BGP is an exterior gateway routing protocol (EGP) that is the standard routing protocol used to facilitate routing exchanges throughout the Internet.

KAREN utilises BGP version 4 (BGPv4) to exchange routing information with directly connected members, associate members, partners and international peering partners.

BGP and KAREN

Members' external routing devices need to be able to make decisions about where to send traffic.  If it is assumed that the members’ ISP provides them with a default route, (i.e. a route to use where the destination is unknown) then the routing device will need to know each of the possible destinations that are reachable via KAREN in order to make an effective routing decision.

The list of routes available via KAREN is dynamic, and it is therefore necessary for the member to be able to hold the entire KAREN routing table in their routing device. 

Additional information

BGP uses TCP (port 179) to exchange routing information between peer systems and provides a number of options that can be used to tightly control routing between network domains.  A number of RFCs contain information about BGP and the way in which it can be used that are relevant to KAREN:

• RFC 1771 – A Border Gateway Protocol Version 4
• RFC 1772 - Application of the Border Gateway Protocol in the Internet
• RFC 1966 - BGP Route Reflection: An Alternative to Full-Mesh IBGP
• RFC 2385 - Protection of BGP Sessions via the TCP MD5 Signature Option
• RFC 2439 - BGP Route Flap Damping
• RFC 2545 - Use of BGP-4 Multi-protocol Extensions for IPv6 Inter-Domain Routing
• RFC 2796 - BGP Route Reflection
• RFC 3065 - Autonomous System Confederations for BGP

Many of these RFC’s and their application are covered in tuning BGP.