1. MPLS Traffic Engineering

2. What is Traffic Engineering?
The ability to put traffic where you want it
Adapt in the face of topology changes
Adhere to administrator-defined policies
Copyright © 1998, Juniper Networks, Inc.

3. Motivation for traffic engineering
IGP metrics tend to attract or repel all traffic
Insufficient granularity
Little predictability
Results are unused capacity and congestion
Copyright © 1998, Juniper Networks, Inc.

4. Traffic patterns
Copyright © 1998, Juniper Networks, Inc.

5. Constraint Based Routing
Use the IGP to distribute more information about the network
Compute paths based on IGP information, policy information
Use RSVP to set up MPLS LSPs
Use MPLS as a forwarding mechanism
Copyright © 1998, Juniper Networks, Inc.

6. IGP information Per link Flooded through IGP area Link bandwidth
Reservation multiplier
Per-priority reserved bandwidth
IPv4 interface address
Resource class
Flooded through IGP area
Copyright © 1998, Juniper Networks, Inc.

7. IGP modifications OSPF opaque LSA IS-IS new TLV, plus subTLVs
implemented
not yet documented
IS-IS new TLV, plus subTLVs
(almost) interoperable
Copyright © 1998, Juniper Networks, Inc.

8. Constrained Shortest Path First
Compute shortest path with
sufficient capacity
minimal IGP path metric
matching resource classes
matching other policies
Result: complete path
Copyright © 1998, Juniper Networks, Inc.

9. CSPF details Similar to a normal SPF, except during link examination:
reject links without capacity
reject links that don’t match color constraints (include or exclude)
reject links that don’t match configured policy (e.g., a loose source route)
Copyright © 1998, Juniper Networks, Inc.

10. RSVP establishes LSPs Propagate label setup along path
Hop by hop propagation
RSVP provides liveness, enforces priorities
Extensions
Negotiate label vales
Allow LSPs to move gracefully
Specify the path
Record the path
Copyright © 1998, Juniper Networks, Inc.

11. Why RSVP?
Existing protocol machinery, doing almost exactly what’s necessary
Change scope from a flow to an LSP
Small number of modifications
No need to inject prefixes into signaling
Already carries nice encoding of traffic description
Copyright © 1998, Juniper Networks, Inc.

12. MPLS forwarding Forwarding structure is now established
At entry points, map traffic for exit points into LSP to exit router
Automatically tied into BGP
Result: most traffic can easily be engineered
Copyright © 1998, Juniper Networks, Inc.