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