top63094 v1.0-ason gmpls mrn overview

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ASON GMPLS MRN Overview

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Course outline

Section 1. ASON GMPLS MRN

Module 1. ASON GMPLS MRN Introduction

Module 2. ASON GMPLS Protocols

Module 3. ASON GMPLS Protections

Module 4. MRN Overview

Welcome to


Section 1. ASON GMPLS MRN

Module 1. ASON GMPLS MRN Introduction

Module 2. ASON GMPLS Protocols

Module 3. ASON GMPLS Protections

Module 4. MRN Overview


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Course objectives

Upon completion of this course, you should be able to:

Upon completion of the course; students should be able to describe MPLS evolution to GMPLS;describe ASON network principles; advantages and value proposition of GMPLS automatic discovery;control layer and link monitoring

Be familiar with the concepts of Shared Risk Group; restoration types and rules; understandmaintenance actions need in case of problems.

The student will also understand the architecture evolution towards a unique control layerintroduced by MRN for OTNWDM and OCS OTN switching cross connections

Welcome to


Upon completion of this course, you should be able to:

Upon completion of the course; students should be able to describe MPLS evolution to

GMPLS; describe ASON network principles; advantages and value proposition of GMPLS

automatic discovery; control layer and link monitoring

Be familiar with the concepts of Shared Risk Group; restoration types and rules; understand

maintenance actions need in case of problems.

The student will also understand the architecture evolution towards a unique control layerintroduced by MRN for OTNWDM and OCS OTN switching cross connections

Your feedback is appreciated!

Please feel free to Email your comments to:

[email protected]

Please include the following training reference in your email:

TOP63094_V1.0-SG Edition 1

Thank you!


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ASON GMPLS MRN OverviewASON GMPLS MRN ASON GMPLS MRN Introduction

1 1 1COPYRIGHT ALCATEL-LUCENT @@YEAR. ALL RIGHTS RESERVED.

Module 1ASON GMPLS MRN Introduction

Section 1

ASON GMPLS MRN

ASON GMPLS MRN OverviewTOP63094_V1.0-SG Edition 1

TOP63094_V1.0-SG-Ed1 Module 1.1 Edition 1

Learning experience powered byAlcatel-Lucent University


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Document History

Edition Date Author Remarks

01 2013-07-15 Lecchi, Vincenzo First edition


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Module objectives

ASON GMPLS introductionUpon completion of this module, you should be able to:

Have an overview of the ASON GMPLS value propositions

Understand what is a control plane

Understand the Standards evolution from MPLS to GMPLS

ASON GMPLS machine model

ASON GMPLS Network Protection

Multi-Region Networks fundamentals


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Module objectives [cont.]



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Table of contents

Page

1 ASON Introduction 7End of module 24


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Table of contents [cont.]

Page


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COPYRIGHT ALCATEL-LUCENT 2013. ALL RIGHTS RESERVED.

@@PRODUCT @@COURSENAME@@SECTIONTITLE @@MODULETITLE

@@SECTION @@MODULE 7

1 ASON introduction

Section 1 Module 1 Page 7


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THE NETWORK CONTROL VISION IN THE PAST

SDH/SONET Rings

Point-Point DWDM

IP/MPLS mesh

Early 2000s point of view

Multi technology networkswithout a real traffic integration

Complex SLA assurance andresilience

No Automated network

No cross-layer operations

ATM Rings

Networks in the past, were considered as the sum of separated

standalone subnetworks, with independent life.

No traffic integration were present, no automation in the processes orcross layer operations.

For this, SLA (Service level agreements) assurance is and was very

complex



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CROSS-LAYER INTELLIGENT CONTROL PLANE VISION

Common control plane:

- GMPLS intelligence

- Multiregion network (MRN)

Converged optical layer:electronic and photonic switching

Electronic and optical layerintegration

Service over circuit

Photonic switching layer

Electronic switching layer

Service over

GMPLS GMPLS

ASON/GMPLS MRN VISIONASON

GMPL

S

Automated network

cross-layer operations

Enhanced SLA assurance and

resilienceMaximized network monetization

The new vision is a unique and automated network, with cross-layer

operations.

To do this a common control plane with GMPLS (Generalized MPLS) + MRN(Multiregion Network) on a unique electronic + photonic layer is proposed.

This allows an enhanced SLA maximizing the network usage



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CONTROL PLANE CONCEPT

NetworkElement

Client, e.g.Service router

Control Plane

Management Plane

Control Plane

Transport/DataPlane

NetworkManagement A Control Plane is a

method of distributedconnection control

OPTICAL

PLANE

S

NMS Network Management System

In the traditional Networks, Services are provided connecting a chain of subnetworkconnections, with no end-to-end visibility of the service.

To introduce an enhancement in the network management the control plane concepthas been created: is a method to coordinate a distributed connection control.

A Network could be seen in separated layer : Transport, Control and management



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Management Plane

centralized network management: Management of ASON and non-ASON NEs

Full awareness of current network state (configuration, paths, alarms)

Stipulation of paths and routes

Separation of network domains

Control Plane Represents a distributed set of protocols running between Network Elements to

manage the ASON;

Consists of Routing Plane and Signaling Plane;

Transport/Data Plane Realizing transmission and switching of data

Consists of: Transport layer realizing classical legacy features and Service Layer

THE OPTICAL CONTROL PLANE CONCEPT

OPTICAL

PLA

NES

GMPLS protocols :

are at the heart of the Optical Control Plane a distributed connection

control that unlocks the potential of the intelligent optical network

GMPLS protocols :

are at the heart of the Optical Control Plane a distributed connection

control that unlocks the potential of the intelligent optical network

GMPLS protocols :

are at the heart of the Optical Control Plane a distributed connection control

that unlocks the potential of the intelligent optical network

A Managed Plane is used to centralize the network management for:

- Ason and Non Ason ntwks

- Full awareness of current network state (configuration, paths, alarms) to set

paths and routes

- ensure the separation of network domains (see the next slides)

Control Plane- Represents a distributed set of protocols running between Network

Elements to manage the ASON: Routing Plane and Signaling Plane

Transport and Data plane

- Realize the transmission and switching layer (physical ntwk)

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WHAT IS ASON?

ASON automates the resource and connection management within the network

ASON could be extended to a multi providers control plane

Signaling is extended in a distributed Control Plane for Networkadministration and Path management

Dynamic signaling-based policy-driven control over OTN (Optical TransportNetwork)

ASON (Automatically Switched Optical Network)

is a network architecture that maximizes the advantages of theOptical Control Plane


is a network architecture that maximizes the advantages of theOptical Control Plane

ASON

GMPL

SASON

What is ASON?


is a network architecture that maximizes the advantages of the

Optical Control Plane

The automation inside control plane allowed by the real time feedback of the

dynamic signaling, is the key element to ensure : elements discovery and

synchronization and efficient control.

