Founded in 1981, KT Corporation (formerly known as Korea Telecom) is the largest provider of telecommunications services in South Korea, offering wireline telephony, high-speed Internet access and wireless services. As a leading provider of nation-wide carrier WAN services, it looked to the OpenDaylight SDN platform to create and deploy a new, highly flexible and scalable Transport SDN (T-SDN) WAN network.
Key challenges to provide transport WAN services
Like other Tier 1 WAN providers, KT faces a complex transport network environment encompassing 12m logical ports, 820k physical ports, 4500 systems and 12 equipment models. Six vendors for core functions such as multiservice provisioning platforms (MSPP), optical cross connect devices (OXC) and Packet Transport Networks multi-access boxes (PTN), as well as strictly defined domain and hierarchal layer architectures created a closed and inflexible system for network control. Each vendor-specific Element Management Systems (EMS) controlled the network element via a combination of standards-based and proprietary interfaces. This siloed approach to network control created high operational expenditure (OPEX) issues; creating a goal for the ODL-based solution to reduce OPEX by 30 percent.
Reducing the time to provide these B2B WAN services was also a goal for this project. Prior to the implementation of T-SDN, an End2End implementation could take several hours requiring the sequential input from multiple domain administrators. Service deployment was delayed due to manual planning and implementation processes. A T-SDN goal was set to reduce service provisioning time to a few minutes.
KT’s solution to centralize control
Based on a community-provided version of OpenDaylight, KT introduced a centralized control element (T-SDN) to create an End2End solution for WAN service provisioning. T-SDN uniquely allows direct management of either the vendor EMS or the actual network element which is essential for rapid path computing.
To reduce deployment time, the prior process was simplified to four steps and completely automated using T-SDN resulting in a service deployment time reduction of 95 percent.
To start, KT adopted the Helium Release of ODL for its service deployment and expects to update to Lithium in 2016. Key reasons for choosing a community version of ODL were the cost and time needed for developing additional plugins. KT integrated ODL with its legacy network management system (NMS) to share topology, inventory and fault information. For rapid path computation, it relied on an in-memory data store and custom YANG model. In addition, ODL’s ability to flexibly add southbound interfaces was key. In addition to the existing OpenFlow, NETCONF and SNMP plugins, KT also developed CORBA and even TL1 interface plugins to connect devices using EMS Northbound Interfaces (NBIs) provided by vendors.
In conclusion, KT’s T-SDN solution showcases the cost, time and flexibility benefits of OpenDaylight. T-SDN simplifies and automates an End2End service provisioning process by providing optimal path computation over multi-vendor devices (i.e. through its Yang model extensions) and the ability to control multiple types of network elements through a variety of standard and custom interfaces such as TL1. In KT’s view, the architecture of its transport network needs to accommodate legacy devices, which means that the ODL SDN controller must be able to flexibly support hybrid network scenarios. Following a two months field trial, KT expects to put its T-SDN into production in January 2016 while considering to leverage and extend its ODL expertise to other parts of its network infrastructure.