data center security

BGP SDN – Centralized Forwarding

by Blog

BGP SDN

The networking landscape has significantly shifted towards Software-Defined Networking (SDN) in recent years. With its ability to centralize network management and streamline operations, SDN has emerged as a game-changing technology. One of the critical components of SDN is Border Gateway Protocol (BGP), a routing protocol that plays a vital role in connecting different autonomous systems. In this blog post, we will explore the concept of BGP SDN and its implications for the future of networking.

Border Gateway Protocol (BGP) is a dynamic routing protocol that facilitates the exchange of routing information between different networks. It enables the establishment of connections and the exchange of network reachability information across autonomous systems. BGP is the glue that holds the internet together, ensuring that data packets are delivered efficiently across various networks.

Scalability and Flexibility: BGP SDN empowers network administrators with the ability to scale their networks effortlessly. By leveraging BGP's inherent scalability and SDN's programmability, network expansion becomes a seamless process. Additionally, the flexibility provided by BGP SDN allows for the customization of routing policies, enabling network administrators to adapt to changing network requirements.

Traffic Engineering and Optimization: Another significant advantage of BGP SDN is its capability to perform traffic engineering and optimization. With granular control over routing decisions, network administrators can efficiently manage traffic flow, ensuring optimal utilization of network resources. This results in improved network performance, reduced congestion, and enhanced user experience.

Dynamic Path Selection: BGP SDN enables dynamic path selection based on various parameters, such as network congestion, link quality, and cost. This dynamic nature of BGP SDN allows for intelligent and adaptive routing decisions, ensuring efficient data transmission and load balancing across the network.

Policy-Based Routing: BGP SDN allows network administrators to define routing policies based on specific criteria. This capability enables the implementation of fine-grained traffic management strategies, such as prioritizing certain types of traffic or directing traffic through specific paths. Policy-based routing enhances network control and enables the optimization of network performance for specific applications or user groups.

BGP SDN represents a significant leap forward in network management. By combining the robustness of BGP with the flexibility of SDN, organizations can unlock new levels of scalability, control, and optimization. Whether it's enhancing network performance, enabling dynamic path selection, or implementing policy-based routing, BGP SDN paves the way for a more efficient and agile network infrastructure.

Matt Conran

Highlights: BGP SDN

BGP SDN, which stands for Border Gateway Protocol Software-Defined Networking, combines the power of traditional BGP routing protocols with the flexibility and programmability of SDN. It enables network administrators to have granular control over their routing decisions and allows for dynamic and automated network provisioning.

Enhanced Flexibility and Scalability: BGP SDN brings unmatched flexibility to network operators. By decoupling the control plane from the data plane, it allows for dynamic rerouting and network updates without disrupting the overall network operation. This flexibility also enables seamless scalability as networks grow or evolve over time.

Improved Network Performance and Efficiency: With BGP SDN, network administrators can optimize traffic flow by dynamically adjusting routing decisions based on real-time network conditions. This intelligent traffic engineering ensures efficient resource utilization, reduced latency, and improved overall network performance.

Simplified Network Management: By leveraging programmability, BGP SDN simplifies network management tasks. Network administrators can automate routine configuration changes, implement policies, and troubleshoot network issues more efficiently. This leads to significant time and cost savings.

Rapid Deployment of New Services: BGP SDN enables faster service deployment by allowing administrators to define routing policies and service chaining through software. This eliminates the need for manual configuration changes on individual network devices, reducing deployment time and potential human errors.

Improved Network Security: BGP SDN provides enhanced security features by allowing fine-grained control over network access and traffic routing. It enables the implementation of robust security policies, such as traffic isolation and encryption, to protect against potential threats.

BGP-based SDN

BGP SDN, also known as BGP-based SDN, is an approach that leverages the strengths of BGP and SDN to enhance network control and management. Unlike traditional networking architectures, where individual routers make routing decisions, BGP SDN centralizes the control plane, allowing for more efficient routing and dynamic network updates. By separating the control plane from the data plane, operators can gain greater visibility and control over their networks.

BGP SDN offers a range of features and benefits that make it an attractive choice for network operators. First, it provides enhanced scalability and flexibility, allowing networks to adapt to changing demands and traffic patterns. Second, operators can easily define and modify routing policies, ensuring optimal traffic distribution across the network.

Another notable feature is the ability to enable network programmability. Using APIs and controllers, network operators can dynamically provision and configure network services, making deploying new applications and services easier. This programmability also opens doors for automation and orchestration, simplifying network management and reducing operational costs.

Use Cases of BGP SDN: BGP SDN has found applications in various domains, from data centers to wide-area networks. In data centers, it enables efficient load balancing, traffic engineering, and rapid service deployment. It also allows for the creation of virtual networks, enabling secure multi-tenancy and resource isolation.

BGP SDN brings benefits such as traffic engineering and improved network resilience in wide-area networks. It enables dynamic path selection, optimizes traffic flows, and reduces congestion. Additionally, BGP SDN can enable faster network recovery during failures, ensuring uninterrupted connectivity.

