How does BGP enable interdomain routing on the internet?

BGP is the protocol that stitches networks from different operational domains. Not only for Internet prefixes but since it became multi protocol (MP-BGP) it has been used as a Swiss Army knife to exchange network reachability data for many different applications, from VPNs to traffic filtering via Flowspec. Unfortunately it’s not secure by design and many proposals to solve that have been made, but as of 2024 none have become de facto standards.

O BGP, ou Protocolo de Gateway da Borda, é um protocolo de roteamento interdomínio que permite que os roteadores de rede compartilhem informa??es de roteamento entre si. Isso permite que os pacotes de dados sejam roteados de uma rede para outra. O BGP é usado para rotear dados entre sistemas aut?nomos (ASs). Um AS é uma rede controlada por uma única organiza??o. A Internet é composta de milhares de ASs. O BGP funciona trocando mensagens de atualiza??o de rota entre os roteadores. Essas mensagens incluem informa??es sobre as redes que cada roteador conhece, bem como as melhores rotas para essas redes.

BGP Is a dynamic routing protocol that is common used like eBGP for AS routing Exchange with other AS. It's possible to use inside the same AS like iBGP, all the router have se same AS Number. Another common use Is the MP-BGP (control Plane/super backbone) multiprotocol BGP for route redistibution from OSPF in a MPLS infrastructure for L3 client network.

BGP is essential for ensuring efficient and reliable communication between different networks, allowing them to dynamically adapt to changes in network topology and availability. It is a key component in the functioning of the global internet infrastructure. BGP operates at the application layer of the Internet Protocol (IP) suite and is designed to make routing decisions based on path, network policies, and rules.

An important point to consider when using BGP is utilizing the route reflector to minimize the number of peering relationship instead of establishing full mesh.

Border Gateway Protocol (BGP) is an interdomain routing protocol designed to provide loop-free routing between separate routing domains that contain independent routing policies (autonomous systems). The Cisco software implementation of BGP version 4 includes multiprotocol extensions to allow BGP to carry routing information for IP multicast routes and multiple Layer 3 protocol address families including IP Version 4 (IPv4), IP Version 6 (IPv6), and Virtual Private Networks version 4 (VPNv4).

BGP works by establishing sessions between BGP peers, exchanging routing information to build a comprehensive view of network paths. BGP routers use this information to determine the best path to route traffic based on policies and metrics like path length, reliability, and network policies. In practice, I've configured BGP in complex scenarios where multiple networks interconnect, observing how BGP's dynamic nature allows networks to adapt to changes quickly, such as rerouting traffic in case of a link failure.

BGP works by allowing routers in different autonomous systems to communicate and exchange information about reachable IP prefixes. Routers establish peering sessions, exchange route updates, and use decision processes to determine the best paths based on attributes. BGP enables efficient routing, path selection, and network stability in the global internet.

From my experience managing large global networks, we use BGP to implement traffic engineering strategies and to enforce routing policies. This includes controlling inbound and outbound traffic, load balancing, traffic shaping, and prioritizing certain paths over others. We do this by exchanging routing information across AS and selecting the best paths, BGP enables routers on different AS to learn routes to networks throughout the internet. This allows data packets to traverse multiple AS to reach their destinations. The AS use BGP to announce the networks they can reach and the preferred paths to reach those networks. This information includes network prefixes (IP address blocks) and associated attributes.

BGP speakers will exchange routes/prefixes as between its neighbours. This is the primary function of BGP. With this, ASN1 will tell ASN2 which other ASNs are on their network and what prefixes it (ASN1) can route to... and vice versa with ASN2. An important feature of BGP is the support of "Communities" which can add further information and value to the prefix being advertised. Another important feature.. BGP plays a huge role in "path-selection".

BGP offers several benefits: it provides robust, scalable interdomain routing; supports a highly available network architecture; allows for policy-based routing decisions; and facilitates internet connectivity redundancy. My experience has shown that BGP's ability to handle network failures and changes dynamically is invaluable for maintaining operational continuity in large-scale networks. Additionally, BGP's flexibility in policy implementation enables tailored traffic routing, optimizing performance and cost.

