Traffic Engineering over MPLS

1. Traffic Engineering over MPLS July 23, 1999 KT Telecom. Network Labs. Hoon Lee KT Telecom.Network Lab. Hoon Lee

2. Contents • Brief introduction to MPLS • MPLS and traffic engineering • Summary KT Telecom.Network Lab. Hoon Lee

3. Introduction to MPLS • MPLS = L2 Label swapping + L3 routing • Assign short fixed length labels to packets at the ingress to an MPLS cloud, which is used to make forwarding decisions inside the MPLS domain. KT Telecom.Network Lab. Hoon Lee

4. MPLS - Basic Concepts • Switching by fixed length Label • Edge: Assign label for dest. addr. based on COS via ToS and place information with the same output queue, and forward along the same path • Core: Label-based switch • Applied to : ATM(VPI/VCI), FR(DLCI), Ethernet(MACaddr) • MPLS is a class based packet forwarding scheme • Advantages of MPLS • High speed IP forwarding by switch • Vendor independent • Support IP multicasting • Multiple-QoS support • Protocol expandability • Independent switching and routing functions KT Telecom.Network Lab. Hoon Lee

5. MPLS Operation • Layer 3 routing + layer 2 forwarding LER: Label Edge Router LSR: Label Switched Router End System End System LER LSR LSR LER IP routing IP routing IP routing IP routing IP routing IP routing ATM ATM ATM ATM ATM ATM MPLS Domain KT Telecom.Network Lab. Hoon Lee

6. MPLS Network Architecture dest QoS label c gold 3 C dest QoS label c c gold bronze 4 1 Label Switch Router (LSR) gold c b 3 bronze 2 gold b 1 • Switching on Label • Label swapping A LER+LSR 3 1 4 2 B Label Edge Router (LER) MPLS Control Component • Full-function Layer 3 routers • Label Binding based on FIB LER+LSR ATM Switch Fabric MPLS Domain KT Telecom.Network Lab. Hoon Lee

7. Router versus MPLS Router Router Router OSPF OSPF OSPF Router-based Internet Routing Table Routing Table Routing Table DA DA DA Next hop Next hop Next hop Packet Forwarding Packet Forwarding Packet Forwarding IP Packet LSR LER LER LDP/OSPF LDP/OSPF LDP/OSPF MPLS-based Internet Routing Table LIB Routing Table LIB DA DA Next hop/Label Next hop Packet Forwarding Label Switch Packet Forwarding IP Packet ATM Switch KT Telecom.Network Lab. Hoon Lee

8. LDP Signaling Signaling LDP IPoA versus MPLS IP over ATM Upper Upper UNI 3.1 PNNI/B-ISUP UNI 3.1 IP IPOA MPOA IPOA MPOA IP ATM ATM Traffic-based routing (Signaling) LER LER MPLS Upper Upper LSR LSR LDP/OSPF LDP/OSPF LDP/OSPF IP MPLS MPLS IP ATM ATM Topology-based routing (LDP) KT Telecom.Network Lab. Hoon Lee

9. Scope and Objectives • Goal: To investigate the issues and requirements for traffic engineering over MPLS in a large Internet backbone • Application areas: To provide scalable differentiated services in the Internet and enterprise networks in combination with RSVP KT Telecom.Network Lab. Hoon Lee

10. MPLSand Internet • Suited to Internet backbone • Easy to construct the VPN by ATM VC • Lower processing OH compared with router based VPN • CoS provision • Guaranteed service via ATM’s QoS capabilities • Differentiated Service capabilities • Favorable to Internet Traffic engineering • Adaptable BW • Per path traffic monitoring KT Telecom.Network Lab. Hoon Lee

11. Traffic Engineering in Internet • TE includes the measurement, modeling, characterization, and control of traffic for performance optimization of networks and user satisfaction • Esp. over MPLS in Internet, the measurement and control are of most interested KT Telecom.Network Lab. Hoon Lee