BGP vs SDN:

BGP, also known as the routing protocol of the Internet, plays a vital role in facilitating communication between autonomous systems (AS). It enables the exchange of routing information and determines the best path for data packets to reach their destinations. With its robust and scalable design, BGP has become the go-to protocol for inter-domain routing.

SDN, on the other hand, is a paradigm shift in network architecture. SDN centralizes network management and allows for programmability and flexibility by decoupling the control plane from the forwarding plane. With SDN, network administrators can dynamically control network behavior through a centralized controller, simplifying network management and enabling rapid innovation.

Synergizing BGP and SDN

When BGP and SDN converge, the result is a potent combination that transcends the limitations of traditional networking. SDN’s centralized control plane empowers network operators to control BGP routing policies dynamically, optimizing traffic flow and enhancing network performance. By leveraging SDN controllers to manipulate BGP attributes, operators can quickly implement traffic engineering, load balancing, and security policies.

The Role of SDN

In contrast to the decentralized control logic that underpins the construction of the Internet as a complex bundle of box-centric protocols and vertically integrated solutions, software-defined networking (SDN) advocates the separation of control logic from hardware and its centralization in software-based controllers. Introducing innovative applications and incorporating automatic and adaptive control into these fundamental tenets can ease network management and enhance user experience.

Recap Technology: EBGP over IBGP

EBGP, or External Border Gateway Protocol, is a routing protocol typically used between different autonomous systems (AS). It facilitates the exchange of routing information between these AS, allowing efficient data transmission across networks. EBGP’s primary characteristic is that it operates between routers in different AS, enabling interdomain routing.

IBGP, or Internal Border Gateway Protocol, operates within a single autonomous system (AS). It establishes peering relationships between routers within the same AS, ensuring efficient routing within the network. Unlike EBGP, IBGP does not involve exchanging routes between different AS; instead, it focuses on sharing routing information between routers within the same AS.

While both EBGP and IBGP serve to facilitate routing, there are crucial differences between them. One significant distinction lies in the scope of their operation. EBGP connects routers across different AS, making it ideal for interdomain routing. On the other hand, IBGP connects routers within the same AS, providing efficient intradomain routing.

EBGP is commonly used by internet service providers (ISPs) to exchange routing information with other ISPs, ensuring global reachability. It enables autonomous systems to learn about and select the best paths to reach specific destinations. IBGP, on the other hand, helps maintain synchronized routing information within an AS, preventing routing loops and ensuring efficient internal traffic flow.

BGP Configuration

Recap Technology: BGP Route Reflection

Understanding BGP Route Reflection

BGP (Border Gateway Protocol) is a crucial routing protocol in large-scale networks. However, route propagation can become cumbersome and resource-intensive in traditional BGP setups. BGP route reflection offers an elegant solution by reducing the number of full-mesh connections needed in a network.

By implementing BGP route reflection, network administrators can achieve significant advantages. Firstly, it reduces resource consumption by eliminating the need for every router to maintain full mesh connectivity. This leads to improved scalability and reduced overhead. Additionally, it enhances network stability and convergence time, ensuring efficient routing updates.

To implement BGP route reflection, several key steps need to be followed. Firstly, identify the routers that will act as route reflectors in the network. These routers should have sufficient resources to handle the increased routing information. Next, configure the route reflectors and their respective clients, ensuring proper peering relationships. Finally, monitor and fine-tune the route reflection setup to optimize performance.

Challenges to Networking

Over the past few years, there has been a growing demand for a new approach to networking to address the many issues associated with current networks. According to the SDN approach, networking operations can be simplified, network management can be optimized, and innovation and flexibility can be introduced.

According to Kim and Feamster (2013), four key reasons can be identified for the problems encountered in managing existing networks:

(1) Complex and low-level network configuration: Network configuration is a distributed task typically configured vendor-specific at the low level. Moreover, network operators constantly change configurations manually due to the rapid growth of the network and changing networking conditions, adding complexity and introducing additional configuration errors to the configuration process.

(2) Growing complexity and dynamic network state: networks are becoming increasingly complex and more extensive. Moreover, as mobile computing trends continue to develop and network virtualization (Bari et al. 2013; Alam et al. 2020) and cloud computing (Zhang et al. 2010; Sharkh et al. 2013; Shamshirband et al. 2020) become more prevalent, the networking environment becomes even more dynamic as hosts are constantly moving, arriving and departing due to the flexibility offered by virtual machine migration, which results in a rapid and significant change of traffic patterns and network conditions.

(3) Exposed complexity: today’s large-scale networks are complicated by distributed low-level network configuration interfaces that expose great complexity. Many control and management features are implemented in hardware, which generates this complexity.

(4) Heterogeneous: Current networks contain many heterogeneous network devices, including routers, switches, and middleboxes of various kinds. As a result, network management becomes more complex and inefficient because each appliance has its proprietary configuration tools.

Because legacy networks’ static, inflexible architecture is ill-suited to cope with today’s increasingly dynamic networking trends and meet modern users’ QoE expectations, network management is becoming increasingly challenging. As a result, complex, high-level policies must be adopted to adapt to current networking environments, and network operations must be automated to reduce the tedious work of low-level device configuration.

