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SDN Router

 

 

SDN Router

The demand for efficient and flexible routing solutions is growing in the rapidly evolving networking world. The emergence of Software-Defined Networking (SDN) has revolutionized the way networks are built and managed. SDN routers, in particular, have emerged as a critical component in modern networks, offering unprecedented control and agility. In this blog post, we will delve into SDN routers’ benefits and how they are transforming the networking landscape.

An SDN router is a fundamental building block of a software-defined network, enabling the separation of the control plane and the data plane. Unlike traditional routers, which have tightly coupled control and data plane functionalities, SDN routers separate these functions, allowing for centralized control and programmability. This decoupling enables network administrators to dynamically control and manage traffic flow, optimize network performance, and implement new services seamlessly.

 

Highlights: SDN Router

  • Changing the network paradigm

The success of SDN makes it clear that operators want to manage networks in a centralized and programmable way. Operating with a central viewpoint brings many advantages to existing networks and for a new data center design guide, significantly enhancing traffic engineering capabilities. However, changing the network paradigm with brand-new technologies comes at an operational and security cost.

  • The Role of Fibbing with OSPF

Fibbing is an OSPF SDN mechanism that controls the forwarding behavior of an unmodified router-speaking OSPF without losing the benefits of distributed routing protocols. It combines the centralized approach of SDN with the advantages of traditional link-state protocols. The workings originate from a combined approach between Princeton University and ETH Zurich. The controller code is available on Github, found at this link.

  • Routing Control

Fibbing is a technique that offers direct control over the router’s forwarding by manipulating the distributed routing protocol. The solution works on the concepts of lying or fibbing to the router to make more effective routing control decisions. In addition, they make OSPF more flexible by adding central control over distributed routing. OSPF operates as usual with shortest path routing, and Fibbing introduces methods to trick the router into computing any path it wants.

 

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

  1. SDN Adoption
  2. SDN Data Center
  3. BGP Port 179
  4. WAN SDN
  5. Forwarding Routing Protocols

 



OSPF SDN.

Key SDN Router Discussion points:


  • Introduction to SDN router and where it can be used.

  • Discussion on OSPF and challenges.

  • What is the role of OSPF SDN?

  • The effect of SDN on OSPF LSAs.

 

Back to Basics With The SDN Router

Highlighting SDN

Software Defined Networking (SDN) is taking the routing control away from the individual network elements and putting it in the hands of a centralized control layer. For instance, an SDN such as OpenFlow lets you choose the correct forwarding information per-flow basis.

This means there need not be any separation on a VLAN level within a data center to enforce traffic separation between tenants. Instead, the controller would have a set of policies that only allow the traffic from within one “VLAN” to be forwarded to other devices within that same “VLAN” on a per source/destination (or flow) basis.

 

Benefits of SDN Routers:

1. Enhanced Network Agility: By centralizing the control plane, SDN routers provide network administrators with complete visibility and control over the network. This enables them to quickly adapt to changing network requirements, allocate resources efficiently, and respond to real-time security threats.

2. Simplified Network Management: SDN routers simplify network management by providing a single interface for configuring, monitoring, and troubleshooting the network. With the ability to programmatically define network policies, administrators can automate routine tasks and reduce the complexity associated with traditional router configurations.

3. Scalability and Flexibility: SDN routers offer unparalleled scalability, allowing networks to grow and accommodate increasing traffic demands efficiently. With programmable routing policies and traffic engineering capabilities, SDN routers enable dynamic network provisioning, ensuring optimal resource utilization and performance across the network.

4. Improved Security: SDN routers provide enhanced security features like fine-grained access control and traffic isolation. By centralizing security policies and implementing them consistently across the network, SDN routers mitigate security risks and provide a robust defense against potential threats.

Real-world Applications:

SDN routers have found wide-ranging applications across various industries. Some notable examples include:

1. Data Centers: SDN routers enable agile and efficient management of large-scale data center networks. By abstracting the network control from the underlying physical infrastructure, administrators can create virtual networks, provision resources on-demand, and implement fine-grained security policies.

2. Wide Area Networks (WAN): SDN routers offer significant advantages in WAN environments. They enable network administrators to optimize traffic routing, dynamically allocate bandwidth, and prioritize critical applications, improving network performance and reducing costs.

