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

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

3. KT Telecom.Network Lab. Hoon Lee
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. KT Telecom.Network Lab. Hoon Lee
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
KT Telecom.Network Lab. Hoon Lee

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

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

9. KT Telecom.Network Lab. Hoon Lee
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. KT Telecom.Network Lab. Hoon Lee
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 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: When network resources are insufficient or inadequate to accommodate offered load (generic cause) 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. 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
KT Telecom.Network Lab. Hoon Lee

18. KT Telecom.Network Lab. Hoon Lee
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. KT Telecom.Network Lab. Hoon Lee
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
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. KT Telecom.Network Lab. Hoon Lee
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 Router 필요
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