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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.

 

sdn-and-bgp

SDN Traffic Optimizations

 

BGP Inbound Traffic Engineering

 

SDN Traffic Optimizations

In today’s digital age, where data consumption is exponentially increasing, efficient network traffic management has become more critical than ever. Traditional networking approaches often struggle to meet the demand, leading to congestion, latency, and poor performance. However, with the advent of Software-Defined Networking (SDN), network administrators now have powerful tools to optimize network traffic and improve overall network efficiency.

SDN is an innovative networking approach that separates the control and data planes. By centralizing network control in a software-based controller, SDN enables administrators to have a holistic view of the network and implement traffic optimizations seamlessly. This centralized control allows for dynamic traffic routing, load balancing, and prioritization, improving network performance.

 

Highlights: SDN Traffic Optimizations

  • Challenges to Multihoming

Multihoming to different transit providers has become an essential service component at the Internet edge. Multihoming allows you to satisfy several high-level requirements, including redundancy. Redundancy is site or device/link level and protects from a single point of failure.

There are several ways to route and manage traffic in and out of multi-homed sites. Some rely on static routing, while others rely on the routing policy capabilities of the inter-domain routing protocol, Border Gateway Protocol (BGP).

 

You may find the following helpful post for pre-information:

  1. WAN SDN 
  2. TCP IP Optimization
  3. BGP SDN
  4. What is BGP Protocol in Networking
  5. Network Traffic Engineering

 



Inbound Traffic Optimization

Key SDN Traffic Optimizations Discussion Points:


  • Introduction to SDN Traffic Optimizations and what is involved.

  • Highlighting the challenges with BGP inbound traffic engineering.

  • Critical points on how this can be solved.

  • Technical details with a use case that uses LISP protocol.

  • A final point on WAN SDN.

 

Back to basics with BGP

Border Gateway Protocol (BGP) is the routing protocol to exchange routing information across the Internet. BGP is considered the glue of the Internet and is the only protocol designed to deal with a network of the Internet’s size. As a result, BGP is sometimes called a distance-path protocol.

BGP does not look at something as simple as hop count or link costs, but it doesn’t keep track of the complete topology of the entire network either. Instead, BGP accomplishes this through neighbor-peer relationships that must be explicitly configured.

 

  • A key point: Lab guide on BGP

Here we have a sample BGP network that consists of two nodes, BGP Peer 1 and BGP Peer 2. We are running iBGP between these BGP peers, which is done by configuring both peers with the same AS number. In our case, this is AS 1. The command: show ip bgp summary is used to determine the status of a BGP neighbor. Remember that BGP runs over TCP port 179 and is a path vector protocol.

 

Port 179
Diagram: Port 179 with BGP peerings.

 

BGP Inbound Traffic Engineering

BGP is great for reducing network complexity and increasing scale at edges, but it has shortcomings concerning path selection. BGP is scalable and robust, but routing decisions based on BGP attributes are flawed. These are driving a requirement for a new approach, SDN traffic optimizations, and triangular routing with the LISP control plane.

For BGP inbound traffic engineering, the protocol validates path attributes. It selects the best path by checking local preference, shortest AS Path, ORIGIN attribute, lower MED attribute, eBGP routes are preferred over iBGP routes, and lower metric to the NEXT-HOP. Although these attributes allow granular policy control, they do not cover aspects relating to path performance. So, how can you add intelligence to BGP?

SDN Traffic Optimizations

 

Traffic Engineering with SDN:

SDN enables administrators to implement advanced traffic engineering techniques to optimize network traffic. By leveraging real-time network analytics and traffic monitoring, SDN controllers can intelligently route traffic based on various parameters such as bandwidth, latency requirements, and network congestion. This dynamic traffic engineering ensures network resources are efficiently utilized, reducing bottlenecks and improving overall network performance.

Quality of Service (QoS) Optimization:

One of the key benefits of SDN is its ability to prioritize certain types of network traffic over others. With SDN, administrators can implement Quality of Service (QoS) policies to ensure critical applications and services receive the necessary bandwidth and low latency they require. By prioritizing traffic based on predefined rules, SDN can guarantee a consistent user experience for essential services while preventing network congestion caused by non-critical traffic.

Scalability and Flexibility:

Traditional networking architectures often struggle to scale efficiently, leading to performance degradation as network demand increases. SDN offers inherent scalability by decoupling network control from the underlying hardware. With SDN, administrators can quickly scale network resources and adapt to changing traffic patterns by dynamically provisioning resources and adjusting traffic flow without requiring manual configuration changes.