ASON automates the resource and connection management within the

network

ASON could be extended to a multi providers control plane

Signaling is extended in a distributed Control Plane for Network

administration and Path management

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GMPLS

is a protocol, or better a set of protocols (protocol suite), introduced inTransport Networks in order to allow automatic traffic routing and distributedrestoration.

The concepts applied in GMPLS are derived from MPLS protocol, which wasintroduced in Ys 80 in order to speed up packet routing in IP-Networks.

GMPLS Control Plane

consists of embedded SW in the NEs of the Transport Network to implementsignaling and automatic routing.

The two main new services provided by GMPLS in a Transport Network are:

On-demand circuit provisioning

Distributed Restoration.

WHAT IS GMPLS?

GMPL

S

What is GMPLS?

GMPLS is set of protocols , introduced in Transport Networks in order to

allow automatic traffic routing and distributed restoration.

MPLS is the original concept at the base of ASON, but it has been updated

and integrated with a set of protocols to produce the GMPLS (Generalized

MPLS) to ensure the distributed restoration (next module)

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ASON improvement on control plane

Management Plane

Control Plane

Transport/DataPlane

ASON

NetworkManagement

ASON NetworkElement

Client, e.g.Service router

Control PlaneNon-ASONNetwork Element

Distributedcontrol plane:

AutoDiscovery

End-to-Endconnectionsetup

Restoration

ASON Automatically Switched Optical NetworkASON (Automatically Switched Optical Network)

The Dynamic signaling-based policy-driven control is realized over OTN andSONET/SDH networks, Signaling is realized via a distributed Control Plane

Key features

Network Administration

Auto discovery of resources and network topology

Multi-vendor inter-working (networking)Multi-layer interworking

Path Management

Dynamic connection setup

Support for end-to-end service provisioning

Bandwidth on Demand Services

Rerouting

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IP

GMPLS Extension to MPLS for multiple switching types:

Packets, Circuits, Lambdas, Ports Routing at NE level

Standardized

Multi technology

MPLS

GMPLS

IP-packet

IP Router

Label

LSP

Control Plane

Node

IP Connectionless service

Packets

IP address

MPLS Connection oriented service

in packet switched network

Routing according toinput/output labels

Label switched path: LSP

Constraint based explicitrouting

THE EVOLUTION FROM MPLS TO GMPLS

We will see the evolution of IP -> MPLS -> GMPLS in the next ASON

Protocols module,

but before let see the Status of the standard

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16




In the control plane two different standard bodies play the main role :

ITU has defined ASON as a control plane architecture concept based on a set ofrequirements laid out in ITU G.807 Recommendation

IETF has defined GMPLS as extension to MPLS protocol suites in order to supportnot only packet but also TDM and OTH network.

In additional OIF (Optical Internetworking Forum) is fosteringinteroperability between vendors and define a profile of GMPLS. ITU has takena very formal top-down approach by setting out requirements

STANDARD BODIES

Historically there are different visions in the communication world: ITU

European and IETF US

For ASON there is a separation and a coordination between the two worldswere ITU has defined ASON, IETF the GMPLS and a new actor OIF that it

has been introduced to ensure the interworking between vendors


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GMPLS / ASON standardization

UNI NNI

Architectureandrequirements

ASON Architecture ASTN Requirements Network control Adaptation of GMPLS protocols

GMPLS

protocols Routing Signaling Link management

Networkinteroperabilityspecifications

OIF is working on IA ImplementationAgreements between vendors

ITU-T International Telecommunication Union Telecommunication Standardization Sector (replaced CCITT in1993)

has not been the only standardization body involved in the conceptualization of the optical control plane

ASON Architecture

ASTN Requirements G.807

Network control G.8080

Adaptation of GMPLS protocols

IETF Internet Engineering Task Force

has developed the Generalized Multiprotocol Label Switching (GMPLS). GMPLS extends the signalling and routingprotocols developed for packet networks and applies them to optical networks.

Routing: OSPF-TE, IS-IS

Signaling: RSVP-TE

Link management: LMP

OIF Optical Internetworking forumhas had the more immediate objective. OIFs goal is to reach interoperable implementation agreements among

vendors. Among all of the standards options, OIF chooses ones that can be deployed quickly with the greatestreturn within a carrier environment.

Alcatel-Lucent has strongly pushed to achieve an interoperable standard on intelligent optical networking, by:

actively participating in the standardization activities of the relevant bodies:

ITU-T for ASON architecture

IETF for protocols

OIF for interworking

propelling the activities of the three bodies in order to minimize the different flavors, and enable end-to-endservices like restoration and bandwidth on-demand in a seamless manner

Alcatel-Lucent has successfully implemented the GMPLS/ASON in several network elements, such as opticalCross Connects and Wavelength Division Multiplexers

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Control Plane Specifications - Example

This is an example of the specifications distributed by the main architecture

topics

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GMPLS model and definition : Overlay Model

The Overlay Model, which is recommended by ITU-T and OIF, considers aseparation of the different technologies involved.

User-Network Interface

Internal Network-Network

Interface

External Network-Network Interface

ASON

GMP

LS

IETF standards have historically pushed a vision of a PEER to PEER model between

elements, derived by the IP world.

The Overlay Model, which is recommended by ITU-T and OIF, considers aseparation of the different technologies involved.

Networks are partitioned into Domains

Domains may be based on vendor, technology or administrative partitioning

Domain edges provide inter-working between vendor-specific protocols.


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GMPLS VALUE PROPOSITION HIGH AVAILABILITY

SLAassurance

< 50ms

No faulttolerance

1 2 3 4

# of simultaneous failures

>50ms

Restorationtime

Unprotected

Source Based Routing (SBR)

Protection andRestoration Combined

(PRC)

High availability and SLA assurance GMPLS based restoration

Services/OperationsAttributes

Key Feature

High availabilityBandwidth monetization

GMPLS restorationGMPL

S

GMPLS INTELLIGENCE Optimal use of Network capacity:Optimum Network Usage needs to recover a resource when it is available again.

GMPLS INTELLIGENCE Optimal use of Network capacity:Optimum Network Usage needs to recover a resource when it is available again.

Why introduce GMPLS?

An important reason is the HIGH AVAILABILITY and network restoration

GMPLS intelligence produce an optimum Network capacity usage (for

example need to recover a resource when it is available again) and it ensures

the SLA feasibility in a very complex Ntwk.

