The encyclopedia · Software & IT · Technical decision · 1989–1994
BGP won internet routing by advertising the whole AS path, not just a destination
RFC 1105 (1989) made routers exchange full autonomous-system paths, so loops were visible and policy could be enforced; every network still uses BGP.
Cisco Systems · IBM
the move
In the 1980s, the Exterior Gateway Protocol (EGP) connected the early Internet, but it could not handle a web of many independent networks. RFC 1105, published in June 1989 by Kirk Lougheed and Yakov Rekhter, proposed a different design.
BGP's key idea was path-vector routing: each route advertisement carries the complete list of autonomous systems it has passed through. That list is enough to construct a graph from which routing loops can be pruned and policy decisions enforced between organizations.
Operators adopted successive versions (BGP-2, BGP-3, BGP-4) as the Internet commercialized. Thirty years on, no successor has replaced BGP-4, which now scales from hundreds of networks and thousands of prefixes to tens of thousands of networks and close to a million prefixes.
why it works
- A visible AS path lets any router detect and drop loops locally.
- Each network keeps its own policy private while negotiating routes.
- Running over TCP made deployment trivial on existing routers.
- Incremental versions let the protocol grow with the network.
what transfers
When a network needs to grow beyond one trusted operator, give every participant the provenance of each route: transparency replaces central control and makes policy decisions local.
what came after
BGP-4 remains the Internet's inter-domain routing protocol, with no viable successor despite known security weaknesses; APNIC describes it as holding the Internet together and closely tied to the business model of interconnection.
references
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