Traffic Engineering

Networks with multiple Border Gateway Protocol (BGP) Autonomous Systems (ASNs) under the same administrative control implement traffic engineering with policy configurations at border edges. Policies are applied on multiple routers distributedly, which can be hard to manage and scale. Any per-prefix traffic engineering changes may need to occur on various devices and levels.

A new BGP Software-Defined Networking (SDN) solution introduced by P. Lapukhov and E. Nkposong proposes a centralized routing model. It introduces the concept of a BGP SDN controller, also known as an SDN BGP controller with a routing control platform. No protocol extensions or additional protocols are needed to implement the SDN architecture. BGP is employed to push down new routes and peers iBGP with all existing BGP routers.

BGP-only Network

A BGP-only network has many advantages, and this solution promotes a more stable Layer 3-only network, utilizing one control plane protocol – BGP. BGP captures topology discovery and links up/down events. BGP can push different information to different BGP speakers, while an IGP has to flood the same LSA throughout the IGP domain.

For additional pre-information, you may find the following helpful:

  1. OpenFlow Protocol
  2. What Does SDN Mean
  3. BGP Port 179
  4. WAN SDN

BGP SDN

BGP Peering Session Overview

In BGP terminology, a BGP neighbor relationship is called a peer relationship, unlike OSPF and EIGRP, which implement their transport mechanism. In place of TCP, BGP utilizes BGP TCP port 179 as its transport protocol. A BGP peering session can only be established between two routers after a TCP session has been established between them. Selecting a BGP session consists of establishing a TCP session and exchanging BGP-specific information to establish a BGP peering session.

A TCP session operates on a client/server model. On a specific TCP port number, the server listens for connection attempts. Upon hearing the server’s port number, the client attempts to establish a TCP session. Next, the client sends a TCP synchronization (TCP SYN) message to the listening server to indicate that it is ready to send data.

Upon receiving the client’s request, the server responds with a TCP synchronization acknowledgment (TCP SYN-ACK) message. Finally, the client acknowledges receipt of the SYN-ACK packet by sending a simple TCP acknowledgment (TCP ACK). TCP segments can now be sent from the client to the server. As part of this process, TCP performs a three-way handshake.

BGP explained
Diagram: BGP explained. The source is IPcisco.

So, how does BGP work? BGP is a path-vector protocol that stores routes in the Routing Information Bases (RIBs). The RIB within a BGP speaker consists of three parts:

  1. The Adj-RIB-In,
  2. The Loc-RIB,
  3. The Adj-RIB-Out.

The Adj-RIB-In stores routing information learned from the inbound UPDATE messages advertised by peers to the local router. The routes in the Adj-RIB-In define routes that are available to the path decision process. The Loc-RIB contains routing information the local router selected after applying policy to the routing information in the Adj-RIB-In.

The Emergence of BGP in SDN:

Software-defined networking (SDN) introduces a paradigm shift in managing and operating networks. Traditionally, network devices such as routers and switches were responsible for handling routing decisions. However, with the advent of SDN, the control plane is decoupled from the data plane, allowing for centralized management and control of the network.

BGP plays a crucial role in the SDN architecture by acting as a control protocol that enables communication between the controller and the network devices. It provides the intelligence and flexibility required for orchestrating network policies and routing decisions in an SDN environment.

Layer-2 and Layer-3 Technologies

Traditional forwarding routing protocols and network designs comprise a mix of Layer 2 and 3 technologies. Topologies resemble trees with different aggregation levels, commonly known as access, aggregation, and core. IP routing is deployed at the top layers, while Layer 2 is in the lower tier to support VM mobility and other applications requiring Layer 2 VLANs to communicate.

Fully routed networks are more stable as they confine the Layer 2 broadcast domain to certain areas. Layer 2 is segmented and confined to a single switch, usually used to group ports. Routed designs run Layer 3 to the Top of the Rack (ToR), and VLANs should not span ToR switches. As data centers grow in size, the stability of IP has been preferred over layer 2 protocols.

  • A key point: Traffic patterns

Traditional traffic patterns leave the data center, known as north-to-south traffic flow. In this case, conventional tree-like designs are sufficient. Upgrades consist of scale-out mechanisms, such as adding more considerable links or additional line cards. However, today’s applications, such as Hadoop clusters, require much more server-to-server traffic, known as east-to-west traffic flow.

Scaling up traditional tree topologies to match these traffic demands is possible but not an optimum way to run your network. A better choice is to scale your data center horizontally with a CLOS topology ( leaf and spine ), not a tree topology.

Leaf and spine topologies permit equidistant endpoints and horizontal scaling, resulting in a perfect combination for optimum east-to-west traffic patterns. So, what layer 3 protocol do you use for your routing design? An Interior Gateway Protocol (IGP), such as ISIS or OSPF? Or maybe BGP? BGP’s robustness makes it a popular Layer 3 protocol for reducing network complexity.