We will see the RESTORATION concepts in the ASON Protections module

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GMPLS INTELLIGENCE MAINTENANCE

Key Feature

Maintenance Maintenance activities andnetwork optimization

Services/Operations Attributes

Shut down, lock, free port

NetworkOperation

Control

Plane

Automatic, semi-automatic or

manual maintenance and network optimization

GMPL

S

GMPLS introduce automation in the maintenance actions with full flexibility.

It is possible in fact to set a full automatic, semi-automatic or manual control

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GMPLS INTELLIGENCE NETWORK PLANNING

Nominal routing

Optimal resourcing

Resource coloring for

Administrative segregation

Key Feature

Network Planning Planning consistencyAvoid blocking point in the network

ControlPlane

NetworkPlanning

nominal

route

active route

reversion

Optimal resourcing,traffic constrains,

administrativesegregation

Services/Operations Attributes

GMPL

S

Another value proposition is the automatic network planning for services and

operations design to avoid blocking points.

NOMINAL route is the new reference idea inside the dynamic GMPLS controlplane

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MRN MULTI REGION NETWORKS and GMPLS

CAPEX reduction

Forwarding and protectingtraffic at the most economicallayer

OPEX reduction

Increases service availability viadisjointedness of main andspare resources in multiplelayers

Harmonizes operations andservices

Avoids traffic hits by using acoordinated reversion strategy

Recovers quickly bycoordinating responses tofailures

Highest network powerefficiency

MRN INTEGRATES PHOTONIC AND ELECTRONIC SWITCHING CONTROL

Path setup from A to B

Photonic switching (WDM)

Electronic switching (ODU)

A BUNI UNI

GMPLS/multi-region network (MRN)control plane

MRN

With traditional networks the separation between photonic and electronic

layers produce a non coordinated and non efficient separation.

MRN (Multiregion network) integrates the two layers for CAPEX and OPEXreduction

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ASON GMPLS MRN Introduction

End of module


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ASON GMPLS MRN OverviewASON GMPLS MRN ASON GMPLS Protocols


Module 2ASON GMPLS Protocols

Section 1ASON GMPLS MRN

ASON GMPLS MRN OverviewTOP63094_V1.0-SG Edition 1

TOP63094_V1.0-SG-Ed1 Module 1.2 Edition 1

Learning experience powered byAlcatel-Lucent University


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Document History

Edition Date Author Remarks

01 2013-07-15 Lecchi, Vincenzo First edition


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Module objectives

ASON GMPLS introduction

ASON GMPLS machine modelUpon completion of this module, you should be able to:

Have an overview of the ASON GMPLS Domains

See the evolution from IP to GMPLS and the related Routing enhancements

Understand the GMPLS building blocks and their implementations

ASON GMPLS Network Protection

Multi-Region Networks fundamentals


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Module objectives [cont.]



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Table of contents

Page

2 ASON GMPLS Machine model 72.1 From IP to GMPLS 132.2 GMPLS 222.3 OSPF ROUTING 272.4 RSVP Signaling 392.5 LMP Link Management 452.6 GMRE Main Blocks 52End of module 57

APPENDIX Labels Format 58


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Table of contents [cont.]

Page


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2 ASON GMPLS machine model

Why we need ASON (Automatically Switched Optical Network)



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ASON views the network as composed of domains which interact with otherdomains in a standardized way, but whose internal operation is protocol-independent and not subject to standardization.

Internal Network-Network

Interface

External Network-Network Interface

AS

ON

GMPLS

ASON GMPLS CONTROL PLANE DOMAINS

User-Network Interface

The problem in an heterogeneous Ntw is the interaction between different areas.

ASON views the NTW divided into DOMAINS, that are interacting with the other in a

STANDARD way.For this the operation inside domains could be protocol independent and notsubject/ critical of standardization.

The domains are connected using standardized interface : E-NNI between carriersand UNI with the final client


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9



ASON Domain Model and Architecture Reference

Carrier

Domain C

UNI E-NNI UNI

Carrier

Domain ACarrier

Domain B

E-NNI

UNI-NUNI-C

ClientClient

Domains may be based on vendor, technology or administrative partitioning

Domain edges provide interworking between vendor-specific I-NNI and UNI-N/E-NNI protocols

UNI (User-Network Interface): standardized interface for clients to request services

from optical network (low trust, high functionality)

E-NNI (External Network-Network Interface): standardized interface providingcall/connection control between domains (low - medium trust)

I-NNI (Internal Network-Network Interface): non-standardized interface (in ITU!)providing connection control within domains (high trust)

The overall architecture and interfaces of the OIF network are shown in thisgraphic, it shows client devices being connected over a multi-carrier network.

The key interfaces the UNI and the E-NNI are control planeinterfaces that allow optical services to be provided to networkusers. The UNI or User Network Interface, allows client devices (on the UNI-C side) to signal (to the UNI-N side) for end-to-end optical connectivitythrough carriers networks. The E-NNI or External Network-Network Interface,provides signaling to set up network resources and provides routing tomaintain a current picture of network resources and topology. This networkmodel is consistent with the Automatically Switched OpticalNetwork or ASON architecture defined by the ITU-T. By distributing thisintelligence though the optical control plane, connection managementbecomes more automated, resilient and adaptable to changing network

conditions.


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1 2 10COPYRIGHT A LCATEL-LUCENT @@YEAR. ALL RIGHTS RESERVED.

DOMAIN-BASED ARCHITECTURE

NE NE

Optical Control Plane must support

Heterogeneous topologies, technologies,

applications and trust relationships

Support control plane-based or management plane-based sub networks

Provide boundaries of policy and information sharing

Provide functional independence between control plane, data plane,management plane.

CarrierDomain C

UNI E-NNI UNI

CarrierDomain A

CarrierDomain B

E-NNI

NE NE NE NE

UNI-NUNI-C

ClientClient

NE NE

NE

NE

Carrier Domain C

E-NNII-NNI

Vendor 1Domain

Vendor 2Domain

Each carrier network may consist of multiple domains containing equipmentfrom individual vendors. Each carrier and vendor domain is shown as an

abstract cloud in the figure. This means each domain does not need toexpose internal topology or addressing outside of the domain, thusimproving scalability and security. The domains either within orbetween carrier networks are connected by an E-NNI. The individualdomains can be advertised either as multiple interconnected border nodes, oras an abstract node depending on carrier administration or policy preference.

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Each domain can use either management or control plane internally Control plane topology can differ from transport plane topology

Domain CDomain A Domain B

UNI E-NNI UNIE-NNI

ClientClient

NM

ASON ARCHITECTURE Requirements

Transport technology and topology can differ in each domain

Control Plane

Transport/Data Plane

In ASON the transport plane could be realized by any technology and

topology.

The control plane could be managed by the NMS (Network ManagementSystem) or by GMPLS control plane

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ASON and Multi-layer model

ASON is focusing on the inter-operability of different types of Networksto simplify and standardize operations. They can be either multi-vendor, multi-layer or multioperator.