Network Virtualization:

SDN provides the foundation for network virtualization, allowing administrators to create virtual networks independent of the underlying physical infrastructure. This virtualization enables the efficient allocation of network resources, isolation of traffic, and simplified network management. By leveraging network virtualization, organizations can optimize their network traffic by creating logical networks that meet specific requirements, such as separating traffic for different departments or applications.

 

SDN Traffic Optimizations and Border 6

Border6’s goal is simple: to develop an innovative routing optimization platform. Their toolset (NSI probe and NSI server) is not a replacement for BGP but a complementary tool. BGP is still required at network edges. The NSI products integrate with the border-routing process to complement the BGP decision process.

Integrating NSI into BGP adds additional intelligence to the BGP routing process and overcomes the issues addressed with BGP inbound traffic engineering. They are allowing engineers to automate, control, and monitor routing policies. For example, they have a Routing Decision Engine ( RDE ) that looks at the cost of transits. It takes into account the monthly subscription cost and the cost of traffic bursts.

 

Inbound traffic optimization

NSI probing and analysis allow them to measure latency and packet loss. The best path is then compared to the original path selected by the BGP process. The entire process lets you compare paths in terms of performance. If BGP does not determine the best path, NSI automates traffic engineering and pushes outbound traffic via the best-performing path.

The NSI probe communicates with the BGP edge routers and sends aggregated data back to the NSI Server. The server then analyzes the data and triggers an action for the NSI probe. You can have multiple NSI probes for various data center topologies at each location.

BGP Inbound Traffic Engineering

Optimizing inbound traffic flow

Enforcing outbound routing is performed without any difficulty. Inbound routing differs as you rely on the upstream 3rd party to take action. You can, however, influence this with AS-PATH prepending, community tagging, and auto-shutdown of defective links. Locator/ID Separation Protocol (LISP) provides more granularity for inbound traffic engineering as it separates the address spaces.

Border 6 supports LISP version 1.1 and can respond to the path available to external servers to reach a preferred network. This is based on NSI measurements. Border 6 is collaborating with French Research Agency ( ANR ) to develop a design to integrate NSI with LISP for inbound traffic optimization. This is an ongoing project and is dependent on the broader scope of a global LISP implementation. And as Mateusz Viste states – “LISP is not going to rule the Internet tomorrow, nor the day after that.

 

Border 6 LISP process

The NSI device registers itself with a MAP server. A LISP Map server is a LISP infrastructure device that advertises host prefixes that are advertising to it. The registration process involves sending the MAP server the customer’s prefix. When other LISP participants need to send a packet to the customer’s prefix, they query the MAP server for its location. The MAP server, in turn, relays it to the NSI device.

NSI identifies who is asking (what remote prefix), and responds with the correct RLOC device. RLOCs identify the location of the prefix. The selection of RLOC is based on where transit gateway Border 6 prefers. This requires LISP tunnels on every customer’s edge routers, making it possible for external entities to send LISP-tunneled packets. Until LISP becomes widely available, Border6 continues other working practices to optimize inbound traffic flows, shortest AS-Path, community tagging, and auto-shutdown of defective links.

 

Other Inbound Optimizations

Standard AS-PATH prepending is a well-known BGP path engineering method. BGP selects paths with the shortest AS path. Setting multiple AS entries to a prefix, announced to each of your transits, will affect inbound traffic flow. Community tagging – is a “work-in-progress” project due this year. Essentially, they can add custom-defined communities to the selected prefix.

Transit providers can match these communities and re-announce them partially. Effectively, traffic engineering-inbound flow. Auto-shutdown of defective links – when NSI detects a failure on one of your transit, it can shut down the BGP session (via ssh access on your router), preventing announcements of your prefix via particular links.

 

NSI route limiter

RAM and CPU are critical components of router resources and should always be protected. Routers at the edge may need to accept large portions of the BGP table, maybe the entire BGP table, consuming many router resources. The global IPv4 routing table has surpassed the 500 thousand route benchmark. We are quickly reaching the hard forwarding capacity limits of many popular routers. NSI has a nice feature known as a route limiter.

It is used for routers that can not accept large BGP tables due to memory or other constraints. NSI can feed low-end customer edge routers routes that NSI selects to match destinations where you send traffic. This frees up RAM and CPU for additional control and data plane tasks. It also lets you use cheaper Layer 3 switches, such as Cumulus or Brocade. Make your WAN edge and BGP platform a proper BGP SDN-powered solution.

Software-Defined Networking (SDN) has revolutionized network traffic optimization by giving administrators unprecedented control and flexibility. With its centralized control, dynamic traffic engineering capabilities, and ability to prioritize critical traffic, SDN enables organizations to improve network performance, reduce congestion, and enhance the overall user experience. As the demand for data continues to grow, SDN will play a crucial role in ensuring efficient network traffic management in the digital era.

 

SDN traffic optimizations