Networking Fundamentals
I firmly believe that you cannot be a good networking engineer1 without a firm grasp of the networking fundamentals, and I couldn’t resist pointing that out a few times (see also certifications-related posts):
- You Must Understand the Fundamentals to Be Successful
- Learning Networking Fundamentals at University?
- Grasp the Fundamentals before Spreading Opinions
- Appreciating the Networking Fundamentals
- When You Find Yourself on Mount Stupid
Regardless of how far down this page you’ll get, these blog posts are a must-read:
- Management, Control, and Data Planes in Network Devices and Systems
- Relationships between Layer-2 (VLAN) and Layer-3 (Subnet) Segments
- On the Usability of OSI Layered Networking Model
I would also suggest exploring these series of blog posts as well as textbooks and other resources I collected:
- Interfaces and Ports
- Packet Forwarding Basics
- Integrated Routing and Bridging (IRB) Designs
- IP Anycast and Anycast Gateways
- Site and Host Multihoming
- High Availability Switching
- Fast Failover
- Unnumbered IPv4 Interfaces
- CLI versus API
- Network State Consistency
The rest of the fundamentals-related blog posts are collected on this page.
Contents |
Network Addressing
Addresses and routes are the basic concepts anyone dealing with a network must (eventually) grasp. These blog posts describe how we got a hierarchy of addresses:
- Names, Addresses, and Routes
- Addresses in a Networking Stack
- Why Do We Need Source IP Addresses in IP Headers?
- Early Data-Link Layer Addressing
- Fibre Channel Addressing
- LAN Data Link Layer Addressing
- Can We Skip the Network Layer?
- Network Layer: Interface or Node Addresses
I also compared the device addresses (used in OSI) and interface addresses (used in TCP/IP):
- Finding Adjacent Nodes
- Reaching Off-Subnet Nodes
- Network State Summarization
- Local (Node) Multihoming
Bridging, Routing, and Switching
There is a single reason we build computer networks (apart from job security): we want them to transport data between the attached endpoints. These blog posts describe some of the interesting details:
- Terminology
- Forwarding Packets Across a Network
- Multi-Layer Switching and Tunneling
- Finding End-to-End Paths: Topology and Endpoints
- Finding Source Routing Paths
Deep Dives
These blog posts dive deeper into interesting topics:
- Why Is OSPF not Using TCP?
- Chasing CRC Errors in a Data Center Fabric
- IBGP, IGP Metrics, and Administrative Distances
- Is Switching Latency Relevant?
- Response: Is Switching Latency Relevant?
- Routing Protocols: Use the Best Tool for the Job
- From Bits to Application Data
- On Routing Protocol Metrics
- OSI Layers in Routing Protocols
If you like them, it’s probably time you start exploring the deep-dive series I already mentioned.
A Bit of a History
These blog posts might help you figure out some less obvious details or give you a historical perspective on why networking technologies evolved to where we are right now:
If you want to dive deeper into historical technologies, you might enjoy the comparison of TCP/IP and OSI (CLNP) protocol stacks:
- Finding Adjacent Nodes
- Reaching Off-Subnet Nodes
- Network State Summarization
- Local (Node) Multihoming
There Be Rants
Long-time readers know I can’t resist a good rant:
- Lies, damned lies and product marketing
- Bridges: a Kludge that Shouldn't Exist
- How Did We Ever Get Into This Switching Mess?
- Response: The OSI Model Is a Lie
- The World in Which IPv6 Was a Good Design
- IPv4, IPv6, and a Sudden Change in Attitude
- Was IPv6 Really the Worst Decision Ever?
Everything Is a Graph
You can represent every network as a graph of network devices (nodes) and links2. Rachel Traylor covered the graph theory in the (free) Network Connectivity, Graph Theory, and Reliable Network Design and Graph Algorithms in Networks webinars; these blog posts might provide some extra details:
Networking Fundamentals Videos
Finally, I published dozens of videos describing the networking concepts as part of the How Networks Really Work webinar that got at least some minor positive feedback. The videos describe:
Business aspects of networking technologies
Some people liked the non-technical take on networking I recorded in 2019 and 2020:
- Define the Problem Before Searching for a Solution
- Know Your Users' Needs
- Should You Build or Buy a Solution?
- High-Level Technology Guidelines
Fallacies of distributed computing
- Fallacies of Distributed Computing
- The Network Is Not Reliable
- End-to-End Latency Is Not Zero
- Bandwidth Is Neither Infinite Nor Cheap
- Networks Are (Not) Secure
- Internet Has More than One Administrator
- Networks Are Not Homogenous
Networking challenges and the importance of a layered approach
- Overview of Networking Challenges
- Introducing Transmission Technologies
- Beyond Two Nodes
- The Need for Network Layers
- Retransmissions and Flow Control in Computer Networks
- Putting the Networking Layers Together
- Breaking the End-to-End Principle
Network Addressing
- Introduction to Network Addressing
- Theoretical View of Network Addressing
- Early Data-Link-Layer Addressing
- Local Area Network Addressing
- Network Layer Addressing
- Comparing TCP/IP and CLNP
- Combining Data-Link- and Network Layer Addresses
- Network Address Assignments
- Network Address Scopes
- The Basics of Network Address Translation (NAT)
Switching, Routing, and Bridging
- Review Questions: Switching, Bridging and Routing
- What Are Bridging, Routing, and Switching?
- Getting a Packet Across a Network
- Multi-Layer Switching and Tunneling
- Finding Paths Across the Network
- Path Discovery in Transparent Bridging and Routing
- Transparent Bridging Fundamentals
- IP Routing Fundamentals
- Comparing Routing and Bridging
- Typical Large-Scale Bridging Use Cases
Routing Protocols
- Routing Protocols Overview
- Link State Routing Protocol Basics
- Link State Routing Protocol Implementations
Lessons Learned from 35 Years of Networking
- Technology Still Matters
- Fundamentals Haven't Changed
- Complexity Will Kill Your System
- Some Services Are Not Worth Delivering
- The Way Forward