Kubernetes has emerged as the de facto standard for containerization and orchestration for managing containerized applications. Among its many features, Kubernetes offers network namespace functionality, which is critical in isolating and securing network resources within a cluster. This blog post will delve deeper into Kubernetes Network Namespace, exploring its purpose, benefits, and how it enhances its overall network management capabilities.
In simple terms, a network namespace is an isolated network stack that allows for the creation of separate network environments within a single Linux kernel. Kubernetes leverages network namespaces to provide logical network isolation between pods, ensuring each pod operates in its virtual network environment.
Table of Contents
Highlights:Kubernetes Network Namespace
The Role of Docker
In addition to my theoretical post on container networking – Docker & Kubernetes, the following hands-on series examines Linux Namespaces and Docker Networking. The advent of Docker makes it easy to isolate the Linux processes so they don’t interfere with one another. As a result, users can run various applications and dependencies on a single Linux machine, all sharing the same Linux kernel. This abstraction is made possible by using Linux Namespaces, which form the docker container security basis.
Before you proceed, you may find the following helpful post for pre-information.
Discussion on the namespace and virtual interface types.
Kubernetes network namespace and docker networking.
Security options with Linux firewall and Netfilter.
Back to Basics: Kubernetes Networking
Kubernetes users generally do not create pods directly. Instead, users create a high-level workload, such as a deployment, which organizes pods according to some intended spec. In the case of deployment, users specify a template for pods, along with how many pods (often called replicas) they want to exist.
There are several additional ways to manage workloads, such as ReplicaSets and StatefulSets. Remember that Pods themselves are ephemeral, suggesting they are deleted and replaced with new versions of themselves.
Benefits of Kubernetes Network Namespace:
1. Enhanced Network Isolation: Kubernetes Network Namespace provides a robust framework for isolating network resources, ensuring that pods do not interfere with each other’s network traffic. This isolation helps prevent unauthorized access, reduces the attack surface, and enhances overall security within a Kubernetes cluster.
2. Efficient Resource Utilization: By utilizing network namespaces, Kubernetes optimizes the utilization of network resources. Pods within a namespace can share the same IP address range while maintaining complete isolation, resulting in more efficient use of IP addresses and reduced network overhead.
3. Simplified Networking Configuration: Kubernetes Network Namespace simplifies the configuration of network policies and routing rules. Administrators can define network policies at the namespace level, allowing for granular control over inbound and outbound traffic between pods and external resources.
4. Scalability and Flexibility: With Kubernetes Network Namespace, organizations can scale their applications without worrying about network conflicts. By encapsulating each pod within its network namespace, Kubernetes ensures that the network resources can scale seamlessly, enabling the deployment of complex microservices architectures.
How Kubernetes Network Namespace Works:
Kubernetes Network Namespace leverages the underlying Linux kernel’s network namespace feature to create separate network environments for each pod. When a pod is created, Kubernetes assigns a unique network namespace, isolating the pod’s network stack from other pods in the cluster.
Each pod has network interfaces, IP addresses, routing tables, and firewall rules within a network namespace. This isolation allows each pod to operate as if it were running on its virtual network, even though it shares the same underlying physical network infrastructure.
Administrators can define network policies at the namespace level, controlling traffic flow between pods within the same namespace and across different namespaces. These policies enable fine-grained control over network traffic, enhancing security and allowing for the implementation of complex networking scenarios.
Six namespaces are implemented in the Linux kernel, enabling the core of container based virtualization. The following diagram displays per process isolation – IPC, MNT, NET, PID, USER, and UTS. The number on the right in the square brackets is each namespace’s unique proc inode number.
To implement namespaces in the Linux kernel, a structure called nsproxy was added. As the name suggests, it’s a namespace proxy. We have several userspace packages to support namespace – util-linux, iproute2, ethtool and wireless iw. In this hands-on series, we will focus on iproute2 userspace allowing management of the network namespace (NET) with the IP NETNS, and IP LINK commands.
Docker networking, essentially a namespacing tool, can isolate processes into small containers. Containers differ from VMs that emulate a hardware layer on the operating system. Instead, they use operating system features like namespaces to provide similar isolation without emulating the hardware layer.
Each namespace has an individual and isolated view, allowing sharing the same host but with individual routing tables and interfaces.
Users may create namespaces, assign ports, and connect for external connectivity. A virtual interface type known as virtual Ethernet (veth) interface is set to namespaces. They act as pairs and have a similar analogy of an isolated tube – what comes in one end must go back out the other.