An Intelligent Optical Networkshould be managed either in an centralizedmanner by traditional Network Management Systems or in a decentralizedway, using Control Planes on each node.

Different technology can beseen as separate layers

When Networks are converging, theselayers have to inter-work dynamicallyto keep control of the OPEX

Ethernet/MPLSLAYER 2

TDM OTN/ODUkLAYER 1

DWDM OTN/OCh/WSONLAYER 0

Different technologies could be used in ASON but seen as separated layers

There is a Standard classification :

LAYER 0 = DWDM-OTN

LAYER 1 = TDM SDH OTN

LAYER 2 = Ethernet / MPLS

LAYER 3 = IP etc

The Management architecture could be centralized using NMS ordecentralized using control plane in each node, and multi-vendor andmulti-operators

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13

@@SEC

Do not delete this graphic elements in here:

All Rights Reserved Alcatel-Lucent @@YEAR

FROM IP TO GMPLS


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Packets, Circuits, Lambdas, Ports

Routing at NE level

Standardized

Multi technology

MPLS

GMPLS







Let see now the IP evolution versus MPLS

The IP Internet Protocol is :Connectionless service

Information is transmitted in packets

Each packet contains source and destination address

Packets are routed according to the routing tables in each router of thenetwork

MPLS Multi-Protocol Label Switching

Connection oriented service in packet switched network (Note: IP provides aconnectionless service only!)

Routing according to input/output labels

Label switched path: LSPMPLS supports traffic engineering - via constraint-basedexplicit routing (Note: not possible with IP!)

Let see in the next slide the reason of MPLS introduction

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MPLS principle in IP-Network

Multiprotocol Label Switching (MPLS)

provides a mechanism for engineering Network Traffic patterns that is independent ofrouting tables. MPLS assigns short labels to the packets that describe how to forwardthem through the Network.

MPLS Network

MPLS Network

Outgoing Router

I-LER Router

E-LER Router

LSP

(Label Switched Path)

LSR = LabelSwitched Router

LSR

LSR Router

LSR Router

Ingress-LabelEdge Router

Egress-LabelEdge Router

Multiprotocol Label Switching (MPLS)

provides a mechanism for engineering Network Traffic patterns that is independent ofrouting tables. MPLS assigns short labels to the packets that describe how to forward

them through the Network.

MPLS use LSR(Label Switched routers) that consists on:

SW, for reading the messages inside the Labels and building up the Routing Tablesaccording;

Matrix for packet forwarding according to the Routing Tables.

At the ingress of an MPLS Network, incoming IP packets are examined and assigned alabel by a Label Edge Router (LER).

The labeled packets are forwarded through Label Switched Path (LSP), where eachLSRmakes a switching decision based on the packets label field.


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Label switching example

UnlabeledPacket arrives

IP

Egress routerremoves label

IP

IP20

Label switching &packet forwardingIngress router

adds label topacket

IP10

IP10

original IP packet with IP Header

MPLS packet with IP Header + Label

IP

The final result of Label-switching is a fast path set-up.

The path which is set-up by MPLS is called LSP (Label Switched Path)

All packets that follow the same path through the MPLS Network and receive the

same treatment at each node are known as a Forwarding Equivalence Class(FEC) .

A circuit set up by using MPLS protocolis called LSP (Label Switched Path).

Ingress router introduce a label in each data packet incoming, LSR will distribute theMPLS packet based on the destination label, Egress router removes the label in theoutgoing stream

MPLS was originally introduced for IP Networks, as a Protocol at Layer-3.


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Path-1

Path-2

Path-3 Path-4

S1

S4S3S2

D

In the above example, the 4 traffic paths have to be routed at minimum costfromthe source Routers to the destination Router, over the physical cables.

Example:

Traffic Demand: Four paths originated by sources S1-S4 to destination D

Example:

Traffic Demand: Four paths originated by sources S1-S4 to destination D

IP Network routing

Let see an example of traffic routing using IP protocols.

The routing rule used by routers is the choice the minimum cost path inside the

network.

The minimum cost is defined during the link (route) creation in the router configuration

phase


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IP Routing solution

IP Routing implementation:

Minimal cost routing: calculated by each router in an independent way


Minimal cost routing: calculated by each router in an independent way

In the traditional Level 3 IP-Networks, an independent forwarding decision is made ateach hop, the IP Header is analyzed, and the next hop is chosen based on this analysisand on the information in the routing table distributed in each Routers, in anindependent way.

Path-1

Path-2

Path-3

Path-4

S1S4S3S2

DIPForwarding

Routing Solution in IP Network.

In the traditional Level 3 IP-Networks, as a packet travels from one router to the next, anindependent forwarding decision is made at each hop. The IP Header is analyzed, and thenext hop is chosen based on this analysis and on the information in the routing table. EachRouter executes, in an independent way, the IP packet forwarding, i.e. it decides the nexthop for each incoming packet, on the basis of the destination address.

Each Router has the Network topology information, in order to perform the minimum costRouting, e.g. by using Dikjstra Routing Algorithm.

Topology information is distributed to the Routers e.g. by means of IGP (Interior GwProtocol).

By using this information, a Router is able to automatically build-up the Routing Table.

The final result is a Traffic Routing, where each requested path is routed with the minimumcost, e.g. with the minimum number of hops.


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IP Routing problems


Disadvantages: It is slow and it creates an unbalanced network


Disadvantages: It is slow and it creates an unbalanced network

1. It can be too slow, because IP forwarding performed packet by packet can be quite longand in case of Network variation, automatic routing tables can require a long time

2. The minimum cost Routing can result into an unbalanced Network, with some links over-loaded and some other links not used at all or under-loaded.

Path-1

Path-2

Path-3

Path-4

S1

S4S3S2 Not Used

MPLSwas originally

invented to overcome

the above two IP

routing problems

MPLS

was originally

invented to overcome

the above two IP

routing problems

Not Used

This process has two disadvantages:

1. It can be too slow, because:

- IP forwarding performed packet by packet can be quite long;

- In case of Network variation, automatic routing tables can require a long time,mainly in a large Network;

2. The minimum cost Routing can result into an unbalanced Network, with some linksover-loaded and some other links not used at all or under-loaded.

MPLS was originally invented to overcome the above two problems.


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MPLS Routing solution

MPLS Routing implementation:

Minimal Cost routing using LSP: The Network load remains Unbalanced

MPLS Routing implementation:

Minimal Cost routing using LSP: The Network load remains Unbalanced

In an MPLS environment, analysis of IP-Headers is performed just once, when a packetenters the MPLS cloud. The packet is then assigned to a stream (FEC ForwardingEquivalence Class), which is identified by a label.

LSP-1

LSP-2

LSP-3

S1

S4S3S2

DLabel Switchingand Label Swap

Label/FEC

assignment

LSP-4

Routing solution in MPLS Network

IP forwarding is speed-up by using Label Switching technique.

IP packets are not forwarded on the basis of the destination address only, but on the basisof their Label and the corresponding FEC.

In a MPLS Network, the ingress Router (I-LSR) inserts the MPLS Label, deciding the FEC(Forwarding Equivalent Class) for the incoming client signals, by grouping packets with thesame characteristics (e.g. with the same priority or with the same destination).

The rest of the Network, i.e. the LSRs, should follow the FEC decided by the Ingress-LSR.

Ingress Router (I-LSR)

Classifies packet to an FEC, generates MPLS header and assigns initial label

Upstream toward all other LSRs in the LSP

Intermediate Routers (LSR)

Forwards MPLS packets using label-switching

Executes one or more routing protocols

Egress LSR (E-LSR)

Removes the MPLS label,

Downstream from all other LSRs in the LSP


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GMPLS Routing Solution

GMPLS Routing implementation:

LSP are routed considering the link bandwidth: The Network is Balanced

GMPLS Routing implementation:

LSP are routed considering the link bandwidth: The Network is Balanced

When traffic is distributed over the Network resources by MPLS-TE, the final routing result isan uniform (balanced) load of the links. GMPLS-TE (MPLS-Traffic Engineering) is animprovement of standard MPLS enabling Multitechnology.

LSP-1

LSP-2

LSP-3

S1S4S3S2

D

Label Switchingand Constraint

Routing

Label/FECassignment

LSP-4

When traffic is distributed over the Network resources by MPLS-TE, the final routing result is

an uniform (balanced) load of the links.MPLS-TE (MPLS-Traffic Engineering) is an improvement of standard MPLS, which adoptsconstraint-based routing criteria. The ultimate goal of Traffic Engineering is to optimize theutilization of Network resources and to minimize traffic congestion. It is a pragmatic way ofhandling traffic problems. One of the design goals for MPLS was to create a tool to achievethis. A description of Traffic Engineering can therefore be as follows:

Traffic Engineering is all about discovering what paths and links are available in theNetwork, what the current traffic usage is within the Network and then directing traffic toroutes other than the shortest so that optimal use is made of the resources within theNetwork. This is achieved by a combination of extensions to the existing IGP routing protocols,traffic monitoring tools and traffic routing techniques

-


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(G)MPLS-TE Link Attributes

Unreservedbandwidth

MaximumReservedbandwidth

(Under-subscription)

Over-subscription

Resourceclass/colour

Maximumbandwidth Traffic

Engineeringmetric

TE-Link parameters

QoSparameters

(G)MPLS-TE extensionto support (G)MPLS allowing distribution of additional TE link attributes:

Link capacity, Protection type, Shared risk group, Supports link bundling

Parameters that are taken into account in MPLS-TE routing:

1. Traffic Engineering Metric (TE metric): Link metric (e.g. delay, jitter)

2. Resource Class/Colour: Administrative group membership per TE link

3. Maximum Bandwidth: true TE link capacity

4. Maximum Reservable Bandwidth: User configurable (by default = maximum link

capacity but may be greater i.e. link over-subscription)

5. Unreserved Bandwidth (per priority): Bandwidth not yet reserved on the TE link

(initial values correspond to the Maximum Reservable Bandwidth)

In practical cases, it is difficult to take into account parameters like delay and jitter; so

the Link bandwidth, with its related attributes, is the main parameter used in constraint

routing applied in Traffic Engineering.


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23

@@SEC



GMPLS


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Packets, Circuits, Lambdas, Ports

Routing at NE level

Standardized

Multi technology

MPLS






GMPLS


GMPLS Generalized Multi-Protocol Label Switching

Evolution of MPLS towards circuit-oriented transport networks (SDH/SONET,DWDM, OTN, ports)

Generalized Multi-Protocol Label Switching (GMPLS) is a key functionality fornext-generation optical transport networks

Combines the benefits of well-proven carrier-class optical transport and IPpacket-based technologies


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MPLS extension to GMPLS

Generalization of label space values (Generalized Label Formatexample in appendix)

in packet the label is a tag used for forwarding; in TDM or WDMNetworks for example, labels identify real physical resources (lambda ortimeslots)

Generalization of LSP

Optical connections/TDM circuits/etc. are the new LSPs (from ControlPlane)

Generalization of TE Link concept and TE attributes to non-packetresources

GMPLS (Generalizing MPLS)Generalization of MPLS-TE concepts for the definition of distributed control

plane protocols also applicable to non-packet Networks

GMPLS (Generalizing MPLS)

Generalization of MPLS-TE concepts for the definition of distributed control

plane protocols also applicable to non-packet Networks

The main reason of the GMPLS introduction is the generalization of the MPLS-TEconcepts for the non-packet technologies and the introduction of the DISTRIBUTED

control plane

25


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GMRE GMPLS CONTROL PLANE IMPLEMENTATION

TransportPlane

NE

ControlPlane

Signaling Routing

Link Management

SDH

/SONET/

OTH

/Etherne

t

GMPLS

ManagementPlane

GMRE: is the GMPLS Routing Engine, it performs the three maintasks: Routing, Signaling and Link Management

GMRE: is the GMPLS Routing Engine, it performs the three maintasks: Routing, Signaling and Link Management

The Control Plane is realized with GMPLS (Generalized Multi Protocol Label Switching).GMPLS is a family of different protocols to perform the required actions to establish anASON. These protocols are transmitted between the NEs. GMPLS is based on the MPLSprotocols for packet based transmission.

According to their function the protocols can be divided into:

Signaling

Routing

Link Management


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GMPLS CONTROL PLANE PROTOCOLS

1. OSPF Routing

Exchanges topology information between

nodes so routes for connections can be

computed

2. RSVP Signaling

Negotiates the allocation and release of

resources to establish connections

3. LMP Link Management

Maintains control channels, supports

neighbor and service discovery

C

D

E

B

A

5

5

6

6

5

55

5

55 5

5

Control Channels

Data LinksGMPLS is a family of different protocols toperform the required actions to

establish the control plane

GMPLS is a family of different protocols toperform the required actions to

establish the control plane

1. OSPF Routing

Exchanges topology information between nodes so routes for connections

can be computed

2. RSVP Signaling

Negotiates the allocation and release of resources to establish connections

3. LMP Link Management

Maintains control channels, supports neighbor and service discovery

Let see in the following chapters dedicated slides on this three topics

27


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28

@@SEC



OSPF ROUTING


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GMPLS CONTROL PLANE Routing

TransportPlane

NE

ControlPlane

Signaling Routing

Link Management

SDH

/SONET

/

OTH

/Ethern

et

GMPLS

ManagementPlane

Routing: in GMPLS routing is performed by OSPF

Routing: in GMPLS routing is performed by OSPF

Routing

OSPF


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30



OSPF ROUTING Concepts

OSPF is a link state protocol

Every node builds a map of the connectivity of the network, in the form of agraph showing which nodes are connected to which other nodes.

A OSPF instance resident on a node has a complete picture of theinternal-network.

Every OSPF router collects information from all peer routers.

The ultimate objective is that every router has identical information about theinter-network, and each router will independently calculate its own bestpaths to destinations.

OSPF is built around a well-known algorithm from graph theory, E. W. Dijkstrasshortest path algorithm.

OSPF

Routing

OSPF is a LINK STATE protocol used to build a map of connectivity in thenetwork.


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31



Link State: Adjacencies and Topological DB

Link State Packet (LSP)is a packet of information generated by anetwork element in a link state routing

Link State Packet (LSP)is a packet of information generated by anetwork element in a link state routing

OSPF

Each router establishes a relationshipcalled adjacency with each of itsneighbors:

Adjacencies are set-up, kept alive and

operated via dedicated protocols

Topological databaseOnce the adjacency is setup, a routersends information to its neighborsexchanging LSAs (Link-stateadvertisements )

Each neighbor receiving an LSA in turnforwards (Floods) the LSA to its ownneighbors


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32



Link State Concepts

Database

OS

PF

Routing tables

Routing tables

Topological database


Link-state advertisements(LSA)

Link-state advertisements(LSA)

LSA

LSA

Link-state advertisements (LSAs)small packet of routing information that is sent between routers

Shortest Path First (SPF) algorithmperformed on the database resulting in the SPF tree

Routing tableslist of the known paths and interfaces


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33



Link State Concepts: Flooding algorithmOSPF

Flooding of link-state information

OSPF uses the Hello Protocol to acquire neighbors and establish anadjacency

Each router on the network announces its own piece of link-stateinformation to all other routers on the network.

The flooding algorithm is reliable, ensuring that all routers in an area haveexactly the same link-state database

Link-state advertisements (LSAs)

small packet of routing information

that is sent between routers

LSA

LSA


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34



Link State Concepts: Building a Topological DB

OS

PF

Building a Topological Database

Each router collects all of this link-state information from other routersand updates a topological database.

The same information can be received from different sources at slightlydifferent time frames.

Using this information, the routers can recreate a topology graph of thenetwork and traverse it using the Dijkstra Algorithm. (SPF)

TopologicalDatabase


collection of informationgathered from LSAs

Shortest Path First (SPF) algorithm

performed on the database resulting inthe SPF tree


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C

D

E

B

A5

5

6

6

5

55

5

55 5

5

Open Shortest Path First (OSPF)

Internet standard (RFC 2328 for IPv4) for routing

Calculates shortest path based on metric costs

Link state routing protocol

Own HELLO mechanism to find own neighbors

Adjacency database and link state database keepnetwork topology

Constrained Shortest Path First (CSPF)

Removes all links from the network graph (pruning),which do not satisfy the constraints (e.g. remove allunprotected links)

Determines the shortest path as in OSPF

OSPF-CSPF ROUTING DEFINITION

OSPF

Constrained Shortest Path First (CSPF)is an extension of shortest path algorithms. The path computed using CSPF is a shortest

path fulfilling a set of constraints. It simply means that it runs shortest path algorithmafterpruningthose links that violate a given set of constraints

Constrained Shortest Path First (CSPF)is an extension of shortest path algorithms. The path computed using CSPF is a shortest

path fulfilling a set of constraints. It simply means that it runs shortest path algorithmafterpruningthose links that violate a given set of constraints

Which is the difference between OSPF and CSPF and why it is need?

Let see in the next example


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OSPF Routing and LSA example

C

D

E

B

A5

5

6

6

5

55

5

55 5

5

Sample Network

Routing Databaseequivalent in all nodes databases

Node A LSA: links: A->B, A->C

Node B LSA: links: B->A, B->D

Node C LSA: links: C->A, C->D, C->E

Node D LSA: links: D->B, D->C, D->E

Node E LSA: links: E->C, E->D

OSPF

OSPF Example: E as head node

E

E

C

C D

D

A

A B

B

5

10

5

1016

x

10x

Shortest pathfrom node E

to othernodes

The shortest path based on link costs only (not number of Hops or nodes)

If there are more than one possible path with the same link cost, then the

fragmentation costs is used to decideIf there are more than one possible path with the same link cost andfragmentation cost, then one is randomly picked.


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CSPF Routing and LSA example

C

D

E

B

A5

5

6

6

5

55

5

55 5

5

Sample Network

Routing Databaseequivalent in all nodes databases

Node A LSA: links: A->B, A->C

Node B LSA: links: B->A, B->D

Node C LSA: links: C->A, C->D, C->E

Node D LSA: links: D->B, D->C, D->E

Node E LSA: links: E->C, E->D

CSPF

E

E

C

C D

D

A

A B

B

5

10

5

1516

10

Failurebetween nodeE and D

link is notused for pathcomputation

CSPF Example: E as head node


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CSPF and OSPF

Routing Database

Routing Database after CSPF

CSPF OSPF

ROUTE

ROUTE

When there is a route calculation request, first CSPF is used to filter the database andthen the shortest path is calculated (OSPF) from the resulting filtered database.

The OSPF route calculation algorithm on the resulting filtered database finds : The shortest path based on link costs only (not number of Hops or nodes)

If there are more than one possible path with the same link cost, then thefragmentation is used to decide (link with the minimum fragmentation is chosen)

OSPF transfer protocol is used with Traffic Engineering Extensions (OSPF-TE) to exchangeall the necessary information about Te-Links for GMPLS

The routing information is stored locally in a database (in memory).

When there is a route calculation request, first CSPF is used to filter the database and thenthe shortest path is calculated (OSPF) from the resulting filtered database.

