Presentation on theme: "Japan Telecom Information & Communication Labs"— Presentation transcript:
1 Japan Telecom Information & Communication Labs Achieving Multimedia QOS over Hybrid IP/PSTN Infrastructures: IP Traffic and Congestion ControlApril 26, 2001Susumu YonedaJapan Telecom Information & Communication Labs
2 Outline IP Transfer Capabilities Generic Traffic & Congestion Controls Service modelsTraffic descriptorsConformance definitionsQoS commitmentsGeneric Traffic & Congestion ControlsSpecific Mechanisms e.g., Diffserv, MPLSConclusion
3 IP Transfer Capabilities: ITU-T SG13 Draft Rec. Y.iptc Dedicated Bandwidth (DBW) IP Transfer CapabilityStatistical Bandwidth (SBW) IP Transfer CapabilityBest-Effort (BE) IP Transfer CapabilityIP 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 DBWSBWBEServiceModelConforming PacketsAssure the negotiated QoSNon-conforming PacketsDiscardedDelivered corresponding to the associated QoSDelivered within the limits of available resourcesAll PacketsForwarded by use of available resourcesTrafficDescriptorsPeak Rate,Peak Bucket Size,The maximum allowed packet sizeDBW’s descriptors + Sustainable Rate, Sustainable Token Bucket Size
5 Conformance Definitions & QoS Commitments DBWSBWBEConformanceDefinitionPacket ArrivalConforming to the GBRA(Rp,Bp)Packet LengthNot exceed the maximum allowed packet sizeConforming to the peak GBRA(Rp,Bp) and the sustainable GBRA(Rs,Bs)QoSCommitmentsSpecified Loss and Delay commitmentsInclude IP QoS Class 0 and 1Specified Loss commitmentInclude IP QoS Class 2No absolute commitment
7 Differentiated Services [DiffServ] Two standard per hop behaviors (PHBs) defined that effectively represent two service levelsExpedited 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 Marker Behavior Aggregate (BA): Uses only the Diffserv Code Point (DSCP) valueMulti-Field (MF): Uses other header info (like protocol, or port numbers, etc.)MarkerAdds DSCP when none existsAdds DSCP as mapped from RSVP reservationChanges to Map from DSCP to IP TOS, or backChanges DSCP as local policy dictates
9 Diffserv Functions (2) Meter Conditioner Accumulates statistics, and provides the inputs to conditioningConditionerProvides 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 MechanismsAt 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’sOSPFIS-ISBGP-4Enhance to carry constraint dataOSPF-TEIS-IS –TEDistribute topology information onlyThe 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 addressTraffic 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 resourcesConstraint based routing is the key to Traffic engineeringConstraint dataLink capacity,Link utilizationResource classPriorityPre-emption etcConstraint based routing is the key to Traffic Engineering
12 Label Distribution Protocols LDPCR-LDPRSVP-TEHop by Hop routingEnsures routers agree on bindings between FEC’s and the labels.Label paths follow same route as conventional routed pathExplicit constraint based routingRoute determined by ingress LSR based on overall view of topology, and constraintsTraffic engineeringCoS and (QoS)fast (50ms) rerouting
13 MPLS Shim Header Structure ...Layer 2 HeaderIP PacketLabel: 20-bit value, (0-16 reserved)Exp.: 3-bits Experimental ( ToS)S: 1-bit Bottom of stackTTL: 8-bits Time To LiveLabelExp.STTL4 OctetsLabel SwitchingLook up inbound label + port (+Exp)to determineoutbound label + port + treatmentHeader operationsSwap (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.
14 Hierarchy via Label stack = Network scalability Layer 2 HeaderLabel 3Label 2Label 1IP PacketWithin each domain the IGP simply needs to allow the Boarder (ingress) routers to determine the appropriate egress boarder routerReducing drastically size of routing table in transit routersMPLS Domain 1MPLS Domain 2Let'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
15 Dynamic-Bandwidth Setting traffictimeLink traffic monitor and dynamic-bandwidth setting.
16 ConclusionProvide a summary of Y.iptc: IP Transfer Capabilities, Service models, Traffic descriptors, Conformance definitions, QoS commitmentsHow 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.