The Global Internet Peering Ecosystem


Figure 7 – The Tier 2 ISP model

Regional Tier 2 ISP Transit Links and Customers. Just as with the Regional Tier 1 ISPs, Regional Tier 2 ISPs sell transit to their customer base, using a variety of techniques to target market and differentiate themselves from the Tier 1 ISPs. These market focus techniques include serving under served or rural areas, focusing on niche markets or focusing on serving specific retail or commercial sectors.

Regional Tier 2 ISP Backbone Backhaul. The subset of Tier 2 ISPs that operate in multiple markets often have backbone links constituting their core backbone network. Other Tier 2 ISPs operate in a single market and do not require any backbone backhaul. Still others utilize transit services as their sole methods of interconnecting their network nodes. These backhaul links are drawn as links out the side of the graphic.

Roughly speaking, all other (non-Tier 1) ISPs can be broadly categorized as Regional Tier 2 ISPs in the Peering Ecosystem.

Definition: A Regional Tier 2 ISP is an Internet Service Provider that purchases transit to reach some destinations within the Internet Region.

Regional Tier 2 ISP Model. The Tier 2 ISP model is similar to the Tier 1 model but includes one (or more) “Upstream” transit connections as shown graphically below.

Regional Tier 2 ISPs Relationship with each other. At the same time there is great heterogeneity of this Regional Tier 2 ISP group, there is also great cooperation, driven by aligned interests. Regional Tier 2 ISPs by definition all purchase transit and therefore generally are interested in peering with others in the region to reduce their transit fees.

Regional Tier 2 ISPs Relationship with Tier 1 ISPs. Tier 1 ISPs are transit providers, as well as competitors for the really big customers. Since the Tier 2 ISPs know that they will be referred to as the “middle man” in competitive situations with the Tier 1 ISPs, they tend not to mention that they purchase transit at all.  Hence Sean Donelan’s comment that “Everyone is a Tier 1 ISP.”

Once a Customer never a peer - The Britain Tier 2 ISP Story. A Tier 2 ISP had grown larger than its upstream ISP and tried to negotiate peering with them. The upstream ISP refused, citing that it does not peer with customers. The Tier 2 ISP terminated its transit and was not successful in obtaining peering for two years, when it became clear that the Tier 2 would never buy transit from the former upstream. This demonstrates the motivations to not peer for reasons of potential revenue loss.

Regional Tier 1’s won’t peer with me. The most common stories heard at Regional Tier 2 ISP forums are stories of Tier 2 ISPs requesting peering with the Tier 1 ISPs.  The Folly of Peering Ratios white paper documents the arguments surrounding one common Tier 1 ISP peering requirement - the requirement for peered traffic to be within certain traffic ratios limits. This requirement effective removes content heavy ISPs and all content providers from the potential peering populations.

Regional Tier 2 ISPs participate in Peering Forums. Peering fora like the Global Peering Forum, Internet Exchange Point member meetings, NANOG Peering BOFs, etc. are all geared toward facilitating the interaction between like minded peering people. Since the Regional Tier 1 ISPs all know who they need to peer with, these fora provide little but entertainment value.  But the Regional Tier 2 ISPs tend to adopt leadership roles in organizing and mobilizing like minded peers in the Peering Community. They are a very social and accepting bunch. After all, it is in their best interests to expand the population of potential peers.

What a Regional Tier 2 ISP  looks like

Regional Tier 2 ISP Motivations

Regional Tier 2 ISP Observed Behavior

Regional Tier 2 ISP Peering Motivations. Tier 2 ISPs have several motivations for Peering, among them are to:

1.Reduce Transit Costs. By directly peering with willing players, traffic is exchanged directly with the peer, and typically is done so settlement-free. This peering traffic therefore reduces the load on and therefore the cost of transit. For Regional Tier 2  ISPs, Peering is one way to reduce transit fees.

2.Improve Performance. Traffic that flows directly between players has lower latency than traffic that first traverses a transit providers network before being handed off to the peer.

3.Have Greater Control over Routing. Some ISPs prefer to have tight control over the path and performance of the traffic. If a poor performing path is preferred by the routing protocols, an alternative path can be configured.

Regional Tier 2 ISP Regional Peering Interconnections.

The Regional Tier 2 ISP generally peers with others using some combination of public (shared peering fabric-based) and private (point-to-point-based) interconnection technology within one or more Interconnection Regions. 

Regional Tier 2 ISPs tend to peer only in Interconnect Regions in which they sell services, and buy transit for the other destinations in the Internet. This creates a diverse population in each Interconnection Region - less of a full mesh of peering than the Regional Tier 1 ISPs who tend to peer with each other in every Interconnect Region in a full mesh. It is worth noting that there are a set of larger Tier 2 ISPs that peer at many exchange points in many Interconnect Regions.

As a result, the category of Tier 2 ISPs is a much broader and more heterogeneous category than that of the Tier 1 ISPs. There is a wider range of peering policies, and the Tier 2 interconnect meshes tends to be more sparse than that of the Tier 1 ISPs. The Tier 2 ISPs after all have an alternative to peering (transit!) For some Tier 2 ISPs, Peering is an optional local routing optimization.

The Regional Tier 2 ISP

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