Networking refresher

Intermediate Docker

Mike Metzger

Data Engineering Consultant

What is networking?

• A computer network consists of systems communicating via a defined method
• Varying levels of communication, physical or logical, referred to as protocols
• Common physical networks include Ethernet and WiFi
• Logical networking includes TCP/IP, HTTP, and SMTP
• Networks are defined in various layers or levels. Often referred to as a networking stack

¹ Photo by Jordan Harrison on Unsplash.

Networking terms

• Host
  • General term for a computer
• Network
  • Group of hosts
• Interface
  • Actual connection from a host to a network, such as Ethernet or WiFi
  • Can be virtual, meaning entirely in software
• LAN
  • Local Area Network, or set of computers at a given location
• VLAN
  • Virtual LAN, or a software LAN

Internet Protocol

• IP
  • Internet protocol, method to connect between networks using IP addresses
• IPv4
  • Version of IP supporting 4.2 billion addresses, currently exhausted
• IPv6
  • Newer version of IP, supporting 2^128 addresses, still being deployed

IPv4: 10.10.10.1

IPv6: 2001:0db8:85a3:0000:0000:8a2e:0370:7334

TCP / UDP

• TCP
  • Transmission Control Protocol, used to reliably communicate between hosts on IP networks
• UDP
  • User Datagram Protocol, used to communicate between hosts on IP where communication is not required.

Ports

• Port
  • Addresses services on a given host, a value between 0 and 65535, used to communicate between hosts via TCP or UDP
  • Ports below 1024 are typically reserved for privileged accounts
  • Values above 1024 are usually ephemeral or temporary ports
  • Applications listen on a port.

Application protocols

• HTTP/HTTPS
  • Application protocol, defaulting to TCP port 80 for web communication. Secure version on TCP 443
• SMTP
  • Email transfer protocol, over TCP port 25
• SNMP
  • Network management protocol, over UDP port 161

Docker and networking

• Can communicate between containers
• Can communicate with the host system
• Depending on settings can communicate with external hosts
• Typical communication is handled by exposing ports from container to host
• Acts like a translation between containers and hosts

Docker and IP

• Containers can have IP addresses
• Use ifconfig <interface> or ip addr show <interface> from within container to find addresses
• Use ping -c <x> <host> to verify connectivity
  • ping -c 3 myhost

Let's practice!

Intermediate Docker