How BGP works with BGP SDN: Centralized forwarding

What is BGP protocol in networking? Regarding internal data structures, BGP is less complex than a link-state IGP. Instead of forming adjacency maintenance and controls, it runs all its operations over Transmission Control Protocol (TCP) and uses TCP’s robust transport mechanism.

BGP has considerably less flooding overhead than IGPs, with a single flooding domain propagation scope. For these reasons, BGP is great for reducing network complexity and is selected as this SDN solution’s singular control plane mechanism.

Peter has written a draft called “Centralized Routing Control in BGP Networks Using Link-State Abstraction,” which discusses the use case of BGP for centralized routing control in the network.

The main benefit of the architecture is centralized rather than distributed control. There is no need to configure policies on multiple devices. All changes are made with an API in the controller.

BGP SDN
Diagram: BGP SDN. The inner workings.

A link-state map 

The network looks like a collection of BGP ASN, and the entire routing is done with BGP only. First, BGP builds a link-state map of the network in the controller memory.

Then, they use BGP to discover the topology and notice link-up and link-down events. Instead of installing a 5-tuple that can install flows based on the entire IP header, the BGP SDN solution offers destination-based forwarding only. For additional granularity, implement BGP flow spec, RFC 55745, entitled “Dissemination of Flow Specification Rules.” 

Routing Control Platform

The proposed method was inspired by the Routing Control Platform (RCP). The RCP platform uses a controller-based function and selects BGP routes for the routers in an AS using a complete view of the available routes and IGP topology. The RCP platform has properties similar to those of the BGP SDN solution.

Both run iBGP peers to all routers in the network and influence the default topology by changing the controller and pushing down new routes. However, a significant difference is that the RCP has additional IGP peerings. It’s not a BGP-only network. BGP SDN promotes a single control plane of BGP without any IGPs.

BGP detects health, builds a link-state map, and represents the network to a third-party application as multiple topologies. You can map prefixes to different topologies and change link costs from the API.

Multi-Topology view

The agent builds the link-state database and presents a multi-topology view of this data to the client applications. You may clone this topology and give certain links higher costs, mapping some prefixes to this new non-default topology. The controller pushes new routes down with BGP.

The peering is based on iBGP, so new routes are set with a better Local Preference, enabling them to be selected higher in the BGP path decision process. It is possible to do this with eBGP, but iBGP can be more accessible. With iBGP, you don’t need to care about the next hops.

BGP and OpenFlow

What is OpenFlow? BGP works like OpenFlow and pushes down the forwarding information. It populates routes in the forwarding table. Instead of using BGP in a distributed fashion, they centralize it. One main benefit of using BGP over OpenFlow is that you can shut the controller down, and regular BGP operation continues on the network.

But if you transition to an OpenFlow configuration, you cannot roll back as quickly as you could with BGP. Using BGP inband has great operational benefits. It is a great design by P. Lapukhov. There is no need to deploy BGP-LS or any other enhancements to BGP.

Future Outlook: As the demand for more agile and efficient networks continues to grow, BGP SDN is expected to play a pivotal role in shaping the future of networking. Its ability to simplify network management, enhance scalability, and improve security makes it an ideal choice for organizations seeking to modernize their network infrastructure.

BGP SDN represents a significant advancement in networking technology, allowing organizations to build agile, scalable, and secure networks. By centralizing control and leveraging BGP’s intelligence, SDN has the potential to revolutionize how networks are managed and operated. As the industry embraces SDN, BGP will continue to play a crucial role in enabling the next generation of network infrastructure.

Summary: BGP SDN

In the ever-evolving networking world, two key technologies have emerged as game-changers: Border Gateway Protocol (BGP) and Software-Defined Networking (SDN). In this blog post, we delved into the intricacies of these powerful tools, exploring their functionalities, benefits, and impact on the networking landscape.

Understanding BGP

BGP, an exterior gateway protocol, plays a crucial role in enabling communication between different autonomous systems on the internet. It allows routers to exchange information about network reachability, facilitating efficient routing decisions. With its robust path selection mechanisms and ability to handle large-scale networks, BGP has become the de facto protocol for inter-domain routing.

Exploring SDN

SDN, on the other hand, represents a paradigm shift in network architecture. SDN centralizes network management and provides a programmable and flexible infrastructure by decoupling the control plane from the data plane. SDN empowers network administrators to dynamically configure and manage network resources through controllers and open APIs, leading to greater automation, scalability, and agility.

The Synergy Between BGP and SDN

While BGP and SDN are distinct technologies, they are not mutually exclusive. They can complement each other to enhance network performance and efficiency. SDN can leverage BGP’s routing capabilities to optimize traffic flows and improve network utilization. Conversely, BGP can benefit from SDN’s centralized control, enabling faster and more adaptive routing decisions.

Benefits and Challenges

The adoption of BGP and SDN brings numerous benefits to network operators. BGP provides stability, scalability, and fault tolerance in inter-domain routing, ensuring reliable connectivity across the internet. SDN offers simplified network management, quick provisioning, and the ability to implement security policies at scale. However, implementing these technologies may also present challenges, such as complex configurations, interoperability issues, and security concerns that need to be addressed.

