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CONCEPT Cited by 1 source

Peer-peer relationship (BGP)

A peer-peer relationship is one of the two primary pairwise business relationships between ASes: two networks exchange traffic settlement-free — neither pays the other — to reach each other's customers.

Export policy per side

Symmetrically:

  • Each peer advertises only its own routes + its own downstream customers' routes to the other.
  • Neither peer advertises routes learned from their providers or other peers.

This restriction is exactly what makes a peer settlement-free work economically: if peers re-advertised upstream routes to each other, they'd be providing transit for free. A violation of this rule is a route leak.

Typical use

Peering happens at Internet Exchange Points (IXPs) or via private links between:

  • Two ISPs with significant bilateral traffic.
  • A content network (CDN) and an ISP serving that CDN's users.
  • Two Tier-1 networks that have no providers at all (they can only peer, so their path to the rest of the Internet is entirely via peers + their own customer cone).

Tier-1 networks

A Tier-1 network is a transit-free network: all of its connections are peer-peer or customer-provider (as the provider). It has no upstream provider. AS6762 (Telecom Italia Sparkle) is named as Tier-1 in the Cloudflare Venezuela post — which matters because in ASPA, a Tier-1 network's ASPA object uses the special AS0 upstream declaration to signal "I have no upstream providers."

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