Guaranteed QoS Synthesiser(GQS)

Bob Briscoe, Peter Hovell

BT Research

Jan 2005

GQS goals (realised)• v cheap Internet-wide statistical guarantees for inter-domain μflows

• cores rarely congest but if/when they do you’re screwed

• uses existing protocols, but not their architectures• RSVP (other signalling possible), DSCP, ECN

• not Intserv, not Diffserv, not e2e ECN

• neither path signalling nor state… • …on core AND border routers

• incremental deployment • scales better as more networks join

• no-one has to trust anyone else• incentives against inter-provider cheating

GQS system arrangement

guaranteedguaranteed

guaranteed (G)

non-guaranteed(N)

reservation signalling

guaranteed

1

2

4

3

Reservationenabled

RSVP/ECNgateway

ECN only

Reserved flow processing

Policing flow entry to G

Meter congestion per peer

Bulk ECN markingG prioritised over N

IP routersData path processing

2

4

33

33

1

1

table of ECN fractionper previousRSVP hop aggregate

b/wbroker

ECN

legendlegendconnection-oriented (CO)connectionless

gatewaysGQSGQS/core COcore CO/core COaccess CO/core CO

ECNECN

ECN

MPLSRSVP-TE

ECN

ECN

variousQoS signalling

access networks

PSTN

heterogeneity

assume app layer

signalling (SIP) initiates out of

band

assume app layer

signalling (SIP) initiates out of

band

data plane functions: ingress GQS explanation easier if we start by assuming we have already admitted a flow

packetarrivespacketarrives

filterspec matches reservation

and passes policer

filterspec matches reservation

and passes policer

Y

N

reserved flow tablefilterspec : flowspec

set traffic class G andset ECN-capable transport

re-mark any spoof G to BE

2

4

33

33

1

1

data plane functions:

virtual queue mgmt(VQM)

CoSgCoSn

qnline rate,

X

2

4

33

33

1

1

trafficclass?trafficclass?

G

N 1

qn

Pn

priorityqueuing

drop (or ECN marking)probability

qg

1

qg+qn

Pg

ECN markingprobability

virtualoutput ~ 99%

X

vg

CoSg

virtualqueue

vg+qn

data plane functions: egress GQS

trafficclass?trafficclass?

G

N

clear traffic class Gclear ECN-capable transport

lookupprev hoplookup

prev hop

reserved flow tablefilterspec : prev RSVP hop

maintainmoving ave

ECN fraction

maintainmoving ave

ECN fraction

previous hop loadprev RSVP hop : ECN fraction

2

4

33

33

1

1

Q wot, no inter-domain signalling gateway?A no

Q wot, no per session inter-domain charging?

A no

could by intercepting signalling, but not necessary,

so if you did I’d hide it

Q can’t X admit calls despite congestion in Y?

A emulate inter-domain policing

monthly charge for bulk ECN counter at each border

dead simple to meter & account

YX2

4

33

33

1

1

NANA

NBNB

NDND

R1S1

IP IP IPIP IP IP IP IPQoS QoS

transpQoS QoS

transp

summary

• it works

• it’s simple

• it’s cheap

• it’s robust

• it’s secure

• it’s deployable

• what else do you want?

status• two implementations (2000-4)

• FreeBSD & Linux

• extensive simulation

• full design documentation

• looking for vendor take-up

status• two implementations (2000-4)

• FreeBSD & Linux

• extensive simulation

• full design documentation

• looking for vendor take-up

Guaranteed QoS Synthesiser(GQS)

spare slides

no time for…

• probing when no active flows between gateway pair

• robustness during re-routes

• ECN mechanisms for incentives• ingress setting of ECT(0) & ECT(1)

• VBR

• preventing starvation

• policy-based admission control

inter-class load self-balancingGuaranteed

Non-Guaranteed

admissionthreshold

TCPop. point

#flows