1. Requirements for Ring Protection in MPLS-TP
John Drake
Adrian Farrel
73rd IETF, Minneapolis, November 2008

2. There is a base requirement
draft-jenkins-mpls-mpls-tp-requirements-01
If protection is supported then
MPLS-TP MAY support mechanisms that are optimized for specific network topologies (e.g. ring). These mechanisms MUST be interoperable with the mechanisms defined for arbitrary topology (mesh) networks.
If optimised mechanisms for ring topologies are supported then they MUST support switching times within 50 ms (depending on CV rate configuration) assuming a reference network of a 16 node ring with less than 1200 Km of fiber, as defined by ITU SG15, Question 9.
73rd IETF, Minneapolis, November 2008

3. What do service providers say?
“We want to deploy MPLS-TP in rings.”
“We want to protect our traffic”
That means we need to provide “ring protection”
But what is a ring?
73rd IETF, Minneapolis, November 2008

4. 73rd IETF, Minneapolis, November 2008
Deployment Scenarios
The network *is* the ring
Deploy routers to replace TDM equipment
Ring as a layer network
The virtual rings imposed on a mesh network to provide connectivity
73rd IETF, Minneapolis, November 2008

5. 73rd IETF, Minneapolis, November 2008
Physical rings
Physical topology is easy…
An arrangement of two or more nodes each with exactly two line-side interfaces
Each node may have multiple “customer-facing interfaces”
That means that the full extent of the MPLS-TP network is the ring
The ring can be used to support connectivity as a layer network
We can extend this idea to allow ring interconnect to make larger networks
73rd IETF, Minneapolis, November 2008

6. 73rd IETF, Minneapolis, November 2008
Layered Network
A ring in the server layer can provide a set of TE links in the client layer
The TE links are protected by the protection within the ring
73rd IETF, Minneapolis, November 2008

7. 73rd IETF, Minneapolis, November 2008
Virtual Rings
We can super-impose a ring onto a mesh
This creates a virtual or logical ring
We can apply ring properties (whatever they are) to this ring
73rd IETF, Minneapolis, November 2008

8. Detailed Requirements
Supplied by ITU based on draft version of G.8132
“T-MPLS Shared Protection Ring”
Summarised and translated into English…
A packet transport ring protection scheme shall:
Be applicable at a packet transport layer, for both logical and physical ring topologies
Operate in the data plane, i.e., be independent of a control plane or a management plane
Have the capability to coordinate protection switching actions with resiliency mechanisms possibly operating at the server layer
Support switching time within 50 ms
Protect pt-to-pt and pt-to-mp connections
Have the capability to disable ring protection on selected links (depending on operator’s need)
Maximize the recovery of all possible traffic, both in case of single and multiple failures (including link and/or node failure)
Allow “administrative” protection switching
Support priority logic to negotiate and accommodate simultaneous requests
Support bidirectional switching (unidirectional protection switching is not required)
Support revertive switching (non-revertive is not required)
Prevent protection switch thrashing
Support the sharing of ring protection bandwidth for best-effort traffic and prioritised protection
Support inter-ring connectivity with single and dual node connectivity
Support vendor interoperability in a single ring or at the shared node/link of interconnected rings
Simplify configuration, maintenance operations, ring upgrade, reliable protection status and alarms reporting
73rd IETF, Minneapolis, November 2008

9. Requirements are not solutions
Important not to drive requirements by statements of existing solutions in other technologies
Requirements should be stated clearly in abstract terms
Requirements should not be unnecessarily limited to rings
Where-ever possible applicable to general mesh networks
We will attempt to meet requirements using existing techniques
MPLS data plane techniques (label stacking, etc.)
MPLS control plane (fast reroute)
GMPLS control plane
Link level protection
End-to-end protection
Segment protection
73rd IETF, Minneapolis, November 2008

10. 73rd IETF, Minneapolis, November 2008
What next?
Do we really need an I-D to describe ring protection requirements?
Which of the requirements listed would not be applicable in generic mesh networks?
It might be valuable to have an applicability statement
How to use existing mechanisms to provide optimized protection in ring deployments
Show how all “ring protection requirements” are solved
73rd IETF, Minneapolis, November 2008