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Global Routing Telemetry

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Understanding BGP

The Postal Service of the Web

The Border Gateway Protocol (BGP) is the routing protocol of the internet. It acts like the postal service for the web, allowing different networks (Autonomous Systems or ASes) to announce which IP addresses they control and discover the most efficient paths to send data to each other. Because BGP relies on trust, it is vulnerable to misconfigurations or malicious attacks known as Route Hijacks.

IP Prefixes & Subnetting

In BGP, we don't route individual IPs, but Prefixes (blocks of addresses). A prefix like 192.0.2.0/24 represents 256 addresses.

  • Specific (/24): A "small" prefix. BGP always prefers the most specific route. A hijacker announcing a /24 can "steal" traffic from a larger /23 announcement.
  • Aggregate (/8): A "large" prefix covering millions of IPs. Used to keep the global routing table manageable.
Learn about Subnetting →

1. Announcing

The Origin AS 'announces' its IP space. Routers propagate this information so that every network knows the path back to the origin.

UserOrigin AS

References

Advanced BGP Topics

Explore the complex protocols and architectural standards built on top of BGP's extensible framework.

Path & Scalability

  • Route Reflection (RFC 4456)

    Eliminates the need for a full iBGP mesh by using reflectors to propagate internal routes.

  • BGP ADD-PATH (RFC 7911)

    Allows advertising multiple paths for the same prefix to enable better ECMP and faster convergence.

  • BGP PIC

    Prefix Independent Convergence allows millisecond failover by using pre-calculated backup paths.

  • Confederations (RFC 5065)

    Dividing a large AS into smaller sub-ASs to simplify management and reduce peering overhead.

Security & Integrity

  • BGPsec (RFC 8205)

    Full path signing. Rarely deployed due to high CPU load; RPKI is the preferred modern alternative.

  • BGP OPSEC (RFC 7454)

    Best practices for securing BGP sessions including TTL security and prefix filtering.

  • RPKI Validation

    Cryptographic verification that an AS is authorized to originate specific IP prefixes.

Traffic Engineering & Resiliency

Modern Overlays