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1 © 2004 Cisco Systems, Inc. All rights reserved. Session Number Presentation_ID MIT CFP, QoSWG October 3 – 4, 2005 Scaling of Distributed CAC Francois Le Faucheur [email protected]
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1© 2004 Cisco Systems, Inc. All rights reserved.Session NumberPresentation_ID
MIT CFP, QoSWGOctober 3 – 4, 2005
Scaling of Distributed CAC
Francois Le [email protected]
222© 2005 Cisco Systems, Inc. All rights reserved.Scaling Distributed [email protected]
Outline
• Components/Properties of Distributed CAC Approach
• Scaling on-path signalling with Diffserv Integration
• Scaling on-path signalling further with Aggregation
• Example of RSVPoDiffserv in Inter-Provider
• Example of RSVP Aggregation over MPLS TE in Inter-Provider
• What if we could further reduce states?
• Conclusions
333© 2005 Cisco Systems, Inc. All rights reserved.Scaling Distributed [email protected]
Components of Distributed CAC Approach
• Clean separation between Bearer Control and Call Control
• Call Control (e.g. SIP) leaves it to Bearer Control to make the right QoS/CAC decisions and report back
• Bearer Control uses on-Path Signalling for “in-band” CAC (e.g. RSVP)
• Tight Synchronization between Call Control (e.g. SIP) and Bearer Control (e.g. RSVP) on end-devices
444© 2005 Cisco Systems, Inc. All rights reserved.Scaling Distributed [email protected]
Tight Synchronisation bw SIP and RSVP
• RFC3312: Integration of Resource Management and SIP
• Concept of “Preconditions” which need to be met before call can be setup
• QoS reservation via RSVP is one possible precondition
• Allows perfect synch between SIP and RSVP reservations on VoIP terminal or GW:
Check bearer before ringing or establishing sessionTear-down session when bearer QoS is lost after session establishment (e.g. due to failure)Take appropriate action (e.g. fast busy, proceed with best effort service) if QoS establishment fails
A B
| ||-------------(1) INVITE SDP1--------------->|| ||<------(2) 183 Session Progress SDP2--------|| *** *** ||--*R*-----------(3) PRACK-------------*R*-->|| *E* *E* ||<-*S*-------(4) 200 OK (PRACK)--------*S*---|| *E* *E* || *R* *R* || *V* *V* || *A* *A* || *T* *T* || *I* *I* || *O* *O* || *N* *N* || *** *** || *** || *** ||-------------(5) UPDATE SDP3--------------->|| ||<--------(6) 200 OK (UPDATE) SDP4-----------|| ||<-------------(7) 180 Ringing---------------|| ||-----------------(8) PRACK----------------->|| ||<------------(9) 200 OK (PRACK)-------------|| ||<-----------(10) 200 OK (INVITE)------------|| ||------------------(11) ACK----------------->|| |
555© 2005 Cisco Systems, Inc. All rights reserved.Scaling Distributed [email protected]
BE
EF/PQ
Properties of Distributed CAC
•Accurate (actual path, actual current state,…)•Adaptive (reacts to reroute, to change in resources, to severe congestion …)•Enforceable at any trust boundary (policing by router)•Supports CAC for multiple independent applications•BUT: requires states in routers
666© 2005 Cisco Systems, Inc. All rights reserved.Scaling Distributed [email protected]
BE
EF/PQ
Scaling on-path signalling with Diffserv Integration
•Control Plane maintains state per reservation•Data Plane relies on Diffserv PHB for packet handling
(and does NOT maintain any state per reservation)•E.g. RSVPoDiffserv scales to O(10,000s) res and O(100s) res/sec
RFC2998: Integrated Services Operation over Diffserv NetworksRFC2961: RSVP Refresh Overhead Reduction
777© 2005 Cisco Systems, Inc. All rights reserved.Scaling Distributed [email protected]
BE
EF/PQ
Scaling on-path signalling with Aggregation
• Data Plane in the Core remains Diffserv• Control Plane maintains state for aggregate reservations only• Core Scalability independent of nb of reservations
-scaling is O (nb_Aggregators**2)
Aggregator De-aggregator
Aggregate Reservation
