North American Network Operators Group

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Re: Question on the topology of Internet Exchange Points

  • From: Patrick W. Gilmore
  • Date: Thu Feb 14 18:29:17 2008

On Feb 14, 2008, at 3:44 PM, Andy Davidson wrote:
On 14 Feb 2008, at 17:02, Kai Chen wrote:

A typical Internet Exchange Point (IXP) consists of one or more network switches, to which each of the participating ISPs connect. We call it the exchange-based topology. My question is if some current IXPs use directly-connected topology, in which ISPs just connect to each other by direct link, not through a network switch?? If so, what's the percentage of this directly-connected case?

ISPs use a "direct link" (PNI) all the time to peer, and they don't need to be a member/customer of an internet exchange point to do so. In fact, the network you want to peer with might not be available at your local IXP even though they're in your local carrier hotel - then it becomes pretty much the only way to peer.

In London, the LINX offer switched *and* unswitched connectivity between members - you can rent fibers from them in order to perform PNI with other members. That the exchange offer this is unusual, and it's offered as an additional service, in order to smooth the process of organising interconnection between member organisations. [ ]

LINX doesn't rent fibers. It's a one-time (NRC) fee for 8 pairs, which are patched to any other member on the service for free for life. (Although I don't know if they promise to keep it free forever, but it's been free for many years with no mention of it changing.)

We (LONAP) don't offer PNI services, and only offer the conventional switch ports, which members normally want so that they can get access to our peering lan and swap some traffic. [] All exchanges offer this connectivity model. We offer private CUG and member-to-member private VLANs, which is similar, but still passes through the switch fabric.

I believe Exchange Point offers a PNI-like service over their network.

But in general, an "Internet eXchange Provider" offers a shared switch. Anything else is really just a meet-me room. For instance, I wouldn't call Suite 1515 (formerly NYCC) an "IXP".