Acknowledging the outlined benefits of BGP in interdomain routing, it's essential to delve into the nuanced challenges associated with its implementation: ? ??????????????????????: While each AS can define its routing policies, the potential downside lies in the complexity of managing policies. Striking a balance between flexibility and maintaining a coherent routing environment demands careful consideration. ? ????????????????????????????????: Disparities in BGP implementations among various vendors may introduce interoperability challenges. Continuous testing and validation are essential to prevent issues related to inconsistent behavior across diverse networks.

BGP provides efficient routing, scalability, policy control, redundancy, fault tolerance, interdomain routing, traffic engineering, path authentication, and support for Internet multihoming.

BGP exists purely because of its flexibility and agility. From simple network design to a very complex one is the range where BGP can deliver tailor-made routing construct to suit the changing business needs and the rampantly changing digital landscape. It has a excellent record in adaption to network changes, offers wide range of traffic engineering and influencing creative options at disposal, you just need to ignite your creatively to turn on the agility!

W/o BGP equals no internet today. A whole host of features are now found in BGP from providing redundancy, resiliency to traffic management/steering etc. At the same time however it also creates exploits that needs to be attention and risk management.

I started my career as an ISP network engineer playing with BGP peering and internet routing on a daily basis. Despite its proven capabilities, BGP still has challenges for Internet routing. An ISP doesn’t have the control over how its traffic is routed through the Internet. Or very little control with BGP communities. By design with BGP anyone could announce that they own Internet prefixes without any ownership verification which leads to BGP hijacking attacks. RPKI is introduced to fix this issue but RPKI should be first 1/ adopted by the whole Internet community and second 2/ RPKI is only used to validate the route origin but not the route path which will not prevent a malicious AS to conduct BGP hijacking..

I don’t agree that BGP is complex. It’s one of the simplest routing protocols out there. Complexity is added due to traffic engineering and routing policies, but that’s not BGP’s fault. The major issue with BGP is that it’s insecure by nature. Peering agreements are established over poorly maintained routing information data from different IRR’s (Internet Routing Registries) such as RADB. Origin validation is now accomplished via RPKI in a globally coordinated effort amongst the different RIR’s, but path validation is still not a reality and we see hijacks taking place every single day in the Internet.

Despite its advantages, BGP has challenges: it can be complex to configure and manage, is vulnerable to misconfiguration and malicious attacks like route hijacking, and doesn't inherently encrypt traffic, posing security risks. I've encountered situations where a misconfigured BGP route caused traffic to be blackholed, demonstrating the need for meticulous management and monitoring. The protocol's complexity and the large global routing table also present scalability and performance challenges.

Network operators encounter various challenges when dealing with BGP, such as complex configuration and management, security vulnerabilities, limited route optimization and traffic engineering capabilities, slow convergence time, concerns regarding routing table growth and scalability, interoperability issues, complicated monitoring and troubleshooting, and the need for scalable route filtering. Addressing these challenges entails having technical expertise, dedicated resources, continuous monitoring, and implementing best practices for BGP configuration and management.

One of the Major challenges of BGP is that it lacks built-in security and validation mechanisms, which in turn makes it vulnerable to misconfigurations, attacks, and hijacks. Additionally, BGP does not consider network performance or quality of service (QoS) metrics, such as latency, bandwidth, or congestion etc.

BGP is integral to modern network architectures like SD-WAN and cloud networking. In SD-WAN, BGP is used for efficient route distribution across wide area networks, optimizing path selection and redundancy. In cloud environments, BGP is often used for routing between the cloud and on-premises data centers, enabling seamless, scalable cloud integration. My work with cloud migrations has often involved leveraging BGP to ensure reliable connectivity and optimal path selection between cloud services and enterprise networks.

SD-WAN?? SDN?? I think we're getting ahead of ourselves if we're talking to newcomers. But .. think of SDN as a peculiar portal build that talks / learns from -your- network and the protocols that operate in it. And depending on how advance your SDN/Portal is, it can tell you (and possibly predict) how well traffic is flowing on it. At the same time, it can become a UI for provisioning, migrations and re-configuring links. All this made only possible if the underlying protocols (BGP) is well understood. Many other protocols can also be controlled vide SDN/WAN.. eg, MPLS, OSPF, IS-IS etc. Again, it all comes down to how advance your SDN/Portal is.

