What is Peering Policy?
ISP Internet interconnection guidelines are a collection of business criteria and technical mechanisms that allow individually managed autonomous networks (ASes) the ability to connect to each other to access and exchange Internet traffic, which takes two primary forms: peering and transit. Peering connections do not require monies to be exchanged between ISPs unlike transit interconnection, but peering does require a mutual agreement between ISPs that provides a set of technical requirements and business criteria. ASes that use both IPv4 and IPv6 addresses are reachable.
Each ISP establishes a set of criteria to determine the networks with which they will interconnect or peer. These peering policies can reflect how the technical and contractual arrangements that network operators negotiate with each other to interconnect are influenced directly by the business objectives and policies of each of the parties.
Peering policies are commonly used to achieve consistency in judging requests for interconnection and typically represent an attempt to set reasonable, transparent and secure boundaries, thereby working to avoid future disagreements if traffic volumes or other factors change. PeeringDB is a resource where many network operators disclose their peering policies and locations to make them easily accessible on a global basis to other network operators.
ISP generally identify with peering policies categorized as open, selective, or restrictive:
- An open peering policy is where the party peers with any other party.
- A selective peering policy requires that the peering entity must meet the criteria directly specified by the peering policy, such as minimum traffic exchanged, number of peering points, etc.
- A restrictive peering policy is where the party does not generally peer with other parties, where peering is the exception and not the norm.
To participate in a peering agreement on the Internet with any party, some basic technical requirements need to be fulfilled. A network looking to peer must have:
- A public Autonomous System (AS) number assigned by a Regional Internet Registry (RIR). Without this, the network does not have a unique "identity" on the Internet to route traffic.
- At least one block of public IP addresses (independent of any upstream provider) assigned by an RIR. These addresses (either IPv4 or IPv6) are what the network "announces" or "advertises" to other networks it interconnects with.
- A network edge router capable of running the BGP protocol, and the technical capability to configure and manage BGP interconnections.
Network operators will often include in their published peering policy a set of technical requirements and operational requirements. Assuming a network meets the necessary technical requirements to participate in peering on the Internet, peering policy requirements may also include:
- Routing: A potential peer is generally required to operate an IP network between the interconnection points and use the Border Gateway Protocol (BGP) to exchange routes at the interconnection points where the peering occurs.
- Network capacity: ISPs may impose minimal requirements on the size of a potential peer's network capacity and require that the potential peer ISP operate a fully redundant backbone network in addition to imposing capacity requirements at peering links.
- Geographic scope: ISPs may impose requirements that state the potential peer must have a backbone presence in an expansive and diverse set of geographies.
- Network traffic volumes: Peering policies may stipulate that the potential peer not exceed an aggregate traffic ratio in a specific direction, for example, the aggregate outbound traffic on the peering links must be no more than twice the volume of aggregate inbound traffic exchanges.
- Filtering: Peering policies may also require the potential peer AS to filter route announcements from its customers by prefix, to ensure that incorrect route announcements do not "leak" across the peering link and that no transit or third-party routes are announced or connected.
Internet Exchange Points (IXP) represent an efficient and cost-effective way for ISPs to exchange traffic locally using "settlement-free" peering, public peering or private peering policies.
ThousandEyes Network Intelligence technology addresses many of the challenges associated with ISPs and companies looking to implement peering relationships. Network operations need detailed and accurate network path visibility, along with routing and application layer data to ensure peering is operating as planned.
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