The OSPF route calculation algorithm on the resulting filtered database finds


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39

@@SEC



LSP RSVP Signalling


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TransportPlane

NE

ControlPlane

Signaling Routing

Link Management

SDH

/SONET

/

OTH

/Ethern

et

GMPLS

ManagementPlane

Signaling: in the GMPLS the signaling is performed by RSVP(Resource Reservation Protocol)

Signaling: in the GMPLS the signaling is performed by RSVP(Resource Reservation Protocol)

Signaling

R

SVP-TE


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41



OSPF-TE and RSVP-TE relationship

RSVP

-TE

OSPF-TE

presents the computed path

as an Explicit Route

OSPF-TE passes ExplicitRoute to RSVP-TE engine

for signaling

Routing tables

Routing tables

Signaling

RSVP-TE

RSVP-TE

RSVP-TE is used in GMPLS Control Plane, to provide: Label distribution

Explicit path configuration

Resource reservation and Admission control

Sequence of operations for Constraint Routing

a) OSPF-TE stores information from IGP (internal gateway protocol) flooding into

the Routing Table named Link State DB (LSDB)b) OSPF-TE stores traffic engineering information in the TE Link State DB (TEDB)

c) OSPF-TE examines user defined constraints for the incoming LSP request:

d) OSPF-TE/SPF performs path computation for the LSP through the TE linktopology

e) OSPF-TE presents the computed path as an Explicit Route

f) OSPF-TE passes Explicit Route to RSVP-TE engine for signaling

All the above operations are performed by the Ingress-LER where the path setuprequest arrived.


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Label Distribution with RSVP-TE

In GMPLS signaling, the Ingress node may suggest a label, and thus have somecontrol over the selection of a label at Egress nodes, but Egress node has theright to reject the Suggested Label and select its own from the available labelspace. As a result the Ingress node will have to reconfigure itself to the new label.

In GMPLS, the Ingress node may restrict the labels that may be used by an LSP(Label Switched Path) along the whole LSP path. This feature is driven from theOptical Domain where wavelengths used by the path must be restricted either toa small subset of possible wavelengths, or even to one specific wavelength.

RSVP

-TE

LSPdirection

(TransitLSR)

(TransitLSR)

In GMPLS signaling, the Ingress node may suggest a label, and thus have somecontrol over the selection of a label at Egress nodes, but Egress node has the right to

reject the Suggested Label and select its own from the available label space. As aresult the Ingress node will have to reconfigure itself to the new label.

In GMPLS, the Ingress node may restrict the labels that may be used by an LSPalong the whole LSP path. This feature is driven from the Optical Domain wherewavelengths used by the path must be restricted either to a small subset of possiblewavelengths, or even to one specific wavelength. This requirement occurs becausesome equipment may only be able to generate a small set of the wavelengths thatintermediate equipment may be able to switch, or because intermediate equipmentmay not be able to switch a wavelength at all, being only able to redirect it to adifferent fiber.


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43



LSP Setup

Setup: Path (R2, R6, R7, R4, R9 ) sent downstream (pre-allocates bandwidth)

Reply: Resv (sent upstream) communicates labels and reserves bandwidth on eachlink

R8R2

R6

R3 R4

R7

R1R5

R9Path (R2, R6, R7, R4, R9)

Path (R6, R7, R4, R9)

Path (R7, R4, R9)

Path (R4, R9)

Path (R9)

LSP Setup Path and Resv messages are sent HOP by HOP, Pathsare refreshed periodically re-sending path message


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EXAMPLE OF OTN LSP SETUP and TUNNEL CREATION

Electronic layerL1

Photonic layer L0

OCH LSP

OCH TUNNEL

ODU LSP

ODUTUNNEL

LOGIC PATH

PHYSICALPATH

LSP Tunnel

Determines a logical association between the source and the destination of a

uni/bi-directional traffic flow for which resource reservation will be required-

May comprise a set of one or more LSP tunnels which physically carry traffic

In this example it is shown a more elaborated Path setup with LSP for optical channelallocation, ODU logical tunnel to establish a logical path between ingress and egress

nodes.Tunnel

Determines a logical association between the source and the destination of a uni/bi-directional traffic flow (traffic trunk) for which resource reservation will be required

May comprise a set of one or more (at least one) LSP tunnels which physically carrytraffic

44


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45

@@SEC



LMP Link Management


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TransportPlane

NE

ControlPlane

Signaling Routing

Link Management

SDH

/SONET

/

OTH

/Ethern

et

GMPLS

ManagementPlane

Link Management: LMP is used to manage the links

Link Management: LMP is used to manage the links

Link Management


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47



Link ManagementLINK MANAGEMENT Concepts

LMP (Link Management Protocol)

a protocol introduced as an extension of RSVP-TE in order to enable thenetwork nodes to share link information between two adjacent NEs, tosynchronize NE link information between NEs, to share alarm

LMP consists of 4 primary procedures, of which the first two are mandatory andthe last two are optional

Control Channel management

Manage multiple control channels between nodes

Link Property Correlation

Discover and agree data link properties

Link verificationMap interface IDs and verify data connectivity

Fault Management

Detect and isolate faults


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48



GMPLS

LINK Maintenance Out of Band and In-band Signalling

GMPLS

I/f_Id 1

I/f_Id 6

I/f_Id 4

Link_Id 4

GMPLS GMPLS

IPCC_IDIPCC_ID IPCC_ID IPCC_ID

I/f_Id 4I/f_Id 8

In GMPLS devices must be able to send and receive protocol messages over

IP control channels (IPCC) a point to point channel

Control channels can be implemented (signaling transport mechanism)

in-Fiber/in-Band (IF/IB): Data Communication Channel (DCC)

in-Fiber/out-of-Band (IF/OB): Separate optical channel

out-of-Fiber/out-of-Band (OF/OB): IP over Ethernet

IPCC with

IB CC

IPCC with

OB CC

IB:In Band

OB:Out of Band


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49



IPCC Maintenance and Protocol Hellos

I/f_Id 1

I/f_Id 6

I/f_Id 4

Link_Id 4

IP_1

I/f_Id 4I/f_Id 8

IP_2IP_1 IP_2

R

R S

SL

L R

R S

SL

L R

R S

SL

L R

R S

SL

L

Adjacency maintenance: Hello message exchanges between neighborsfor independent detection of LMP, routing and signaling software failures

GMPLS provides:

LMP instance (L): LMP Hello message are exchanged

OSPF instance (R): OSPF Hello message are exchanged

RSVP-TE instance (S): RSVP-TE Hello message are exchanged

LMP (L) maintains control plane adjacencies by exchanging LMP Hellomessages enabling, in turn, control channel failure detection

LMP Hello: lightweight keep-alive that allows LMP reacting rapidly to controlchannel failure(s) activating (if possible) a parallel control channel (ifavailable) reduces probability of unnecessary removal of associatedrouting adjacencies due to loss of OSPF Hellos

LMP Hellosdo not eliminate the need to exchange RSVP-TE and OSPFHellos

Control channels used by OSPF and RSVP TE for message exchange may be thesame as the LMP control channels


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50



ManualConfigurationDISCOVERY

BootstrapmessageAUTO-DISCOVERY

Data Link(s) Correlated

IP ControlChannel Setup

LMP adjacency up

Data Links

Correlation(Link Summary)

Link VerificationIn-Band Test

message

TE Link(s) Identified

TE Link processing through IGP-TE (Interior Gw Protocol)

START = No CC (LMPAdjacency down)

Data Links

Correlation(Link Summary)

LMP = Link Management Protocol

Data Link and TE Link Discovery (LMP) Example

Hello timersnegotiated and hellomessages exchanged

LMP Control Channel management performs control channel set-up

Neighbor control channel address discovery via config

message Nodes negotiate acceptable control channel parameters (hello

timer and hello dead timer) via config message

Hello protocol monitors health of control channels

Nodes exchange channel status messages to supervisecontrol channel status. In case of fault LMP activates anothercontrol channel via a config message

Neighbor address discovery

Config message sent to a multi-cast address (224.0.0.1) in

case of in-band control channel Config message sent to the neighbor LMP controller address

in case of out-of band control channel. The neighbor LMP

address has to be configured by operator in this case.


