BGP Protocol: Routing and Advantages

BGP allows the classification of network routes based on paths, network policies, or rule sets configured by a network administrator, ensuring loop-free routing and building a clear and optimized path for data travel from source to destination.

The BGP Protocol or Border Gateway Protocol refers to a standardized exterior gateway protocol that is used for exchanging routing and reachability information between different autonomous systems (AS) on the internet. It helps in directing network packets through the various networks that make up the internet, ensuring data sent from one computer to another arrives efficiently.

Table of Contents

• How does Border Gateway Protocol work?
• What is BGP routing?
• Advantages of BGP Protocol

How does Border Gateway Protocol work?

BGP works by establishing connections with BGP peers, exchanging BGP messages, selecting the best path based on path attributes, and advertising the best path to peers, all while preventing routing loops using the Path Vector algorithm. 

The protocol also supports route aggregation and policy-based routing. It involves complex processes and mechanisms to ensure efficient and loop-free routing between different autonomous systems (AS) on the internet. Below is a technical explanation of the working of BGP:

1. Establishment of BGP Session:

• TCP Connection: BGP establishes a TCP connection on port 179 between the BGP peers. This connection is used for exchanging BGP messages.
• BGP Peering: BGP routers form a peer relationship, known as a BGP session, to exchange routing information. Peers are established manually by configuring each router with the IP address of the other router.

2. Exchange of BGP Messages:

• OPEN Message: After the TCP connection is established, each BGP router sends an OPEN message to negotiate parameters and authenticate each other.
• UPDATE Message: BGP routers exchange UPDATE messages to advertise new routes or withdraw previously advertised routes.
• KEEPALIVE Message: KEEPALIVE messages are exchanged to maintain the connection and verify that the peers are reachable.
• NOTIFICATION Message: If errors occur, a BGP router sends a NOTIFICATION message and closes the connection.

3. Path Attributes and Route Selection:

• AS Path: BGP uses path attributes, such as the AS path, to make routing decisions. The AS path is a list of AS that the routing information has traversed.
• Route Selection: BGP selects the best path based on path attributes, including AS path, next-hop IP address, and others. The selected path is then added to the BGP routing table.

4. Advertisement of Best Path:

• BGP advertises the best path to all BGP peers. If a better path is found, BGP updates the peers with the new path.

5. Path Vector Algorithm:

• BGP uses the Path Vector algorithm to prevent routing loops by carrying the AS path information with the route. If a BGP router receives a route containing its own AS in the AS path, it will reject the route to prevent a loop.

6. Route Aggregation and Filtering:

• BGP can aggregate multiple IP prefixes into a single route advertisement, reducing the size of routing tables.
• BGP also allows policy-based routing, where routes can be filtered based on various attributes, allowing network administrators to control the routing behaviour.

What is BGP routing?

Understanding BGP (Border Gateway Protocol) routing is crucial for several reasons, especially for network administrators, engineers, and anyone involved in managing and designing network infrastructures. It is also important for troubleshooting network issues related to routing. It enables the identification and resolution of routing problems, ensuring the smooth operation of network services. 

BGP (Border Gateway Protocol) routing is a mechanism used to make decisions about the path that data should take to traverse the internet or a network of autonomous systems (AS). It is a path vector protocol that determines the most efficient and reliable route for data packets to travel between different networks, ensuring that the data reaches its destination correctly and efficiently. BGP routing ensures the efficient and optimal path for data transmission between different autonomous systems.

How Does BGP Routing Work?

1. Establishing Connections: BGP establishes a connection between BGP peers (routers) in different autonomous systems. This connection, known as a BGP session, is established over TCP and allows the routers to exchange routing information.
2. Exchange of Network Information: BGP routers exchange network path information through BGP messages. This information includes various path attributes, such as the AS path, which is a list of AS that the route has traversed.
3. Path Selection: BGP analyzes the path attributes of received routes to determine the best path to reach each network. The decision is based on factors such as the shortest AS path, highest weight, and other configurable attributes. The selected best path is then added to the BGP routing table.
4. Advertising the Best Path: The BGP router advertises the best path to all its peers, ensuring that other routers know the most efficient path to route the traffic to reach a specific network.
5. Handling Path Changes: BGP continuously monitors the network paths. If a path becomes unavailable, BGP will select an alternative path from the available paths in its routing table. If a new better path is found, BGP will update the best path and advertise the change to its peers.
6. Loop Prevention: BGP uses the AS path attribute to prevent routing loops by rejecting any route advertisement that contains its own AS number in the AS path.

Advantages of BGP Protocol

BGP Protocol has the following advantages due to which it is used:

• Internet Operation: BGP is the protocol that makes the internet work by connecting different networks worldwide. It is fundamental to the operation of the internet, ensuring that data can be sent and received across global networks.
• Network Stability: BGP contributes to network stability by continuously monitoring paths and making dynamic adjustments. It can reroute traffic in the event of a path failure, ensuring uninterrupted network services.
• Policy Implementation: BGP helps network administrators in implementing routing policies. Knowledge of BGP is essential for setting up policies that can control the network traffic flow, ensuring adherence to organizational requirements and standards.
• Security: Understanding BGP is crucial for network security. BGP knowledge helps in identifying and mitigating BGP-related security issues such as route hijacking and leaks, protecting the network from potential vulnerabilities.
• Troubleshooting: Knowledge of BGP routing is vital for troubleshooting network issues related to routing. It enables the identification and resolution of routing problems, ensuring the smooth operation of network services.
• Network Design: For designing robust and efficient network architectures, understanding BGP routing is essential. It helps in making informed decisions for network design, ensuring scalability, reliability, and efficiency.