Achieving Multimedia QOS over Hybrid IP/PSTN Infrastructures: IP Traffic and Congestion Control

1. Achieving Multimedia QOS over Hybrid IP/PSTN Infrastructures:IP Traffic and Congestion Control April 26, 2001 Susumu Yoneda Japan Telecom Information & Communication Labs

2. Outline • IP Transfer Capabilities • Service models • Traffic descriptors • Conformance definitions • QoS commitments • Generic Traffic & Congestion Controls • Specific Mechanisms e.g., Diffserv, MPLS • Conclusion

3. IP Transfer Capabilities:ITU-T SG13 Draft Rec. Y.iptc • Dedicated Bandwidth (DBW) IP Transfer Capability • Statistical Bandwidth (SBW) IP Transfer Capability • Best-Effort (BE) IP Transfer Capability IP Transfer Capability: a set of network capabilities provided by IP based network to transfer a set of IP packets under a given classification.

4. Service Models & Traffic Descriptors

5. Conformance Definitions & QoS Commitments

6. Generic Traffic & Congestion Controls • Traffic Control Functions • Network Resource Management • Admission Control • Parameter Control • Packet Marking • Traffic Shaping • Packet Scheduling • Congestion Control Functions • Packet Discard Control • Routing (Proposed)

7. Differentiated Services [DiffServ] • Two standard per hop behaviors (PHBs) defined that effectively represent two service levels • Expedited Forwarding (EF): A single codepoint (DiffServ value). EF minimizes delay and jitter and provides the highest level of aggregate quality of service. Any traffic that exceeds the traffic profile (which is defined by local policy) is discarded. • Assured Forwarding (AF): Four classes and three drop-precedences within each class (so a total of twelve codepoints). Excess AF traffic is not delivered with as high probability as the traffic “within profile,” which means it may be demoted but not necessarily dropped.

8. Diffserv Functions (1) • Classifier • Behavior Aggregate (BA): Uses only the Diffserv Code Point (DSCP) value • Multi-Field (MF): Uses other header info (like protocol, or port numbers, etc.) • Marker • Adds DSCP when none exists • Adds DSCP as mapped from RSVP reservation • Changes to Map from DSCP to IP TOS, or back • Changes DSCP as local policy dictates

9. Diffserv Functions (2) • Meter • Accumulates statistics, and provides the inputs to conditioning • Conditioner • Provides queue selection and treatment,policing (shaping traffic) by adding delay or dropping packets in order to conform to the traffic profile described in the SLA with destination or source (depending whether this is an egress or ingress point). • Authenticates the traffic for admission control.

10. MPLS Mechanisms • At the first hop router in the MPLS network, the router makes a forwarding decision based on the destination address (or any other information in the header, as determined by local policy) then determines the appropriate label value -- which identifies the Forwarding Equivalence Class (FEC) -- attaches the label to the packet and forwards it to the next hop. • At the next hop, the router uses the label value as an index into a table that specifies the next hop and a new label. The LSR attaches the new label, then forwards the packet to the next hop.

11. MPLS Routing protocols Start with existing IGP’s • OSPF • IS-IS • BGP-4 • Enhance to carry constraint data • OSPF-TE • IS-IS –TE Distribute topology information only Constraint data Link capacity,Link utilization Resource class Priority Pre-emption etc Constraint based routing is the key to Traffic Engineering

12. Explicit constraint based routing Route determined by ingress LSR based on overall view of topology, and constraints Traffic engineering CoS and (QoS) fast (50ms) rerouting Label Distribution Protocols • LDP • CR-LDP • RSVP-TE Hop by Hop routing Ensures routers agree on bindings between FEC’s and the labels. Label paths follow same route as conventional routed path

13. MPLS Shim Header Structure MPLS "shim" headers ... Layer 2 Header IP Packet Label: 20-bit value, (0-16 reserved) Exp.: 3-bits Experimental ( ToS) S: 1-bit Bottom of stack TTL: 8-bits Time To Live Label Exp. S TTL 4 Octets Label Switching Look up inbound label + port (+Exp) to determine outbound label + port + treatment Header operations Swap (label) Push (a new header) Pop (a header from stack) MPLS encapsulations are also defined for ATM and Frame relay.

14. Hierarchy via Label stack= Network scalability Layer 2 Header Label 3 Label 2 Label 1 IP Packet Within each domain the IGP simply needs to allow the Boarder (ingress) routers to determine the appropriate egress boarder router Reducing drastically size of routing table in transit routers MPLS Domain 1 MPLS Domain 2 MPLS Domain 3

15. Dynamic-Bandwidth Setting traffic time Link traffic monitor and dynamic-bandwidth setting.

16. Conclusion • Provide a summary of Y.iptc: IP Transfer Capabilities, Service models, Traffic descriptors, Conformance definitions, QoS commitments • How does it work with many other existing traffic engineering mechanisms? • Traffic engineering as well as congestion controls would work well when traffics are effectively monitored and conformance is checked. • Utilize Y.iptc for the conformance monitoring purposes.