14.1 mpls te principle

MPLS TE All rights reserved
MPLS (Multi-protocol Label Switching) has been successfully configured and applied in many large networks. MPLS TE is a perfect combination technology of MPLS and TE, providing best resources architecture and most resources usage percentage.
HUAWEI TECHNOLOGIES CO., LTD.
MPLS TE user guide
Upon completion of this course, you will be able to:
know detailed TE concepts and models
know MPLS technology specifics and priorities
Master MPLS TE background and function module
Chapter 2 MPLS introduction
Chapter 3 MPLS TE
1.1 What is TE
1.2 TE before MPLS
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Concept of TE
Two engineering concepts can accompany with the growth of network size:
NE (Network Engineering)
NE is the process of how to plan, design and implement a network to satisfy the real traffic requirements. First real traffic requirements exsit, then start network design and implementation.
TE (Traffic Engineering)
TE is the process of how to configure existing network equipments to make traffic transmitted normally. First network equipments exist, then configure .
NE (Network Engineering) and TE (Traffic Engineering)
NE means building a new network after surveying, planning, designing the resources requirements.
TE is redesigning, reconfiguring the exists network equipments to improve network performance.
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What is TE
“Traffic Engineering is the process of controlling how traffic flows through one’s network so as to optimize resource utilization and network performance”
(Global Crossing, IEEE)
“A major goal of Internet Traffic Engineering is to facilitate efficient and reliable network operations whiles simultaneously optimizing network resource utilization and performance.”
RFC 2702 Requirements for Traffic Engineering over MPLS
Reduce OPEX costs through more efficient bandwidth usage
Avoid possible part link busy or empty through appropriate rearranging traffic
Make the best use of network resources and improve network performance through good redesigning traffic
TE target
Performance oriented services: enhanced services QoS performance. i.e. effect to packet loss, latency, throughput and SLAService Level Agreement
Performance oriented resources: optimize resources usage. Bandwidth is precious resource, to arrange them efficiently is the core target of TE
performance
TE QoS performance is mainly indicated in MPLS DS-TE. The fundamental is classified traffic at the ingress of TE tunnel, provide diff-service
1.1 What is TE
1.2 TE before MPLS
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Earlier TE introduction
TE is not the result of MPLS, it is general technology project
Before MPLS TE, technology mainly used to provide Traffic Engineering are:
ATM TE
IP TE
ATM TE and IP TE
Be clear that TE is not one part of MPLS, they are two different technology, however, if we combine them together, we can have their each superior function and prohibit inferior function
IP TE can be easily used without much detailed technology
IP TE cannot control transmission path based on traffic sources, but on destination forwarding
IP TE mainly change special link cost value of IGP metric to control traffic
IP TE
IP TE is simple but not accurate, it can be seen a technology under IGP SPF and destination-based traffic adjustment. The priority is simple, work well with exists IP technology and weakness is also obvious, with possible part link be busy or empty, moreover, bad extensibility
IP TEfish problem
All traffic from R1 or R2 will select R3-R4-R5 path arriving R8
R2
R8
R1
under-utilized alternate path
R3
R4
R5
R6
R7
10
10
10
10
10
IP TE has only one shortest path algorithm, all traffic will be forwarded by smallest cost value without considering link bandwidth factor. Thus, it is possible to find some busy or empty link.
Here, if all traffic from R1 or R2 select R3-R4-R5, this link will be busy, and R3-R6-R7-R5 will be empty.
IP TEfish problem
Change R3-R6-R7-R5 cost value, all traffic from R1 or R2 will shift on it
R2
R8
R1
IP routing: destination-based shortest path route
After change the other link cost value, all traffic will have a shift, so the previous link be empty again.
Work with such IGP protocol, we can not make two different path for R1-R8 and R2-R8 respectively.
With a large size network, it is very difficult to adjust network path to specific traffic by changing special link cost value, so this method has a bad extensibility.
