The Traditional World

Before we address how containers facilitate virtualization, let’s address the basics. In the past, we could solely run one application per server. However, the open-systems world of Windows and Linux didn’t have the technologies to safely and securely run multiple applications on the same server.

So, whenever we needed a new application, we would buy a new server. We had the virtual machine (VM) to solve the waste of resources. With the VM, we had a technology that permitted us to safely and securely run applications on a single server. Unfortunately, the VM model also has additional challenges.

Migrating VMs

For example, VMs are slow to boot, and portability isn’t great — migrating and moving VM workloads between hypervisors and cloud platforms is more complicated than it needs to be. All of these factors drove the need for new container technology with container virtualization.

How do containers facilitate virtualization? We needed a lightweight tool without losing the scalability and agility benefits of the VM-based application approach. The lightweight tool is container-based virtualization, and Docker is at the forefront. The container offers a similar capability to object-oriented programming. It lets you build composable modular building blocks, making it easier to design distributed systems.

Container Networking

In the following example, we have one Docker host. We can list the available networks for these Docker hosts with the command docker network ls. These are not WAN or VPN networks; they are only Docker networks.

Docker networks are virtual networks that allow containers to communicate with each other and the outside world. They provide isolation, security, and flexibility to manage network traffic flow between containers. By default, when you create a new Docker container, it is connected to a default bridge network, which allows communication with other containers on the same host.

Notice the subnets assigned of 172.17.0.0/16. So, the default gateway ( exit point) is set to the docker0 bridge.

Types of Docker Networks:

Docker offers various types of networks, each serving a specific purpose:

1. Bridge Network:

The bridge network is the default network that enables communication between containers on the same host. Containers connected to the bridge network can communicate using IP addresses or container names. It provides a simple way to connect containers without exposing them to the outside world.

2. Host Network:

In the host network mode, a container shares the network stack with the host, using its network interface directly. This mode provides maximum network performance as no network address translation (NAT) is involved. However, it also means the container is directly exposed to the host’s network, potentially introducing security risks.

3. Overlay Network:

The overlay network allows containers to communicate across multiple Docker hosts, even in different physical or virtual networks. It achieves this by encapsulating network packets and routing them to the appropriate destination. Overlay networks are essential for creating distributed and scalable applications.

4. Macvlan Network:

The Macvlan network mode allows containers to have MAC addresses and appear as separate devices. This mode is useful when assigning IP addresses to containers and making them accessible from the external network. It is commonly used when containers must be treated as physical devices.

5. None Network:

The non-network mode isolates a container from all networking. It effectively disables all networking capabilities and prevents the container from communicating with other containers or the outside world. This mode is typically used when networking is not required or desired.

Guide Container Networking

You can attach as many containers as you like to a bridge. They will be assigned IP addresses within the same subnet, meaning they can communicate by default. You can have a container with two Ethernet interfaces ( virtual interfaces ) connected to two different bridges on the same host and have connectivity to two networks simultaneously.

Also, remember that the scope is local when you are doing this, and even if the docker hosts are on the same underlying network but with different hosts, they won’t have IP reachability. In this case, you may need a VXLAN overlay network to connect containers on different docker hosts.

Container-based Virtualization

One critical benefit of container-based virtualization is its portability. Containers encapsulate the application and all its dependencies, allowing it to run consistently across different environments, from development to production. This portability eliminates the “it works on my machine” problem and makes it easier to maintain and scale applications.

• Scalability

Another advantage of containerization is its scalability. Containers can be easily replicated and distributed across multiple hosts, making it straightforward to scale applications horizontally. Furthermore, container orchestration platforms, like Kubernetes, provide automated management and scaling of containers, simplifying the deployment and management of complex applications.

• Security

Security is crucial to any virtualization technology, and container-based virtualization is no exception. Containers provide isolation between applications, preventing them from interfering with each other. However, it is essential to note that containers share the same kernel as the host OS, which means a compromised container can potentially impact other containers. Proper security measures, such as regular updates and vulnerability scanning, are essential to ensure the security of containerized applications.

