Transcript Routing in Optical Networks

Routing in Optical Networks
IP and MPLS in Optical Domain
Markus Isomäki
Agenda
• Trends in IP over optical networking
– Traditional and new models
• Optical network terminology and evolution
– Future expectations
• IP routing in optical domain
– Different models
– Requirements & possible solution frameworks
• MPLS in optical domain - MPLambdaS
• Proposed enhancements for routing and signaling
– OSPF/IS-IS and RSVP/CR-LDP
Standardization Organizations and
Industry Foras
• Internet Engineering Task Force (IETF)
– MPLS Working Group
– IP over Optical Working Group starting
• ITU-T SG 13
– Optical Transport Network architecture and requirements
• ODSI
– Allow IP routers to make dynamic bandwidth requests to the
optical network
– Started in January 2000
• Optical Internetworking Forum (OIF)
Traditional Model IP over ATM over SDH
• IP routers connected to each other via ATM switches
which are connected to each other over SDH
• Known problems
– Different management (fault, configuration, …) at each layer
adds complexity
– Each layer has independent routing = Overlay
• Different physical & logical topology
– Redundant functionality at each layer
• Multiplexing, QoS (mapping mismatch), protection…
=> ATM will not survive in the backbone
Current Model - IP over SDH
IP over SDH Pros & Cons
• Advantages compared to IP over ATM over SDH
– Easier management
– No “cell tax”
– IP QoS mapping straightforward
• Major drawbacks
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Protection switching consumes half of the capacity
Cumbersome provision of connections - no dynamics
Still two layers of management
Circuit switched!!!
May stop at 9.9 Gbps (STM-64 / OC-192)
=> More flexible & dynamic methods needed
– IP Optimization wanted!!!
Other Existing Models
• Gigabit Ethernet in Metro networks (10GE in 2001?)
– Simple & cheap
– No standard protection technology
– Reach may cause problems
• Cisco Systems’ Dynamic Packet Transfer (DPT)
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Dual ring like FDDI
Spatial reuse of capacity
No unused protection capacity
Good for multicast
Proprietary
Toward IP over Optical Networking
The common view is this
But how to do routing, path setup, QoS, traffic
engineering, protection & restoration etc.
=> Basic IP has not enough intelligence!
Optical Network Evolution & Terminology
• Wavelength Division Multiplexing (WDM)
– Multiple colors in a single fiber, each color carries SDH,
Gigabit Ethernet etc.
– Density grows every year
• Optical Cross-Connects (OXC)
– A box that switches a wavelength from an incoming fiber to
an outgoing fiber
– Wavelength continuity or conversion
– All-optical (transparent) or electro-optical (opaque)
– Erbium doped fiber amplifiers (EDFA)
IP over Optical Vision
Routers connected to each other over
OXC core using WDM wavelenghts
Composite Link
4λ
Optical Switches
Composite Link
3λ
IP Router
Router Interconnection
Requirements
• The routers have to be able to dynamically (ondemand) make connections to each other
– Fast provision!!!
– Connection capacity
• Protection and restoration needed
– Ask for a protected connection (1+1, 1:1, M:N)
• Traffic engineering
– Constraint-based and explicit routing
=> Use IP routing in the optical domain?!!!
Routing Models
• Overlay
– Independent routing on different layers
– Router is client to optical network (some kind of UNI), optical
switch computes the path (IP router does not “see” the
topology of the optical network)
– Similar to Classical IP over ATM or MPOA
– Good when optical network owned by different organization
than the router network
• Integrated / Peer
– Single routing instance run over both networks
– Router is able to compute the path
• Augmented
– Separate routing instances, some information leaked
MultiProtocol Lambda Switching
• IDEA: Use MPLS control plane machinery to
implement traffic engineering, restoration etc. in
OXCs (also SDH equipment) - Wavelength ~ Label
MPLS
Control Plane
Control Adaptation
OXC Switch
Controller
OXC Switch Fabric
OXC Data Plane
MPLambdaS Benefits & Specialities
• Real-time provisioning of connections
• Distributed IP routing control
• No need for new control protocols
Optical domain
(Like nested LSPs)
OXCs unable to terminate LSPs
MPLambdaS & OXC Requirements
• OXCs should be able exchange control information
– Control plane topology may be different from data plane (inband or out-of-band control); (Similar to SS7)
• Automatic neighbor discovery and registration
– Neighboring nodes should know which fiber ports are
connected to each other
• Robustness
– A transient fault at the control plane should not affect the
existing connections (soft state unacceptable?)
– Fast restoration (fault handling)
Enhancements for Routing Protocols
OSPF and IS-IS
• New link attributes (TLVs)
– Link type
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Packet switch capable
TDM capable
Lambda switch capable
Fiber switch capable
Forwarding adjacency
Also information
on physical properties
• BER
• Wavelength conversion
– Link media type
• SDH, Gigabit Ethernet etc.
• Termination capability
– Shared Risk Link Group information
• For example, if two fibers are in the same conduit they are in
the same SRLG => Cannot be used for each other’s protection
Enhancements for Signaling Protocols
RSVP and CR-LDP
At least two proposals submitted
• Label objects should contain information on
– Fiber
– Lambda
– Channel
• Convey information on requested media type
• Capability to request protected connections!
• For RSVP reservation confirmation should be used
Conclusions
• Future networks based on IP routers connected to
each other via Optical Cross-connects
• IP routing and MPLS good candidates for controlling
OXCs - IP optimization & synergy
• Enhancements needed for routing & signaling
protocols
=> Will happen because major support: Cisco, Nortel, ...
• Other solutions possible
– Use of GSMP
– Use of traffic driven connection setup