12. MPLS and Traffic Engineering • DiffServ treats traffic with similar characteristics and QoS supports in aggregation • In MPLS, traffic trunk is an aggregation of traffic flows of the same class which are placed inside a label switched path • Traffic trunks can be viewed as objects to be routed, so they are similar to VCs in ATM KT Telecom.Network Lab. Hoon Lee

13. Attractiveness of MPLS for TE • Explicit label switched paths can be easily created • MPLS allows for both traffic aggregation and disaggregation • Easy integration with constraint-based routing • MPLS lowers overhead significantly KT Telecom.Network Lab. Hoon Lee

14. TE Performance Objectives (PO) 1. Traffic oriented: -Aspects that enhance the QoS of traffic streams - In a single class BE Internet, minimization of packet loss & delay and maximization of throughput are key measures - In a DiffServ Internet, Statistically bounded POs ( PDV, PLR, PTD) might become useful 2. Resource oriented: -Aspects pertaining to the optimization of resource utilization: Subsets of network resources do not become over utilized & congested while other subsets along alternate feasible paths remain under utilized 3. Common objectives:Minimizing the congestion, esp., a prolonged congestion period KT Telecom.Network Lab. Hoon Lee

15. Congestion Control: Cause • Congestion occurs: 1. When network resources are insufficient or inadequate to accommodate offered load (generic cause) 2. When traffic streams are unevenly distributed to available resources (unbalanced engineering) <- caused by the dynamic routing protocols such as RIP, OSPF, etc., because they select the shortest-path to forward packets KT Telecom.Network Lab. Hoon Lee

16. Congestion Control: Counter attacks • For case 1: (i) Expand capacity by providing more resources ; (ii) Apply classical CC techniques (rate limiting, window flow control, queue management, scheduling, etc) ; (iii) Both • For case 2: Adopt load balancing through efficient resource allocation: Constraint-based routing (CR), an important tool for TE in MPLS KT Telecom.Network Lab. Hoon Lee

17. (QoS guarantee) (Increase network utilization) Given the QoS request of a flow or an aggregated flow, it returns a route that is most likely to be able to meet the requirements CR considers (1) network topology, (2) requirements of the flow, (3) resource availability of the links, etc Constraint-based Routing(CR) as TE • CR = QoS-routing + policy of network In the end, CR may find a longer but lightly loaded path. So, traffic is evenly distributed KT Telecom.Network Lab. Hoon Lee

18. MPLS and Internet QoS • Extending RSVP into WAN environment has failed (Limited scalability) • To force to cooperate all the points and reserve BW p2p is not practical • Set ToS field and indicate the QoS level, and aggregate the pakcet with the same class • Pass them along the same route (traffic trunk) with simple path finding KT Telecom.Network Lab. Hoon Lee

19. DiffServe and MPLS • DS is based on the concept of PHB • Main objectives of DS: - Scalability (Millions of networks) - Full speed (Gbps) • DS’s strategy: - Flow aggregation - Push all the state and control to the edges • DS’s class: Premium, Assured, and BE KT Telecom.Network Lab. Hoon Lee

20. Traffic & Resource Control Architecture Control Performance Monitoring Network management Determine the control policy Modify the TM parameter Modify the routing parameter Modify the resource attributes Control action Observe the state of the network Modify bandwidth Modify routing Characterize the traffic KT Telecom.Network Lab. Hoon Lee

21. Traffic management in MPLS CAC UPC: ATM Forum’s GCRA / Worse Best Effort from PS or AS rather than tagging & dropping Congestion control and load balancing via CR QoS guarantee in combination with DS KT Telecom.Network Lab. Hoon Lee

22. Summary • Single paradigm does not care all: We have to know the pros and cons concerning the selection of paradigm ATM network Router network 특정VC에 특정량의 BW를 할당-> QoS 보장/ 트래픽 제어 가능 Data forward 속도가 빠름 Per-VC 트래픽 통계치 보유 ATM Cell Overhead 과다 망 경계에 Router필요 Double configuration 필요 DS 와 MPLS로써 Router망도 고속화, QoS 보장 및 TE이 가능 Data Overhead 적음 Single configuration으로 충분 KT Telecom.Network Lab. Hoon Lee