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IP TE weakness
It is far less enough that calculate path only based on IGP metric value, instead of considering bandwidth, link properties and others factor
IP TE is essentially destination-based forwarding technology, it is hop-by-hop forwarding, can not control traffic by sources
IP TE is connectionless-oriented, can not support Explicit Routing
IP TE weakness
ATM TE
ATM TE mainly generated by PVC through traffic source to traffic destination
ATM TE is connection-oriented, can be well and easily done to arrange traffic flow and put QoS
ATM TE is necessarily applied in full-mesh network, which exists of ON² problem, results in bad extensibility
ATM TE is end-to-end TE, not so as to IP TE hop-by-hop
ATM TE
FR TE and ATM TE can be put in the same class, both of them based on full-mesh
Physical architecture: Layer 2ATM/FR built base on ATM TE
Logically: the full-mesh network consists of all Layer 3Routers equipments, in this network, each router has unique VC connected with any other router
L3
L3
L3
L3
L3
L3
L3
L2
L2
L2
L2
L2
L2
L3
L3
L3
L3
L3
Physical
Logical
L3 is Layer 3 equipment, generally is router, L2 is Layer 2 equipment, generally is ATM/FR switch
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ATM TE weakness
In case of carry out ATM TE in traditional IP network, telecom operator need to buy new ATM/FR equipments, it will increases OPEX costs in a large scale
ATM TE will bring extra and more complex network management costs
Two layer network: ATM and IP equipments are difficult to manage together
Different equipment will bring extra training works, technique support works, and project implement works
Full-mesh network architecture exists of ON² problem, bad extensibility
IP over ATM will results in extra Cell Tax
ATM TE weakness
Question
IP TE and ATM TE have their superiority and inferiority respectively, how can we do to keep superiority and to discard inferiority
Chapter 3 MPLS TE
MPLS basis
In MPLS network, the IP packet is added with one or more MPLS header at the length of 32 bits
MPLS is a concept between OSI layer 2 and layer 3 which can support variety of network protocol (IPV4/IPV6/ATM/FR)
Earlier MPLS technology intent is improving router forwarding speed
MPLS packet
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MPLS basiscont.
20 bits label, mapping traffic into LSP, in the range of 16-1,000,000
EXP consists of 3 bits, indicate MPLS QoS
S has only 1 bit, indicate the last label in the label queue
TTL has the same function as IP has, the purpose is inspecting and avoiding generating routing loop in Frame mode
MPLS header
TTL
Label
EXP
S
There are two type of data switch mode in data communication network, IP network is a typical Frame switch network, and ATM / FR are the other typical cell switch network
MPLS superiority
MPLS technology use fixed length label searching instead of traditional IP routing longest match search method, rapidly improve forwarding speed, this is the beginning MPLS intension
MPLS can combine IP and ATM well, save extra cell tax of IPOA
MPLS true superiority is to provide variety of value-added service:
MPLS VPN
MPLS QoS
Chapter 3 MPLS TE
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MPLS TE development
In Sept, 1999, RFC 2702Requirements for Traffic Engineering Over MPLSgive detailed necessary conditions of building network based on MPLS TE, make a good fundamental for MPLS TE development and application
Since TE is a global complex system project, generating and implementation is fairly difficult, nowadays, only small number of network provider can provide scaleable application
MPLS TE is a perfect combination of MPLS and TE, which is definite trend of large scale network provider building core network and backbone
MPLS TE development
Our equipment of VRP5 version can generate MPLS TE well, will be implemented in CN2 project in the second period
RSVP-TE
RSVP-TE technology is mature, has been scaleable applied, but too complex and bad extensibility
CR LDP-TE
CR LDP-TE technology is not very mature, rarely applied, but simple, good extensibility
RSVP-TE is widely and mainly used
MPLS TE realization method
Support tunnel preempt function by different priority
Support failure inspection switch function, when one link or node fail, the other can quickly take over
Support pre-creating backup LSP
MPLS TE necessary condition
MPLS TE necessary condition2
Support LSP tunnel auto re-optimize by the change of network resource
Support LSP tunnel bandwidth auto adjustment by the change of network bandwidth
Support explicit path, can be set include or exclude node by field requirement
Support priority LSP tunnel, different priority traffic will input into different tunnel respectively with DiffServ
MPLS TE necessary condition
Packet forwarding
Four elements can guarantee basic traffic forwarding, but not very accurate
MPLS TE also support some high level specification
FRRFast Reroute
MPLS TE four elements
Four elements will be given detailed information in the coming slides
1, flood link state information including bandwidth and link properties
2, calculate path from source to destination by CSPFConstraint Shortest Path Firstalgorithm
3, setup end-to-end LSP and distribute label by extend RSVP protocol
4, put traffic into LSP tunnel
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TE is separate from MPLS essentially, the original intent is well utilize whole network resources
MPLS is a combination of IP and ATM both superiority, can provide variety of applications, i.e. MPLS VPN, MPLS TE
MPLS TE is perfect combination of MPLS and TE technology, can make network resources well optimized, improve network performance
Summary
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14.1 mpls te principle

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