Peering basics: Public vs. private peering

When we make NOC announcements, we often mention our peering connections. We assume that the readers of those messages technically understand peering. But as they say, assumption is the mother of all mistakes. Sometimes it’s good to start with the basics of things. In this blog, we’ll take a closer look at peering and examine the differences between public and private peering.

So, what is peering? In its most simple form, it is defined as the interconnection of two different networks so they can exchange traffic between them. This means the traffic goes directly from one network to the other, allowing them to reach each other’s customers. As this is mutually beneficial for those involved, the network owners usually don’t charge each other to peer. Now, I should note that having many peering connections doesn’t mean that you are able reach the whole internet – you only reach the networks (and their customers) you peer with. This is why a quality network should also be connected to at least two transit providers (preferably tier 1 networks). However, transit providers charge a sizable fee, making peering a cost-effective alternative.

There are two types of peering – public and private:

  1. Public peering is performed across a shared network called an Internet Exchange Point (IX or IXP). Through an Internet Exchange you can connect to many other peers using one or more physical connections, thereby optimizing the cost per peer when sending traffic to many different networks. Internet Exchanges often charge a port and/or member fee to keep their infrastructure intact.
  2. Private peering is performed by creating a direct physical connection (usually consisting of one or more 10GE fibers) between two networks. The connection is made from only one network to another, for which you pay a set fee to the owner of the infrastructure that is used (such as a datacenter). This makes private peering a sensible option when you need to send large volumes of traffic to one specific network, as the cost per megabit goes down when more traffic is exchanged.

Because of the way these types of peering are designed, each offers several (dis)advantages:

Public Peering Private Peering
Advantage
  • Efficient usage of ports
  • Hundreds of peers available at the larger IXs
  • Easy to administrate
  • New peers added instantly on a daily basis
  • Guaranteed capacity
  • Easy to monitor
  • More reliable than public peering
  • More secure than public peering
Disadvantage
  • Port and/or member fees for the IX
  • Only cost-effective for large volumes of traffic
  • Takes more time to setup new peering connections

When you’re a network engineer, you’re constantly looking for fast and reliable ways to ensure data reaches its destination. As peering is a cost-effective solution for this fascinating puzzle, usually enabling us to offer you bandwidth at really low prices. There are also other advantages to peering, which we will look at in the next peering blog. In the meantime, if you have any questions, don’t hesitate to drop me a line in the comments below.

4 Responses to “Peering basics: Public vs. private peering”

  • Andreas:

    Thanks for those highly interesting articles!
    How does public peering work in detail?
    Lets say I want to peer with 30 other small networks at an IX.
    So I pay a monthly fee to the IX, and geht a switchport in return.
    Then what?
    Do I automaticly peer with all other networks at that IX, all sharing the bandwidth of my port?
    Or do I have to put a 48 port switch in the IX somewhere, connect the uplinkport to my ‘IX-port’, and run 30 cables to the switches of my peering partners and ask all of them individually if they want to peer with me? Again all sharing the bandwidth of my IX-port?
    Are VLANs used somehow to reduce cable clutter?

    How does it work exactly?

  • An Internet Exchange is a big layer2 network. You get a switchport and an IP address from an Internet Exchange range. The rest is done using BGP. You can create BGP sessions to other members of the IX. With the help of route-servers, which are present at most exchanges, you don’t have to configure BGP sessions with all members. Most of them can be reached by just having sessions to route-servers.

    It might happen that not everyone wants to peer with you, but the majority will probably be willing.

  • This is really interesting, You’re an overly skilled blogger.

    I’ve joined your rss feed and sit up for looking for extra of your
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  • sidd:

    Hi Grzegorz–

    Thanks for the article. Can you explain little more about the public and private perrings with an example. At our company we purchased a 45mbps circuit from an ISP and pay monthly charges to them- to connect to internet- will that be considered as Private peering or public peering.

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