Introduction

Important terms

Autonomous System (AS): a network or group of networks that belongs to a single organization and is connected to the Internet
Autonomous System Number (ASN): a 16-bit or 32-bit number that identifies an autonomous system
Border Gateway Protocol (BGP): the routing protocol used by Internet routers to exchange routing information between autonomous systems
Regional Internet Registry (RIR): an organization that manages the allocation and registration of Internet number resources such as IPv4 and IPv6 address space and AS numbers within a region of the world
American Registry for Internet Numbers (ARIN): the regional Internet registry for the United States, Canada, and many Caribbean and North Atlantic islands
Internet Routing Registry (IRR): a public database of routing information that can be used for matching networks to origin ASNs
Resource Public Key Infrastructure (RPKI): a cryptographic method of signing records that associate a BGP route announcement with the correct originating AS number

BGP is the routing protocol used by all Internet service providers and many of their customers
BGP routers may originate routes or prefixes for their own AS, or they may announce routes learned from another AS they are connected to
An ISP router typically has the full Internet routing table in memory and knows one or more paths to every prefix announced to the Internet
When there are multiple paths to a destination, the router uses a calculation based on BGP route attributes and locally administered policy to determine the best route

IRR serves three purposes:
- provides a means to publish your own routing intentions
- provides the information necessary to build route filters
- aids in troubleshooting and network management by providing information about other networks
RPKI serves two purposes:
- provides a cryptographic means to publish your own routing intentions
- provides a cryptographic means for validating routes you receive

The early Internet was built on trust between the connected networks. BGP has no built-in security, so any ASN can announce any prefix!
Network operators are generally well-behaved and announce the correct routes
Now the Internet has 5 billion users (about 70,000 active ASNs)
Routing issues can cause financial losses, compromise of data, or even loss of life!
Money and political gain are powerful incentives for some to tamper with Internet routing
- Hackers and scammers
- Unfriendly governments or adversaries
Mistakes happen — misconfigurations or software bugs can cause route leaks, loops, and traffic loss. Remember this outage caused by a misconfiguration by DQE in 2019?
Many providers use IRR to build filters. You must maintain up-to-date IRR entries to ensure all backbone carriers will carry your routes!
- "But I don't have IRR, and my providers are carrying my routes just fine!"
- Most likely one or more of your providers has created IRR records on your behalf, a practice known as "proxy registration". You should maintain your own IRR records rather than rely on a carrier to get them right. The records may have been created be a carrier you no longer use.
Many providers filter RPKI invalid routes but still accept RPKI unknown routes. You get the most protection against route hijacking by signing your route advertisements with RPKI so they are RPKI valid.