The container registry API will be adopted by the OCI (Open Container Initiative) to standardize the container images. The API is based on Docker’s V2 protocol will be further integrated with Docker’s toolset and it will be used by the cloud vendors as well.

About Docker Register API V2 Protocol

“In the technical era, where containerization and cloud technologies are on the boom, communities need a reliable standard to distribute the images throughout the network. And this is necessary to accelerate the interoperability with a neutral base to evolve the specifications.”

Docker’s V2 protocol is the current version of the protocol whose objective is to pull images among users and registries. Based on its endless benefits, it has been adopted in OCI and made sure that all the implementations are followed nicely.

What is different in V2 protocol from the previous version?

According to a report submitted by the Docker’s engineer, more than forty billion images have been pushed with the protocol as of now. The V2 protocol has significant improvements over the previous versions and the major benefit is that tight coupling of images has been removed within Docker tools itself.

The architecture of V1 protocol was not suitable that led to the discovery of fresh version. In the new version, the security levels have been improved significantly and image definitions are also simplified to a larger extent. Some of the highlighting benefits of the V2 fresh protocol includes –

  • Excellent security techniques
  • Performance levels are optimized.
  • The bandwidth usage has been minimized.
  • The chances of backend corruption are also reduced significantly.

Based on one survey, not only the Docker hub registry but a plenty of cloud vendors have already started supporting the V2 protocol. This would work as a living document to explain to users what is specific and what to keep for the future changes. Only the accepted changes would be added to the API and conflicted modifications will be kept for the future.

There is one section where you can quickly get the detail what is new and different. Also, you can mark the specifications that will be focused later and this is just an option, not the mandatory requirement.

How images are verified in Docker registry V2 protocol?

Docker engine runs the instance of the image that needs to verify. The engine contacts the registry and requests to verify the signature to make sure that request has been generated from the trusted source only. As soon as signatures are approved, you can download the individual layers otherwise untrusted registry will return a manifest.

It not only checks the signature and source of the image but also makes sure that images were not altered in between. Once all individual layers are downloaded, it will give you a confirmation that content perfectly matches to the request was asked by the manifest.

Resumable Push & Pull

Take an example, one image upload was initiated by some Company and server connection is lost in between before the actual transfer. In this case, the server will again put the request for image reload and Docker register would identify the request and reload the remaining part only that was started earlier. This is the way, how image loading and the overall performance levels can be improved and made faster ultimately.

The same process is true when images are uploaded by the Companies. In case of connectivity loss, the upload process would resume from the same point where it was left earlier. This is the best way to save your GBs by avoids downloading and uploading of repeated data.

Further, take an example when Company uploaded two similar layers to the servers without knowing the fact that they are identical. Here, the registry will identify the duplicate content and notifies the client that this particular file is not necessary. This will help the user to decide either he wants to keep data or remove it.

In brief, you can optimize the database performance and storage space as per your requirements in your budget only.

Final Words:

OCI has standardized other aspects of container ecosystem in past to push the images and runtime specification. The standardization of V1 protocol was announced last year. Here, standardization of new layer V2 in OCI is another achievement by the Linux Foundation.

It happened based on terms and policies of OCI, started with a proposal then discussion and voting. With the warm acceptance, the protocol has become an integral part of container ecosystem and it will flourish as a part of OCI.

Contributor:  Manchun Kumar, Digital Marketing Consultant,

Author Bio: Manchun  Pandit loves pursuing excellence through writing and has a passion for technology. he has successfully managed and run personal technology magazines and websites. he currently writes for, a global training company that provides e-learning and professional certification training.

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