Jon Turner [email protected] arl.wustl/arl

Jon [email protected]

http://www.arl.wustl.edu/arl

Extreme NetworkingAchieving Nonstop Network Operation Under Extreme Operating Conditions

DARPA PI Meeting, July 23-26, 2002

2 - Jonathan Turner - July 24, 2002

Project Overview Motivation

»data networks have become mission-critical resource»networks often subject to extreme traffic conditions»need to design networks for worst-case conditions» technology advances making extreme defenses

practical Extreme network services

»Lightweight Flow Setup (LFS)»Network Access Service (NAS)»Reserved Tree Service (RTS)

Key router technology components»Super-Scalable Packet Scheduling (SPS)»Dynamic Queues with Auto-aggregation (DQA)»Scalable Distributed Queueing (SDQ)


Switch Fabric

IPP

OP

P

FPX

SPC

TI

IPP

OP

P

FPX

SPC

TI

IPP

OP

P

FPX

SPC

TI

IPP

OP

P

FPX

SPC

TI

IPP

OP

P

FPX

SPC

TI

IPP

OP

PFPX

SPC

TI

ControlProcessor

Prototype Extreme RouterField Programmable Port Ext.

NetworkInterfaceDevice

ReprogrammableApplication

Device

SDRAM128 MB

SRAM4 MB

Field Programmable Port Extenders

Smart Port Card

Sys.FPGA

64MB

Pentium

Cache

NorthBridge APIC

ATM Switch Core

Transmisson Interfaces

Embedded Processors


Resource Reservation in Internet? Bandwidth reservation can provide dramatically

better performance for some applications. Obstacles to resource reservation in Internet.

» distaste for signaling protocols» perceived complexity of IntServ+RSVP» requires end-to-end deployment» little motivation for service providers

How to get resource reservation in Internet?» keep it simple

focus on top priorities - one-way unicast flows avoid complex signaling - leverage hardware routing

mechanisms

» make it useful when only partially deployed» provide motivation for ISPs to deploy it


10 Mb/s available 5 Mb/s

available

2 Mb/s availabl

e

5 Mb/s available

20 Mb/s availabl

e

20 Mb/s availabl

e

Basic LFS Operation

One way, unicast setup with partial reservation.»complete reservations locally when bandwidth released

Optional ack returned by far-end access router. Reservation may terminate explicitly or time out. May alter reserved bandwidth but no re-routing.

A

B

Reserve 8 Mb/s to B

Select best next hop

Reserve bandwidth

Select path and attempt to reserve

Select path and reserve

Complete reservatio

n


Soft Reservations Basic LFS provides firm reservations.

»user guaranteed bandwidth until releases Can extend to provide soft reservations as well.

»soft reservation can be adjusted by the network as traffic changes

»can be intermixed with firm reservations to provide a firm minimum, plus more bandwidth as available

Uses of soft reservation.»apps. that need guaranteed minimum and can

sometimes use more, but can adjust use to what’s available

»more rapidly responding congestion control for traditional best-effort traffic


Basic IP Option for LFS

length op. Rrateflags Arate code

IP header(fixed part)

trace

IP payload

Code identifies LFS option. Operations

» request firm reservation» request soft reservation» release state

Flags» sender status request» sender network status request» public network status request» intra-domain status request» congested path

Rrate: requested rate. Arate: allocated rate. Trace used by each domain to

track usage.

Allocated rate stored at “last hop” router for status generation

F.P. rates with 4 bit mantissa, 4 bit exponent.» specify rates from 64

Kb/s to 4 Gb/s , 6% “granularity”


Use of Trace Field

Network providers need to monitor LFS usage for network management and accounting purposes.» trace field used by ingress router of each domain to

mark LFS packets with domain-specific identification»egress router of each domain maintains record of each

LFS flow, including copy of trace field»end-to-end records created through off-line accounting

resolution mechanisms

domain U domain V domain WX

Y

Z

B

A

X

Y

Z

acct. record[A,B,..] thru X

acct. record[A,B,..] thru Z

acct. record[A,B,..] thru Y


Status Reporting

Basic LFS option supports sender status and trace field for accounting.

Network providers likely to want more.»sender net status allows LFS service verification»public net status allows “end-to-end” status check» intra-domain status for verifying local status »each “extra” status report requires insertion of

requestor’s IP address, increasing LFS option length

ISP Vrcvr. LAN

sender LAN ISP U

sender status

sender net status

public net status

intra-domain status


Partial Deployment Receivers need not be LFS-aware.

