Transcript Protection Options for IP Over Optical Transport

Protection Options for IP
Over Optical Transport
Larry McAdams
[email protected]
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© 1999, Cisco Systems, Inc.
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Agenda
• The Issues with SONET
• Protection at the Optical Layer
• Protection at the IP Layer
• Comparison of the Options
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A Tale of Two SONETs
• SONET is the standard for optical
transport
Multiplexing hierarchy based on DS0
Fast protection switching for all traffic
• SONET has two parts
Protocol --> framing structure, signaling
Architecture --> self-healing rings
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SONET Architecture and IP
San Francisco
New York
Graphic courtesy of
Andy Wright, Williams
• IP traffic is largely distance independent
• Longer circuits complicate scaling and
provisioning of SONET rings
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SONET Architecture and DWDM
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DCS
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Graphic courtesy of
Andy Wright, Williams
• Cross-connecting circuits between
multiple rings is difficult and slow
• DWDM just multiplies the problem
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Enter The OXC
San Francisco
New York
• Optical Cross-connects (OXCs) change
the architecture from rings to meshes
Improved transport efficiency
Traffic engineering at OC-48
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Optical Intelligence
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DWDM
Switch Matrix
DWDM
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• OSPF-like protocols provide topology and
network state information
Each node maintains copy of database
Information is broadcast in SONET overhead
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OXC Protection
• Unlike SONET, OXC-based networks offer
several classes of restoration for different
traffic types:
Mission Critical -- Predetermined restoration
path with pre-allocated capacity
Premium Internet -- Predetermined restoration
path without pre-allocated capacity
Public Internet -- Restoration path calculated in
the fly
Low Priority Traffic -- Pre-emptable working
path, may be unprotected
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And Then Came MPLS
IP
MPLS “Glue”
Constraint
VPN Multi-Service
Based
Migration
Routing
• Connections for the connection-less
• A Unifying control plan for packets, cells
and circuits
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MPLS Link and Node Protection
• Provides temporary routing around a
failed link or node
Rerouting in under 50 msec
Scalable to 1000s of MPLS tunnels
Uses SONET signaling and nested labels
Only involves routers at end of link
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MPLS Path Restoration
• Path restoration, or route re-optimization,
occurs in parallel with link protection
• Failure signaled to head-end of MPLS
tunnel by IGP or RSVP
• Head-end router selects new path via
Dijkstra computation or switches to preassigned MPLS back-up tunnel
• Entire restoration/re-optimization process
completes in seconds
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Comparison of Approaches
• Both approaches work (fast and efficient)
• Both approaches scale and have CoS
Optical granularity is OC-48 circuits
MPLS granularity is aggregated tunnels
• The choice should be based on services
Optical for Layer 1 services
MPLS for Layer 3 services
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Divide and Conquer?
San Francisco
New York
• The network is really one big entity
• Optical intelligence knows about capacity
• IP intelligence knows about reachability
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Marriage of the Millennium
• Multi-Protocol Lambda Switching (MPlS)
can unify the optical and data control
planes
Optimized path/circuit restoration
Simplified provisioning
Lower cost of operation
• IETF is working on MPlS in the MPLS WG
http//www.ietf.org/internet-drafts/draftawduche-mpls-te-optical-00.txt
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