/wiki / cn

application-layer

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for broken link [[application-layer]] — needs human content. This page was referenced 2 times and was missing, so a stub was created to keep the graph connected.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of application layer.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Application Layer

Connections

Related: Index — auto stub, needs proper links to wiki/cn/dns.md, wiki/cn/socket-api.md

Edge Cases & Gotchas

To be written.
To be written.

arp-cache

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[arp-cache]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of arp cache.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Arp Cache

Connections

Related: Index — auto stub for singleton [[arp-cache]] from wiki/cn/arp.md

Edge Cases & Gotchas

To be written.
To be written.

authentication

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for broken link [[authentication]] — needs human content. This page was referenced 2 times and was missing, so a stub was created to keep the graph connected.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of authentication.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Authentication

Connections

Related: Index — auto stub, needs proper links to wiki/cn/lcp.md, wiki/cn/ppp-protocol.md

Edge Cases & Gotchas

To be written.
To be written.

automatic-repeat-request

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[automatic-repeat-request]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of automatic repeat request.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Automatic Repeat Request

Connections

Related: Index — auto stub for singleton [[automatic-repeat-request]] from wiki/cn/go-back-n.md

Edge Cases & Gotchas

To be written.
To be written.

carrier-sense

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[carrier-sense]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of carrier sense.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Carrier Sense

Connections

Related: Index — auto stub for singleton [[carrier-sense]] from wiki/cn/csma.md

Edge Cases & Gotchas

To be written.
To be written.

collision-detection

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for broken link [[collision-detection]] — needs human content. This page was referenced 2 times and was missing, so a stub was created to keep the graph connected.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of collision detection.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Collision Detection

Connections

Related: Index — auto stub, needs proper links to wiki/cn/jam-signal.md, wiki/cn/csma-cd.md

Edge Cases & Gotchas

To be written.
To be written.

collision

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for broken link [[collision]] — needs human content. This page was referenced 3 times and was missing, so a stub was created to keep the graph connected.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of collision.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Collision

Connections

Related: Index — auto stub, needs proper links to wiki/cn/jam-signal.md, wiki/cn/binary-exponential-backoff.md

Edge Cases & Gotchas

To be written.
To be written.

csma-ca

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for broken link [[csma-ca]] — needs human content. This page was referenced 3 times and was missing, so a stub was created to keep the graph connected.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of csma ca.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Csma Ca

Connections

Related: Index — auto stub, needs proper links to wiki/cn/csma-cd.md, wiki/wireless-n/csma-cd.md

Edge Cases & Gotchas

To be written.
To be written.

data-link-layer

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[data-link-layer]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of data link layer.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Data Link Layer

Connections

Related: Index — auto stub for singleton [[data-link-layer]] from wiki/cn/ppp-protocol.md

Edge Cases & Gotchas

To be written.
To be written.

error-detection

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[error-detection]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of error detection.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Error Detection

Connections

Related: Index — auto stub for singleton [[error-detection]] from wiki/cn/decapsulation.md

Edge Cases & Gotchas

To be written.
To be written.

half-duplex

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[half-duplex]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of half duplex.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Half Duplex

Connections

Related: Index — auto stub for singleton [[half-duplex]] from wiki/cn/full-duplex.md

Edge Cases & Gotchas

To be written.
To be written.

ipcp

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[ipcp]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of ipcp.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Ipcp

Connections

Related: Index — auto stub for singleton [[ipcp]] from wiki/cn/ncp.md

Edge Cases & Gotchas

To be written.
To be written.

ipv4

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[ipv4]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of ipv4.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Ipv4

Connections

Related: Index — auto stub for singleton [[ipv4]] from wiki/cn/ip-protocol.md

Edge Cases & Gotchas

To be written.
To be written.

ipv6

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[ipv6]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of ipv6.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Ipv6

Connections

Related: Index — auto stub for singleton [[ipv6]] from wiki/cn/ip-protocol.md

Edge Cases & Gotchas

To be written.
To be written.

local-area-network

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[local-area-network]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of local area network.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Local Area Network

Connections

Related: Index — auto stub for singleton [[local-area-network]] from wiki/cn/arp.md

