1

ASTN/ASON and GMPLS Overview and Comparison

By,

Kishore Kasi Udayashankar

Kaveriappa Muddiyada K

Motivations Complex process of provisioning of end-to-end transport service

Heterogeneous transport networks

Automation of end-to-end provisioning

Ability to offer more service

Directly integrate IP clients over WDM

How? “intelligence” into the control plane of OTN

automatic and seamless circuit provisioning

unified control binding technologies

Benefits? cost reduction and better quality of network operation

simplified and rapid network configuration

switched services and dynamic bandwidth assignment

ASTN/ASON ITU-T Recommendation G.805/G.8080

Architecture that defines the components and interactions between components

Distributed control plane

Task of control planes

Call and connection control

Path control based on network state

Discovery for self configuration

ASTN/ASON (Continued…)Protocols must support multi-layer, multi-vendor network

Layering

Administrative partitioning

Operational partitioning

Types of interfaces in the control plane

GMPLSUnified control plane for packet and circuit switching technologies

Four interfaces.

Interface Switching Capability

No NNIs.

GMPLS (Continued…) Extension of routing protocols

OSPF-TE and ISIS-TE

Signaling protocols, RSVP-TE and CR-LDP

Label Switched Paths (LSP)

Multi-layer Resource Model Representation

In GMPLS Basic topology abstraction is TE link

Link interface can support one or more interface switching types defined

Interface Switching Capability (ISC)

ISC descriptor describes related TE properties

A particular resource on a link is represented by a label

In GMPLS (Continued...) Basic service abstraction is a LSP

Concept of hierarchical LSP

LSP in server region represented as TE link or Forwarding adjacency in client region

Client LSP routed over a TE link == tunneled within a server LSP

Multi-layer Resource Model Representation

In ASON ISC concept has been reduced

Optical part of OTN hierarchy is mapped to LSC

Digital path layers of OTN and SDH hierarchy is mapped to TDM

In ASON (Continued…)

In ASON (Continued…)

Transport networks functional model G.805

Client/server association between adjacent layers

Each layer partitioned to reflect internal structure

In ASON (Continued…)

Partitioning concepts

Starting from the smallest indivisible subnetwork

Contained and containing subnetwork

Contained subnetwork cannot provide connectivity not available in containing subnetwork

Ports on boundary of containing subnetworks and interconnection capability are represented by contained subnetworks

In ASON (Continued…)

Partitioning concepts (contd…)

In ASON (Continued…)

Layering concepts

Layer networks in a client-server model

Termination and Adaptation Functions

Topology and connectivity not visible to client

In ASON (Continued…)

Overview of MPLS/GMPLS Concepts

Forward Equivalence Class

Label

LSR

LSP

Label allocation

Next Hop Label Forwarding Entry (NHLFE)

Route selection

From: Dr. Harry Perros, Connection Oriented Networks (CSC 576), Fall ‘06

From: Dr. Harry Perros, Connection Oriented Networks (CSC 576), Fall ‘06

Control Plane Architecture

In GMPLS

Peer model

Overlay model

Augmented model

Control Plane Architecture

In ASON

Protocol neutral way

Support various transport infrastructure

Applicable irrespective of control plane that has been subdivided into domains

In ASON (Continued…) General model of policy

System is a collection of components

System boundary

Nested system boundaries

Policy port as filters

In ASON (Continued…) General model of federation

Creation, deletion and maintenance of connections across multiple domains

Community of domains

Domains cooperate for connection management

Joint Federation Model and Cooperative model

In ASON (Continued…)

Joint federation Model Cooperative Model

In ASON (Continued…) Architectural components

Connection controller (CC) component

Routing controller (RC) component

Link resource manager component

Traffic policing (TP) component

Call controller component

Discovery agent (DA)

GMPLS Control Plane, Policy-based Management and Information Modeling

Policy based Management (PBM) Improve collaboration between management

and GMPLS control plane. Extending Policy Core Information models

(PCIM) with policy events. Diverse local and global decision logic

distributed among multiple network elements and network layers.

Discussion Items

Advantages and Features. Types of GMPLS policies and actions – few

examples Control plane and PBM architecture. GMPLS managed entities Two uses cases to explain PBM in GMPLS

Advantages

Dynamic, flexible and cooperative interworking Traffic engineering (TE) capabilities brought by

GMPLS. Improve operational efficiency. New services requires complex and dynamic

configurations of network resources. Avoid configuring node-by-node and consider

entire network domain as a whole. Increase automation by using rule sets.

