SDN MIGRATION STRATEGIES The Case for Transitioning to an SDN-enabled Network

Transcription

1 WHITE PAPER SDN MIGRATION STRATEGIES The Case for Transitioning to an SDN-enabled Network Software Defined Networking (SDN) enables open, programmable, and application-aware networks that bring many benefits to network operators, including generation of new revenue from new services, more efficient network utilization, and streamlined operations. In order to gain these benefits in the real world, operators must pragmatically evolve existing networks to harness the true capabilities of SDN technology. This paper describes three key migration strategies that can be employed to evolve a multi-layer network to a Software Defined Network - Management System Migration, Hybrid Mode Migration, and Chameleon Mode Migration.

2 NETWORK TRANSITION AND SDN CONTROL Software Defined Networking (SDN) technology offers many advantages in router, packet optical and optical network design (L3 L0). These advantages are described in Coriant s white paper, The SDN Transformation: A Framework for Sustainable Success. Next, it s important to understand why networks should migrate from existing non-sdn networks to SDN-controlled networks, as well as some of the techniques. In the overall SDN network presented in Figure 1, the service control function is supported in the Optical Controller and Packet Controller. A Network Orchestrator (or Upper Controller) coordinates inter-layer service control. The Management function (provisioning, alarms, etc.) is retained in the Manager. POLICY & EXTERNAL DATA APP APP APP NETWORK ORCHESTRATOR CONTROL PLANE SERVERS IN DATA CENTER OPTICAL CONTROLLER PACKET CONTROLLER MANAGER OTHER OPERATORS MPLS FABRIC ACCESS Optical Core Packet Switch Service Edge FIGURE 1: THE SDN NETWORK In a Software Defined Network, the control and forwarding plane (or data plane) functions of traditional network elements are separated. The role of the element management system also changes where the service establishment function is separated and likewise moved into the SDN orchestrator and controller elements. 2 SDN MIGRATION STRATEGIES

3 MANAGEMENT SYSTEM MIGRATION In current, non-sdn/non-ason optical networks, the management system and management interfaces are used to establish services. With the introduction of SDN, service establishment is done via the SDN controller, which controls the sub-tending network elements (NEs). SDN supports real-time control of services when the interface between the controller and NE can support real-time transactions. A necessary and valuable method to ease migration to SDN is providing support for existing management interfaces in the SDN controller. This allows SDN control of legacy NEs that do not support new SDN interfaces (i.e., OpenFlow). It also enables the control of third-party NEs via their management interfaces. The result is end-to-end service management via the SDN controller across SDN-capable, legacy and third-party NEs. The capability does not provide universal real-time SDN control, but greatly increases the scope of SDN control in a migrating network. This method can be used as the initial deployment strategy to make service introduction programmable and automated, independent of the management system. It can also then be used to control third-party NEs that are not under direct SDN control (e.g., OpenFlow or other SDN protocols). In an ASON-controlled optical system, three service control mechanisms are possible: Management System, ASON, and SDN. In this case, control of resources is assigned to one method and resource control locking methods enable the migration to SDN. This is the same process previously followed during the introduction of ASON control to management control. In packet networks using the IP/MPLS control plane, additional migration techniques must be used. The following sections discuss these methods. IP/MPLS NETWORKS - HYBRID MODE IP/MPLS networks use routing protocols (e.g., OSPF, BGP) to control the forwarding of packets. When introducing SDN into an IP/MPLS network, it is unrealistic to expect all NEs to flash over to SDN control. This means that the NEs that are not under SDN control continue to expect routing protocol exchange with NEs that are under SDN control. Hybrid Mode is the case where an NE supports SDN control interfaces and legacy routing protocols. This mode is only required in those NEs that are connected to non-sdn controlled legacy NEs. In Figure 2, the Hybrid Mode is represented by the gray and purple edge NEs. CORIANT 3

4 POLICY & EXTERNAL DATA APP APP APP NETWORK ORCHESTRATOR CONTROL PLANE SERVERS IN DATA CENTER OPTICAL CONTROLLER PACKET CONTROLLER MANAGER OTHER OPERATORS MPLS ACCESS Optical Core Packet Switch Service Edge FIGURE 2: HYBRID MODE In this mode, network elements have the capability to support both SDN control interfaces and legacy control interfaces/routing protocols, enabling simultaneous operation under both control architectures. This method is similar to that used in the Coriant 8800 Smart Router Series that successfully migrated operator networks of hundreds of ATM NEs to MPLS routing by supporting both ATM and MPLS control mechanisms in a Hybrid Mode. IP/MPLS NETWORKS CHAMELEON MODE An optimization of Hybrid Mode moves the IP/MPLS routing protocol support to the Packet Controller in the IP/MPLS Network Chameleon Mode. The advantage here is that the edge NEs no longer have to support the legacy routing protocols. This mode removes complexity (both hardware and software) and associated cost from the NE. Figure 3 shows the location of the legacy protocol support. The Chameleon Mode requires the edge NEs to forward legacy protocol messages to the Packet Controller, protocol handling in the Controller, and forwarding back via the NE to the connected Legacy NE. The Packet Controller in effect acts as a Virtual Router for each connection. The required performance is handled by the Packet Controller s virtual compute environment. 4 SDN MIGRATION STRATEGIES

5 POLICY & EXTERNAL DATA APP APP APP NETWORK ORCHESTRATOR CONTROL PLANE SERVERS IN DATA CENTER OPTICAL CONTROLLER PACKET CONTROLLER MANAGER LEGACY CP PROTOCOLS OTHER OPERATORS MPLS ACCESS Optical Core Packet Switch Service Edge FIGURE 3: CHAMELEON MODE In this mode, IP/MPLS routing protocol support is virtualized in the Packet Controller, simplifying and lowering the costs of network elements. CONCLUSION SDN offers many advantages to network design including programmability, agility and NFV of control to name a few. However, in most cases SDN is not being deployed in greenfield networks. A viable SDN introduction must use migration techniques like those described in this paper to enable SDN to be deployed in real-world networks. CORIANT 5

6 ABOUT CORIANT Coriant is a global leader in dynamic, multi-layer transport networking solutions from metro access to the optical core. Founded as an independent company in 2013, Coriant was built upon the distinguished heritage of technology innovation and engineering excellence of Nokia Siemens Networks Optical Networks, Tellabs, and Sycamore Networks. We serve over 500 customers globally, including 90% of the world s top 50 service providers. The Coriant product portfolio leverages industry leadership in metro packet optical networking, best-in-class optical transmission (LH/ULH) performance and scalability, and innovative IP/MPLS edge routing technology optimized for LTE and LTE-Advanced networks. Our value proposition includes comprehensive care offerings and a proven track record of delivering world-class service and support excellence to the largest and most demanding networks in the world. Visit us at These trademarks are owned by Coriant or its affiliates: Coriant, Coriant Dynamic Optical Cloud, mtera, and Transcend. Other trademarks are the property of their respective owners. Statements herein may contain projections regarding future products, features, or technology and resulting commercial or technical benefits, which may or may not occur. This publication does not constitute legal obligation to deliver any material, code, or functionality. This document does not modify or supplement any product specifications or warranties. Copyright 2014 Coriant. All Rights Reserved. 74C.0068 Rev. A 10/14