The pairing enables namespace connectivity. Users may also connect namespaces using Open vSwitch. The following screenshot displays the creation of a namespace called NAMESPACE, a veth pair, and adding a veth interface to the newly created namespace. As discussed, the IP NET and IP LINK commands enable interaction with the network namespace.
The following screenshot displays IP-specific parameters for the previously created namespace. The routing table will only show specific namespace parameters, not information from other namespaces. For example, the following ip route list command does not display the 192.168.1.1/24 interface assigned to the NAMESPACE-A.
This is because the ip route list command looks into the global namespace, not the routing table assigned to the new namespace. Instead, the command will show different route table entries, including different default gateways for each namespace.
Kubernetes Network Namespace & Docker Networking
Installing Docker creates three networks that can be viewed by issuing the docker network ls command: bridge, host, and null.Running containers with a specific –net flag highlights the network in which you want to run the container. The “none” flag puts the container in no network, so it’s completely isolated. The “host” flag puts the container in the host’s network.
Leaving the defaults places the container into the bridge default network. The default docker bridge is what you will probably use most of the time. Any containers connected to the default bridge, like a flat VLAN, can communicate freely. The following displays the networks created and any containers attached. Currently, no containers are attached.
The image below displays the initiation of the default Ubuntu image pulled from the Docker public registry. There are plenty of images up there that are free to pull down. As you can see, Docker automatically creates a subnet and a gateway. The docker run command starts the container in the default network.
With this setup, it will stop running if you don’t use crtl+p + ctrl +q to exit the container. Running containers are viewed with the docker ps command, and users can connect to a container with the Docker attach command. \
IPTables
Communication between containers can be restricted with IPTables. The Linux kernel uses different IPtables according to the protocol in use:
IPtables for IPv4 – net/ipv4/netfliter/ip_tables.c
IP6table for IPv6 -net/ipv6/netfliter/ip6_tables.c
arptables for ARP -net/ipv4/netfliter/arp_tables.c
ebtables for Ethernet – net/bridge/netfilter/ebtables.c
They are essentially a Linux firewall before the Netfilter,providing a management layer for adding and deleting Netfilter rules and displaying statistics. The Netfilter performs various operations on packets traversing the network stack. Check the FORWARD chain; it has a default policy of ACCEPT or DROP.
All packets reach this hook point after a lookup in the routing system. The following screenshot shows the permit for all sources of the container. If you want to narrow this down, restrict only source IP 8.8.8.8 access to the containers with the following command – iptables -I DOCKER -i ext_if! -s 8.8.8.8 -j DROP
In addition to the default networks created during Docker installation, users may create user-defined networks. User-defined networks come in two forms – Bridge and Overlay networks. Bridge networks support single-host connectivity, and containers connected to an overlay network may reside on multiple hosts.
The user-defined bridge network is similar to the docker0 bridge. An overlay network allows containers to span multiple hosts, enabling a multi-host connectivity model. However, it has some prerequisites, such as a valid data store.
Summary:Kubernetes Network Namespace
Kubernetes, the powerful container orchestration platform, offers various features to manage and isolate workloads effectively. One such feature is Kubernetes Network Namespace. In this blog post, we deeply understood what Kubernetes Network Namespace is, how it works, and its significance in managing network communications within a Kubernetes cluster.
Section 1: Understanding Network Namespace
Kubernetes Network Namespace is a virtualized network stack that isolates network resources within a cluster. It acts as a logical boundary, allowing different pods and services to have their own network configuration and routing tables. Using Network Namespace, Kubernetes ensures that each workload operates within its defined network environment, preventing interference and maintaining security.
Section 2: Benefits of Kubernetes Network Namespace
One of the significant advantages of Kubernetes Network Namespace is enhanced network segmentation. By segregating network resources, Kubernetes enables better isolation, reducing the risk of network conflicts and potential security breaches. Additionally, Network Namespace facilitates improved resource utilization by efficiently allocating IP addresses and network policies specific to each workload.
Section 3: Working with Kubernetes Network Namespace
Administrators and developers can leverage various Kubernetes objects and configurations to utilize Kubernetes Network Namespace effectively. This includes creating and managing namespaces, deploying pods and services within specific namespaces, and configuring network policies to control traffic between namespaces. Understanding and implementing these concepts ensures a robust and well-organized network infrastructure.
