MPLS/SDN 2013 International Conference: Path Computation and Instantiation in Software Defined...
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Transcript of MPLS/SDN 2013 International Conference: Path Computation and Instantiation in Software Defined...
www.isocore.com/mpls2013
Path Computation and Instantiation in Software Defined Networks Using Stateful
PCE
Siva Sivabalan Santiago Alvarez Cisco Systems
2
Why PCE as an SDN Component?
• SDN premise: programmatic, centralized control can contribute to greater network agility, optimization, customization and automation
• PCE architecture already enables centralized path computation for large, multi-domain and multi-layer networks
• PCE provides a good starting point for implementing an SDN model in WAN
• Commercially available implementation of base functionality available for at least 5 years
• Recent extensions (SDN driven): stateful PCE, PCE-initiated LSPs, Segment Routing support
PCE: One Piece of the SDN WAN Puzzle
3
DC/Cloud Providers
Customers
DC SDN Customer SDN
Workflow Orchestration/Apps
Collector Programming
Application Engine
NGN WAN
Viz & Analytics
APPS
APIs
IP/MPLS Segment Routing
Multi-Layer
SDN WAN
APPS
Stateless and Stateful PCE
4
PCEP
Stateful PCE
TED
LSP DB
Stateful PCC
• More optimal centralized path computation (e.g. LSP state, resource usage, policy, network analytics, etc.)
• Enables centralized path initiation and update control
• Requires LSP state synchronization (LSP database)
• Limited ability to optimize network resources • No knowledge of previously established
paths • Not well suited for SDN deployments • Still useful for inter-domain MPLS-TE in
non-SDN deployments
PCEP
Stateless PCC
Stateless PCE
TED
PCEP
Passive Stateful PCE
TED
LSP DB
Stateful PCC
Active and Passive Stateful PCE
5 5
PCEP
Active Stateful PCE
TED
LSP DB
Stateful PCC
• PCC or PCE may initiate path setup • PCC may delegate update control to PCE • PCC may revoke delegation • PCE may return delegation
• PCC initiates path setup • PCC retains control on path updates • PCE learns LSP state to optimize path
computation
PCE has update control over delegated
paths PCC maintains update control
over paths
Active Stateful PCE PCE-Initiated and PCC-Initiated LSPs
6 6
• PCC may initiate path setup based on distributed network state
• Can be used in conjunction with PCE-initiated paths
• Tighter integration with application demands • PCE can be part of controller architecture
determining what paths to set up and when
PCEP
PCC-Initiated (Active Stateful PCE)
TED
LSP DB
Stateful PCC
PCEP
PCE-Initiated (Active Stateful PCE)
TED
LSP DB
Stateful PCC
Application initiates LSP
via PCE
PCC initiates LSP based on
local policy
PCE Path Profiles
7 7
• Path computation profile centralized on PCE
• PCC initiates LSP and only specifies destination and profile id
• Path usage profiles preconfigured on PCC • PCE initiates LSP and references usage
profile id to apply
PCC-Initiated (Active Stateful PCE)
TED
LSP DB
Stateful PCC
PCE-Initiated (Active Stateful PCE)
TED
LSP DB
Stateful PCC
PCEP Create / Initiate
Path computation parameters,
path profile 10
Path Comp
Path Usage
Path Comp
Path profile 10
PCEP Request
Destination, path profile 10
Path Comp
Path Usage
Path Comp
Path profile 10
Path profile 10
PCE Extensions for Segment Routing (SR)
• Segment routing enables source routing based on segment ids distributed by IGP
• PCE specifies path as list of segment ids
• PCC forwards traffic by pushing segment id list on packets
• No path signaling required • Minimal forwarding state • Maximum network forwarding
virtualization • The state is no longer in the
network but in the packet
PCEP
Stateful PCE
TED
LSP DB
Stateful PCC
Node SID
Adjacency SID
Forwarding table remains constant
In Out Int L1 L1 Intf1 … … … L7 L7 Int3 L8 Pop Intf3 … … … L9 Pop Intf5
Application Path
Request
9
Summary
• Stateful PCE is an important SDN enabler providing centralized path computation optimization
• Different degrees of centralization (computation, updates, initiation, configuration)
• PCE and SR provide a very compelling SDN solution • Tight application integration • Maximum network forwarding
virtualization
PCE
Stateless Stateful
Passive Active
PCE Initiated paths
PCC Initiated paths
10
References
• A Path Computation Element (PCE)-Based Architecture RFC 4655
• Applicability of Stateful Path Computation Element (PCE) draft-zhang-pce-stateful-pce-app
• PCEP Extensions for Stateful PCE draft-ietf-pce-stateful-pce
• PCEP Extensions for PCE-initiated LSP Setup in a Stateful PCE Model draft-crabbe-pce-pce-initiated-lsp
• PCE Path Profiles draft-alvarez-pce-path-profiles
• PCEP Extensions for Segment Routing draft-sivabalan-pce-segment-routing
www.isocore.com/mpls2013
Thank you!