Guaranteed QoS Synthesiser GQS

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Guaranteed QoS Synthesiser(GQS)

• Bob Briscoe, Peter Hovell
• BT Research
• Jan 2005

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GQS goals (realised)

• v cheap Internet-wide statistical guarantees for
  inter-domain µflows
• cores rarely congest but if/when they do youre
  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

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GQS system arrangement
IP routers
Data path processing
Reservationenabled
Reserved flow processing
1
Policing flow entry to G
2
table of ECN fraction per previousRSVP hop
aggregate
RSVP/ECNgateway
Meter congestion per peer
4
ECN only
Bulk ECN markingG prioritised over N
3
reservation signalling
guaranteed
guaranteed
guaranteed (G)
guaranteed
non-guaranteed(N)
4
heterogeneity
legend
connection-oriented (CO) connectionless gateways
GQS GQS/core CO core CO/core CO access CO/core CO
variousQoS signallingaccess networks
b/w broker
PSTN
MPLSRSVP-TE
ECN
ECN
ECN
ECN
ECN
assume app layer signalling (SIP) initiates
out of band
ECN
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data plane functions ingress GQS
explanation easier if we start by assuming we
have already admitted a flow
set traffic class G and set ECN-capable transport
Y
filterspec matches reservation and passes
policer

packetarrives
N
re-mark any spoof G to BE
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data plane functionsvirtual queue mgmt(VQM)
ECN markingprobability
Pg
1
qgqn
G
priorityqueuing
trafficclass?

CoSg
CoSn
line rate,X
qn
qg
N
Pn
1
qn
drop (or ECN marking)probability
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data plane functions egress GQS
maintain moving ave ECN fraction
clear traffic class Gclear ECN-capable transport
lookupprev hop
G
trafficclass?
N
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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 Id hide it ?
• Q cant 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

Y
X
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summary

• status
• two implementations (2000-4)
• FreeBSD Linux
• extensive simulation
• full design documentation
• looking for vendor take-up

• it works
• its simple
• its cheap
• its robust
• its secure
• its deployable
• what else do you want?

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Guaranteed QoS Synthesiser(GQS)

• spare slides

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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

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inter-class load self-balancing
Guaranteed
admissionthreshold
Non-Guaranteed
TCPop. point
flows