Stanford University

TCP Switching: Exposing circuits in the Internet

Pablo Molinero-FernándezNick McKeown

Stanford University

Stanford University

Why was the Internet packet-switched (PS) in the first place?

• PS uses the link bandwidth very efficiently

• PS networks are robust due to the little state kept at the intermediate nodes

• Current Internet shows very low link utilization, so there is no need to be efficient

• SONET can reroute in 50 ms vs. several seconds for IP. Robustness is not unique to PS

Stanford University

How the Internet really is

SONET/SDH

IP Routers

IP Routers

YourLocal

CentralOffice

YourLocal

Central Office

Stanford University

Need to optimize processing rather than link efficiency

0,1

1

10

100

1000

10000

1985 1990 1995 2000 Fib

er C

apac

ity

(Gb

it/s

)

FiberopticsDWDM

Source: SPEC95Int; Prof. Miller, Stanford Univ., 2000

0,1

1

10

100

1000

10000

1985 1990 1995 2000

Pro

cess

ing

Po

wer

(S

pec

95In

t b

ench

mar

k) 2x / 2 years 2x / 7 months

Slow Routers Fast Links

Stanford University

How is the Internet today

• There is a lot of circuit switching (CS), in the form of SONET

• Today we are interested in the completion time of our browsing requests

• CS is out there, but IP sees it as static point-to-point links

• CS can provide smaller completion times

Stanford University

TCP SWITCH: Using TCP connections to establish circuits

Ingress TCP-SW

Core TCP-SW

Egress TCP-SW

Destina-tion

Source

SYN

SYN+ACK

DATA

ACCEPTED

ACCEPTED

IPRouters

TCPSwitches

•Expose circuits to IP

•Optimize for the common case

–TCP traffic

–Data packets

Stanford University

TCP SWITCH: Using TCP connections to establish circuits

Ingress TCP-SW

Core TCP-SW

Egress TCP-SW

Destina-tion

Source

SYN

SYN+ACK

DATA

ACCEPTED

ACCEPTED

IPRouters

TCPSwitches

Stanford University

Objectives of TCPSwitch

• Primary goals:• Expose circuits to IP• Optimize for the common case

– TCP traffic (90% of packets)– Data packets (1 out of 10)

• Secondary goals:• Interoperability with existing equipment • Use of optics and off-the-shelf switches• QoS and best-effort

Stanford University

TCPSwitch results

• Implementation of ingress TCPSwitch– Linux 2.4 router, inside kernel– Data switching: similar performance as a router

with a classifier (e.g. policer)

• Simulation of TCPSwitch network– In ns-2– Avg response time between 1/2 and 1/10, for

some blocking prob (0%-3%)– Some TCP inefficiencies noticeable with very

short flows

• Work in progress