• Tooling

Container-based virtualization also offers various tools and platforms for application development and deployment. Docker, for example, is a popular containerization platform that provides a user-friendly interface for building, running, and managing containers. It simplifies container image creation and enables developers to package their applications and dependencies.

Understanding Kubernetes Networking Architecture

Kubernetes networking architecture comprises several crucial components that enable seamless communication between pods, services, and external resources. The fundamental building blocks of Kubernetes networking include pods, nodes, containers, and the Container Network Interface (CNI). r.

Network security is paramount to any Kubernetes deployment. Network policies provide a powerful tool to control ingress and egress traffic, enabling fine-grained access control between pods. Kubernetes has the concept of network policies and demonstrates how to define and enforce them to enhance the security posture of your Kubernetes cluster.  

Applications of Container-Based Virtualization:

1. DevOps and Continuous Integration/Continuous Deployment (CI/CD): Containerization enables developers to package applications, libraries, and configurations into portable and reproducible containers. This simplifies the deployment process and ensures consistency across different environments, facilitating faster software delivery.

2. Microservices Architecture: Container-based virtualization aligns well with the microservices architectural pattern. Organizations can develop, deploy, and scale each service independently using containers by breaking down complex applications into more minor, loosely coupled services. This approach enhances modularity, scalability, and fault tolerance.

3. Hybrid Cloud and Multi-Cloud Environments: Containers provide a unified platform for deploying applications across hybrid and multi-cloud environments. With container orchestration tools, organizations can leverage the benefits of multiple cloud providers while ensuring consistent deployment and management practices.

How do containers facilitate virtualization?

• Container-Based Applications

Now, we have complex distributed software stacks based on microservices. Its base consists of loosely coupled components that may change and software that runs on various hardware, including test machines, in-house clusters, cloud deployments, etc. The web front end may include the following:

• Ruby + Rail.
• API endpoints with Python 2.7.
• Stack website with Nginx.
• A variety of databases.

We have a very complex stack on top of various hardware devices. While the traditional monolithic application will likely remain for some time, containers still exhibit the use case to modernize the operational model for conventional stacks. Both monolithic and container-based applications can live together.

The application’s complexity, scalability, and agility requirements have led us to the market of container-based virtualization. Container-based virtualization uses the host’s kernel to run multiple guest instances. Now, we can run multiple guest instances (containers), and each container will have its root file system, process, and network stack.

Containers allow you to package an application with all its parts in an isolated environment. They are a complete abstraction and do not need to run dependencies on the hosts. Docker, a type of container (first based on Linux Containers but now powered by runC), separates the application from infrastructure using container technologies. 

Similar to how VMs separate the operating system from bare metal, containers let you build a layer of isolation in software that reduces the burden of human communication and specific workflows. An excellent way to understand containers is to accept that they are not VMs—they are simple wrappers around a single Unix process. Containers contain everything they need to run (runtime, code, libraries, etc.).

Linux kernel namespaces

Isolation or variants of isolation have been around for a while. We have mount namespacing in 2.4 kernels and userspace namespacing in 3.8. These technologies allow the kernel to create partitions and isolate PIDs. Linux containers (Lxc) started in 2008, and Docker was introduced in Jan 2013, with a public release of 1.0 in 2014. We are now at version 1.9, which has some new networking enhancements.

Docker uses Linux kernel namespaces and control groups, providing an isolated workspace, which offers the starting grounds for the Docker security options. Namespaces offer an isolated workspace that we call a container. They help us fool the container.

We have PID for process isolation, MOUNT for storage isolation, and NET for network-level isolation. The Linux network subsystem has the correct information for additional Linux network information.

Container-based application: Container operations

Containers use schedulers. A scheduler starts containers on the correct host and then connects them. It also needs to manage container failover and handle container scalability when there is too much data to process for a single instance. Popular container schedulers include Docker Swarm, Apache Mesos, and Google Kubernetes.

The correct host is selected depending on the type of scheduler used. For example, Docker Swarm will have three strategies: spread, binpack, and random. Spread means node selection is based on the fewest containers, disregarding their states. Binpack selection is based on hosts with minimum resources, i.e., the most packed. Finally, random strategy selections are chosen randomly.

Containers are quick to start.

