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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
GMPLS • Unified 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…) • 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
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…) Cooperative Model Joint federation 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.
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. Features (Continued…)
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……
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. Control Plane and PBM Architecture
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.
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.
Description  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  May be asked to renegotiate due to network or node limitation
Continued…  connection setup is delegated to TEC which checks against path selection policy rules with LPDP  signaling controller (SgC) requests LPDP to check against signaling control policy rules.  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.
Description [1a] TE link emits TCA to TEC, internal signal. [1b] TE link emits TCA to Management Plane (MP), CP-MP interaction notification.  TEC requests PEP to invoke event policy rule.  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…  LPDP evaluates path computation/selection policy rules and delegates TEC to enforce policy decisions.  TEC triggers SgC for setup of server layer.  If success, TEC will check LSA update policy and Information dissemination policy to initiate LSA update. . 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.