From LAN to VXLAN: Networking Basics for Non-Network Engineers

Course Progress

Start lesson

Reset Progress<br>Are you sure you want to reset your progress for this lesson? This action cannot be undone.<br>Cancel<br>Reset

close

Lesson on<br>Discussion  Discord

This lesson was created by a community author. Community content is reviewed by the iximiuz Labs team on a best effort basis.

Lesson  in  Computer Networking Fundamentals For Developers, DevOps, and Platform Engineers Published: May 18, 2024

From LAN to VXLAN: Networking Basics for Non-Network Engineers

What is a LAN?<br>Starting with the most basic concept...<br>LAN (Local Area Network) -<br>[broadly] a computer network that interconnects computers within a limited area such as a residence, school, office building, or data center.<br>A LAN is not limited to a single IP subnetwork.<br>Like a Wide area network (WAN),<br>a LAN can consist of multiple IP networks communicating via routers.<br>The main determinant of a LAN is the locality (i.e. proximity) of the participants, not the L3 topology.

What is a Network Link?<br>Network link - a physical and logical network component used to interconnect [any kind of] nodes in the network.<br>All nodes of a single network link use the same link-layer protocol.<br>Examples:<br>A group of computers connected to a network switch (Ethernet)<br>A set of smartphones connected to a Wi-Fi access point (non-Ethernet)<br>Etc.

What is a Network Segment?<br>Network segment - [again, broadly] a portion of a computer network.<br>The actual definition of a segment is technology-specific.<br>In the next units, we will cover different types of network segments.

What is an L1 Segment?<br>L1 segment (aka physical segment , aka Ethernet segment ) -<br>a network segment formed by an electrical (or optical) connection between networked devices using a shared medium.<br>Nodes on a single L1 segment have a common physical layer.<br>The simplest example of the contemporary L1 segment is a point-to-point connection between two end-nodes via a patch or crossover cable.

The most typical occurrence of L1 segment today, though, are the links between servers and the corresponding top-of-rack switch in a data center:<br>Blue lines are the L1 segments.

It's OK if the comic replicas on the picture above don't make much sense to you yet.<br>The next unit will try to explain the evolution of the L1 segment technology that led to the modern switch devices.

Evolution of Physical Segments<br>In the early days of the Ethernet, a group of computers connected to a shared coaxial cable was forming a physical segment<br>(aka bus topology).<br>A coaxial cable served as a shared medium between multiple nodes .<br>Everything sent by one of the nodes was seen by all other nodes of the segment.<br>Thus, the nodes were forming a single broadcast domain .<br>👌 This is OK because it had useful properties, which are still relied on today.

However, since multiple nodes could be transmitting frames simultaneously over a single cable, collisions were likely to occur.<br>Hence, an L1 segment was also forming a single collision domain<br>👎 This is undesirable and should be mitigated by hardware or software.

Ethernet as it started, 100 000 years ago.

As an evolution of the Ethernet technology,<br>twisted-pair cables connected to a common repeater hub replaced the shared coaxial cable<br>(aka star topology).<br>When a node on one of the hub's ports was transmitting frames,<br>they were retransmitted from all the other ports of the hub.<br>The retransmission of frames was as-is,<br>i.e. no modification or filtration of frames was happening (hubs were pretty dumb devices).<br>All nodes connected to the hub still were forming a single L1 segment<br>(hence, a single broadcast domain 👌, hence a single collision domain 👎).<br>Evolution of Ethernet, 500 A.D.

📖  Both coaxial and hub-based approaches are now obsolete!

Today, the star topology is prevailing.<br>However, hubs have been replaced by more advanced network switch devices (aka bridges).<br>An L1 segment de facto was reduced to a single point-to-point link between an end-node and a switch (or a switch and another switch).<br>Since there are only two nodes on a physical link the potential collision domain became very small.<br>👍  Actually, most of the modern wiring is full-duplex, so collisions cannot occur at all.

Curious, what happened to the broadcast domain?<br>Then keep reading!<br>Ethernet via network switch, present day.

🤓  Beware that the terms switch and bridge that are used interchangeably in this lesson are in their original historical meaning.<br>Here, a bridge is a shortcut for a "multi-port bridge" and a switch is a shortcut for a "Layer 2 switch", which were pretty much the same thing back in the day.<br>Today, these two devices, together with an L3 router, blended into one hardware device, often also called a "switch" (and its corresponding virtual device is called a "Linux bridge", so some confusion is inevitable).<br>In the next lesson,<br>we will discuss the difference between bridges and switches in more detail.

What is a...