Transcript Traffic Engineering over MPLS

Traffic Engineering over MPLS
July 23, 1999
KT Telecom. Network Labs.
Hoon Lee
KT Telecom.Network Lab. Hoon
Lee
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Contents
• Brief introduction to MPLS
• MPLS and traffic engineering
• Summary
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Lee
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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.
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Lee
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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
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MPLS Operation
• Layer 3 routing + layer 2 forwarding
End System
LER: Label Edge Router
LSR: Label Switched Router
End System
LER
LSR
LSR
LER
IP
routing
IP
routing
IP
routing
IP
routing
IP
routing
ATM
ATM
ATM
ATM
ATM
IP
routing
ATM
MPLS Domain
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MPLS Network Architecture
dest
c
c
b
A
QoS
label
gold
1
bronze 2
gold
1
dest
c
c
b
QoS
label
gold
3
bronze 4
gold
3
C
Label Switch Router
(LSR)
• Switching on Label
• Label swapping
LER+LSR
3
1
2
4
B
Label Edge Router
(LER)
• Full-function Layer 3 routers
• Label Binding based on FIB
MPLS Control Component
LER+LSR
MPLS Domain
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ATM Switch Fabric
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Router versus MPLS
Router-based
Internet
IP Packet
MPLS-based
Internet
IP Packet
Router
Router
Router
OSPF
OSPF
OSPF
Routing
Table
Routing
Table
Routing
Table
DA
Next hop
Packet
Forwarding
DA
Next hop
Packet
Forwarding
DA
Next hop
Packet
Forwarding
LER
LSR
LER
LDP/OSPF
LDP/OSPF
LDP/OSPF
LIB
Routing
Table
Routing LIB
Table
DA
Next hop/Label
Packet
Forwarding
Label Switch
DA
Next hop
Packet
Forwarding
ATM Switch
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IPoA versus MPLS
IP over ATM
Upper
IP
UNI 3.1
PNNI/B-ISUP
Signaling
IPOA
MPOA
Upper
UNI 3.1
Signaling
IPOA
MPOA
ATM
IP
ATM
Traffic-based routing (Signaling)
LER
MPLS
Upper
IP
LER
LDP/OSPF
LSR
LDP
LDP/OSPF
LSR
Upper
LDP/OSPF
LDP
MPLS
MPLS
ATM
IP
ATM
Topology-based routing (LDP)
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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
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Lee
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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
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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
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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
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Attractiveness of MPLS for TE
• 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
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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:
prolonged congestion period
Minimizing the congestion, esp., a
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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 shortestpath to forward packets
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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
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Lee
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Constraint-based Routing(CR) as TE
• CR = QoS-routing + policy of network
(QoS guarantee)
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
(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
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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
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Lee
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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
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Traffic & Resource Control Architecture
Control
Performance
Monitoring
Determine the
control policy
Observe the
state of the
network
Modify the TM
parameter
Modify the
routing
parameter
Characterize
the traffic
Modify the
resource
attributes
Network
management
Modify
bandwidth
Modify
routing
Control action
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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
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Lee
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Summary
• Single paradigm does not care all: We have to
know the pros and cons concerning the selection of
paradigm
ATM network
특정VC에 특정량의 BW를 할당
-> QoS 보장/ 트래픽 제어 가능
Router network
Data forward 속도가 빠름
DS 와 MPLS로써 Router망도
고속화, QoS 보장 및 TE이
가능
Per-VC 트래픽 통계치 보유
Data Overhead 적음
ATM Cell Overhead 과다
Single configuration으로 충분
망 경계에 Router 필요
Double configuration 필요
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