Future of PCE
Dhruv Dhody, Sr. System Architect, Huawei Technologies
What is PCE?
A Path Computation Element (PCE)
is an entity (component,
application, or network node) that is
capable of computing a network
path or route based on a network
graph and applying computational
constraints.
PCE – What?
• Path Computation Element
• Server or high end router
PCE
• Path Computation Client
• Ingress, NMS
PCC
• PCE Protocol to communicate between PCC and PCE(s)
• A TCP based protocol
PCEP
PCE specializes in complex path computation across
various domains on behalf of its path computation
client (PCC) with enhanced scalability.
Instead of head-end router doing the path
computation, it is ask PCEs to cooperate and obtain
E2E path.
PCE – Where?
PCE, The Journey so far…
A brief history of PCE
PCE – Intra-domain
BRPC – PCE Inter-domain
Confidentiality in PCEP
Objective Functions
Protection Path
P2MP Hierarchy of PCE (H-PCE)
GMPLS network
Inter-layer
And then, Stateful PCE
Stateless PCE provides mechanisms to perform path
computations in response to PCC requests. It utilized only the Traffic Engineering database
(TEDB) to do this computation.
Along with network state (TEDB), Stateful PCE also stores the state of all the computed paths or LSPs
and their resources (LSP-DB).
Stateful PCE
Passive Active
TEDB LSPDB
It uses the TEDB and LSPDB while path
computation, but computation is done only
when requested by PCC.
It allows the LSP to be delegated to the
PCE where PCE becomes the owner of
the LSP and can change any attribute of
the LSP at anytime.
Stateful PCE Function Meaning Message
Capability
Negotiation
Both the PCC and the PCE must announce during PCEP session
establishment that they support PCEP Stateful PCE.
Open
State
Synchronization
After the session between the PCC and a stateful PCE is initialized,
the PCE ust lear the state of a PCC‘s LSPs efore it a perfor path computations or update LSP attributes in a PCC.
PCRpt
(report)
LSP State Report A PCC sends an LSP state report to a PCE whenever the state of an
LSP changes.
PCRpt
LSP Control
Delegation
A PCC grants to a PCE the right to update LSP attributes on one or
more LSPs; the PCE becomes the authoritative sour e of the LSP‘s attributes as long as the delegation is in effect; the PCC may
withdraw the delegation or the PCE may give up the delegation.
(active stateful PCE only)
PCRpt,
PCUpd
LSP Update
Request
A PCE requests modification of attributes on a PCC's LSP. (active
stateful PCE only)
PCUpd
(update)
Global Reoptimization Stateful PCE
automatically re-
optimize the
network paths
such that overall
network gets
opti ized…
LSP path taken completely depend on the
order of tunnel configuration.
Problems
• The order in which LSP are setup can lead to blocking resources for other LSPs.
• To resolve such deadlock, the administrator intervention is required.
• Many links in the network remain unutilized
PCE Solution
• Active Stateful PCE can modify the LSP path at any time
• This allow stateful PCE to automatically re-optimize the global network without traffic disruption
PCE-Initiated
Setup, maintenance and
teardown of PCE-initiated
LSPs
Under the stateful PCE
model, without the need
for local configuration on
the PCC…
Allowing for a dynamic
network that is centrally
co trolled a d deployed…
Environments where the
LSP placement needs to
change in response to
applicatio de a ds…
Agile software-driven
network operation, and
can be seamlessly
integrated into a
controller-based network
architecture…
LSP Initiate via PCEP
• A new PCInitiate Message
PCE with Segment Routing (SR)
PCEP
Protocol
Stateful PCE with SR
• PCE prepare label stack of node and adjacency labels
SR Path
• PCE can respond to network events like congested links and update the label stack – no RSVP-TE signaling
PCE Optimization
PCE is the magic
component of SR!!
1417
1568
1923
payload
Stateful PCE Extn
Optical
GMPLS controlled Networks
Support for flex-grid,
WSON
Inter-Layer, VNTM
P2MP
Support for Multicast Service –
MVPN, IPTV
Delegating P2MP Path
Computations and
optimizations
Others
Sync Optimization
Backup Stateful PCE
Inter-domain and Inter-layer considerations
PCE in SDN!!!
