Introduction

There are many different routing protocols used in computer networks that allow communication between various devices. BGP in computer networks is one of the most important protocols used to exchange data between different AS (Autonomous Systems). It’s the standard protocol for communication between ISPs and also between businesses and ISPs. BGP contains complete routing information to all destinations.

BGP uses the routing data to track which networks are reachable and broadcasts that data to other BGP systems. We recommend OSPF BGP Training to learn this protocol in-depth.

What is BGP in computer networks?

BGP in Computer Networks stands for Border Gateway Protocol, and it’s a type of EGP (Exterior Gateway Protocol), and to be precise, it’s a type of Path-Vector Routing Protocol. It is considered the backbone of modern networks. BGP is responsible for finding the best paths for data to travel between autonomous systems (AS). Autonomous systems are basically large networks or a group of networks under a single administrator. Without it, the internet might collapse.

BGP also allows effective communication between independent networks, such as Internet Service Providers (ISPs) and enterprises. So, it enables effortless data transmission on a global scale.

We have shown in the figure below:

The main purpose of BGP is to choose the best path for sending data across the internet. While surfing the web, data is sent over many networks before arriving at its final destination. BGP analyzes all potential data transmission pathways and chooses the most efficient one.

For example: When a user in India wants to access a website based on servers in the United States, BGP ensures that the two locations can communicate quickly and effectively.

History of BGP in Networking

BGP was initially developed in 1989 as a replacement for the older exterior gateway protocol to address the growing routing complexity. BGP-1 was the first version of it, and it laid the groundwork for inter-network routing. However, it evolved quickly.

In 1994, BGP-4 became standard, and it is still being used in modern networking because of its ability to handle CIDR. This evolution allowed BGP to manage Internet addresses efficiently and protect the exhaustion of available IP addresses.

Why is the Border Gateway Protocol important?

Border Gateway Protocol matters because it keeps the internet running smoothly every day. Think of BGP as the traffic controller for the entire internet. Without it, your emails would get lost. Your videos would never load. Online shopping would stop working.

BGP connects thousands of different networks worldwide. Each internet company runs its own network. BGP helps these networks talk to each other and share traffic.

When you visit a website, your request might travel through ten different companies. BGP makes sure each company knows where to send your data next. It picks the best route available.

The protocol also provides backup routes. If one path breaks, BGP finds another way around. This keeps the internet working even when cables get cut, or servers crash. Major companies like Google and Amazon depend on BGP. Banks use it for secure transactions. Hospitals rely on it for patient systems.

BGP basically holds the internet together. Without this protocol, we would have thousands of separate networks that cannot communicate. The global internet as we know it would not exist.

How does BGP (Border Gateway Protocol) works?

BGP in Computer Networks uses a routing table to manage data packets and allows routers to exchange data with each other. The BGP process on the router is responsible for generating routing table information which is further based on various factors such as:

• Receiving information from other routers.
• Information that is included in the RIB (routing information base). RIB is a data table that is saved on a server that is located on the BGP router.

TCP connection and TCP port 179 are utilized by BGP in order to exchange data and messages.

Using the routing table and the attributes of the best possible paths, BGP selects the most efficient one for data transmission. Some of these attributes are AS path, next hop, IGP metric, and origin, which influence the routing decisions of the routers. BGP routers use a complex algorithm called the BGP decision process to select the best route for each destination network based on these attributes.

Routers that support BGP protocol in networking may generate graphs that map networked pathways within or between autonomous systems by exchanging information about available or new paths. This maintains the reliability of information flow in networks, boosts network stability, and avoids loop formation.

Autonomous Systems

In order to supervise organizations like ISPs, universities, and governments, autonomous systems were implemented. These systems consist of several independent networks, yet they are managed as a single entity. Major companies’ network infrastructures often consist of many smaller networks that are geographically separated yet linked via a common operating environment.

Each of your computers and other devices connected to the internet is linked to an AS. IANA (Internet Assigned Numbers Authority) is mainly responsible for managing autonomous systems.

