TM8106
Optical Networking
Multi-Protocol Label Switching-Transport Profile
(MPLS-TP)
By
Ameen Chilwan
Syllabus:
[1] MPLS Transport Profile (MPLS-TP): A Set of Enhancements to the Rich MPLS Toolkit, Juniper Networks, Whitepaper,
2011.
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[2] Dieter Beller, Rolf Sperber, MPLS-TP – The New Technology for Packet Transport Networks, 2nd DFN Forum, 2009.
Outline
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Transport Networks
MPLS-TP Basics
Standardization History
MPLS-TP Components
 OAM
 Control Plane
 Resiliency
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Synchronization
Physical Infrastructure Support
Deployment Options
Misconceptions about MPLS-TP
Conclusion
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Transport Networks
• Goal of transport network
• Requirements
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Packet-based Transport Network
• MPLS has been serving as one for almost a decade
 Connection-oriented and Packet-based
 Designed to carry L3 IP Traffic
 Establishes IP traffic paths
 Associates these paths with arbitrarily assigned labels
• GMPLS extends MPLS
 Label switching for
• TDM (SONET/SDH)
• Wavelength (λ)
• Spatial switching (incoming ports to outgoing ports)
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MPLS-TP Emergence
• Lacks some features of SDH-like networks
 Operation, Admin and Management (OAM)
 Resiliency
 Scalable operations
 High availability
 Performance monitoring
 Multi-domain support
• IETF and ITU-T joined forces to enhance MPLS
 MPLS-TP
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MPLS-TP Background
• Drivers for MPLS-TP
 Rise in demand for service sophistication
• Bandwidth-hungry services
 Pressure to reduce operational cost (OPEX)
 Maximize the value per bit
• Lead to a technology that is almost SDH-like
 Carrier-grade
 Packet-switched
 With OAM features
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MPLS-TP Overview
• Takes a subset of MPLS/GMPLS
• Enhance with some functionalities
 Network Management (e.g. FCAPS)
 Dynamic provisioning of transport paths via control plane
 Provide restoration functions
 E2E path provisioning across networks/domains
• Characteristics
 Connection oriented
 Client and physical layer agnostic
 OAM similar to SDH-like networks
 Protection schemes
 Network provisioning via centralized NMS
 GMPLS Control plane applicable
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Standardization History
• ITU-T will define requirements
• IETF will work on protocol extensions
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MPLS-TP Components
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Operation, Admin and Management
• Dedicated OAM packet
 interspersed into the associated user traffic flows
 Created and processed by maintenance end-points
 Intermediate points can also process them & collect data
• OAM Tools
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OAM Functions and Tools
• Functions
 Fault Detection (e.g. connectivity check)
 Fault Localization (e.g. loopback, lock)
 Performance Monitoring (e.g. delay, loss)
• Tools (Existing MPLS tools extended)
 Bidirectional Forwarding Detection (BFD)
 LSP Ping
 LSP Trace
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OAM Enhancements
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Associated Channel (ACh)
• MPLS-TP shall work without IP functionality
 MPLS uses Ach for framing, forwarding and encapsulation
 Enhanced by GACh and GACh Label (GAL)
 Support in-band control channels
• GACh
 Ensure congruency between OAM packets and data path
 Indicates tagged packet must be processed by special function
 Not suitable for static provisioning
• Because negotiated when pseudowire was setup
• Solved using GAL (reserved value of 13)
– Enables easy extraction at end- and mid-point nodes
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Control Plane (Static and Dynamic)
• Responsible for setup of LSP
• MPLS has mature and dynamic control plane
 OSPF-TE, IS-IS-TE, RSVP-TE and BGP
• Current transport networks have static control plane
 using NMS
• MPLS-TP
 Can have both static or dynamic
 Dynamic has advantages like:
• Scaling
• Advanced protection functions (e.g. LSP tail-end protection)
• Restoration
 Distributed control plane
• Signaling, routing and TE
 Decoupled from data plane
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MPLS-TP Control Plane (contd…)
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Resiliency
• Mechanisms in MPLS
 LSP fast reroute
 Pseudowire redundancy
 Path protection
• Enhancements in MPLS-TP
 OAM-triggered protection
 Optimizing protection in ring topologies
• Circuit networks are interconnected rings
• Fast reroute works but inefficient
• Wrapping and steering implemented in MPLS-TP
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Synchronization
• Approaches
 An overlay synchronization network
• Requires parallel network
 Distributed reference clock
• Reference clock at least at the edges
 Forwarding of clock information across packet domain
• Synchronization protocol
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Synchronization (contd..)
• Packet based clock
recover solution
 Adaptive Timing
• Encapsulated and
de-capsulated
at
packet edge nodes
between TDM and
packet domain
 Differential Timing
• Both edge nodes
performing
interworking
have
access to reference
clock
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Physical Infrastructure Support
• MPLS-TP over SDH/SONET, PDH and OTN
 ITU-T defines Generic Framing Procedure (GFP)
• Encapsulate variable length payload of various client signal
• Contains User Payload Identifier (UPI)
• MPLS-TP uses same UPI point code as MPLS
• OTN includes WDM network layer for transport of a variety of
OTN client signals
• SONET/SDH uses virtual concatenation to form transmission
pipelines with larger capacities
• MPLS-TP over Gigabit Ethernet
• Two-octet long Ether Type field in Ethernet II Indicates which
protocol is encapsulated in payload
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Deployment Options
• Access and aggregation network
 Major migration from circuit to packet happening nowadays
• OAM enhancements will allow more visibility into Core
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Misconceptions about MPLS-TP
• MPLS-TP is a new technology, not part of MPLS
 It is a subset of MPLS with some enhancements
• Extensions in MPLS-TP are not applicable in MPLS
 Actually meant to apply in MPLS to make it broadly applicable
• MPLS-TP requires substantial changes in MPLS
 Design goal of MPLS-TP is to keep MPLS architecture
• MPLS-TP require static provisioning
 Supports both static and dynamic control planes
• Requires forklift hardware upgrades
 Might be true for some vendors, but not always, not in Juniper
at least
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Conclusion
• MPLS-TP is
 Subset of MPLS/GMPLS
 Enhancements esp. OAM
• Fault management
• Performance monitoring
 E2E integration with existing and next generation MPLS networks
• MPLS-TP intended to
 Tie together
• service routing
• transport platforms
 Advantages of tying together
• Consistent operations and OAM functions across networks
• Seamless interworking with IP/MPLS networks
• Scalability due to multiplexing capability
• Supports huge variety of services encapsulated into pseudowires
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