OSPF vs BGP: Which Routing Protocol to Use?

Posted on August 15, 2018

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John

Both OSPF (Open Shortest Path First) and BGP (Border Gateway Protocol) are routing protocols that make routing decisions across the Internet. They represent a set of rules or algorithms that instruct network routers on how to communicate with each other, so they can redirect traffic to the best path. OSPF vs BGP, what are their differences? How to choose between the two?

what is ospf vs bgp

OSPF vs BGP: What Are the Differences?

The main difference between OSPF and BGP is that OSPF is an intra-domain routing protocol using link state routing, and the routing operation is performed inside an autonomous system while BGP is the inter-domain routing protocol that uses path vector routing, with the routing operations performed between two autonomous systems. Some other distinctions between OSPF vs BGP include:

Configuration: OSPF is easily-configured while BGP configuration is a lot more complex.
Convergence rate: OSPF can achieve convergence (the time a router takes to share and update the latest routing information) faster. In contrast, the BGP has a slow convergence rate.
Network topology or design: OSPF is a type of hierarchical network topology or design while BGP is a type of mesh topology or design.
Resources requirement: OSPF requires intensive use of memory and CPU resources. With BGP on the other hand, the size of the routing table dictates the required device resources.
Scale: BGP is more flexible and scalable than OSPF and it is also used on a larger network.
Preferred path: OSPF is used to determine the fastest route while BGP puts emphasis on determining the best path.
Protocol: In OSPF, internet protocol is used. While in BGP, transmission control protocol is used.

Here is a chart summarizing the differences of OSPF vs BGP:

	OSPF	BGP
Gateway Protocol	Internal gateway protocol	External gateway protocol
Implementation	Easy	Complex
Convergence	Fast	Slow
Design	Hierarchical network possible	Meshed
Need for device resources	Memory and CPU Intensive	Scaling is better in BGP although it relies on the size of the routing table
Size of the networks	Used on primarily smaller scale network which could be administered centrally	Mostly used on large scale networks such as the internet
Function	The fastest route is preferred over shortest	Best path is determined for the datagram
Algorithm Used	Dijkstra algorithm	Best path algorithm
Protocol	IP	TCP

OSPF vs BGP: How to Choose?

If you are conducting internal routing, such as routing within a site, company, or campus, you will want to use OSPF. BGP is typically needed at a site edge, where you route out to the public internet. If you are looking at building in-site with multiple homes, you might want to consider BGP. Moreover, for enterprise network, pick OSPF as your routing protocol. As a developed and mature protocol, OSPF is supported by the vast majority of network vendors. As a service provider, adopt the BGP to carry your customers' routes. Generally, most of the service providers would use IGP to carry Infrastructure IPs and BGP to carry customer routes.

Although BGP is used between multiple autonomous systems as an external routing protocol, many network giants like Microsoft and Facebook would use it internally – in this case, BGP is typically fit for very large networks which OSPF fails to handle. One of the many reasons that BGP does not function well as an internal gateway protocol is that it is very slow to converge.

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