What is an IXP? - Internet Exchange Point

What is an Internet Exchange Point?

An Internet eXchange Point (IXP) is a physical location through which Internet infrastructure companies such as Internet Service Providers (ISPs), CDNs, web enterprises, communication service providers, cloud and SaaS providers connect to exchange Internet traffic. Network access points (NAPs) are the predecessors of IXPs. These Internet exchange locations collocate different networks and allow network providers to share transit interconnections outside their network. By having a presence inside of an IXP location, companies can shorten their path to the transit coming from other participating networks, thereby reducing latency, improving round-trip time, and potentially reducing costs.

The earliest of IXPs can be traced back to the creation of Network Access Points (NAPs) when the National Science Foundation Network (NSFNET) was decommissioned. That began in 1994, a carefully orchestrated plan for transitioning the NSFNET backbone service to private industry.

At its core, an IXP is essentially a data center containing network switches that route traffic between the different network operators who share the costs of maintaining the physical infrastructure. According to the PeeringDB database, there are more than 600 IXPs around the world (as of April 2018). IXPs are essentially large Layer 2 LANs built with one or many Ethernet switches interconnected together across one or more physical buildings.

IXPs came into existence to remedy the deficiency of peering connections among Autonomous Systems (ASes). IXPs help reduce the portion of an ISP's traffic that must be delivered via their upstream transit providers, thereby reducing the average per-bit delivery cost of their service. IXPs play an essential role in reducing the cost of transit connections over the Internet.

Who Connects to an IXP?

Any network that wants to peer with other networks can connect to Internet Exchange Points. Typically, Internet service providers (ISPs) are at the head of local IXP users, selling Internet access to their customers. This allowed an ISP's customers to readily connect to each other at exchange points. More recently, exchange point customers are often content providers, who peer with ISPs to get their content to the ISPs' customers. Content providers also connect to exchange points to exchange traffic with each other.

The following list of companies includes a representative list of companies and organizations that use IXPs across a broad spectrum of needs:

  • CenturyLink
  • Windstream
  • Verizon Digital Media Services
  • Bharti Airtel UK Limited
  • Twitter
  • Linkedin
  • Salesforce.com
  • Google
  • Microsoft
  • Amazon
  • Digital Reality
  • Williams College

Just this short list shows how much IXPs are relied upon to exchange traffic with the Internet. IXPs have become a huge part of the Internet ecosystem that is integral to the digital experience of users in businesses and organizations alike.

IXP Protocol & Agreements

Each ISP connected to an IXP must negotiate bilateral peering with other ISPs with which it wishes to peer. A single connection to the IXP allows secure connectivity to numerous providers. At IXPs, traffic is often exchanged between member companies with no cost. This relationship is called settlement-free peering.

Though common, data is not always transferred without cost within an IXP. Large network providers with comparable market share are more likely to peer with other large networks but may charge transit costs to smaller networks. In a single IXP, member companies may have different agreements with several different members. In instances like this, a company may configure their routing to make sure that they optimize for reduced costs or other optimal routing conditions such as reducing the number of hops using the Border Gateway Protocol (BGP) protocol.

IXP Models

IXPs offer a lower cost alternative to routing domestically destined traffic abroad. IXP viability is calculated for interested ISPs by comparing the cost of IP transit to the cost of domestic peering.

IXPs models fall roughly into five categories:

  • Nonprofit associations, consortia, or private companies. This is primarily a European model — AMS-IX, LINX, MIX
  • Managed by Research Networks, Universities, Research Centers — VIX, BNIX, NaMeX
  • Provided by co-location providers — Equinix, Digital Realty Trust, China Telecom
  • Commercial companies — DE-CIX
  • Sustained by government bodies — Top-IX, MyIX

Whether commercially focused or not, most IXPs are owned and managed independently of carriers, ISPs, and Internet exchange co-location providers, thereby establishing network neutrality. In many cases, IXPs are run and managed by consensus between the ISPs benefiting from the existence of the IXP. Some IXPs limit themselves to offering switched infrastructure to facilitate ISP interconnections, while others offer technical services to augment basic global connectivity.

ThousandEyes Network Intelligence technology addresses many of the challenges associated with ISPs looking to connect with an IXP. But more broadly than that, IXPs are also becoming an essential cog of Internet connectivity for business service providers, educational institutions, SaaS providers, and other scaled web enterprises. ThousandEyes can help these organizations to understand and manage user experiences and underlying connectivity over a myriad of Internet networks that they rely on, including their IXP connectivity.

Network operations teams need detailed and accurate network path visibility, along with routing and application layer data to ensure IXP interconnections are operating as planned.