PCE & SDN
Stateful PCE as evolutionary
approach to SDN.
In SP network with existing investment in
IP/MPLS devices, active stateful PCE can
offer centralized control over the LSPs as a
simple evolutionary approach for SDN.
PCC
PCEP
Protocol
PCC
Stateful PCE Server
Abstraction & Algorithms over Stateful PCE
PCE in ODL
• PCEP session
• Stateful PCE
• Instantiation Capability
• Support for SR
PCEP
ABNO: Application-Based Network Operation
PCE at the heart of the ABNO architecture providing a set of tools for
path computation, multi-layer control, state and instantiation etc using
existing building blocks!
APP+NET
Network
Stratum
Application Stratum
App Arbiter
Net Arbiter PCE
Cross Stratum Optimization (CSO) - Optimization of
Datacenter and Network resources - which can only be
achieved via joint effort & information exchange - to cross
optimize between stratums.
PCE plays a crucial role in network optimization by understanding
the application needs!
ACTN
PNC 1
Access/MPLS-TP BH PNC 2
MPLS Core
PNC 4
Access/MPLS TP BH
PNC 3
Optical Core
EP 1
EP 2
EP 3
1
2
CNC
MDSC
PCE PCE PCE PCE
PCE
Customer
Controller
Multi-domain
Service
coordinator
Network
controllers
Abstraction and
Control of Transport
Networks
ACTN
Ability to build virtual network operation
on multi-layer, multi-domain topology
Policy Enforcement Ability to request/
respond/ instantiate VNs
Dynamic/On-demand VN Modification
Ability to Coordinate multi-domain path
computation
Ability to perform E2E Path Restoration
PCE
PCE, What's next?
Towards PCECC
PCC
PCEP
Protocol
PCC
Stateful PCE with Initiation
PCEP
Protocol
All nodes are PCC
PCECC – PCE as a central controller
Free from signaling protocols
PCECC communicates
to all nodes
PCECC
responsible for
label allocation
Central controller!
RSVP Signaling
With Segment Routing
Use of PCEP for Label (SR-SID) Distribution
Use Node label for Best Effort SR-BE
LSP
Use Label Stack of Node and Adjacency
for Traffic Engineered SR-TE LSP.
PCE can also be used for
Label management
Modes
Basic
Forwarding similar to RSVP-TE without RSVP-
TE signaling
Use of local label along the LSP path
PCECC allocates local label and downloads to
LSR
Rest processing similar to stateful PCE
SR-BE
Forwarding similar to LDP without LDP/IGP-SR
signaling
Use of SR Node label (global) to distribute
label map
PCECC allocates global label and distribute
them
Each LSR rely on local IGP for the next hop
SR-TE
Forwarding similar to IGP-SR-TE
Use of SR node and Adj label allocated and
distributed by PCECC
Rest processing similar to stateful PCE with SR
Basic Mode Path: RT1 – RT4 – RT6
LabelUpd to download labels along the path
1026
payload 1028
payload
1. Request PCECC to initiate LSP
2. PCECC computes the path and allocates label along the path for each node
3. PCE sends PCInitiate message to the ingress and Ingress sends PCRpt message back
4. PCECC sends PCLabelUpd to each node along the path with label information to download
5. PCECC sends PCUpd to the ingress and PCC sends PCRpt back with status-up.
With SR
PCE allocates Labels (SID) for node, Adjacency.
1417
4106
payload 4106
payload
LabelUpd for label mapping for node and adjacency.
But, that’s not it…
PCE in…
NFV
• PCE at the Infrastructure layer
• Can be a VNF itself?
SFC
• Service Function Chaining via PCE
The Northbound PCE(P)
• Abstract Topology
• PCEP-LS or TED export
• REST interfaces
IoT
• Smart Cities
• PCE in IPv6-based Deterministic Networks
Thank You!