Section 4: Best Practices for Kubernetes Network Namespace
While working with Kubernetes Network Namespace, following best practices is crucial for maintaining a stable and secure environment. Some recommendations include properly labeling pods and services with namespaces, implementing network policies to control traffic flow, regularly monitoring network performance, and considering network plugin compatibility when using third-party solutions.
Conclusion:
Kubernetes Network Namespace is vital in managing network communications within a Kubernetes cluster. By providing isolation and segmentation, it enhances security and resource utilization. Understanding the concept of Network Namespace and following best practices ensures a well-structured and efficient network infrastructure for your Kubernetes deployments.
Containerization has revolutionized the way we develop, deploy, and manage applications. Organizations have gained newfound flexibility and scalability by encapsulating applications in lightweight, isolated containers. However, as the number of containers increases, so does the networking complexity among them. This blog post will explore container networking, its challenges, solutions, and best practices.
Container networking refers to the communication and connectivity between containers within a distributed system. Unlike traditional monolithic applications, containers are designed to be ephemeral and can be dynamically created, scaled, and destroyed. This dynamic nature necessitates a flexible and efficient networking infrastructure to facilitate seamless communication between containers, regardless of their physical location.
Highlights: Container Networking
Network Services
The most common network service is to allow a source to reach an application endpoint. Nowadays, the network function no longer solely satisfies endpoint reachability; it is fully integrated into the application. And in the case of OpenShift networking, the Route and Sevice construct provides both reachability and an abstraction layer for application access.
In the past, applications had three standard components; cache, web server, and database. Applications look very different now. Several services are interacting, completely decoupled into units, and packaged in containers; all are mobile and may move around.
Before you proceed, you may find the following helpful:
Introduction to Container networking and its operations.
Discussion Docker default networking and different Docker network types.
Namespaces, port mapping and traffic flow.
Kubernetes networking and the Pod concept.
A final note on container services.
Back to basics with Container Networking
Docker Networking
The Docker networking model uses a virtual bridge network by default, defined per host, and a private network where containers attach. The container’s IP address is allocated a private IP address, which indicates containers operating on different machines cannot communicate with each other.
In this case, you will have to map host ports to container ports and then proxy the traffic to reach across nodes with Docker. Therefore, it is up t the administrator to avoid port clashes between containers. Kubernetes networking handles this differently.
Challenges in Container Networking:
Container networking presents several challenges that must be addressed to ensure optimal performance and reliability. Some of the key challenges include:
1. Network Isolation: Containers should be isolated from each other to prevent unauthorized access and potential security breaches.
2. IP Address Management: Containers are assigned unique IP addresses, which can quickly become challenging to manage as the number of containers grows.
3. Scalability: As the container ecosystem expands, the networking infrastructure must scale effortlessly to accommodate the increasing number of containers.
4. Service Discovery: Containers need a reliable mechanism to discover and communicate with other services within the network, especially in a microservices architecture.
Solutions and Best Practices:
To overcome these challenges, several solutions and best practices have emerged in the realm of container networking:
1. Container Network Interface (CNI): CNI is a specification that defines how container runtimes interact with networking plugins. It enables easy integration of various networking solutions into container orchestration platforms like Kubernetes and Docker.
2. Overlay Networking: Overlay networks create a virtual network that spans multiple hosts, allowing containers to communicate seamlessly, regardless of physical location. Technologies like VXLAN, GRE, and WireGuard are commonly used for overlay networking.
3. Network Policies: Network policies define the rules and restrictions for incoming and outgoing traffic between containers. Organizations can enforce security and control network traffic flow within their containerized environments by implementing network policies.
4. Service Mesh: Service mesh technologies, such as Istio and Linkerd, provide advanced networking capabilities, including traffic management, load balancing, and observability. They enhance the resilience and reliability of containerized applications by offloading complex networking tasks from individual services.
Container Networking: A Different Application Philosophy
Computing is distributed over multiple elements, and they all interact arbitrarily. Network integration allows the application to be divided into several microservice components. Microservices allow the application to be packaged into pieces and deployed on different hosts or even different cloud providers.
The application stack no longer belongs to a single server. Small composable units enhance application replication and fault tolerance services. All this is made possible by using containers and the ability to interconnect them.
Containers offer a single-purpose environment. They are a bunch of lightweight namespaces and processes sharing a common kernel. Typically, you don’t run a full stack in a single container.