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51

@@SEC



GMRE Main Blocks


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52



Data Link

Controller

Path Computation Module

Path Computation (CSPF)

and Selection

TE Link

Database

TE Link

Admission Control

& Policy

Routing Controller

Routing Adjacencies (Hello)

Routing Table

TE - Data Link

control and

maintenance

IPCC Controller

Link State

Database

GMPLS Controller

Database Exchange/Flooding

CC Maintenance

(Hellos) and

Configuration

P/R State Blocks

Signalling Controller

Hello (Adjacencies)

GMRE GMPLS Engine main blocks

CSPFPath

Computation

CSPFPath

Computation

Signalingcontroller

Signalingcontroller

Routingcontroller

Routingcontroller

TE-Link admissioncontrol and policy

TE-Linkadmission

control and policy

LMP: linkmanagement

protocol

LMP: linkmanagement

protocol

Let resume the GMRE engine with the main blocks and functions


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53



Data Link

Controlle

r

Path Computation

Module

TE Link

Routing Controller

Routing Table

IPCC

Controller

GMPLS Controller

SignallingController


CSPF

Builds and maintain topology of the transportnetwork

Calculate constrained LSPs to be signaled viaRSVP-TE

Signaling controller

Implements all RSVP-TE related functionalities

Neighbor adjacency monitoring

RSVP-TE message set signaling and refresh

LSP state management

Routing controller

Disseminate TE-Linkinformation via linkstate advertisements

Builds and maintain the topology of the controlplane network

Builds the TE-link and LSA database


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54



Data Link

Controlle

r

Path Computation

Module

TE Link

Routing Controller

Routing Table

IPCC

Controller

GMPLS Controller

SignallingController


LMP: link management protocol

Setup and maintenance of IPcommunication channels

Build associations between data links andTE-links

Correlation and verification of TE-Links withadjacent nodes

Verification of data links

TE-Link admission control andpolicy

Deals with admission control of bandwidthrequests (including priority management),implements policies related to link resourceusage (e.g. how to allocate bandwidth on aTE-link) etc..


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55



Data Link

Controller

Path Computation Module

Path Computation (CSPF)

and Selection

TE LinkDatabase

TE LinkAdmissionControl & Policy

Routing Controller

Routing Adjacencies (Hello)

Routing Table

2b

TE - Data Linkcontrol and

maintenance

3a

IPCC

Controller

2a

Link State

Database

GMPLS Controller

Database xchange/Flooding

3c

2c

Maintenance(Hellos) and

Configuration

3b

P/R State Blocks

1a

1b

Signalling Controller

Hello (Adjacencies)

GMPLS RSVP-TE Flows

Hello Signalling Messages (Trigger/Refresh)

OSPF TE Flows

[2a] [2b] HelloDatabaseDescription/LS Request[2c] LS Update/Ack

LMP IP Control ChannelMaintenance andConfiguration

[3a]Hello and Config

LMP Data Link Control[3b] Verification,Property Correlation and

Fault Management

LMP Data LinkVerification

[3c] (in-band) Testmessages

LMP Link Management Flows

In this example there are the main protocols and the relative senders.

RSVP-TE from signaling controller

OSPF-TE flows from Routing controller

LMP using IP CC from data link controller


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ASON GMPLS ProtocolsEnd of module


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@@SEC



APPENDIX Labels Format


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MPLS Label

Label Fields:

Label (20bits) Indicates a class (FEC=Forwarding Equivalent Class

EXP (3 bits) (experimental) 3 bits used for priority S (1 bit) (stacking bit) indicates the inner label, in a label stack (creates LSP tunnel

within LSP)

TTL (8 bits) (time to live) indicates the max delay, in terms of max number of hops thepacket can yet perform in the Network, before reaching destination; it isdecremented in each traversed node where it is processed and causes packetdiscarding when expires.

TCP headerIP header

DATA

MPLS Label

TCP/IP Packet

Shim

header

TCP/IPpacket with

MPLS

TTLLabel (20-bits) EXP S

32 bits

MPLS Label

The slide shows a TCP/IP packet modify by inserting a MPLS Labelin front of the IP-Packet.

The term label switching relies on associating a small, fixed-format label with each datapacket, at each hop across the Network. Each packet is forwarded based on the value ofincoming label and transmitted onward with a new label value.

The label is swapped and the data is switched, at based on the label value.

In an MPLS Network, packets are labelled by the insertion of an additional piece of informationcalled the shim header or the MPLS Label

In the above example, the label is placed between the Transport (TCP) header and the Network(IP) header.

A label is a short, fixed length, locally significant identifier which is used to identify a FEC(Forwarding Equivalent Class). The packet assignment to a FEC, and so the Label values, aredecided by the border Routers in the Network.

Each Network node (called LSR= Label Switching Router) maintains a look-up table (LFIB=Label Forwarding Information Base) to allow it to determine the next hop for the data, on thebasis of the Label values.

The LFIB contains a mapping of:

[incoming interface, incoming label] [outgoing interface, outgoing label]

The label is used as entry in the LFIB.

Signalling protocol are used to exchange label mapping information between the LSRs.


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In MPLS technology the label is the numerical 20 bit identifier that is inserted inthe MPLS label defined by RFC 3032.

In TDM technologies the label identifies a Timeslot (e.g. VC4,ODU-1 etc..)

In light technologies the label identifies a OCH

32 bits

RSVP-TE Label concept

MPLS Label value (20-bits)

A "labeled packet" is a packet into which a label has been encoded. In somecases, the label resides in an encapsulation header which exists specifically

for this purpose. In other cases, the label may reside in an existing data linkor network layer header, as long as there is a field which is available for thatpurpose. The particular encoding technique to be used must be agreed to byboth the entity which encodes the label and the entity which decodes thelabel.

RSVP

-TE

A short, fixed length identifier (32 bits)

Sent with each packet

Local between two routers

top63094 v1.0-ason gmpls mrn overview

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