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Q&A: How does BGP propagation for routed customers work?

Question

How does the Internal BGP propagated for routed customers work? 

  • What measures are applied to ensure traffic takes the best path within the network?
  • How does traffic flow across the scrubbing network?

 

Environment

  • DDoS
    • Routed
    • BGP

 

Answer

Silverline's routed service leverages BGP to route customer traffic through scrubbing centers, and back to the customers infrastructure.

Customer's prefixes are originated and propagated via the interconnect method, usually GRE tunnels, to all the scrubbing centers and then to the upstream providers. 

  • Within the Silverline infrastructure, BGP metrics are applied to ensure every customer route takes the best path once within the Silverline infrastructure. These metrics are not applied to announcements to Silverline carriers.
  • BGP metrics are added at each Silverline scrubbing center. The metric of the lowest score is considered the best path. Traffic entering a scrubbing center where GRE tunnels are provisioned will always prefer the direct route over the tunnels.

For example, a client in Asia trying to access a customer's resource enters the Silverline network via the Asia scrubbing center(s), then traffic will be routed through the backbone to the EU scrubbing center where the customer has GRE tunnels configured, see below:

Routing.jpeg

The above scenario will compare the following routes and applied metrics:

  • ASIA --> EU = 1800
  • ASIA --> US EAST = 2300
  • (ASIA --> US West = 1700) + (US West --> US East = 750) = 2450

The 1800 metric will be determined as the best path.

The above metric numbers are examples, as metrics are determined by a number of factors, including health metrics.

 

Customer can prefer the GRE tunnels for delivery, this can be achieved by following the BGP Configuration for DDoS Protection Setup

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