Ideally, only one process per container, which makes them very lightweight. VMs with guest O/S is resource-heavy; containers are a far better option if the application can be containerized.
However, containers offer an utterly different endpoint type for the network. With virtual machine spinning, they arrive and disappear quickly, measured in milliseconds, not seconds or minutes. The speed is down to their light properties. Some containerized application transactions only live for the length of transaction time. The infrastructure and network must be pre-built to support this type of endpoint.
Docker networking comes with several Docker network types and setups. The latest release is Docker version 1.10 and has some enhancements, including linking with user-defined networks. They are other solutions available to enhance Docker networking functionality.
Docker is pluggable and allows ecosystem partners to plug into Docker networking. Project Calico offers a pure IP-based solution that utilizes the same principles of the Internet. Every host is an IP router. Calico uses a Felix agent and a BGP BIRD demon. This would be a clean option if the application only needs Layer 3 connectivity.
The weave is another solution that operates an overlay function and aims to fit the multi-data center requirements. Each host in a Weave network thinks it belongs to one large switched fabric. The physical locations are abstracted, and they all have reachability. A multi-datacenter solution must concern itself with metrics other than endpoint reachability.
Container Networking with Linux Kernel and User Namespaces
Inside each container, a bunch of resources, such as network interfaces and file systems, are unique. These resources look as if they are isolated even though the containers share the Linux kernel. Global resources are abstracted to appear as if they were unique per container. An abstraction that is made available by the use of Linux namespaces.
Namespaces initially provided resource isolation for the first Linux containers project, offering a process virtualization solution. They do not create additional operating system instances on the host but instead use a single system with resource isolation.
Similarly, FreeBSD, where Jails provides resource isolation while running one kernel instance. In 2002, mount namespaces were the first type of Linux namespace with kernel 2.4.19. User namespaces emerged with kernel 3.8.
The Different Namespaces
Containers have namespaces for each type of resource. We have six namespaces.
Mount namespace makes the container feel like it has its filesystem.
UTS namespace offers individual hostnames and domain names.
User namespace provides isolation between the user and group IDs.
IPC namespace isolates message queue systems.
PID namespace offers different PIDs inside the container.
Finally, the network namespace gives the container a separate network stack. When you issue the docker ps command, you will see what ports are bound; these ports are on the namespace network interface.
Docker Networking and Docker Network Types
Install docker creates three network types – bridge, host, and none. You cannot delete these networks; you only interact with the default bridge network. There is the option to create user-defined networks and customized plugins.
Network plugins (LibNetwork project) extend the docker network to support additional networking features such as IP VLAN or macvlan. User-defined networks can take the form of bridge or overlay networks.
Bridge networks have a single-host local scope, and overlay networks have multi-host global scope. The diagram below displays the default bridge and the corresponding attached containers. The driver is “default,” meaning it has local scope.
The user-defined bridge is similar to the default bridge0. Containers from the same host are added and can cross-communicate. External access is not prohibited, but you can expose network sections with port mappings.
The user-defined overlay networking feature enables multi-host networking using the VXLAN networking driver called libnetwork and Docker’s libkv library. One of the requirements for the overlay function to work is for a valid key-value store.
The Docker libkv library supports Consul, Etcd, and ZooKeeper. With Docker default networking, a veth pair is created – one veth pair is put inside the container and the other outside in the namespaces. All are connected via the docker bridge. The veth is mapped to appear as eth0 in the container, using Linux namespaces.
Container networking, port mapping, and traffic flow.
Docker container networking cross-communicate if they are on the same machine and thus connect to the same virtual bridge. Containers can also connect to multiple networks at the same time. By default, containers on different machines can not reach other. Cross-communication on different nodes must be allocated ports on the machine’s IP address, which are then proxied to the containers.
Port mapping is used to provide access to the container from the outside. Docker allocates a DNAT port in the range of 49153 – 65535. This additional functionality continues to use the default Docker0 bridge but adds IPtables rules for the DNAT.
When you spin up a container and do a port mapping, you can see it inside the docker ps command that you have a port mapping from, for example, the host 8080 to container 80. IPtables is setting a port mapping between 8080 to the IP addresses assigned to the container.
The problem with Docker is that you may have to coordinate ports and plenty of NAT. NAT was designed to address the shortage of IPv4 addresses and was only meant to be used for a short period. It is so ingrained in people’s minds we still see it come out in fresh designs.
