Linux Networking Fundamentals

• Docker networking uses the kernel’s networking stack to create high level networking feature of Docker
• Docker Networking is Linux Networking
• Also refer OSI Networking Model over here

Building Blocks

Linux Bridge

• This is layer 2 device with virtual implementation of physical switch inside Linux Kernel
• Forwards the traffic based on MAC address by inspecting traffic.

Network Namespace

• Isolated network stack in kernel with its own interfaces, routes & firewall rules

Virtual Ethernet Devices or veth

• Linux networking interface that acts as connecting wire between two two network namespaces

iptables

• Generic table structure that defines rules & commands as part of the netfilter framework.

Docker Networking Architecture

• Docker Networking Architecture is based on Container Networking Model.

note: Image from Docker

CNM Constructs – Sandbox

• Contains the configuration of the containers network stack.
• Includes routing tables, container’s interfaces, DNS setting etc.
• Sample implementation could be Linux Network Namespace or any other similar concept.

CNM Constructs – Endpoint

• Joins sandbox to the Network.
• This abstracts actual connection to the network away from application.
• Maintains portability for applications, so that they can use different network drivers

CNM Constructs – Network

• Collection of endpoints having connectivity b/w themselves

CNM Driver Interfaces

• CNM provides two pluggable & open interfaces to leverage additional functionality and control in the network
  • Network Drivers
  • IPAM Drivers

Docker Native Network Drivers

• Host
  • Container uses the networking stack of the host.
• Bridge
  • Creates a bridge on the host that is managed by Docker.
  • All containers on Bridge Driver can communicate among themselves
  • Default Driver
• Overlay
  • Used for multi-host networks.
  • uses local linux bridges & VXLAN to overlay container-to-container networking
• MACVLAN
  • uses Linux MACVLAN bridge to establish connection b/w container interfaces & parent host interfaces
  • MAC address can be attached to each container
• None

Docker Networking Scopes

• Local: provides connectivity within host
• Swarm: provides connectivity across swarm cluster

Tutorials

• Bridge
• Host
• Overlay

Host Network Driver

• In host network driver all the containers are in same network namespace(sandbox)

Bridge Network Driver

Default Bridge Network Driver

User-Defined Bridge Networks

note: All the images are picked from Docker Documentations