»web site may use LFS to reserve bandwidth for streaming media - users benefit, even without LFS-aware hosts

Issues with non-contiguous LFS domains.» route changes may create “orphan reservations”»no simple way to determine status reporter

No support for non-contiguous LFS domains.»LFS router forwarding to a non-LFS router (or host) strips

LFS option and implements status reporting status report includes IP address of reporting router, letting

sender know how far the reservation went Public IP carrier can accept LFS option from client

networks (LAN) even if client net is not LFS-aware. Clients may use tunnel to access LFS service.


Regulating LFS Use - Net Access Svc

Permitting unconstrained access to LFS creates big security vulnerability.

Limit use to authorized users. Limit number of reservations and amount of

reserved bandwidth by authorized users.»access router keeps record and enforces limits»complication - user may use LFS from multiple locations

maintain records in distributed set of servers - each server keeps records for some fraction of the users - use hashing to select

Access router needs means to identify user.»host IP address insufficient (DHCP, NAT)»encryption-based authentication (IPSEC)

Combine access control with usage accounting. What special issues arise with multiple domains?


LFS Video Demo Configuration

Wavelet-coded video with and without LFS.» competing datagram traffic» with no reservation, lost packets cause poor video quality» with reservation, high quality preserved

video source

cross traffic

sources

cross traffic sinks

video sink

100 Mb/s links


Video Demo - No Reservation

video flow - no reservation

datagram cross traffic flow 1


video source cross traffic sources all sinks


Video Demo - With Reservation

video flow - with reservation



video sink cross traffic sinks


Competing LFS Flows

no reservations

flow 1 - no reservation

flow 2 - reservation added

flow 3 - no reservation

reservation for flow 2 sources

sinks

sink 2

sink 1


Partial Reservation

flow 1 - partial reservation made

sink 1

flow 2 source 1

sink 3


Completing Partial Reservation

flow 1 - completes partial reservation

sink 1

sink 3

flow 2 - drops reservation


Addition of Flow 3 Reservation

sink 3

flow 3 - adds reservation

sink 2


Performance of LFS at Single Link

m = number of flows link can carry exponential session times for flows, infinite queue

1.E-16

1.E-14

1.E-12

1.E-10

1.E-08

1.E-06

1.E-04

1.E-02

1.E+00

0.00 0.05 0.10 0.15 0.20 0.25t (unit = average service time)

Pr{

dela

y>t}

m=50

100

200

400

load=.7

OC-48 link can carry 200 flows

of 12 Mb/s

very few flows

experience any delay

Pareto distributed session times

make little difference


Sensitivity to Load and Hop Count

1.E-12

1.E-11

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

0.00 0.05 0.10 0.15 0.20 0.25

t (unit = average service time)

Pr{

dela

y>t}

load=.7

m=200

hops=1 4 16

1.E-16

1.E-14

1.E-12

1.E-10

1.E-08

1.E-06

1.E-04

1.E-02

1.E+00

0.00 0.05 0.10 0.15 0.20 0.25

t (unit = average service time)

Pr{

dela

y>t}

load=.9

.8

.6

.7

m=200

at 90% load, less than 1 flow in 100 delayed

more than 12% of session time

delay probability scales linearly with number of

hops


Overload Performance

0.5

0.6

0.7

0.8

0.9

1.0

0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2

offered load

"carr

ied

load

" no buffer

infinite buffer

m=50

100

200

400

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20

offered load

Fract

ion

"R

eje

cted

"

infinite buffer

m=50 100 200 400

no buffer

with infinite buffer, no sessions get

small delays (10%)

with no buffer most sessions still

succeed

buffer reduces rejection fraction

at low loads


Summary LFS provides simple reservations for QoS.

»no complex signaling, wire speed setup» limited deployment can be broadly beneficial»support for usage monitoring & accounting gives

network providers a motivation to deploy service Network access service for regulating usage.

»preliminary specification has been developed»uses IPSEC for host/user authentication

Performance analysis, simulation study underway.

Routing issues.»evaluate QoS routing with multiple-choice forwarding» link state distribution for inter-domain routing» inter-domain routing policies

Jon Turner [email protected] arl.wustl/arl

Documents

Transcript of Jon Turner [email protected] arl.wustl/arl