Why Use BGP?
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Even if you are not a large network on the internet, BGP is the standard for multi-homing, load-balancing, and redundancy:
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Single-provider / single-homed – Not typically a strong candidate for BGP, but may still use it to advertise networks to the ISP. single-homed networks are not eligible for a public AS from RIRs.
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Single-provider / Multi-homed – Common to follow RFC2270 suggestion to use a single private AS (64512 to 65535) to get the benefit of BGP while preserving public ASN.
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Multi-provider / Multi-homed – Highly redundant, typically with dedicated routers to each ISP. Requires public ASN. Large memory footprint
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Route summarization makes routing scalable.