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!