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BGP (Border Gateway Protocol) vs OSPF (Open Shortest Path First)

BGP (Border Gateway Protocol) vs OSPF (Open Shortest Path First)

The internet is arguably the most useful bit of technology we have, but when you get into the nuts and bolts of how it actually works, it can be a lot.

The best way to master potentially challenging networking concepts is one idea at a time. With that in mind, we can focus today on two common connection protocols: BGP and OSPF.

What Is BGP?

Border gateway protocol (BGP) is a topology used to connect devices across the internet. It’s a best-parth topology protocol which means it focuses on finding the best route rather than the shortest or fastest route. It’s also an inter-domain protocol, meaning it’s designed to connect devices that are not in the same domain.

Before getting into the details of how it functions, it’s easiest to understand BGP at a broad level. If you try to connect to a website somewhere in the world, networking tools have to figure out how to make that connection work. There are conceivable miles of connections between you and your target, and that leaves room for a lot of different paths.

Overall, you can think about major nodes or hubs between you and your destination. BGP specializes in planning a route amongst those hubs. They’re often called autonomous systems, and they include major servers and centers that route traffic along the internet.

How Does It Work?

Ok . BGP plans a route across the broad network of autonomous systems. How?

This is done via a data routing protocol. Basically, peering sessions allow the protocol to acquire information in order to route a connection path.

You see, autonomous systems are always changing. That means there need to be constantly updated data tables that hold the routing data from one autonomous system to the next. 

BGP taps into these data tables in order to inform routing policies. Basically, the autonomous systems keep up-to-date information, and the protocol follows rules according to those maps.

Here’s where it gets interesting. The autonomous systems tend to be powerful, expensive systems, and they aren’t all owned by the same organizations. To connect to a website, your packets might have to travel through systems owned by ISPs, the government, schools, or more. Because of this, BGP often has to pay in order to access routing information from the autonomous systems.

What this really means is that BGP doesn’t just optimize according to latency or throughput. It also optimizes around costs, which is the fundamental reason it’s a best path topology protocol rather than a fastest or shortest route protocol.

Pros and Cons

This makes BGP an interesting and powerful protocol for long-distance, complicated connections. But, it’s not a universal protocol, and it’s important to understand why.

BGP shines in terms of adaptability, scalability, and efficiency. These traits allow it to trace paths through worldwide connections across the internet.

At the same time, it’s not the fastest or most direct protocol. As a result, it’s not great for smaller scale networking — especially intranet connections.

What Is OSPF?

Those pros and cons are why other protocols exist, and one of them is the open shortest path first (OSPF) protocol.

Whereas BGP shines in interconnecting autonomous systems, OSPF zooms in a bit. As the name implies, this protocol tries to find the fastest path through a series of viable connections, and it does this with a hierarchical topology. It also uses a link-state routing algorithm to achieve its goals.

What this means is that OSFP aims to find the best routing path through simultaneously connected networks. Or, you could say that it specializes in minimizing connection paths through a single autonomous system.

How Does It Work?

That’s really the key. OSPF can route through multiple autonomous systems, but that’s not the primary design goal. Instead, as an optimizer through smaller total connections, OSPF takes a look at the routing data shared by autonomous systems. This data is framed within an IP network, giving OSPF the information it needs to pick a path.

Routers exchange the necessary information, and OSPF is able to craft a route that minimizes delays.

Pros and Cons

Where does OSPF shine, and where does it leave things to be desired?

At its core, OSPF is great at utilizing topology data to optimize network pathing. Even better, it can zero in on specific standards and metrics, allowing it to optimize according to different lines set by the administrator.

On the downside, OSPF struggles with scale. It can take a while to compute the end-to-end routes.


Based on all of that, which should you be using?

In most cases, the nature of the connection tells you what you need to know. If you’re doing intranet connections, OSPF is faster and more useful. If you’re doing internet connections, then BGP shines.

In reality, the two work well together. A single autonomous system might use OSPF to route data through its own devices and localized network. Meanwhile, BGP is mapping the master, large-scale routes for packets sent across great distances.


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