When two or more independent systems need to be connected, they use BGP to handle the routing of packets between them. BGP uses the AS to identify a system uniquely. This is of utmost significance for routing and administering routing tables for autonomous systems and other networks around their borders.

Features of BGP in Computer Networks

BGP is packed with many features. Here are a few:

• Scalability: BGP is capable of handling the vast size of the global internet. So, it is very scalable.
• Path Vector: BGP is a Path vector protocol. So, it maintains the path a route has taken, which prevents routing loops.
• Policy-Based Routing: It allows network administrators to use custom routing policies and decide how data flows through the network.
• Loop Prevention: It uses the AS Path attribute to identify and avoid routing loops.

Characteristics Of Border Gateway Protocol (BGP)

The main characteristics of the Border Gateway Protocol are:

• BGP is a path vector protocol that tracks the full route to destinations. It runs over TCP port 179 for reliable message delivery.

• BGP makes routing decisions based on policies rather than just shortest paths

• It uses autonomous system numbers to identify different network operators.

• BGP prevents routing loops by rejecting paths that contain its own AS number 

• Route advertisements include detailed path information and network policies.

• The protocol sends only changes instead of complete routing table updates.

• BGP takes time to converge after network changes for stability reasons

• Manual configuration is required – BGP routers do not discover neighbors automatically.

• The protocol supports both IPv4 and IPv6 address families.

• BGP allows network operators to control traffic flow through policy settings

• It provides multiple paths to destinations for redundancy and load balancing.

• BGP focuses on reachability rather than optimal performance metrics

Functions of Border Gateway Protocol (BGP)

BGP in computer networks plays a crucial role in the functioning of the Internet by performing various vital functions. These functions include managing route information, selecting the most efficient route, providing redundancy measures to prevent routing errors, offering security through authentication mechanisms, and allowing communication between different network types.

• Maintaining Route Information: It maintains an accurate routing table by constantly adding new routes and updating the existing ones. BGP utilizes this table for deciding how to transmit data from one network to another.
• Selecting the best route: BGP in computer networks determines the most effective route for data transmission based on a number of factors, including distance and latency. In most cases, BGP routers will have many potential pathways to choose from and prioritize the one with the best performance.
• Detecting loops in routing paths: The Border Gateway Protocol (BGP) relies on a series of algorithms referred to as the BGP Decision Process to identify and reduce routing path loops. This process helps optimise packets’ transmission by selecting the most efficient route, thereby minimizing bandwidth consumption and avoiding unnecessary diversions.
• Providing security: It utilizes a preconfigured password or key to authenticate messages exchanged between routers. This measure helps guarantee that only authorized entities are able to engage in the exchange of information while simultaneously preventing malicious actors from preventing the flow of traffic.

Elements of BGP

Some of the Key elements of BGP are:

• BGP speakers are routers that run the protocol and exchange routing information

• Autonomous System numbers identify different network organizations and operators

• BGP sessions connect routers through TCP connections for reliable communication

• Path attributes contain extra details about each route, like origin and preferences

• Prefixes represent the actual IP address ranges being advertised

• BGP messages carry different types of information between connected routers

• OPEN messages start new sessions and exchange basic configuration details

• UPDATE messages announce new routes or withdraw old ones

• KEEPALIVE messages maintain active sessions between neighbors

• NOTIFICATION messages report errors and close broken sessions

• Route policies control which paths get accepted or rejected

• Communities tag routes with special labels for policy decisions

• Local preferences help routers pick the best path among multiple options

Types of BGP

There are two types of BGP:

iBGP (Internal Border Gateway Protocol)

It stands for internal BGP and is mainly used in single AS to maintain consistent routing information between routers. iBGP runs inside a single organization’s network. It helps routers within the same autonomous system share external routing information they learned from other networks. All iBGP routers within the network must connect to each other in a full mesh topology.  

iBGP never changes the next-hop address when passing routes between internal routers. It also uses a higher administrative distance than external BGP to prefer external routes over internal ones. 

