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My friend: Hi Ibrahim, I have a question for you.
- Me: Please, go ahead.
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My friend: I want to understand the difference between VNF and CNF, so could you clarify it?
- Me: Sure. While VNFs (Virtualized Network Functions) and CNFs (“Cloud-Native Functions” or “Containerized Network Functions”) both aim to virtualize network functions, they differ in their approach. So, VNF will virtualize the HW using the hypervisor which will share the COTS HW resources between the VMs (Virtual Machines) and VMs will be isolated from each other as each VM will have its own operating system (OS) which is the guest OS. One VNF contains one or more VMs based on the configuration and tasks that this VNF will do. VNFs tend to replicate the traditional network function architecture in a virtual environment and hence the SW or applications of the old legacy solutions can be taken as it is and deployed over VMs while CNFs are not doing that.
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My friend: So, how CNFs are working?
- Me: As an evolution from VNFs, CNFs are designed and implemented to run over containers rather than VMs. CNFs leverage the principles of cloud-native computing, breaking down functions into smaller, independent services for greater flexibility and scalability which are called microservices. So, CNFs are a group of containers that are running many microservices inside. So, the SW or applications of the legacy solutions should have further rearchitecting like decomposing it into microservices. CNFs are virtualizing the OS, so all CNFs will share the same host OS. As containers are more lightweight than VMs, so HW is better utilized as more containers can run on the same HW, also containers are more easier to be portable to run over any infrastructure as each container has all its dependencies such as files, libraires, etc. and containers’ image size are much less than VM images. So, CNFs offer greater flexibility and scalability, less down time than VNFs allowing for frequent upgrades to live applications without impacting end consumers.
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My friend: So, which solution can be used in Cloud RAN?
- Me: Let me say that when the virtualization started in mobile network, the core network was the first section to be virtualized and VNFs were implemented as core is more easier than RAN because it is more centralized than the RAN which is distributed everywhere. So, core networks started with VNFs and now moving to CNFs. While at RAN side, the RAN guys learned the lessons from the core network and mostly to start with CNFs as it is more efficient and have many advantages than VNFs.
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My friend: Thank you very much, you made it very clear.
- Me: You are most welcome.
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