Sessions And Peers; Establish A Session - Dell Force10 Z9000 Configuration Manual

Figure 18. BGP Routers in Full Mesh
The number of BGP speakers each BGP peer must maintain increases exponentially. Network management quickly becomes
impossible.

Sessions and Peers

When two routers communicate using the BGP protocol, a BGP session is started. The two end-points of that session are Peers. A
Peer is also called a Neighbor.

Establish a Session

Information exchange between peers is driven by events and timers. The focus in BGP is on the traffic routing policies.
In order to make decisions in its operations with other BGP peers, a BGP process uses a simple finite state machine that consists of
six states: Idle, Connect, Active, OpenSent, OpenConfirm, and Established. For each peer-to-peer session, a BGP implementation
tracks which of these six states the session is in. The BGP protocol defines the messages that each peer should exchange in order
to change the session from one state to another.
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Border Gateway Protocol IPv4 (BGPv4)