The BGP protocol was designed to facilitate dynamic routing between different organizations and institutions, many of which manage a considerable number of devices. A collection of devices managed under a single administration is referred to as an Autonomous System (AS). Using the BGP protocol, each AS can execute its own traffic engineering strategies with minimal interaction, often acting unilaterally. SD-WAN is an overlay network that requires connectivity provided by various underlying providers. Therefore, the BGP protocol is a common and well-established method to integrate an overlay service layer with minimal impact or interaction with a wide range of connectivity providers.

BGP is crucial in SD-WAN and cloud environments. In SD-WAN, BGP is used as a routing protocol to establish connectivity and exchange routing information between different branches. It enables dynamic traffic routing across various network connections based on factors like cost, latency, and quality of service. In the cloud, BGP is employed to establish secure connections between on-premises networks and cloud service providers, facilitating efficient routing of traffic. BGP forms the foundation for connectivity management in both SD-WAN and cloud settings, ensuring optimized routing and seamless integration between network domains.

I wouldn’t say BGP relates directly to SD-WAN. It’s mostly used underneath on the service providers networks, but the SD-WAN mesh of tunnels can be routed using any routing protocol, mostly the link state kind of IGP. As for the cloud, BGP can be used to import and export prefixes to the cloud infrastructure.

Learning about BGP involves a mix of theoretical study and practical experience. Start with foundational networking concepts, then move on to specialized BGP resources like books, online courses, and RFCs. Practical experience, whether through real-world configuration or simulated environments, is invaluable. I've found that participating in networking communities and seeking mentorship from experienced professionals accelerates the learning process, providing insights and real-world examples that deepen understanding.

For an immersive dive into BGP mastery, complement theoretical learning from books and blogs with hands-on practice in EVE-NG, an advanced network emulation platform. Create dynamic scenarios, experiment with route reflectors, peer groups, and BGP policies to fortify your skills. Engage with tech forums and communities to amplify your knowledge sharing and troubleshooting prowess. Elevate your BGP game – it's not just about reading, it's about hands-on tech exploration!

El uso de simuladores o Máquinas virtuales para probar recursos y explotar las diferentes capacidades de este protocolo es la base de todo estudio, así se parte en los Institutos más destacados y así mismo se termina de instruir en el tema. Las aplicaciones que permiten simular redes de todo tipo nos permiten explorar en qué situaciones o en que momentos es mejor aplicar ciertas características de enrutamiento comparándolas con otras. Además, muchos vendors e Ingenieros de renombre han escrito libros con paso a paso y formas de aplicar BGP y otros protocolos para su uso básico y avanzado. Partir de la base es el mejor método para aprender cosas nuevas.

BGP's capability to exchange routing information between different AS'es and its flexibility in policy-based decision-making are essential in establishing and maintaining interdomain routing on the internet as It enables the global connectivity and reachability that underpins how data moves and reaches across various networks/destinations.

So, each domain managing hosts and group of Network routers ll be managed by an organization. Looking upon domains from routing perspective, transit and stub domain shall be the classification. Domains shall be interconnected to allow host inside to exchange IP packets with other domains. Such links performs nothing but an interdomain routing over BGP in short. In such cases, a peer relationship gets established between client and provider exchanging packets over interdomain link. Same follows up when provider connects with other large/LD carrier to exchange packets over web.

As I mentioned before, I consider BGP a simple and straightforward protocol. There’s no training of certification that will get you ready for the Internet. That you’ll only learn from hands on experience.

BGP (Border Gateway Protocol) enables Internet interdomain routing. It's a path vector protocol, maintaining paths to reach IP prefixes. Routers in different autonomous systems (ASes) exchange reachability info, using AS paths. BGP routers establish peering for this. They share updates containing reachable IP prefixes and associated AS paths. Path selection factors include AS path length and policies. BGP ensures stability and convergence in global routing, crucial for Internet functionality.

BGP es un protocolo robusto y complejo que permite mantener una comunicación estable y escalable con el resto de la red con la cuál se conecta, pero esto no hace que el protocolo sea infalible. No existe una encriptación de la data que se maneja en este protocolo, por lo que implica una falencia en seguridad que otros protocolos y sistemas de QoS se encargan de proteger y hacen que la red se mantenga estable. De esta misma forma, gracias a BGP se nos permite trazar la información y los paquetes que se manejan en este protocolo para así poder identificar hacia donde va nuestro tráfico y que direcciones o equipos alcanzan las redes con las que trabajamos.