Large networks often use route reflectors to reduce the number of required iBGP connections. This makes management easier while maintaining the same functionality and reliability that full mesh provides. 

eBGP (External Border Gateway Protocol)

When two internet service providers want to share traffic, they use eBGP sessions. These connections happen at network borders where different companies meet. eBGP routers typically connect directly to each other through dedicated links. 

Unlike internal BGP, eBGP changes the next-hop address when advertising routes. It also uses a lower administrative distance, making external routes more trusted than internal ones. This ensures traffic takes the most direct path between networks. 

eBGP sessions require careful coordination between network operators. Both sides must agree on policies, IP addresses, and connection details. The protocol automatically adds the local AS number to route advertisements, which prevents routing loops between different networks. 

Most internet routing happens through eBGP connections between major providers and smaller networks. 

Here are the main differences between the two.

Difference Between External BGP and Internal BGP

EBGP is used to exchange routing information between different autonomous systems (AS), while IBGP is used to exchange routing information within the same AS.

Below we have discussed the basic difference between EBGP and IBGP in a tabular form.

Factors	EBGP	IBGP
Administrative Distance (AD)	The default administrative distance in the case of EBGP is 20.	The default administrative distance in the case of EBGP is 200.
TTL (Time-To-Live)	EBGP peers by default set TTL to 1.	IBGP peers by default set TTL to 255.
Loop prevention	AS-path attribute is checked for the presence of its own AS number.	In the case of the IBGP, Split-horizon is used for loop prevention.
Topology	No need for full mesh topology.	Full mesh topology is required in IBGP.
Attributes	EBGP modifies some attributes, such as AS_PATH and NEXT_HOP, when sending routes to another AS.	IBGP preserves the attributes received from eBGP and does not change them when sending routes within the same AS.

These are the differences between the two BGP types.

BGP Messages

It relies on four message types to perform efficiently.

1. Open: It is used to establish a connection between peers.
2. Update: It is used to share route information, which involves advertising new paths and withdrawing outdated paths.
3. Notification: This one is used to alert peers to any errors or issues so that the session is closed if necessary.
4. Keepalive: It is used to maintain the connection by periodically exchanging these messages.

BGP Path Attributes

BGP relies on path attributes, known as BGP attributes, to make intelligent routing decisions. Some of these are:

• Local Preference: This attribute shows the preference of a route.
• AS Path: It tracks the AS numbers a route has traversed.
• Aggregator: It is used to specify the AS number and IP address of the router that executed route aggregation.

Role of BGP Protocol in Today’s Technology

Apart from the application of BGP for large-scale networks that we already have discussed, BGP is used in various technological domains. Let’s discuss the role of BGP in today’s technology in detail.

SDN and Cloud

Software-defined networks (SDNs) use the BGP to regulate traffic routing in response to network conditions dynamically. And in the field of cloud computing, BGP serves the purpose of interconnecting virtual networks and guaranteeing accurate traffic direction to designated destinations.

Cybersecurity

Since BGP can be used to monitor network traffic and block harmful activities, it is also playing a larger role in the fight against cybercrime. Security experts may defend their networks from attack by studying BGP routing data to find signs of attack.

IoT (Internet of Things)

BGP’s ability to route data between devices and networks makes it more crucial in the IoT industry. BGP provides a flexible and effective means of transmitting data between networks and the ever-growing number of Internet-enabled gadgets.

BGP Route Information Management Functions

• Route Storage – Each BGP that uses route storage has its own set of databases in which it keeps instructions for connecting to other networks. In addition, BGP may access routing information stored in databases.
• Route Update – This process uses particular approaches to determine when and how to use the data gathered from peers to update the routes effectively. BGP updates messages with routing information as it learns it. These are stored in a routing table that’s accessible once the system is started.
• Route Selection – Each BGP utilizes a process to determine the optimal routes to individual networks across the internet by using the data stored in its route databases.
• Route Advertisement – When more than one path is possible, BGP will only advertise the optimal path to its neighbors. The network operates more effectively because only routes that are likely to be successful are advertised.

How does OSPF compare to BGP?