How do containers facilitate virtualization? First, they are quick. Starting a container is much faster than starting a VM—lightweight containers can be started in as little as 300ms. Initial tests on Docker revealed that a newly created container from an existing image takes up only 12 kilobytes of disk space.

A VM could take up thousands of megabytes. The container is lightweight, as its references point to a layered filesystem image. Container deployment is also swift and network-efficient.

Fewer data needs to travel across the network and storage fabrics. Elastic applications that have frequent state changes can be built more efficiently. Both Docker and Linux containers fundamentally change application consumption. 

As a side note, not all workloads are suitable for containers, and heavy loads like databases are put into VMs to support multi-cloud environments. 

Docker networking

Docker networking is an essential aspect of containerization that allows containers to communicate with each other and external networks. In this document, we will explore the different networking options available in Docker and how they can facilitate seamless communication between containers.

By default, Docker provides three networking options: bridge, host, and none. The bridge network is the default network created when Docker is installed. It allows containers to communicate with each other using IP addresses. Containers within the same bridge network can communicate with each other directly without the need for port mapping.

As the name suggests, the host network allows containers to share the network namespace with the host system. This means containers using the host network can directly access the host system’s interfaces. This option is helpful for scenarios where containers must bind to specific network interfaces on the host.

On the other hand, the non-network option completely isolates the container from the network. Containers using the none network cannot communicate with other containers or external networks. This option is useful when running a container in complete isolation.

Creating custom networks

In addition to these default networking options, Docker also provides the ability to create custom networks. Custom networks allow containers to communicate with each other, even if they are not in the same network namespace. Custom networks can be made using the `docker network create` command, specifying the desired driver (bridge, overlay, macvlan, etc.) and any additional options.

One of the main benefits of using custom networks is the ability to define network-level access control. Docker provides the ability to define network policies using network labels. These labels can control which containers can communicate with each other and which ports are accessible.

Closing Points on Docker networking

Networking is very different in Docker than what we are used to. Networks are domains that interconnect sets of containers. So, if you give access to a network, you can access all containers. However, you must specify rules and port mapping if you want external access to other networks or containers.

A driver backs every network, be it a bridge or overlay driver. These Docker-based drivers can be swapped out with any ecosystem driver. The team at Docker views them as pluggable batteries.

Docker utilizes the concept of scope—local (default) and Global. The local scope is a local network, and the global scope has visibility across the entire cluster. If your driver is a global scope driver, your network belongs to a global scope. A local scope driver corresponds to the local scope.

Containers and Microsegmentation

Microsegmentation is a security technique that divides a network into smaller, isolated segments, allowing organizations to create granular security policies. This approach provides enhanced control and visibility over network traffic, preventing lateral movement and limiting the impact of potential security breaches.

Microsegmentation offers organizations a proactive approach to network security, allowing them to create an environment more resilient to cyber threats. By implementing microsegmentation, organizations can enhance their security posture, minimize the risk of lateral movement, and protect their most critical assets. As the cyber threat landscape continues to evolve, microsegmentation is an effective strategy to safeguard network infrastructure in an increasingly interconnected world.

• Docker and Micro-segmentation

Docker 0 is the default bridge. They have now extended into bundles of multiple networks, each with independent bridges. Different bridges cannot directly talk to each other. It is a private, isolated network offering micro-segmentation and multi-tenancy features.

The only way for them to communicate is via host namespace and port mapping, which is administratively controlled. Docker multi-host networking is a new feature in 1.9. A multi-host network comprises several docker hosts that form a cluster.

Several containers in each host form the cluster by pointing to the same KV (example -zookeeper) store. The KV store that you point to defines your cluster. Multi-host networking enables the creation of different topologies and lets the container belong to several networks. The KV store may also be another container, allowing you to stay in a 100% container world.

Final points on container-based virtualization

In recent years, container-based virtualization has become famous for deploying and managing applications. Unlike traditional virtualization, which relies on hypervisors to run multiple virtual machines on a single physical server, container-based virtualization leverages lightweight, isolated containers to run applications.

