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

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

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.

Service Models & Traffic Descriptors DBW SBW BE Service Model Conforming Packets Assure the negotiated QoS Non-conforming Packets Discarded Delivered corresponding to the associated QoS Delivered within the limits of available resources All Packets Forwarded by use of available resources Traffic Descriptors Peak Rate, Peak Bucket Size, The maximum allowed packet size DBW’s descriptors + Sustainable Rate, Sustainable Token Bucket Size

Conformance Definitions & QoS Commitments DBW SBW BE Conformance Definition Packet Arrival Conforming to the GBRA(Rp,Bp) Packet Length Not exceed the maximum allowed packet size Conforming to the peak GBRA(Rp,Bp) and the sustainable GBRA(Rs,Bs) QoS Commitments Specified Loss and Delay commitments Include IP QoS Class 0 and 1 Specified Loss commitment Include IP QoS Class 2 No absolute commitment

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)

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.

Diffserv Functions (1) Classifier Marker 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

Diffserv Functions (2) Meter Conditioner 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.

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.

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 The first part of automating the establishment of LSP’s is to have a routing protocol distribute topology information, and the current IGP’s OSPF, IS-IS and RIP do that. However these protocols simply enable an individual router to decide the port that is on the shortest path to the destination IP address Traffic engineering is seen as an essential element of running an effective large best effort IP network, and to address the needs of traffic engineering the routing protocols must be enhanced to provide much more data. For example the capacity of all the links between the ingress and egress node, the current utilization of each link, the delay across the link, whether the whole span has protection switching or not and so on. We may also want to set by management some link characteristics ie resource classes that allow the ingress LSR to include or exclude certain resources Constraint based routing is the key to Traffic engineering Constraint data Link capacity,Link utilization Resource class Priority Pre-emption etc Constraint based routing is the key to Traffic Engineering

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 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

MPLS Shim Header Structure ... 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) This is the basic MPLS packet format. The 32-bit MPLS field is known as a "shim header". This comes from an engineering term - a "shim" is a thin strip of material used to makes parts fit correctly. When you fold up a beer mat to stop a bar table from wobbling you are using a shim! The first 20 bits of the field actually represent the label. The next three bits are currently "experimental" and must be set to zero. The next bit indicates if this label is part of a stack of labels. If the S-bit is zero, then this is the only label. The Time To Live (TTL) field is as per a normal IP packet, and is there for the same purpose (loop detection). MPLS encapsulations are also defined for ATM and Frame relay.

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 Let's look a bit more closely at those labels. MPLS labels can be stacked one on top of another. The way that this stacking is build up and stripped off can lead to nested MPLs domains, as I show above... MPLS Domain 3

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

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.