Conclusion:

In conclusion, BGP and SDN have revolutionized the networking landscape, offering unprecedented control, flexibility, and efficiency. BGP’s role as the backbone of inter-domain routing, combined with SDN’s programmability and centralized management, paves the way for a new era of networking. As technology advances, a deep understanding of BGP and SDN will be essential for network professionals to adapt and thrive in this rapidly evolving domain.

What does SDN mean

BGP has a new friend – BGP-Based SDN

by Blog

BGP-Based SDN

The world of networking continues to evolve rapidly, with new technologies and approaches emerging to meet the growing demands of modern communication. Two such technologies, BGP (Border Gateway Protocol) and SDN (Software-Defined Networking), have gained significant attention for their impact on network flexibility and management. In this blog post, we will delve into the fascinating intersection of BGP and SDN, exploring how they work together to empower network administrators and optimize network operations.

Border Gateway Protocol (BGP) serves as the backbone of the internet, facilitating the exchange of routing information between networks. BGP enables dynamic routing, allowing routers to determine the best paths for data transmission based on various factors such as network policies, path preferences, and traffic conditions. It plays a crucial role in inter-domain routing, where multiple networks connect and exchange data.

Software-Defined Networking (SDN) introduces a paradigm shift in network management by decoupling the control plane from the data plane. In traditional networks, network devices such as switches and routers possess both control and data plane functionalities. SDN separates these functions, with a centralized controller managing the network's behavior and forwarding decisions. The data plane, consisting of switches and routers, simply follows the instructions provided by the controller.

When BGP and SDN converge, we unlock a new realm of network possibilities. SDN's centralized control and programmability complement BGP's routing capabilities, offering enhanced flexibility and control over network operations. By leveraging SDN controllers, network administrators can dynamically adjust BGP routing policies, optimize traffic flows, and respond to changing network conditions in real-time. This dynamic interaction between BGP and SDN empowers organizations to adapt their networks to ever-evolving requirements efficiently.

The combination of BGP and SDN brings forth several advantages and opens up exciting use cases. Network operators can implement traffic engineering techniques to optimize network paths, improve performance, and minimize congestion. They can also utilize SDN's programmability to automate BGP configuration and provisioning, reducing human errors and accelerating network deployment. Additionally, BGP-SDN integration facilitates the implementation of policies for traffic prioritization, security, and load balancing.

The convergence of BGP and SDN represents a powerful synergy that empowers network administrators to achieve unprecedented levels of flexibility, control, and efficiency. By combining BGP's robust routing capabilities with SDN's programmability and centralized management, organizations can adapt their networks swiftly to meet evolving demands. As the networking landscape continues to evolve, the BGP-SDN combination will undoubtedly play a pivotal role in shaping the future of network architecture.

Matt Conran

Highlights: BGP-Based SDN

Understanding BGP and SDN

1- BGP (Border Gateway Protocol) is a routing protocol used to exchange routing information between different networks on the internet. On the other hand, SDN is an architectural approach that separates the control plane from the data plane, allowing network administrators to centrally manage and configure networks through software.

2- BGP-based SDN combines the power of BGP routing with the flexibility and programmability of SDN. Network operators gain enhanced control, scalability, and agility in managing their networks by leveraging BGP as the control plane protocol in an SDN architecture. This marriage of BGP and SDN opens up new possibilities for network automation, policy-driven routing, and dynamic traffic engineering.

3- One critical advantage of BGP-based SDN is its ability to simplify network management. With centralized control and programmability, network operators can define policies and rules that govern their networks’ behavior.

4- This paves the way for efficient traffic engineering and the ability to respond dynamically to changing network conditions. Additionally, BGP-based SDN provides better scalability, allowing for the distribution of control plane functions across multiple controllers.

BGP SDN Challenges:

While BGP-based SDN holds immense potential, it also poses certain challenges. One of the primary concerns is the complexity of implementation and migration. Integrating BGP with SDN requires careful planning and coordination to ensure a smooth transition. Moreover, security and privacy considerations must be considered when deploying BGP-based SDN, as centralized control introduces new attack vectors that must be mitigated.

Critical Components of BGP SDN:

a. BGP Routing: BGP SDN leverages the BGP protocol to manage the routing decisions between different networks. This enables efficient and optimized routing and seamless communication across various domains.

b. SDN Controller: The SDN controller acts as the centralized brain of the network, providing a single point of control and management. It enables network administrators to define and enforce network policies, configure routing paths, and allocate network resources dynamically.

c. OpenFlow Protocol: BGP SDN uses the OpenFlow protocol to communicate between the SDN controller and the network switches. OpenFlow enables the controller to programmatically control the forwarding behavior of switches, resulting in greater flexibility and agility.

