Introduction - Versatile Routing and Services with BGP: Understanding and Implementing BGP in SR-OS (2014)

Versatile Routing and Services with BGP: Understanding and Implementing BGP in SR-OS (2014)


As defined in the base specification for the Border Gateway Protocol (BGP), the primary function of a BGP speaking system is to exchange network reachability information with other BGP speakers while including information on the list of Autonomous Systems that the reachability information traverses. This information can be used to construct a graph of AS connectivity for this reachability, while at the same time removing routing loops and providing operators the ability to implement local policy.

The intention was clear. At its conception, BGP was to be used for exchanging Internet routes between Autonomous Systems/Internet Service Providers. As a result, the protocol was built with characteristics that above all provided a level of stability among the constant churn of the Internet routing table.

During the last 15 or so years the use of BGP has evolved significantly. From a deployment perspective, operators have learned from experience and shared those experiences with the wider community to everybody's mutual benefit. BGP is well understood and is considered a mature protocol. From a service delivery perspective, the evolution is two-fold:

· The Internet is no longer perceived as a best-effort service. Instead, it has become a must-have, always-on service for businesses and homes.

· BGP's scalability and flexibility, together with its numerous hooks that allow for application of policy, have made it the Service Provider's protocol of choice for service enablement.

So, while BGP remains the primary protocol for inter-domain route exchange, its use for delivery of intra-domain services has increased significantly. The base protocol has been extended many times to provide the ability to carry new reachability information. It thereby enables Service Providers to effectively deliver new services with minimum impact on their existing IP infrastructure using a known and deployed protocol. In addition, the protocol is evolving into new areas such as Data Centers with the advent of Ethernet VPN.

While this is happening and BGP is being used more and more to deliver business critical services, other base characteristics have changed. BGP is historically a slow-converging protocol, but fast-reconvergence upon failure has become an absolute requirement for delivery of high-profile services. Many potential consumers use fast reconvergence upon failure as a measuring stick of network performance. Incidents that result in the failure of BGP have become totally unacceptable, and so the base protocol has had to become more robust than early implementations.


The purpose of this book is to provide you with an all-encompassing single reference guide to the BGP implementation within Alcatel-Lucent SR-OS. It aims to equip you with sufficient knowledge to feel competent and confident about the technology you are addressing, and be able to maximize and optimize your implementation of BGP using SR-OS.

The book looks at how services can be delivered and how efficient routing can be achieved in both native IP networks and MPLS networks. It covers how you can use BGP to provide services such as Layer-2 VPNs and Layer-3 VPNs, as well as native or VPN-aware multicast and IPv6. At the core infrastructure layer, it looks at how you can use BGP to deliver scalable IP/MPLS networks using inter-AS and inter-domain scenarios.

In addition, the book covers techniques that you can use to improve path visibility and improve reconvergence times. It also looks at how procedures for error handling have evolved from the base BGP specification. It aims to detail the implications and considerations for each technology, and it gives design tips where appropriate.

For each feature, function, or technology that the book covers, the aim is to provide an overview of what it is and how it operates at a protocol level. The book then details the configuration requirements with CLI and debug outputs used to aid understanding. The objective is that you have a full understanding of the technology in question together with the knowledge of how to implement it in SR-OS.


The book is primarily intended for IP design and engineering communities. Familiarity with Alcatel-Lucent SR-OS is not a requirement, although readers who are familiar with SR-OS will recognize configuration examples and Command Line Interface (CLI) outputs.

You can read each chapter as a standalone chapter if, for example, you need some guidance on how to implement and configure a particular service and/or function, or even just to learn how a particular technology works. On the other hand, an avid reader passionate about BGP may choose to read from cover to cover.

To keep this book to a manageable size, I do not discuss the basic operation of BGP as a path vector protocol. Numerous other reference books provide this introductory information, and I assume that knowledge to be a prerequisite.

Want to Practice Some of These Configs?

You may want to try some of what you learn in this book in an SR-OS lab. Alcatel-Lucent can help you with its MySRLab Service.

The MySRLab Service provides you with remote access to a hosted Service Router lab so you can:

· Test new network and service features.

· Build your service routing knowledge and configuration skills.

MySRLab features include:

· Remote, private access to a service router lab, available 24x7

· Separate labs for wire-line and mobility lab applications

· More than 50 lab practice scenarios and solution keys (optional)

· Access to traffic simulation and analysis tools