Ports and NAT are problematic at scale and expose users to cluster-level issues outside their control. It brings the risk of port conflicts and many complexities to scheduling.
A key point: Kubernetes
Kubernetes networking does not use any NAT. Instead, it applies IP addresses at the Pod scope level. Remember that containers within a Pod share network namespaces, including their IP address. This means containers within a Pod can all reach each other’s ports on localhost. Kubernetes makes finding and configuring Kubernetes services much easier due to the unique IP addresses per Pod model.
Kubernetes network namespace has two fundamental abstractions – Pods and Services. Pods are essentially scheduling ATOMs in Kubernetes. They represent a group of containers, tightly integrated, sharing resources and fate. An example of an application container grouping in a Pod might be a file puller and a web server.
Frontend / Backend tiers usually fall outside this category as they can be scaled separately. Pods share a network namespace and talk to each other as local hosts.
Pods are assigned a private IP that is routable within the internal fabric. Docker doesn’t give you an IP; you must do weird things like going through a host and exposing a port. Not a great idea, as you may have issues and operational complexities with the deployment of ports.
With Kubernetes, all containers talk to each other, even across nodes, without NAT. The entire solution is NAT-less, flat address space. Pods can talk to Pods without any translations. Communications on ports can be done but with well-known port numbers avoiding service discovery systems like DNS-SD, Consul, or Etcd.
Container network and services
The second abstraction is services. Services is a similar analogy to that of a load balancer. They are groups of Pods that act as one. It may be better to reference the service with an IP address, not a Pod. This is because Pods can go away, but services are more dedicated.
A typical flow would be something like this – a client on a cluster looks for IP for a particular service. The Kubernetes nodes that it is running on do an iptables DNAT. Instead of going to the service, it reroutes to the Kube proxy. The Kube proxy is a proxy running on every Kubernetes node.
It programs iptables rules to trap access to service IPs and redirect them to the backends using round-robin load balancing. It places a watch on the API server to know what pods are active and ready to serve requests.
Several implementations include Google Compute Engine, Flannel, Calico, and OVS with GRE/VxLAN to support the IP-per-pod model. OpenVSwitch connects Pods on different hosts with GRE or VxLAN. The Linux bridge replaces the docker0 bridge, encapsulating traffic to and from Pods. Flannel may also be used with Kubernetes.
It creates an overlay network and gives a subnet to each host. Flannel can be used on cloud providers that cannot offer an entire /24 to each host. Flannels’ flannel agent runs on each host and controls the IP assignment. Calico, already mentioned, is also an IP-based solution that relies on traditional BGP.
Conclusion:
Container networking is a critical aspect of modern application development and deployment. As organizations continue to embrace containerization, understanding the challenges and implementing appropriate solutions and best practices is crucial for building a robust and efficient networking infrastructure. By leveraging container networking technologies, organizations can unlock the full potential of containerized applications, enabling seamless communication, scalability, and security in their distributed systems.
Container-based virtualization, or containerization, is a popular technology revolutionizing how we deploy and manage applications. In this blog post, we will explore what container-based virtualization is, why it is gaining traction, and how it differs from traditional virtualization techniques.
Container-based virtualization is a lightweight alternative to traditional methods such as hypervisor-based virtualization. Unlike virtual machines (VMs), which require a separate operating system (OS) instance for each application, containers share the host OS. This means containers can be more efficient regarding resource utilization and faster to start and stop.
Highlights: Container Based Virtualization
Traditional Deployment Models
So how do containers facilitate virtualization? Firstly, the traditional application deployment was based on a single-server approach. As a result, one application was installed per physical server, wasting server resources, and components such as RAM and CPU were never fully utilized. There was also considerable vendor lock-in, making moving applications from one hardware vendor to another hard.
Then, the world of hypervisor-based virtualization was introduced, and the concept of a virtual machine (VM) was born. Soon after, we had container-based applications. Container-based virtualization introduced container networking, and new principles arose for security around containers, specifically, Docker container security.
Introducing hypervisors
We still deployed physical servers but introduced hypervisors on the physical host, enabling the installation of multiple VMs on a single server. Each VM is isolated from its operating system. Hypervisor-based virtualization introduced better resource pooling as one physical server could now be divided into multiple VMs, each hosting a different application type. This was years better than single-server deployments and opened the doors to open networking.
The VM deployment approach increased agility and scalability as applications within a VM are scaled by simply spinning up more VMs on any physical host. While hypervisor-based virtualization was a step in the right direction, a guest operating system for each application is pretty intensive. Each VM requires RAM, CPU, storage, and an entire guest OS. All of which consume resources.
