This document discusses how software-defined networking (SDN) can be used as a set of tools to program and control MPLS networks in a more flexible way. It describes several SDN components that could be used together, such as BGP-LS to extract topology information, stateful path computation elements (PCEs) to control services, and a proposed interface to the routing system (IRS) to programmatically control routers. The document argues that combining existing protocols like these with a centralized control plane separated from the data plane could enable new services and more programmatic control over MPLS networks.
2. Agenda
• Some Definitions Needed (SDN)
• Why consider SDN?
• SDN as a toolkit
• Fine-grain programming
• An interface to routing and policy
• Enabling services
• A programmable MPLS network
2
3. What do we mean by SDN?
• Software
• It’s all software!
• We are looking for automation
• Tools or applications
• Driven or Defined
• Does it matter?
• Networks
• Micro-management of forwarding decisions
• Control of end-to-end paths
• Whole-sale operation of network
• Is it all about the buzz?
• Shiny-thing Desparately Needed
• $ome Dollars Now
3
4. What will we do with SDN?
• Make our networks better
• Provide cool services at lower prices
• Reduce OPEX and simplify network operations
• Enable better monitoring and diagnostics
• Make better use of deployed resources
• Converged services are the future
• Converged infrastructure is the future
4
5. The SDN Toolbox
• To a network, all configuration tools look like hammers
• One size does not fit all
• SDN is about engineering the routers to allow better tools
to be designed and applied
5
6. MPLS Data Plane Programmability
• Label stacking, popping, and swapping
• MPLS as a cross-connect technology (NHFLE)
• Prefix-to-label mapping (LFIB)
• Integration with underlying data plane
• Encapsulation rules
• Data link addresses
6
IP Packet IP Packet
Prefix
LFIB
Out i/f, label
MPLS Packet MPLS Packet
In i/f, label
NHFLE
Out i/f, label In i/f, label
NHFLE
Pop
7. Applications and Protocols for MPLS Data Plane
Programmability
• An application is software that runs remotely
• That demands a protocol and a data encoding
• Element Management
• IETF : SNMP/MIBs, Netconf/YANG
• Proprietary : CLI, GUI, XML
• Legacy : TL1 …
• Network Management
• Coordinated connection set-up is just coordinated element management
• Control plane / data plane separation
• Use an existing configuration protocol
• IETF : GSMP (RFC 3292), ForCES (RFC 5810)
• ONF : OpenFlow
7
8. Control Plane / Data Plane Separation
• Support legacy / cheap devices
• Experiment with new routing protocols
• Integrate dynamic routing with static control
• Avoid “complexities” of routing protocols
8
Data plane
Control plane
SDN
Programming
Language
9. Functional Control at a Higher Level
• Operators want to build and deploy services
• “Make a pseudowire for me”
• “Optimize my traffic loading”
• “Provision a layer 3 VPN”
• “Show me how my network is being used”
• “Configure my data center”
• “Manage security and policy”
• “Provide service callendaring”
• Needs a higher-level interaction with the network
• Demands more sophisticated control of routers
• Must integrate with standard routing features
9
10. Leveraging Existing Tools
• New services and features for rapid deployment
• There are plenty of existing tools
• Leverage implemented and deployed protocols
• We can put them together to enable high function
SDN in MPLS networks
• May need some extensions
• Avoid long development cycles
10
11. BGP-LS to Extract Topology Information
• Information about the network
• Nodes and links
• Link state
• Up-to-date TE capabilities
• Delay and other quality information
• Status of existing LSPs / tunnels
• Used for network monitoring, analysis, and planning
• Critical input to path computation (e.g., via PCE)
• Fundamental component unspecified in the PCE architecture
• BGP-LS is a set of simple extensions to BGP
• Client is any node listening to the IGP
• For example an ASBR or a Route Reflector
• Server can not be a very light-weight BGP implementation
• Reduces dependency on IGP sniffing
11
12. Stateful PCE for Control of Services
• Early work on PCE was stateless
• PCE knows state of network
• PCE does not recall anything about previous computations
• PCE does not know about existing provisioned services
• Except as described on new computation requests
• Stateful PCE was always in the architecture
• Retain information about provisioned LSPs
• New extensions to PCEP
• Allow explicit activation of LSPs from the PCE
• Receive information from network about LSPs
• Provides key components for bandwidth callendaring
12
13. Integrating the Components
13
• IGP enhanced for TE and link quality
• BGP-LS reports to PCE
• PCE requests LSPs
• Normal LSP signaling
• LSP status reports
PCE
14. Making New Tools
• Can’t do everything with what have already
• Interface to the Routing System (IRS)
• A programmatic interface to routers
14
14
Data Plane
FIB
RIBs and RIB Manager
Policy DB
Routing and
Signaling Protocols
Topology DB
OAM, Events and
Measurement IRS Agent
IRS Client IRS Client
Router
Server
Application
Application
Application
IRS Protocol & Data
Encoding
15. Enabling Services
• Service enablement and turn-up is complex
• Existing tools help with planning
• Commissioning through scripts or work-plans
• SDN can be a set of tools to enable services
• L3VPN delivery
• Data center interconnect
• Bandwidth callendaring
• Mult-layer connectivity and virtual links
15
16. Service Example : Multi-layer
• SDN can coordinate multiple network layers
• May both be MPLS networks
• Involves many SDN components
16
PCE
Traffic demand
Service request
VNTM
TEDB
PCE
BGP-LS
IRS
PCEP
RSVP-TE
GMPLS
IGP-TE
IRS
IRS
OpenFlow
& IRS
Virtual Link
PCEP
TEDB
IRS
Policy
IGP-TE
17. Service Example : L3VPN with Callendaring
• Which PEs to use?
• How to connect PEs?
• What load? When?
• What redundancy? QoS? Security?
• How to connect to the Internet?
• Planned support for high bandwidth services
17
DB Replication
Content
Streaming
Data Transfer
18. Putting the Tools into the Box
• SDN will possibly remain buzz and hype
• Or maybe it will evolve into bickering between
proponents of different solutions
• Or it could become a comprehensive set of tools
• Configuration tools
• RIB and policy control
• Topology and LSP management
• Service enablement
• Potential to enable a rich set of functions in future
MPLS networks
18
19. SDN - Pandora’s Toolbox?
A mess of overlapping
tools and protocols with too
many features and
functions?
19
Or a cornucopia of riches?