Benefits of BGP SDN:

a. Enhanced Flexibility: BGP SDN allows network administrators to tailor their network infrastructure to meet specific requirements. With centralized control, network policies can be easily modified or updated, enabling rapid adaptation to changing business needs.

b. Improved Scalability: Traditional network architectures often struggle to handle the growing demands of modern applications. BGP SDN provides a scalable solution by enabling dynamic allocation of network resources, optimizing traffic flow, and ensuring efficient bandwidth utilization.

c. Simplified Network Management: BGP SDN’s centralized management simplifies network operations. Network administrators can configure, monitor, and manage the entire network from a single interface, reducing complexity and improving overall efficiency.

Use Cases for BGP SDN:

a. Data Centers: BGP SDN is well-suited for data center environments, where rapid provisioning, scalability, and efficient workload distribution are critical. By leveraging BGP SDN, data centers can seamlessly integrate physical and virtual networks, enabling efficient resource allocation and workload migration.

b. Service Providers: BGP SDN allows service providers to offer their customers flexible and customizable network services. It enables the creation of virtual private networks, traffic engineering, and service chaining, resulting in improved service delivery and customer satisfaction.

BGP Technologies in BGP SDN

Understanding BGP Route Reflection

A – 🙂 BGP route reflection is a technique used to alleviate the burden of full-mesh connectivity in BGP networks. Traditionally, in a fully meshed BGP configuration, all routers must establish a direct peer-to-peer connection with every other router, resulting in complex and resource-intensive setups. Route reflection introduces a hierarchical approach that reduces the number of required connections, providing a more scalable alternative.

B – 🙂 Route reflectors act as centralized points within a BGP network and reflect and propagate routing information to other routers. They collect BGP updates from their clients and reflect them to other clients, ensuring a simplified and efficient distribution of routing information. Route reflectors maintain the overall consistency of the BGP network while reducing the number of required peer connections.

C- 🙂 To implement BGP route reflection, one or more routers within the network need to be configured as route reflectors. These route reflectors should be strategically placed to ensure efficient routing information dissemination. Clients, also known as non-route reflectors, establish peering sessions with the route reflectors and send their BGP updates to be reflected. Route reflector clusters can also be formed to provide redundancy and load balancing.

Understanding BGP Multipath

BGP multipath, short for Border Gateway Protocol multipath, is a feature that enables the use of multiple paths for traffic forwarding in a network. Traditionally, BGP selects a single best path based on attributes like AS path length, origin type, and MED (Multi-Exit Discriminator) value. However, with BGP multipath, multiple paths can be utilized simultaneously, distributing traffic across multiple links.

Enhanced Network Performance: BGP multipath optimizes network performance by load-balancing traffic using multiple paths. This helps avoid congestion on specific links and ensures efficient utilization of available bandwidth, resulting in faster and more reliable data transmission.

Improved Resilience: BGP multipath enhances network resilience by providing redundancy. In case of link failures or congestion, traffic can be automatically rerouted through alternative paths, minimizing downtime and ensuring continuous connectivity. This dramatically improves the overall reliability of the network infrastructure.

Prefer EBGP over iBGP

Understanding BGP Basics

As a path-vector protocol, BGP differs from other routing protocols in its ability to make routing decisions based on multiple criteria. It establishes connections between autonomous systems (AS) and exchanges routing information to determine the best path for data to follow. By grasping the fundamentals of BGP, we can better comprehend the path selection process.

BGP considers a range of attributes when selecting the most optimal routing path. These attributes include but are not limited to the AS path length, the route’s origin, the next-hop IP address, and various other metrics. Understanding these factors allows network engineers to fine-tune BGP path selection and optimize the data flow.

SDN and BGP

BGP SDN, or Border Gateway Protocol Software-Defined Networking, combines two powerful technologies: the Border Gateway Protocol (BGP) and Software-Defined Networking (SDN). BGP, a routing protocol, facilitates inter-domain routing, while SDN provides centralized control and programmability of the network. Together, they offer a dynamic and adaptable networking environment.

While Border Gateway Protocol (BGP) was initially designed to connect networks operated by different companies, such as transit service providers, providers of large-scale data centers discovered that it could be used for spine and leaf fabrics.

BGP can also be used as an SDN because it already runs on all routers. According to the diagram below, each router in the fabric is connected to an iBGP controller.

Augmented Model

After the iBGP sessions are established, the controller can read the entire topology to determine which path the flow should be pinned to and which flows should avoid the path over which the flow is passing.

An augmented model uses a centralized control plane that interacts directly with a distributed control plane (eBGP). Interestingly, the same protocol used to push policy (the southbound interface) is also used to discover and distribute topology and reachability information in this hybrid model implementation.

The Role of SDN

Before we start our journey on BGP SDN, let us first address what SDN means. The Software-Defined Networking (SDN) framework has a large and varied context. Multiple components, including the OpenFlow protocol, may or may not be used. Some evolving SDN use cases leverage the capabilities of the OpenFlow protocol, while others do not require it.

OpenFlow is only one of those protocols within the SDN architecture. This post addresses using the Border Gateway Protocol (BGP) as the transfer protocol between the SDN controller and forwarding devices, enabling BGP-based SDN, also known as BGP SDN.

BGP and OpenFlow

– BGP and OpenFlow are monolithic, meaning they are not used simultaneously. Integrating BGP to SDN offers several use cases, such as DDoS mitigation, exception routing, forwarding optimizations, graceful shutdown, and integration with legacy networks.

