1. Bearer Control for VoIP and VoMPLS Control Plane Francois Le Faucheur Bruce Thompson Cisco Systems, Inc. Angela Chiu AT&T March 30, 2000

2. Outline Objectives Reference Model Bearer Control for VoIP Bearer Control for VoMPLS Summary

3. Objectives Focuses on –intra-domain bearer control –environments that require guaranteed QoS and abilities to perform call admission control Refinements to the VoMPLS Framework and Reference model

4. VoIP/VoMPLS Reference Model Propose model: current model in VoMPLS Framework + the separation: –VoMPLS MG = (VoIP) MG + MIWF (Media Inter-Working Function) –VoMPLS SG = (VoIP) SG + SIWF (Signal Inter-Working Function) MG & SG: PSTN to IP inter-working MIWF & SIWF: IP to MPLS inter-working Advantage: allow a VoMPLS endpoint to coexist and inter-operate with –existing VoIP endpoints –existing native IP transport networks

5. MIWF & SIWF MIWF: –implement functionality of an MPLS edge node –perform inter-working between VoIP QoS Bearer Control and MPLS based QoS services SIWF: implement functionality of an MPLS edge node

6. Bearer Control for VoIP Bearer Control (BC): establish, modify, and release the logical connection between GWs With VoIP, default connectivity is permanently available, but may not be always appropriate IP QoS Bearer Control: resource reservation and QoS establishment in environments where service providers want to guarantee adequate quality to voice calls

7. Requirements on Call Control Protocol For the call control protocol, it’s necessary to include provisions for specifying the codec type, packetization period, parameters to determine traffic parameters in QoS reservation => included in existing call control protocols useful to advertise and negotiate requirements for IP QoS Bearer Control Ongoing work in IETF: I-D “Integration of Resource Management and SIP for IP Telephony”

8. Signaling for IP QoS BC Establishment Architecture: separate QoS signaling from application level signaling--call control protocol Using a network level protocol designed for network resource reservation and QoS signaling => RSVP

9. Scaling IP QoS BC with RSVP Multiple options to scale per-call RSVP signaling: Simplest: carry the per-call RSVP messages through an IP core transparently => rely on pre-provisioned resource in the core Option 2: use Int-Serv over Diff-Serv –scalability advantage in the user plane with aggregate Diff-Serv classification/scheduling Option 3: scale further in the control plane using RSVP reservation aggregation

10. Dynamic Resize Aggregate Rsv GW PSTN Call Agent CPE GW PC Ph or GW PC Ph or GW GW Initial capacity established pair-wise between Backbone Routers Bandwidth can be increased (or decreased) as tie lines fill (or under- utilized) Resizing can be done based on local policy and algorithm New calls rejected only if tie line capacity can not be increased

11. Coordination with Call Control Goal: having the ability to reject a call due to a failure in network level admission control => require coordination with call control Ongoing efforts: I-D “Architectural Considerations for Providing Carrier Class Telephony Services Utilizing SIP-based Distributed Call Control Mechanisms” I-D “Integration of Resource Management and SIP for IP Telephony” ITU-T, SG16/Q13, “Enhancement for Synchronizing RSVP with Slow Start”

12. Bearer Control for VoMPLS Connectivity: use RSVP or CR-LDP + benefit from –Constraint-based routing –Fast reroute QoS and resource reservation: identical to the solutions for VoIP With Diff-Serv in the core, use “MPLS Support for Diff-Serv” for inter-working With RSVP as the Bearer Control protocol, –w/o aggregation: map a RSVP reservation to an LSP –w/ RSVP aggregation: map multiple RSVP reservations to a shared LSP => scalable core

13. VoMPLS Bearer Control for Compression/Multiplexing Both RSVP and CR-LDP may be used to signal the corresponding information –RSVP: I-D “Simple Header Compression” Take into account the compression gains locally on some hops –I-D “Integrated Services in the Presence of Compressible Flows” Recommendation: define the corresponding compression identifiers for the compression scheme(s) that may be defined for VoMPLS

14. An MPLS Tie Line GW PSTN Call Agent CPE GW PC Ph or GW PC Ph or GW GW GB TE Tunnel w/ Fast Re-route for Voice RSVP Admission Control RSVP Aggregation RSVP Signalling for Compression/Multiplexing

15. Summary Recommendations for progress of the VoMPLS Framework Reference Model be generalized to cover VoIP as well as VoMPLS to clarify that –inter-working situations involving any mix of MPLS and non-MPLS transport are within the scope of the Framework. –many existing items of work in IETF for VoIP are applicable to VoMPLS.

16. Recommendations (cont.) Recognize and adopt the following existing IETF work on Bearer Control for VoIP: solutions for advertisement and negotiation of Traffic Parameters and QoS Bearer Control requirement in Call Control protocols; solutions for QoS Bearer Control signaling; solutions for coordination between call control and QoS Bearer Control. Recognize the proposed approach for achieving aggregated MPLS processing in the core.