14 of 14

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