3. Internet Service Providers (ISPs): SDN routers empower ISPs to deliver innovative services and offerings to their customers. With programmable routing policies, ISPs can offer tailored services, implement Quality of Service (QoS) guarantees, and ensure optimal utilization of network resources.

 

SDN Router: OSPF SDN

OSPF is still destination-based forwarding, meaning a device will forward all packets with the same destination address to the next hop. Paths are computed as the shortest path over a shared weighted graph. The Fibbing mechanism does not try to change OSPF default behavior. However, the mechanisms involved in the solution enable the forwarding of different flows destined for the same destination over different paths, increasing link utilization and the total available bandwidth. The controller introduces fake nodes and links through standard routing-protocol messages.

 

OSPF SDN: How can I use existing protocols to program my network with SDN?

Routing protocols are an excellent API for programming a router’s state. Vendors may incorporate different implementations and CLI contexts, but they all speak the same protocol and follow RFC guidelines. Routing protocols are well known, and their behaviors have been studied for years.

Vendors have enhanced and optimized OSPF differently, but its framework does not change. Using OSPF in the context of SDN, you are leveraging over 25 years of solid engineering. Combining SDN with existing routing protocols to enhance forwarding behavior is not new.

The first solution was the routing control platform (RCP), proposed by Princeton University and AT&T Labs-Research. The RCP solution has an IGP viewer and a BGP function to provide a central function. More recently, P. Lapukhov & E. Nkposong proposed a centralized routing model and introduced the concept of BGP SDN.

Petre solution uses a BGP controller to manipulate BGP parameters (Local Preference) and influence forwarding. It enables networks to run only BGP routing with enhanced traffic behavior.

 

OSPF SDN

  • How do you move traffic over a less congested link? 

With OSPF-TE, you can change the cost or deploy some other 3rd party product, which is potentially expensive. If you want to change the forwarding state and don’t want to configure complex nested route maps or policy-based routing (PBR), the only remaining resource available to you is the routing protocol.

Fibbing is limited to the semantics of OSPF destination-based forwarding and is less potent than OpenFlow traffic optimizations. You can change the forwarding paths for specific prefixes, but you don’t have OpenFlow’s total traffic engineering flexibility. But you can use the solution with FlowSpec to gain extra granularity.

 

OSPF forwarding address

  • There are two ways to lie to a router: a Global lie and a Local lie.

Fibbing inserts extra Type-5 LSA, allowing you to set a third-party next-hop with the Forwarding Address (FA) feature. Type-5 are external link LSAs used to advertise external routes. They are flooded through the OSPF domain and point packets for those external addresses. The concept of an FA within a Type-5 LSA allows the selection of third-party next hops. The solution relies on third-party next hops to influence packet forwarding.

The FA is usually set to 0.0.0.0, meaning packets should be sent directly to the ASBR. In a Fibbing configured network, Type-5 LSA is injected with an FA to direct traffic to the destination at a better cost; the forwarding address is set with a specific address combined with a preferred metric. The costs can be tweaked to attract more or fewer people.

There are two ways to influence forwarding with Type-5 LSA. One way is where the forwarding address is resolvable by ALL routers in the network. The FA is injected into the IGP, and all nodes can reach it. This method is used to make global decisions.

The other method is to have a locally known FA, influencing individual OSPF router decisions. For this, they create an FA for every next hop in the network, which has to be statically configured. On every router on your network, you need a static host route for each outgoing interface that you need to include for Fibbing. One fake static route per interface needs to be done once. If the FA is configured to be one of these, only that single router will use it.

The benefit of using a Type 5 LSA is that it does not cause a full SPF; it’s the distance vector part of OSPF. The impact is small and linear with the number of LSA. The team at Princeton and Zurich propose the Fibbing solution can scale to 100,000 Type-5 LSA.

Conclusion:

SDN routers have emerged as a cornerstone of modern networking, offering unprecedented control, scalability, and agility. By decoupling the control plane from the data plane, SDN routers enable network administrators to dynamically adapt to changing network requirements, simplify network management, and enhance security. With their wide-ranging applications in data centers, WANs, and ISPs, SDN routers are poised to reshape the networking landscape, ushering in a new era of flexibility and efficiency.