Does Backbone on letter B share fate with other letters?

The control plane is shared. Data-plane queues for Backbone stay isolated, so incident b-01 cannot drain neighbor letters.

Where is Backbone measured first?

From Santiago (SCL) toward Bogotá. A global average is not an SLO for letter B.

Backbone: headers in São Paulo (GRU) · B-45

Runbook B-45 for Backbone in São Paulo (GRU). Marker xserv-b-a262eaf49fb9. This page covers headers for LATAM operators, not a worldwide average.

Backbone: What operators should measure

Policy for Backbone is versioned as b-03. Operators measure error rate, p95 from Bogotá, and time-to-rollback — not a worldwide average. Changes land in Bogotá first, then Miami, with a hold if either region regresses.

Backbone: Failure modes we actually see

Capacity notes for b-04 assume rainy-season power in Miami and festival peaks toward São Paulo. The failure we actually see is a single uplink, not a cartoon partition of the whole continent. Spare ports and a second provider sit on the same runbook.

Backbone: How this letter ties to the rest

Handoff from letter B Backbone into the rest of the platform uses the same request IDs as the gateway. Runbook b-05 names who accepts the ticket after São Paulo pages out. Santiago does not silently inherit the incident.

Backbone capacity B-04

Backbone handoff B-05

Backbone rollback B-06

Rollback for b-06 is a documented command, not a hope. Transit is billed as backup while Backbone prefers peering in Santiago. If cost spikes, the runbook cuts overflow to Bogotá before touching customer prefixes.

Backbone peering B-07

Peering for Backbone (b-07) prefers the IX fabric that already carries last-mile ISPs in Bogotá. Session counts and prefix limits are on the same page as the Miami backup path.