Networking reference data
Network protocols, models, and architecture.
Topic guide
What Networking covers
Networking reference data describes how bytes get from one machine to another: the layered models that organize protocols (OSI and TCP/IP), the addresses and ports that name endpoints, the DNS records that map names to them, the routing protocols that choose paths, and the transport changes that separate HTTP/1.1 from HTTP/2 and HTTP/3. Almost everything here is a convention agreed in an RFC, so the details are precise and checkable, but real networks add middleboxes, NAT and filtering that the clean models leave out.
Key ideas
- Layering and encapsulation
- Each layer wraps the data from the layer above with its own header. A web request becomes an HTTP message, then a TCP segment, then an IP packet, then an Ethernet frame.
- Port
- A 16-bit number that, together with an IP address and protocol, identifies a specific service on a host. Well-known ports are conventions, not guarantees.
- TCP vs UDP
- TCP gives ordered, reliable delivery with connection setup; UDP sends independent datagrams with no delivery guarantee. QUIC rebuilds reliability on top of UDP.
- DNS record
- A typed answer from the Domain Name System. The type (A, AAAA, MX, TXT) says what kind of data the name maps to.
- Routing
- Choosing the next hop for a packet. Interior protocols such as OSPF run inside one organization; BGP exchanges reachability between autonomous systems on the internet.
- NAT
- Network address translation rewrites addresses and ports so many private hosts share a public IP address, which breaks the end-to-end assumption of the original design.
- Latency vs bandwidth
- Latency is how long one bit takes to arrive; bandwidth is how many bits per second a link carries. Round trips, not raw bandwidth, dominate many protocol designs.
Common pitfalls
- Treating well-known ports as certain. A service can run on any port, and firewalls often decide what is reachable.
- Mapping the OSI model onto real protocols too literally. TCP/IP does not have separate session and presentation layers, and several protocols span layers.
- Assuming HTTP/3 uses its own port or TCP. It runs over QUIC on UDP, usually port 443.
- Forgetting that DNS also uses TCP (for large responses and zone transfers) and now encrypted transports such as DNS over TLS.
Using it from an agent
- When a user asks 'what port does X use', give the default and say it is a convention that the deployment may change.
- Quote the layer number and the layer name together when using the OSI model; the numbers are what people refer to in conversation.
- For DNS questions, ask for the record type before answering; the same name has different answers per type.
Start with: Common Network Ports · OSI Model Layers
Datasets in Networking
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Common Network Ports
Well-known TCP and UDP ports for common network services.
45 entries -
DNS Fundamentals
Common DNS record types and their purposes.
16 entries -
HTTP/2 and HTTP/3 Features
Key features and improvements introduced in HTTP/2 and HTTP/3 over HTTP/1.1.
13 entries -
Network Topologies
Common physical and logical network layouts.
10 entries -
OSI Model Layers
The seven layers of the OSI reference model.
7 entries -
Routing Protocols
Algorithms and protocols that determine packet paths.
12 entries -
TCP/IP Protocol Suite
Layers and core protocols of the TCP/IP model.
4 entries
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