BGP Flow

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Example Presentation Script

1. BGP Session Overview

Hello everyone. Today, we will delve into the details of the BGP session establishment process. BGP is an internet routing protocol that facilitates the exchange of routing information between different autonomous systems. Establishing a stable BGP session is critical for efficient traffic forwarding across the internet.

2. TCP Connection Establishment

A BGP session commences with a TCP 3-way handshake on port 179. After establishing a reliable connection, the session proceeds to the Open message exchange phase to negotiate the fundamental parameters for the BGP session.

3. Open Message Exchange and Keepalive Message Exchange

The Open message exchange establishes BGP parameters such as version, autonomous system number, and Hold Timer. Hold Timer defines the session’s inactivity timeout. Keepalive messages maintain the connection by periodically exchanging messages. If no Keepalive message is received within the Hold Time, the session terminates.

4. Update Message Transmission and Path Selection

The core of the BGP session lies in the Update message transmission. Update messages contain new, modified, or withdrawn routing information. They include network, next hop, and path attribute information, enabling routing table updates and optimal path selection.

5. Withdrawal Message and Loop Prevention

Obsolete routing information is announced through Withdrawal messages and subsequently removed from the routing table. AS path information prevents routing loops and allows each AS to control the exchanged routing information.

6. Conclusion

The BGP session establishment process comprises TCP connection establishment, Open message exchange, Keepalive message exchange, Update message transmission, path selection, Withdrawal message, loop prevention, and policy enforcement. This process ensures a stable BGP session and facilitates efficient routing information exchange.