Both OSPF and BGP are routing protocols that help networks find the best paths to send data, but they work in very different ways and places. Let’s understand the basic difference between OSPF and BGP.

• OSPF works well for company networks with hundreds of routers. BGP can handle the entire internet on a massive scale. Small businesses pick OSPF, while internet providers choose BGP.

• OSPF only works inside one organization’s network. BGP works both inside networks and between different organizations.

• OSPF is easier to configure and set up. BGP needs more expertise and careful planning.

• OSPF uses a tree-like structure with clear levels. BGP creates a web where everyone connects to everyone. OSPF has areas and zones, while BGP has autonomous systems.

• OSPF notices broken links and fixes routes quickly. BGP takes more time to make routing changes.

• OSPF uses more CPU power and memory on each router. BGP’s resource needs depend on how many routes it knows. A full BGP table needs several gigabytes of memory.

• OSPF shines in office networks and data centers. BGP rules the internet and wide area networks. Cloud providers use both protocols together.

• OSPF shares complete network maps with all routers. BGP only advertises the best paths it knows.

• OSPF calculates the shortest paths using link costs. BGP makes decisions based on business policies.

How to secure BGP?

Protecting BGP takes careful planning and multiple security layers working together.

• First, verify who connects to your network. Use strong passwords and certificates between routers. Never trust connections without proper authentication. This blocks fake routers from joining your network.

• Create strict filters for incoming routes. Make lists of valid IP ranges and reject anything suspicious.

• Watch your routing tables closely. Set up alerts for unusual changes or new route announcements. Automated monitoring tools can spot problems faster than humans.

• Update router firmware regularly. Old software has vulnerabilities that hackers love to exploit. Install security patches quickly when vendors release them.

• Use route validation systems like RPKI. These tools check if route announcements are real before accepting them.

• Keep detailed records of your security policies and filter rules. Good documentation saves time during crisis situations.

Advantages of BGP

Here are some benefits of BGP in Computer Networks-

• Scalability
• Internet-wide reachability
• Path selection and policy control
• Fault tolerance and redundancy
• Load balancing
• Traffic engineering
• Policy-based routing
• Inter-operability
• Security
• Internet backbone management

Disadvantages of BGP

Here are some disadvantages of BGP Protocol in Networking –

• Slow convergence time
• Vulnerability to routing attacks
• Lack of built-in encryption
• Limited support for traffic engineering
• Difficulty in troubleshooting and debugging
• Dependence on manual configuration and management
• Inefficient handling of frequent route updates

Future of BGP in Computer Networks

As networking evolves, so does BGP. Seeing the current trends like automation, shifting towards AI and ML, and security enhancements, BGP is set for the future and won’t lose its scope in the near future.

Frequently Asked Questions

Q1. Where is BGP used?

BGP (Border Gateway Protocol) is used in the internet infrastructure to facilitate routing and exchange of routing information between different autonomous systems (ASes).

Q2. How many types of BGP are there?

Mainly there are two types of BGP. These are:

• EBGP: EBGP stands for external border gateway protocol. It is a routing protocol that exchanges network information between autonomous systems on the internet.
• IBGP: IBGP stands for Internal Border gateway protocol. It is a routing protocol that is used to exchange routing information between routers within the same autonomous system.

Q3. What is the BGP format?

BGP (Border Gateway Protocol) uses a message-based format for communication, with messages exchanged between routers in the form of variable-length packets containing different types of BGP messages such as Open, Update, Keepalive, and Notification.

Q4. What are the 6 stages of BGP?

BGP (Border Gateway Protocol) operates through six stages: Idle, Connect, OpenSent, OpenConfirm, Established, and Active. These stages represent the progression of a BGP session from initialization to full routing table exchange and stable connectivity.

Conclusion

BGP in computer networks is the protocol that connects different networks on the Internet and enables them to exchange routing information. BGP is a dynamic and flexible protocol that can adapt to network topology and traffic conditions changes.  

We hope that this post has given you a better understanding of BGP protocol in networking and its role in the Internet. You can also check out – BGP Interview Questions and Answers.