Training series · NetFun I · level 1

Network Fundamentals I: from bits to the LAN

Layers 1 and 2, from the units a network counts in to the frame a switch forwards: the layer model and the bodies that write the standards, copper, fibre and radio, the Ethernet frame and its addresses, VLANs, spanning tree and link aggregation, and Wi-Fi as layers 1 and 2.

How the series works

1. Read the parts in order. Each one builds on the ones before it, and every part's page shows where you are in the series and what comes next.
2. Each module ends with a stated outcome: what you will be able to do once you have read it.
3. Practise on the tools each module names. They run in your browser, with nothing to install.
4. Parts still being written are named in their places, so the series shows its whole shape from the start.

The series, module by module

1. Module 1 The map and the units 7 parts

   Place a protocol on the layer model, count in bits and bytes without mixing the two kinds of kilo, and know which body writes which standard.

   1. 1 The OSI Model in Practice: Mapping Real Traffic to Seven Layers
   2. 2 Bits, bytes and the two kinds of kilo: why a 56k file takes eight seconds on a 56k modem
   3. 3 How Networking Inherited Two Alphabets
   4. 4 The IEEE 802 family, group by group
   5. 5 The RFC series: how the internet writes itself down
   6. 6 Local, Wide and the Words That Stopped Meaning Distance
   7. 7 The protocol wars: how TCP/IP won against everyone's expectations

   Practice with: Bits, bytes and throughput

2. Module 2 Layer 1, the physical path 8 parts

   Follow a signal through copper, fibre and radio, from the wiring closet to the last mile and the sea floor, and say what the physical layer can and cannot be blamed for.

   1. 1 Structured cabling: the system behind the wall jack
   2. 2 Ethernet physical layers, from 10BASE-T to 400GBASE: naming, auto-negotiation, duplex, and the mismatch that cripples a link
   3. 3 Fibre basics: multimode and single-mode, the grades and their colours, connectors and polarity, the loss budget, and why dirt is the first suspect
   4. 4 Transceivers: The Ridiculed Paper, and the Part of the Network You Can Hold
   5. 5 The Last Mile: From POTS to Always-On
   6. 6 GPON: How One Fiber Serves a Whole Neighborhood
   7. 7 The radio spectrum: which frequencies go how far, and why
   8. 8 Submarine cables: the internet is a rope on the seabed

   Practice with: Cable run planner

3. Module 3 Layer 2, frames and switching 9 parts

   Read an Ethernet frame and the addresses in it, say what a switch, a bridge and a router each decide, and explain VLANs, spanning tree and link aggregation.

   1. 1 The Ethernet frame, field by field: preamble to FCS, the 802.1Q tag, and the sizes that matter
   2. 2 What Is an OUI, and How MAC Addresses Are Assigned
   3. 3 ARP and MAC Addresses: How IP Finds Ethernet
   4. 4 Switch, Router, Firewall: Who Does What on the Path
   5. 5 Bridges and Switches: One Idea, Solved Twice
   6. 6 VLANs and 802.1Q trunking: tagged, untagged, native, and the voice VLAN
   7. 7 Spanning tree in one article: why a blocked port is the feature, and how RSTP and MSTP made it fast
   8. 8 Link aggregation and LACP: several links that act as one, and the protocol that keeps them honest
   9. 9 Jumbo frames: when 1500 bytes stops being enough

   Practice with: OUI / MAC vendor lookup · MTU / MSS calculator

4. Module 4 Wireless as layers 1 and 2 4 parts

   Explain what Wi-Fi changes at the first two layers: its generations, the handshake an attack once broke, and port-based access control with 802.1X.

   1. 1 Wireless: The Islands Problem, and the Protocol Given Away
   2. 2 Wi-Fi: a shared medium pretending to be a cable, and everything that follows from that
   3. 3 KRACK and Dragonblood: what happened after WEP, and why a proven-secure handshake still broke
   4. 4 802.1X and the EAP methods: the port, the envelope, and the choice that carries the security

   Read, not practised: no tool on the site works at this layer yet.

When you finish: NetFun II, the next level.