Internet Interconnections

The Internet is often called ‘the network of networks’ because it is the result of interconnection of different networks, also known as Autonomous Systems (AS). The interconnection ecosystem consists of a variety of different types of interconnections, which can be largely categorised as private and public, between networks of different sizes.

Network operators provide their customers with connectivity to the wholeInterconn of the rest of the Internet. They do this by either purchasing ‘transit’ from major networking companies, paying for their traffic on a volume basis, or negotiating ‘private peering’ arrangements with other network operators, where traffic is exchanged ‘settlement free’, in order to reduce their costs.  This traffic will not be for ‘all possible routes’, but only for the parts of the Internet operated by the other operators.

There are different interconnection and peering policies used by operators (open, selective, restrictive, closed, etc). The largest ‘backbone’ networks (usually called Tier 1 networks) do not purchase transit from anyone, but operate solely on a peering basis. ‘Tier 2’ networks have peering-only arrangements in large geographical regions, but use a Tier 1 for remote locations. This is a quite complex ecosystem  on which ENISA has done a first study in 2010  to better understand the needs of a more secure and resilient interconnected network environment.

The ENISA "Inter-X: Resilience of the Internet Interconnection Ecosystem" study was the first step ENISA took towards studying this area. The study was interested in the resilience of the system of interconnections between Internet networks. The project focused not only in the actual interconnections, but also in the arrangements, agreements, contracts and incentives that underpin them. Together all of this is referred to as the ecosystem. It was found that the resilience of this ecosystem depends on the resilience of the individual components. The resilience of the ecosystem as a whole, however, depends on the resilience of the sum of those components and their interactions.

More specifically ENISA:
• Took stock and qualitatively analysed the state of the resilience of the Interconnection ecosystem, including the barriers and incentives
• Collected information on existing practices, policies and management approaches with key experts and stakeholders –at an international level;
• Delivered a final report with the recommendations and a list of good practices

In 2011 ENISA followed up on a few of the recommendations of the Inter-X study, with a study on the Resilience of Internet Interconnections. This study was focused on assessing the technical issues (e.g. logical, physical, application layers, replication and diversity of services and data, data centres), the peering and transit issues (e.g. SLAs), market, policy and regulatory issues.

In 2013 ENISA released Understanding the importance of the Internet Infrastructure in Europe - Guidelines for enhancing the Resilience of eCommunication Networks continuing further its work in this area.

In 2014 ENISA released  Threat Landscape and Good Practice Guide for Internet Infrastructure  which maps the assets composing an Internet infrastructure and the applicable threats, giving an overview of emerging trends, and providing adapted security measures.

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