BGP Terminology (RFC 4271)

BGP Protocol and Components

• BGP (Border Gateway Protocol): A standardized protocol for routing information exchange between autonomous systems.
• AS (Autonomous System): A collection of networks under a single organization's control with a common routing policy.
• IGP (Interior Gateway Protocol): Used for routing information exchange within an autonomous system.
• EGP (Exterior Gateway Protocol): Used for routing information exchange between autonomous systems.
• AS Number (Autonomous System Number): A unique identifier assigned to an autonomous system.
• BGP Speaker (Border Gateway Protocol Speaker): A device or software component participating in BGP routing.
• BGP Speaker Internal (Internal BGP Speaker): A BGP speaker within an autonomous system.
• BGP Speaker External (External BGP Speaker): A BGP speaker interfacing with external autonomous systems.

Routing Information Management

• Routing Information Base (RIB): A database storing routing information.
• Adj-RIB-In: Part of RIB storing routes received from BGP peers.
• Adj-RIB-Out: Part of RIB storing routes selected for advertisement.
• Local-RIB: The primary routing table storing BGP routes.
• Local-RIB-In: Part of Local-RIB storing routes received from BGP peers.
• Local-RIB-Out: Part of Local-RIB storing routes selected for advertisement.
• Forwarding Information Base (FIB): A data structure used for routing decisions.
• Forwarding Table: Table containing routing decisions for packet forwarding.

BGP Message Types and Attributes

• Update Message: Used to communicate changes in network reachability.
• Path Attribute: BGP attribute providing information about a route.
• AS Path: BGP attribute representing the sequence of ASes a route traversed.
• Next Hop: BGP attribute indicating the next router for packet forwarding.

BGP Session and Communication

• Neighbor: A BGP peer, another BGP speaker with which routing information is exchanged.
• Session: The connection between two BGP speakers for routing information exchange.
• Peer: Another BGP speaker with which routing information is exchanged.
• BGP Identifier: A unique 32-bit number identifying a BGP speaker.
• Hold Time: A timer indicating the BGP session's validity.
• Keepalive Timer: Ensures the continued liveliness of a BGP session.
• Message Header: Contains information about the BGP message.
• Message Length: Specifies the total length of the BGP message.

BGP Message Types

• OPEN Message: The first message to establish a BGP session.
• UPDATE Message: Communicates changes in network reachability.
• NOTIFICATION Message: Indicates errors or terminates a BGP session.
• KEEPALIVE Message: Maintains the liveliness of a BGP session.

Route Types and Information

• Route: A path to a specific destination on a network.
• Reachable Route: A route that is reachable and can be used for packet forwarding.
• Unreachable Route: A route no longer available for packet forwarding.
• Withdrawn Routes: Routes removed from the routing tables.
• IP Prefix: A representation of an IP address range.
• IP Address Family: Classification of IP addresses based on characteristics or types.

Protocol Details

• TCP Port Number: A 16-bit number identifying specific services in a TCP/IP network.
• Version Number: Indicates the version of BGP being used.
• Error Code: A value indicating the nature of an error in BGP messages.
• Error Subcode: Provides additional details about errors indicated by the error code.