July 23, 1999
KT Telecom. Network Labs.
Hoon Lee
KT Telecom.Network Lab. Hoon
Lee
1

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

• 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
3

• 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
4

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

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

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

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

• 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
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• 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
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• 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
11

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

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
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• 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 shortestpath to forward packets
KT Telecom.Network Lab. Hoon
Lee
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• 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
16

• CR = QoS-routing + policy of network
(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
In the end, CR may find a longer but lightly loaded path.
So, traffic is evenly distributed
KT Telecom.Network Lab. Hoon
Lee
17

• 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
18

• 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
19

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

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
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• Single paradigm does not care all: We have to know the pros and cons concerning the selection of paradigm
ATM network
특정 VC 에 특정량의 BW 를 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
Router network
DS 와 MPLS 로써 Router 망도
고속화 , QoS 보장 및 TE 이
가능
Data Overhead 적음
Single configuration 으로 충분
KT Telecom.Network Lab. Hoon
Lee
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