– Some of these use cases are available using OpenFlow Traffic Engineering; others, like graceful shutdown and integration with the legacy network, are easier to accomplish with BGP SDN. 

– When BGP and OpenFlow are combined, they create a powerful synergy that enhances network control and performance. BGP provides the foundation for inter-domain routing and connectivity, while OpenFlow facilitates granular traffic engineering within a domain.

– Together, they enable network administrators to fine-tune routing decisions, balance traffic across multiple paths, and enforce quality of service (QoS) policies.

BGP Add Path Feature

The BGP Add Path feature is designed to address the limitations of traditional BGP routing, where only the best path to a destination is advertised. With Add Path, BGP routers can advertise multiple paths to a destination network, providing increased routing options and allowing for more efficient traffic engineering. 

Introducing the Add Path feature brings several benefits to network administrators and service providers. Firstly, it enables better load balancing and traffic distribution across multiple paths, leading to optimized network utilization. Additionally, it enhances network resiliency by providing alternative paths in case of link failures or congestion. 

Before you proceed, you may find the following post helpful:

  1. BGP Explained
  2. Transport SDN
  3. What is OpenFlow
  4. Software Defined Perimeter Solutions
  5. WAN SDN
  6. OpenFlow And SDN Adoption
  7. HP SDN Controller

BGP-Based SDN

What is BGP?

What is the BGP protocol in networking? Border Gateway Protocol (BGP) is the routing protocol under the Exterior Gateway Protocol (EGP) category. In addition, we have separate protocols, which are Interior Gateway Protocols (IGPs). However, IGP can have some disadvantages.

Firstly, policies are challenging to implement with an IGP because of the need for more flexibility. Usually, a tag is the only tool available that can be problematic to manage and execute on a large-scale basis. In the age of increasingly complex networks in both architecture and services, BGP presents a comprehensive suite of knobs to deal with complex policies, such as the following:

• Communities

• AS_PATH filters

• Local preference

• Multiple exit discriminator (MED

Highlighting BGP-based SDN 

BGP-based SDN involves two main solution components that may be integrated into several existing BGP technologies. First, we have an SDN controller component that speaks BGP and decides what needs to be done. Second, we have a BGP originator component that sends BGP updates to the SDN controller and other BGP peers. For example, the controller could be a BGP software package running on Open Daylight. BGP originators are Linux daemons or traditional proprietary vendor devices running the BGP stack.

What does SDN mean
Diagram: What does SDN mean with BGP SDN?

Creating an SDN architecture

To create the SDN architecture, these components are integrated with existing BGP technologies, such as BGP FlowSpec (RFC 5575), L3VPN (RFC4364), EVPN (RFC 7432), and BGP-LS. BGP FlowSpec distributes forwarding entries, such as ACL and PBR, to devices’ TCAMs. L3VPN and EVPN offer the mechanism to integrate with legacy networks and service insertion. BGP-LS extracts IGP network topology information and passes it to the SDN controller via BGP updates.

**Central policy, visibility, and control**

Introducing BGP into the SDN framework does not mean a centralized control plane. We still have a central policy, visibility, and control, but this is not a centralized control plane. A centralized control plane would involve local control plane protocols establishing adjacencies or other ties to the controller. In this case, the forwarding devices outright require the controller to forward packets; forwarding functionality is limited when the controller is down.

If the BGP SDN controller acts as a BGP route reflector, all announcements go to the controller, but the network runs fine without it. The controller is just adding value to the usual forwarding process. BGP-based SDN architecture augments the network; it does not replace it.

Decentralizing the control plane is the only way; look at Big Switch and NEC’s SDN design changes over the last few years. Centralized control planes cannot scale.

Why use BGP?

BGP is well-understood and field-tested. It has been extended on many occasions to carry additional types of information, such as MAC addresses and labels. Technically, BGP can be used as a replacement for Label Distribution Protocol (LDP) in an MPLS core. Labels can be assigned to IPv6 prefixes (6PE) and labeled switched across an IPv4-only MPLS core.

BGP is very extensible. It started with IPv4 forwarding, and address families were added for multicast and VPN traffic. Using multiple addresses inside a single BGP process was widely accepted and implemented as a core technology. The entire Internet is made up of BGP, and it carries over 500,000 prefixes. It’s very scalable and robust. Some MPLS service providers are carrying over 1 million customer routes.

The use of open-source BGP daemons

There are many high-quality open-source BGP daemons available. Quagga is one of the most popular, and its quality has improved since it adopted Cumulus and Google. Quagga is a routing suite that provides IGP support for IS-IS and OSPF. Also, a BIRD daemon is available. The implementation is based around Internet exchange points as the route server element. BIRD is currently carrying over 100,000 prefixes.

Using BGP-based SDN on an SDN controller integrates easily with your existing network. You don’t have to replace any existing equipment, deploy the controller, and implement the add-on functionality that BGP SDN offers. It enables a preferred step-by-step migration approach, not a risky big bang OpenFlow deployment.