So, what exactly is container-based virtualization, and why is it gaining traction in the technology industry? In this blog post, we will explore the concept of container-based virtualization, its benefits, and how it differs from traditional virtualization.

Operating system-level virtualization

Container-based virtualization, also known as operating system-level virtualization, is a form of virtualization that allows multiple containers to run on a single operating system kernel. Each container is isolated from the others, ensuring that applications and their dependencies are encapsulated within their runtime environment. This isolation eliminates application conflicts and provides a consistent environment across deployment platforms.

Critical advantages of container virtualization

One critical advantage of container-based virtualization is its lightweight nature. Containers are designed to be portable and efficient, allowing for rapid application deployment and scaling. Unlike virtual machines, which require an entire operating system to run, containers share the host operating system kernel, reducing resource overhead and improving performance.

Another benefit of container-based virtualization is its ability to facilitate microservices architecture. By breaking down applications into more minor, independent services, containers enable developers to build and deploy applications more efficiently. Each microservice can be encapsulated within its container, making it easier to manage and update without impacting other application parts.

Greater flexibility and scalability

Moreover, container-based virtualization offers greater flexibility and scalability. Containers can be easily replicated and distributed across hosts, allowing for seamless horizontal scaling. This ability to scale quickly and efficiently makes container-based virtualization ideal for modern, dynamic environments where applications must adapt to changing demands.

Container virtualization is not a complete replacement.

It’s important to note that container-based virtualization is not a replacement for traditional virtualization. Instead, it complements it. While traditional virtualization is well-suited for running multiple operating systems on a single physical server, container-based virtualization is focused on maximizing resource utilization within a single operating system.

In conclusion, container-based virtualization has revolutionized application deployment and management. Its lightweight nature, isolation capabilities, and scalability make it a compelling choice for modern software development and deployment. As technology continues to evolve, container-based virtualization will likely play a significant role in shaping the future of application deployment.

Container-based virtualization has transformed how we develop, deploy, and manage applications. Its lightweight nature, scalability, portability, and isolation capabilities make it an attractive choice for modern software development. By adopting containerization, organizations can achieve greater efficiency, agility, and cost savings in their software development and deployment processes. As container technologies continue to evolve, we can expect even more exciting possibilities in virtualization.

Google Cloud Data Centers

### What is a Cloud Service Mesh?

A cloud service mesh is essentially a network of microservices that manage and optimize communication between application components. It operates behind the scenes, abstracting the complexity of inter-service communication from developers. With a service mesh, you get a unified way to secure, connect, and observe microservices without changing the application code.

### Key Benefits of Using a Cloud Service Mesh

#### Improved Observability

One of the standout features of a service mesh is enhanced observability. By providing detailed insights into traffic flows, latencies, error rates, and more, it allows developers to easily monitor and debug their applications. Tools like Prometheus and Grafana can integrate with service meshes to offer real-time metrics and visualizations.

#### Enhanced Security

Security in a microservices environment can be complex. A cloud service mesh simplifies this by providing built-in security features such as mutual TLS (mTLS) for encrypted service-to-service communication. This ensures that data remains secure and tamper-proof as it travels across the network.

#### Simplified Traffic Management

With a service mesh, traffic management becomes a breeze. Advanced routing capabilities allow for blue-green deployments, canary releases, and circuit breaking, making it easier to roll out new features and updates without downtime. This level of control ensures that applications remain resilient and performant.

### The Role of Container Networking

Container networking is a critical aspect of cloud-native architectures, and a service mesh enhances it significantly. By decoupling the networking logic from the application code, a service mesh provides a standardized way to manage communication between containers. This not only simplifies the development process but also ensures consistent network behavior across different environments.

### Popular Cloud Service Mesh Solutions

Several service mesh solutions have emerged as leaders in the industry. Notable mentions include:

– **Istio:** One of the most popular service meshes, Istio offers a robust set of features for traffic management, security, and observability.

– **Linkerd:** Known for its simplicity and performance, Linkerd focuses on providing essential service mesh capabilities with minimal overhead.

– **Consul Connect:** Developed by HashiCorp, Consul Connect integrates seamlessly with other HashiCorp tools, offering a comprehensive solution for service discovery and mesh networking.