Introducing Virtualization
Another advantage of virtualization is the ability to isolate applications or services. Each virtual machine operates independently, with its resources and configurations. This enhances security and stability, as issues in one virtual machine do not affect others. It also allows for easy testing and development, as virtual machines can be quickly created and discarded.
Virtualization also offers improved disaster recovery and business continuity. By encapsulating the entire virtual machine, including its operating system, applications, and data, into a single file, organizations can quickly back up, replicate, and restore virtual machines. This ensures that critical systems and data are protected and can be quickly recovered during a failure or disaster.
Furthermore, virtualization enables workload balancing and dynamic resource allocation. Virtual machines can be dynamically migrated between physical servers to optimize resource utilization and performance. This allows for better utilization of computing resources and the ability to respond to changing workload demands.
You may find the following helpful post before proceeding to how containers facilitate virtualization.
Key Container Based Virtualization Discussion points:
Introduction to containerized technologies.
The role of container based applications.
Discussion on container networking and Linux kernel.
A final note on microsegmentation.
A key point – Video 1: Video on hypervisor-based virtualization
The hypervisor allows multiple operating systems to share a single physical host enabling multiple container-based applications on one physical host. Many call the hypervisor a simple software or lightweight operating system running on a host. However, its attack surface is far more significant than a normal O/S as it could hold hundreds of virtual machines running their independent OS and application set, all having the potential for compromise.
Back to Basics: Containers and Container Virtualization
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 every time 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. But, unfortunately, the VM model has additional challenges too.
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 which drove the need for a new technology of containers with container virtualization.
How do containers facilitate virtualization? So, 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 acts at the forefront. The container offers a similar capability to that of object-oriented programming. They let you build composable modular building blocks, making it easier to design distributed systems.
A key point: Lab Guide on Container Networking
In the following example, we have one docker host. We can list the available networks to these docker hosts with the command docker network ls. These are not WAN or VPN networks; these are only docker networks.
Docker networks are virtual networks allowing 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 none 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.
A key point: Lab Guide on Container Networking
You can attach as many containers 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 together.
Container-based Virtualization
One of the critical benefits 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.
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.
Application Landscape Changes
The application landscape has changed from a monolithic design to a design consisting of microservices. Today applications are constantly developed. Patches usually patch only certain parts of the application, and the entire application is built from loosely coupled components instead of existing tightly coupled ones.
The entire application stack is broken into components and spread over multiple servers and locations, all requiring cross-communication.
For example, users connect to a presentation layer, the presentation layer then connects to some shopping cart, and the shopping cart connects to a catalog library. These components are potentially stored on different servers, maybe different data centers.
The application is built from several small parts, and these tiny parts are known as microservices. Each component or microservice can now be put into a lightweight container – a scaled-down VM.
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.
Container based virtualization
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 up an application with all its parts in an isolated environment. It is a complete abstraction and does 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 separates the operating system from bare metal. It lets 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. The task of a scheduler is to start containers on the correct host and then connect them. In addition, it 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 selection of the correct host depends 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., 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 as low 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 they are just referenced points 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 to support multi-cloud environments, heavy loads like databases are put into VMs.
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 that containers using the host network can directly access the network interfaces of the host system. This option is helpful for scenarios where containers must bind to specific network interfaces on the host.
On the other hand, the none 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 created 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.
A key point – Video 2: Docker containers and Docker networking.
In this video, we will go through some basics of containers. The building blocks of containers are namespaces and control groups. However, they share the host kernel, which is a security concern. We will also address container orchestrators with Kubernetes and discuss PODs, Services, NAT, and VXLAN.
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. 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. Local scope driver corresponds to 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 that 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 is the one that 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 of the critical advantages of container-based virtualization is its lightweight nature. Containers are designed to be portable and efficient, allowing for rapid deployment and scaling of applications. 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 how applications are deployed and managed. 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.
Shopping Basket
We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. By clicking “Accept”, you consent to the use of ALL the cookies.
This website uses cookies to improve your experience while you navigate through the website. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. We also use third-party cookies that help us analyze and understand how you use this website. These cookies will be stored in your browser only with your consent. You also have the option to opt-out of these cookies. But opting out of some of these cookies may affect your browsing experience.
Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information.
Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. It is mandatory to procure user consent prior to running these cookies on your website.