Edge Cases & Gotchas

To be written.
To be written.

mru

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[mru]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of mru.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Mru

Connections

Related: Index — auto stub for singleton [[mru]] from wiki/cn/lcp.md

Edge Cases & Gotchas

To be written.
To be written.

multiple-access

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[multiple-access]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of multiple access.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Multiple Access

Connections

Related: Index — auto stub for singleton [[multiple-access]] from wiki/cn/csma.md

Edge Cases & Gotchas

To be written.
To be written.

multiprotocol

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[multiprotocol]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of multiprotocol.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Multiprotocol

Connections

Related: Index — auto stub for singleton [[multiprotocol]] from wiki/cn/ncp.md

Edge Cases & Gotchas

To be written.
To be written.

network-layer

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[network-layer]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of network layer.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Network Layer

Connections

Related: Index — auto stub for singleton [[network-layer]] from wiki/cn/icmp.md

Edge Cases & Gotchas

To be written.
To be written.

osi-model

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[osi-model]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of osi model.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Osi Model

Connections

Related: Index — auto stub for singleton [[osi-model]] from wiki/cn/layered-model.md

Edge Cases & Gotchas

To be written.
To be written.

packet-loss

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[packet-loss]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of packet loss.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Packet Loss

Connections

Related: Index — auto stub for singleton [[packet-loss]] from wiki/cn/congestion-control.md

Edge Cases & Gotchas

To be written.
To be written.

ping

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[ping]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of ping.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Ping

Connections

Related: Index — auto stub for singleton [[ping]] from wiki/cn/icmp.md

Edge Cases & Gotchas

To be written.
To be written.

pppoe

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[pppoe]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of pppoe.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Pppoe

Connections

Related: Index — auto stub for singleton [[pppoe]] from wiki/cn/ppp-protocol.md

Edge Cases & Gotchas

To be written.
To be written.

protocol-header

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for broken link [[protocol-header]] — needs human content. This page was referenced 2 times and was missing, so a stub was created to keep the graph connected.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of protocol header.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Protocol Header

Connections

Related: Index — auto stub, needs proper links to wiki/cn/decapsulation.md, wiki/cn/encapsulation.md

Edge Cases & Gotchas

To be written.
To be written.

protocol-suite

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[protocol-suite]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of protocol suite.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Protocol Suite

Connections

Related: Index — auto stub for singleton [[protocol-suite]] from wiki/cn/protocol.md

Edge Cases & Gotchas

To be written.
To be written.

random-access

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[random-access]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of random access.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Random Access

Connections

Related: Index — auto stub for singleton [[random-access]] from wiki/cn/binary-exponential-backoff.md

Edge Cases & Gotchas

To be written.
To be written.

receiver-buffer

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for broken link [[receiver-buffer]] — needs human content. This page was referenced 2 times and was missing, so a stub was created to keep the graph connected.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of receiver buffer.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Receiver Buffer

Connections

Related: Index — auto stub, needs proper links to wiki/cn/flow-control.md, wiki/cn/selective-repeat.md

Edge Cases & Gotchas

To be written.
To be written.

retransmission

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[retransmission]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of retransmission.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Retransmission

Connections

Related: Index — auto stub for singleton [[retransmission]] from wiki/cn/negative-acknowledgment.md

Edge Cases & Gotchas

To be written.
To be written.

routing

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[routing]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of routing.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Routing

Connections

Related: Index — auto stub for singleton [[routing]] from wiki/cn/ip-protocol.md

Edge Cases & Gotchas

To be written.
To be written.

session

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[session]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of session.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Session

Connections

Related: Index — auto stub for singleton [[session]] from wiki/cn/stateful-protocol.md

Edge Cases & Gotchas

To be written.
To be written.

simplex

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[simplex]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of simplex.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Simplex

Connections

Related: Index — auto stub for singleton [[simplex]] from wiki/cn/full-duplex.md

Edge Cases & Gotchas

To be written.
To be written.

stateless-protocol

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[stateless-protocol]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of stateless protocol.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Stateless Protocol

Connections

Related: Index — auto stub for singleton [[stateless-protocol]] from wiki/cn/stateful-protocol.md

