mcadams

Protection Options for IP Over Optical Transport: 

Protection Options for IP Over Optical Transport Larry McAdams lmcadams@cisco.com

Agenda: 

Agenda The Issues with SONET Protection at the Optical Layer Protection at the IP Layer Comparison of the Options

A Tale of Two SONETs: 

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

SONET Architecture and IP: 

SONET Architecture and IP IP traffic is largely distance independent Longer circuits complicate scaling and provisioning of SONET rings Graphic courtesy of Andy Wright, Williams

SONET Architecture and DWDM: 

SONET Architecture and DWDM Cross-connecting circuits between multiple rings is difficult and slow DWDM just multiplies the problem

Enter The OXC: 

Enter The OXC Optical Cross-connects (OXCs) change the architecture from rings to meshes Improved transport efficiency Traffic engineering at OC-48

Optical Intelligence: 

Optical Intelligence OSPF-like protocols provide topology and network state information Each node maintains copy of database Information is broadcast in SONET overhead

OXC Protection : 

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

And Then Came MPLS: 

And Then Came MPLS Connections for the connection-less A Unifying control plan for packets, cells and circuits

MPLS Link and Node Protection: 

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

MPLS Path Restoration: 

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 pre-assigned MPLS back-up tunnel Entire restoration/re-optimization process completes in seconds

Comparison of Approaches: 

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

Divide and Conquer?: 

Divide and Conquer? The network is really one big entity Optical intelligence knows about capacity IP intelligence knows about reachability San Francisco New York

Marriage of the Millennium: 

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/draft-awduche-mpls-te-optical-00.txt