Internet Network Peering – Discussion with Peter Cohen, Industry Expert

Why does one house with a cable connection to the Internet have great performance, and the house next to them with a different Internet provider have marginal or potentially poor performance? The answer may lie in the sometimes dark art of Internet peering.

Peter Cohen

Peter Cohen stopped by to discuss the topic, and try and shed some light on peering recently at the North American Network Operator’s Group (NANOG) conference in Philadelphia. Peter has worked in the peering community for more than 12 years, with experience at some of the largest Internet Service Provider networks in the United States, as well as managing peering for Telia-Sonera, the national telecom network of Sweden.

“Peering is a voluntary interconnection of administratively separate Internet networks for the purpose of exchanging traffic between the customers of each network.” Wikipedia

Savageau: Peter, why is peering important to Internet networks?

Cohen: Peering cuts out the middle man, allowing networks to connect directly to each other without a transit or intermediate network (such as Verizon, AT&T, or Sprint). In addition, peering helps networks to improve data throughput, reduce some operating costs, and provide some protection against high transit pricing (by Tier 1 and transit network providers).

Savageau: Do all networks peer?

Cohen: Peering is not for everybody. Smaller networks and enterprise networks generally do not have enough traffic (to make peering worth it). Also, a lot depends on a network’s location. Peering normally occurs in large markets, such as the NFL cities. A network needs to have other networks or content providers who want to peer with them. You also need to have an ASN number (autonomous system network), which is reserved for those networks who have a need (traffic volume) to peer with multiple networks and content delivery networks.

Peering is not a free connection to the rest of the Internet. When a networks peers with another network, they only receive routes available directly on that network’s, or customers of that network (if it is a larger regional network which provides Internet services to both access networks and smaller content networks). In addition to having peering relationships with one or more networks, unless a network is among the largest (which we call Tier 1 Internet networks), they will still need a “default route” for routing network traffic to the rest of the global Internet.

A default route, also known as the gateway of last resort, is the network route used by a router when no other known route exists for a given IP packet’s destination address. All the packets for destinations not known by the router’s routing table are sent to the default route. Wikipedia

Savageau: Where do networks peer?

Cohen: Networks peer in larger cities where there is a higher density of other networks and content providers. In Los Angeles the Wilshire Corridor in downtown LA has several locations, such as One Wilshire where networks can connect at either public Internet Exchange Points/IXPs, or through private network interconnections (PNIs).

Los Angeles supports several large public exchange points, including those managed by Equinix, Switch and Data – as well as the (CoreSite) Any2 Exchange. Other cities such as New York, San Francisco, and Miami are also major points of peering in the Internet community.

Savageau: How is peering done differently in the United States, versus Europe or ASIA?

Cohen: A lot of the US peering model was developed early in the development of public Internet. There were very few commercial networks present in the Internet, and those networks peered with each other. As the Internet of the 1980s and early 1990s was “hubbed” in the United States, those early American networks were built from the beginning with global views of Internet routing – thus becoming the first Tier 1 networks.

Peter Cohen Tablet Engineering

The Europeans and Asians were a little later to the game. Many of the early non-US networks were operated by national carriers with very little reason to peer with or support competitive networks within their countries (no reason to make your competition stronger and more competitive in your national market). Thus the national carriers only peered at points within the United States, and since those networks did not have global Internet routing visibility, they had to buy transit from the American Tier 1 Internets.

Even today, in some countries national carriers will not peer within their own market, but will peer with competitors at peering points and exchanges outside of their home country.

On the other hand, the European networking community did learn from the American experience, and today the largest pubic exchange points exist outside of the United States, allowing smaller networks and content companies to gain all the advantages of local peering, without the need to “hairpin” their traffic through a Tier 1.

Savageau: Is the current model of peering in the US good enough? Change needed?

Cohen: Traditionally networks which peer come in two types. Those who only peer with private network interconnections/PNIs, and those who peer at public exchanges, and also support PNIs. PNIs are most useful when traffic on a public exchange hits a certain threshold, and then it makes more sense for the networks to interconnect with much higher capacity individual circuits.

A new model emerging in the US is with remote exchange point connections (Remote IXP Access). Remote IXP access allows a network geographically separated from a major public peering point to lease a long distance circuit, usually around a Gigabit, and “test the waters” by connecting to the IXP. If the peering point effectively serves the needs of the remote IXP access network, then they may at some point establish a direct point of presence the facility supporting the IXP.

The only real drawback of remote IXP access is that without a physical router present at the data center or carrier hotel housing the IXP, they are limited to the single exchange point connection, and cannot establish a PNI with another network at the facility.

Savageau: Final question. Most difficult topic for last! Give me your feelings on the topic of net neutrality, how it is currently affecting the Internet community, and how you think it will evolve.

Cohen: Many of the current policies in effect between networks and content providers are purely based on internal politics. That’s why you may go into a neighborhood and find an Internet Service Provider giving outstanding performance to one customer, and across the street you will get poor performance. Most local Internet providers are called MSOs, or Multi-Service Operators. MSOs include cable TV companies, phone companies, and satellite TV companies.

One MSO, such as AT&T, may determine the content providers should pay a higher rate to subsidize the cost of network build outs. A cable company MSO may determine that peering with content networks is the best policy.

There is no regulation at this level, and the ultimate victims are end users in the home. End users who believe they are paying a flat rate to their MSO to receive the best possible performance on their home Internet connection – but at the end of the day are receiving service performance based in a large part n the personalities of persons making decisions on peering models, not necessarily on business rules or objectives.

Savageau: Peter, keep looking out for us


Peter Cohen has been involved in the Internet since the 1990’s starting out at CAIS Internet.  He has held a wide range of positions and has worked extensively with peering, transit, interconnections and network design/colocation for ISPs, Carriers and other Internet related companies around the world.  His work and travel have brought him to more than 35 countries and 5 continents.  He is a frequent speaker at NANOG, Ripe, and other industry events worldwide.

Presently Peter works at Switch & Data where he facilitates interconnections among customers and the PAIX product.  He lives with his wife and two children in McLean, Virginia.  He enjoys cooking, reading, golf and tennis in his spare time.

%d bloggers like this: