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

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Presentation on theme: "KT Telecom.Network Lab. Hoon Lee 1 Traffic Engineering over MPLS July 23, 1999 KT Telecom. Network Labs. Hoon Lee."— Presentation transcript:

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

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

3 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.

4 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(MAC addr) –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

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

6 KT Telecom.Network Lab. Hoon Lee 6 MPLS Network Architecture Label Edge Router (LER) MPLS Control Component Label Switch Router (LSR) ATM Switch Fabric Full-function Layer 3 routers Label Binding based on FIB Switching on Label Label swapping LER+LSR MPLS Domain LER+LSR A C B destQoSlabel cgold 1 1 c bronze2 2 1 gold b 3 4 destQoSlabel cgold 3 c bronze4 3 gold b

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

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

9 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

10 KT Telecom.Network Lab. Hoon Lee 10 MPLS and 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 ATMs QoS capabilities Differentiated Service capabilities –Favorable to Internet Traffic engineering Adaptable BW Per path traffic monitoring

11 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

12 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

13 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

14 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

15 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

16 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

17 KT Telecom.Network Lab. Hoon Lee 17 Constraint-based Routing(CR) as TE CR = QoS-routing + policy of network 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 (QoS guarantee)(Increase network utilization) CR considers (1) network topology, (2) requirements of the flow, (3) resource availability of the links, etc In the end, CR may find a longer but lightly loaded path. So, traffic is evenly distributed

18 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

19 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) DSs strategy: - Flow aggregation - Push all the state and control to the edges DSs class: Premium, Assured, and BE

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

21 KT Telecom.Network Lab. Hoon Lee 21 Traffic management in MPLS UPC: ATM Forums 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 CAC

22 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 networkRouter network VC BW -> QoS / Data forward Per-VC ATM Cell Overhead Router Double configuration DS MPLS Router, QoS TE Data Overhead Single configuration


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