Features

Standardized operational processes in multi-vendor environments.

Policy rule - Network operator has control over state changes for a given network function.

Adapting and changing behavior at runtime. Translating SLA, network and management

areas (eg. Routing, configuration, fault management) into policies.

Adding/deleting/modifying policies in policy repository.

Features (Continued…)

PBM Framework Policy based admission

control.

Policy Information Models “Policies are used to control

the state that a managed object is in at any given time; the state itself is modeled using an information model”.

Policy core Information Model (PCIM), MIB, PIB.

Policy rule – It is a binding of a set of policy actions to a set of policy conditions.

Policies and Policy Actions

Admission Control Policy Call/connection admission action, Call/connection

Rejection Action.

Signaling Control Policy Signaling recovery action

TE Routing Policy Link State Advertisement action, Manage TE Info action

Path Computation and Selection Policy Path computation action, Link Type selection action

Load Distribution Policy Load distribution action

Recovery related policies……

Control Plane and PBM Architecture

Need for a separate Control Plane (CP)

Fundamental principles of GMPLS CP Separating protocol generic

and application specific mechanisms.

TE Link as a unique application specific entity.

Two-stage OSPF architecture and database.

TE Link – resource aggregates that are encoded as links with TE attributes.

OSPF-TE with opaque LSA capabilities along with topology LSA distribution.

GMPLS Managed Entities

Features of NOBEL Information Model. Specifies managed entities and represents control

plane (CP) Components, capabilities, interworking of CP

components.

CP Element represents a control plane instance hosted by a CP node.

Separate instances of managed entities for control plane and transport plane entities.

Managed entities representing CP Elements and components

Use Case 1

Combined call and connection setup via User Network Interface (UNI). Considering circuit switch capable GMPLS network. SLA/SLS information installed in policy and service

admission repository. Global call admission directives in global Call admission

policy decision point (PDP) downloaded by policy execution point (PEP).

Local and node specific connection admission policies in global connection admission PDP.

Call and Connection Setup via UNI

Description

[1] connection request using call setup messages over UNI

[1b] comparing client id and port with call admission directives, does not match.

[2a] call level parameters translate into network resource related requirements and evaluated by LPDP.

[2b] requirements verified against general connection admission policy

[3] May be asked to renegotiate due to network or node limitation

Continued…

[4] connection setup is delegated to TEC which checks against path selection policy rules with LPDP

[5] signaling controller (SgC) requests LPDP to check against signaling control policy rules.

[6] ingress node signals modified call setup request.

Use Case 2

Event Driven TE Policy action for TE link utilization threshold crossing event. Emits threshold crossing alert (TSA). use case example - Predefined percentage (say 85%) of

the current forwarding adjacency (FA) packet switched connection (PSC) link unreserved bandwidth is consumed.

TE link utilization thresholds are set.

TE Control action – New FA PSC LSP New FA TDM LSP eg. At the server layer.

Event Driven TE Policy Action

Description

[1a] TE link emits TCA to TEC, internal signal.[1b] TE link emits TCA to Management Plane

(MP), CP-MP interaction notification.[2] TEC requests PEP to invoke event policy rule.[3] PEP forwards decision request to PDP (local,

global or both)[3a],[3b] LPDP evaluates load-distribution action

policy rule. If it does not succeed, create LSP create action policy is evaluated with global PDP.

Continued…

[4] LPDP evaluates path computation/selection policy rules and delegates TEC to enforce policy decisions.

[5] TEC triggers SgC for setup of server layer.[6] If success, TEC will check LSA update policy and

Information dissemination policy to initiate LSA update.

[7]. TEC updated TEDB with new FA-LSP and notifies MP about result of policy decision [8a]

[8b] TE Link emits state change notification to inform MP.

Bibliography• G.805 ITU-T specification• G.8080 ITU-T specification• ASON Current status of standardization work, B.

Zeuner, G. Lehr, Deutsche Telekom• ASON and GMPLS – The battle of optical control

plane– Data connection limited.

• Control plane for Optical networks: The ASON Approach, Andrzej Jajszczyk, AGH University of science and technology, Krakow, Poland

• ASON and GMPLS – Overview and Comparision, S. Tomic, B. Statovci-Halimi, A. Halimi

• GMPLS Control Plane, policy based management, and information Modelling, H.Lonsethagen, et. al.