QoS in MPLS SMU CSE 8344

Strategy To support end-to-end QoS as in IP MPLS not an end-to-end protocol Efficient ways of mapping QoS to LSPs Traffic Engineering key to QoS SMU CSE 8344

QoS Models Best effort Int-serv. Diff-serv. Future Original IP service Fist IP effort to support QoS Diff-serv. Simple, scalable Future Int+ Diff+ TE with e2e SLAs SMU CSE 8344

Integrated Services and RSVP Service Classes Guaranteed service Controlled load MPLS support of RSVP New object (label object) carried inside RSVP RESV message Down-stream label allocation Once the label binding is over, only the edge router concerned with which packets belong to the reserved flow Can aggregate multiple micro-flows to realize pipes between sites New RSVP object carried in the PATH message (LABEL REQUEST) SMU CSE 8344

RSVP Scalability Micro-flow reservations scale badly (Not RSVP by itself) Aggregation will help reduction of complexity RSVP Refresh reduction RSVP a soft state protocol and hence need refresh Unreliable and hence need high frequency refresh Solutions Reliable delivery through ACKS – reduced refresh rate once the ACK received Summary refresh – send the IDs instead of the whole message; can combine multiple message IDs SMU CSE 8344

Differential Services Need to map DSCP to labels How to set the right value? Who sets the DSCP value? What does a router do when a packet with a DSCP value arrives? DSCP defines PHB (Per Hop Behavior) Default – equivalent to best effort as in IP Expedited Forwarding (EF) Should be forwarded with minimal delay All the packets with EF marking put in a dedicated EF queue Arrival rate less than the service rate Assured Forwarding Defined in the form of AFxy – x defines the class and y specifies the drop preference Example AF11, AF12, AF13 … Who sets the values Based on the application, hosts do it Router sets it based on locally configured policies – arrival interface, BW etc. SMU CSE 8344

MPLS Support for DS Map the DSCP to label Map into the 3-bit EXP field (E-LSP) Limits the PHBs to 8 (as opposed to 64 possibilities) Requires Shim-label support No additional signaling required What if more than 8 PHBs Use explicit LSP (hence label distribution)to represent PHBs (L-LSP) SMU CSE 8344

E-LSP vs. L-LSP R1 R2 R3 R1 R2 R3 AF1y packets Default packets L-LSP for AF1y AF1y packets L-LSP for Default R1 R2 R3 Default packets SMU CSE 8344

E-LSP vs. L-LSP (Cont’d) Minimal label usage Conforms to classical DS model L-LSP Arbitrarily large no. of PHBs Possibility engineer different paths for various PHBs Combinations are also possible SMU CSE 8344

Explicit Congestion Notification (ECN) Congestion control vs. avoidance Drop the packet vs. CE (Congestion experienced) bit set Accommodation nodes with varying capabilities In IP use the two bits left in the TOS field ECT – ECN capable transport CE How to do it in MPLS May have maximum 1-bit available Code the possible three states into two states and do the corresponding mapping SMU CSE 8344

POLICY-BASED NETWORKING CISCO QoS Framework POLICY-BASED NETWORKING VPNs Multimedia Video Conference, Collaborative Computing Mission Critical Services VoIP PROVISIONING & MONITORING Hybrid MPLS DiffServ IntServ Signaling Techniques (RSVP, DSCP*, ATM (UNI/NNI)) Classification & Marking Techniques (DSCP, MPLS EXP, NBAR, etc.) Congestion Avoidance Techniques (WRED) Traffic Conditioners (Policing, Shaping) Congestion Management Techniques (WFQ, CBWFQ, LLQ) Link Efficiency Mechanisms (Compression, Fragmentation) Frame Relay PPP HDLC SDLC ATM, POS FE,Gig.E 10GE Wireless Fixed,Mobile BroadBand Cable,xDSL SMU CSE 8344