On Terminology And Names

“It is important to distinguish between the concepts of an object, and the name(s) of that object. This has resulted in widespread confusion between the properties of the name, and those of the object itself.” A great line by J. Noel Chiappa and one very applicable to the process of Settlement Free Interconnection (SFI) or “peering” as it is commonly known.

When people say “peering” what they most often mean is a bi-lateral settlement free interconnection. This is a business term, not a technical term, because the properties of the interconnection are orthogonal to the business relationship that causes that interconnection to exist. What are these properties?

  1. Customer and network infrastructures routes (and only those routes) are exchanged
  2. Transit (peer routes, exchange routes) are not exchanged

From #1 and #2 above, only “on-net” routes are exchanged, which means that only “on-net” traffic destined for the network’s customers and infrastructure is exchanged.

That is the technical property of a “peering” session. The flow of money is orthogonal to the mechanics of interconnection. If there is a contract or some financial relationship between the two networks, then it is termed either Settlement Based Interconnect (SBI) or “paid peering.” The properties of the interconnect remain unchanged.

So to sum up, I would like to use the following terms for interconnection universally:

  • Interconnection with “on-net” routes and no settlement: SFI
  • Interconnection with “on-net” routes and settlements: SBI

6 Responses to On Terminology And Names

  1. Patrick W. Gilmore says:

    Fine suggestions. But then you will run into the people who think “SFI” means the core “transit-free” networks.

    And I assume you will leave “transit” to mean, uh, transit?

    • vijaygill says:

      The interconnection type is not dependent on network, for those core transit-free networks, I thought we already had a name for them: tier 1!

  2. Przemyslaw Karwasiecki says:

    Customer or Customer’s routes?

    It is a sincere question — if I run ISP, and have my customers with their ASes,
    and I advertise their routes, is such interconnection still consider peering?

    Let’s assume that I will build such interconnection with Google, and no money
    will change hands between me and Google, but I am paid by my customers,
    is it SFI or SBI?

  3. Przemyslaw Karwasiecki says:

    Thanks for the answer!

    Recently I have had a dispute about semantics of the word “peering”,
    and the other party was insisting that in any case you are receiving
    prefixes with AS_PATH longer than 1, such interconnection should be called
    transit, simply because you are traversing same AS to reach final destination.

    Now I have an indisputable point to defend my point 🙂


  4. This is a well timed article. I usually enjoy the TWiG podcast but a recent episode with its “Google doesn’t pay for bandwidth because it owns its own fibre and has Peering” argument had me pulling my hair out. These things definitely need to be understood more by the general public.

    The general opinion seems to be that Peering == Free which is just not true. Even with SFI there are network costs to be met.

    I would be interested to know if you are planning on completing this taxonomy to include “off-net” route exchange in a future post.

    An obvious extension could be: SFG / SBG for Settlement free and settlement based global routes exchange (deliberately avoiding the word Transit which has almost as much baggage as Peering). And I guess SFP / SBP when only partial routes are exchanged but the routes are not limited to on-net destinations.

    I am also interested by the or in “If there is a contract or some financial relationship”. Does this mean you consider the common “traffic ratios not to exceed 1:N” clause in a peering agreement would make it an SBI even though no money is changing hands?

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