IGP to the controller?

Why not run OSPF or ISIS to the controller? IS-IS is extendable with TLVs and, too, can carry a variety of information. The real problem is not extensibility but the lack of trust and policy control. IGP extension to the SDN controller with few controls could present a problem. OSPF sends LSA packets; there is no input filter. BGP is designed with policy control in mind and acts as a filter by implementing controls on individual BGP sessions.

BGP offers control on the network side and predicts what the controller can do. For example, the blast radius is restricted if the controller encounters a bug or is compromised. BGP also provides excellent policy mechanisms between the SDN controller and physical infrastructure. 

Introducing BGP-LS

SDN requires complete topology visibility. The picture is incomplete if some topology information is hidden in IGP and other NLRIs in BGP. If you have an existing IGP, how do you propagate this information to the BGP controller? Border Gateway Protocol Link-State (BGP-LS) is cleaner than establishing an IGP peering relationship with the SDN controller. 

BGP-LS extracts network topology information and updates it to the BGP controller. Once again, BGPv4 is extended to provide the capability to include the new Network Layer Reachability Information (NLRI) encoding format. It sends information from IS-IS or OSPF topology database through BGP updates to the SDN controller. BGP-LS can configure the session to be unidirectional and stop incoming updates to enhance security between the physical and SDN worlds.

A key point: SDN controller cannot leak information back

As a result, the SDN controller cannot leak information back into the running network. BGP-LS is a relatively new concept. It focuses on the mechanism to export IGP information and does not describe how the SDN controller can use it. Once the controller has the complete topology information, it may be integrated with traffic engineers and external path computing solutions to interact with information usually only carried by an IGP database.

For example, the Traffic Engineering Database (TED), built by ISIS and OSPF-TE extensions, is typically distributed by IGPs within the network. Previously, each node maintained its own TED, but now, this can be exported to a BGP RR SDN application for better visibility.

BGP scale-out architectures

SDN controller will always become the scalability bottleneck. It can scale better when it’s not participating in data plane activity, but eventually, it will reach its limits. Every controller implementation eventually hits this point. The only way to grow is to scale out. 

Reachability and policy information is synchronized between individual controllers. For example, reachability information can be transferred and synchronized with MP-BGP, L3VPN for IP routing, or EVPN for layer-2 forwarding.

BGP SDN

Utilizing BGP between controllers offers additional benefits. Each controller can be placed in a separate availability zone, and tight BGP policy controls are implemented on BGP sessions connecting those domains, offering a clean failure domain separation.

An error in one available zone is not propagated to the next available zone. BGP is a very scalable protocol, and the failure domains can be as large as you want, but the more significant the domain, the longer the convergence times. Adjust the size of failure domains to meet scalability and convergence requirements. 

BGP SDN combines the power of BGP routing and SDN to create a networking paradigm that enhances flexibility, scalability, and manageability. By leveraging BGP SDN, organizations can build dynamic networks that adapt to their changing needs and optimize resource utilization. As the demand for faster, more reliable, and flexible networks continues to grow, BGP SDN is poised to play a critical role in shaping the future of network infrastructure.

Summary: BGP-Based SDN

In today’s rapidly evolving technological landscape, software-defined networking (SDN) has emerged as a groundbreaking approach to network management. One of the key components within the realm of SDN is the Border Gateway Protocol (BGP). In this blog post, we delved into the world of BGP SDN, exploring its significance, functionality, and how it transforms traditional networking architectures.

Understanding BGP

BGP, or Border Gateway Protocol, is a routing protocol that facilitates the exchange of routing information between different autonomous systems (AS). It plays a crucial role in determining the optimal path for data packets to traverse across the internet. Unlike other routing protocols, BGP operates on a policy-based routing model, allowing network administrators to have granular control over traffic flow and network policies.

The Evolution of SDN

To comprehend the importance of BGP SDN, it is essential to understand the evolution of software-defined networking. SDN revolutionizes traditional network architectures by decoupling the control plane from the underlying physical infrastructure. This separation enables centralized network control, programmability, and dynamic configuration, enhancing flexibility and scalability.

BGP in the SDN Paradigm

Within the SDN framework, BGP plays a pivotal role in interconnecting different SDN domains, providing a scalable and flexible solution for routing between virtual networks. By incorporating BGP into the SDN architecture, organizations can achieve dynamic network provisioning, traffic engineering, and efficient handling of network policy changes.

Benefits of BGP SDN

The integration of BGP within the SDN paradigm brings forth numerous benefits. Firstly, it enables seamless interoperability between SDN and traditional networking environments, ensuring a smooth transition towards software-defined infrastructures. Additionally, BGP SDN empowers network administrators with enhanced control and visibility, simplifying the management of complex network topologies and policies.

Conclusion:

In conclusion, BGP SDN represents a significant milestone in the networking industry. Its ability to merge the power of BGP with the flexibility of software-defined networking opens new horizons for network management. By embracing BGP SDN, organizations can achieve greater agility, scalability, and control over their networks, ultimately leading to more efficient and adaptable infrastructures.