888© 2005 Cisco Systems, Inc. All rights reserved.Scaling Distributed [email protected]
BE
EF/PQ
Scaling on-path signalling with Aggregation
Aggregator De-aggregator
Aggregate Reservation
RFC3175: RSVP Aggregation over IPdraft-ietf-tsvwg-rsvp-dste: RSVP Aggregation over MPLS TE/DS-TEdraft-lefaucheur-tsvwg-rsvp-ipsec: RSVP Aggregation over IPsec tunnels
999© 2005 Cisco Systems, Inc. All rights reserved.Scaling Distributed [email protected]
Example Application: CAC for Trunking of 2G/2.5G/3G Mobile Voice
BTS
BTS
MSC MSC
PSTN
MSC V
VV
One RSVP reservation for all calls between a given pair of VoIP Trunk GW
One TE Tunnel per pair of PEs
V
IP/MPLSSGSN GGSNBTSSGSNGGSN
GW1
GW2
PE1
PE2
nb_PEs & nb_GWs are O(10s):O(10s) of res per GW & O(low100s) of res per PEO(10s) of TE tunnels per PE & O(low1000s) of TE Tunnels per P
P1 P2
101010© 2005 Cisco Systems, Inc. All rights reserved.Scaling Distributed [email protected]
CAC for Trunking of Voice With Aggregate RSVP reservation on GW
Call Agent GW2PE2PE1GW1INVITE
INVITE183183
PathResv
PathResv
UPDATE
OKRINGING
GW knows codec/bw
PE1 does CAC of 100 callson PE1-PE2 tunnel
PE2 does CAC of 100 callson PE2-PE1 tunnel
GW knows codec/bw
GW initiates RSVP for100 calls
GW initiates RSVP for 100 calls
INVITE INVITE183183
UPDATE
OKRINGING
GW knows codec/bw
GW knows codec/bw
GW knows this call fits in RSVP reservation
GW knows this call fits in RSVP reservation
Call 1
Call 2
111111© 2005 Cisco Systems, Inc. All rights reserved.Scaling Distributed [email protected]
Example of RSVPoDiffserv in Inter-Provider
RSVP ignored RSVP ignored
RSVPprocessed
Example: CAC on inter-provider links
O(10,000) calls per Gig linkO(100,000) calls per 10G link
Reservations Enforceable at boundary
121212© 2005 Cisco Systems, Inc. All rights reserved.Scaling Distributed [email protected]
Example of RSVP Aggregation over MPLS TE in Inter-Provider
Example: Edge-to-Edge CAC across inter-provider Core
MPLS-TE
MPLS-TE
Inter-AS MPLS-TE
O([ Nb_Edge_per-AS * nb_AS ]**2) tunnels across inter-provider boundaryeg 50 PEs/AS, 3 AS 15,000 tunnels (total over all inter-provider links)Use of inter-AS MPLS TE techniques:
- inter-AS FRR- Path Computation Elements
TE tunnel reservations enforceable at boundary
131313© 2005 Cisco Systems, Inc. All rights reserved.Scaling Distributed [email protected]
What if we could even further reduce states in Core and on inter-provider links?
Example: Edge-to-Edge CAC across inter-provider Core
ECN
ECNECN
•Only per-COS ECN state in Core and inter-provider links•RSVP/ECN Edge routers converting ECN in proper Bearer Control•O(Nb_Edge_per-AS * nb_AS) ECN-closed-loop states per RSVP/ECN Edge•ECN scheme?•Performance (for admission control and for severe congestion handling)?•Enforceable at provider boundary ?
RSVP
RSVPECN closed loop
per PE pair
RSVP/ECN Edge Routers
141414© 2005 Cisco Systems, Inc. All rights reserved.Scaling Distributed [email protected]
Conclusions• Components of a Distributed CAC Approach in place in IETF
- Synchronisation of Call Control and Bearer Control- Protocol for Bearer Control (RSVP, NSIS)
• Integration with Diffserv allows O(10,000s) scalability• Aggregation allows scalability independently of nb of calls;
scales with O(nb_Aggregators ** 2) instead• For CAC on Interprovider links, Diffserv Integration allows
distributed approach to scale for current multi-Gig links requirements and probably multi-10 GigE links
• For CAC through backbone and on interprovider links, Aggregation techniques allow scaling for requirements of “controlled” inter-provider peerings
• A solution with reduced states in core and inter-provider links could allow further cost reduction of distributed approach (and further scaling in open inter-provider environments)
• That solution must not compromise key properties (determinism, fast reaction to severe congestion, enforceability,…)