Edge Cases & Gotchas

To be written.
To be written.

tcp-segment

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[tcp-segment]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of tcp segment.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Tcp Segment

Connections

Related: Index — auto stub for singleton [[tcp-segment]] from wiki/cn/encapsulation.md

Edge Cases & Gotchas

To be written.
To be written.

traceroute

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[traceroute]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of traceroute.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Traceroute

Connections

Related: Index — auto stub for singleton [[traceroute]] from wiki/cn/icmp.md

Edge Cases & Gotchas

To be written.
To be written.

transmission-error-detection

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[transmission-error-detection]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of transmission error detection.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Transmission Error Detection

Connections

Related: Index — auto stub for singleton [[transmission-error-detection]] from wiki/cn/stop-and-wait.md

Edge Cases & Gotchas

To be written.
To be written.

voip

2026-09-19T00:00:00.000Z

The Problem

Auto-created stub for singleton broken link [[voip]] — referenced once and was missing. Keeps graph connected per AGENTS.md:199.

Formal Definition

Per Wikipedia: “To be written.”

Explanation

Stub — fill with plain language explanation of voip.

How It Works

To be written.
To be written.
To be written.
To be written.

Visual Explanation

Semantic Network

Key Properties

To be written.

Real-World Example

# TODO: add example for Voip

Connections

Related: Index — auto stub for singleton [[voip]] from wiki/cn/udp.md

Edge Cases & Gotchas

To be written.
To be written.

Cn -- Map of Content

2026-09-02T00:00:00.000Z

Map of Content for Cn — 41 concepts. Start here to navigate cn.

Core Concepts

Acknowledgment — concept
ARP — concept
Best Effort Delivery — concept
Binary Exponential Backoff — concept
Congestion Control — concept
Connectionless Service — concept
Connection-Oriented Service — concept
CD — concept
CSMA — concept
Cumulative Acknowledgment — concept
Datagram — concept
Decapsulation — concept
DNS — concept
Encapsulation — concept
Flow Control — concept
Full-Duplex Communication — concept
Go-Back-N ARQ — concept
ICMP — concept
IP Protocol — concept
Jam Signal — concept
Layered Model — concept
LCP — concept
NCP — concept
Negative Acknowledgment — concept
Piggybacking — concept
PPP Protocol — concept
Network Protocol — concept
Reliable Data Transfer — concept
Selective Repeat ARQ — concept
Sequence Numbers — concept
Service Access Point — concept
Network Service — concept
Service Primitives — concept
Sliding Window Protocol — concept
Socket API — concept
Stateful Protocol — concept
Stop-and-Wait Protocol — concept
TCP — concept
Three-Way Handshake — concept
UDP — concept
Virtual Circuit — concept

Mechanisms & How Things Work

Pages that explain processes/flows.

Comparisons & Tradeoffs

(No synthesis yet — create via ingest or query —save)

acknowledgment

2026-04-30T00:00:00.000Z

The Problem

The sender needs to know whether the receiver successfully received a packet. Without feedback, the sender would never know if data was lost or corrupted.

Core Idea

A control message sent by the receiver back to the sender confirming successful receipt of data, typically referencing the sequence number of the received data.

How It Works

Receiver gets a packet, validates it (checksum, etc.)
Receiver sends ACK with sequence number (or expected next sequence number)
Sender receives ACK and knows data was delivered
If sender doesn’t receive ACK within timeout, it retransmits the data
Cumulative ACKs acknowledge all data up to a certain sequence number

Visual Explanation

Key Properties

Confirms successful delivery to sender
Can be cumulative (acknowledge multiple packets at once)
Can be piggybacked on data packets (in full-duplex protocols)
Timeout + lack of ACK triggers retransmission

Semantic Network

Connections

Built from: Reliable Data Transfer — core mechanism
Built from: Sequence Numbers — ACKs reference these
Related: Piggybacking — ACK attached to data packet
Related: Cumulative Acknowledgment — acknowledges through seq num
Contrasts with: Negative Acknowledgment — NAK signals failure

Edge Cases & Gotchas

ACK loss can cause unnecessary retransmission (sender times out)
Duplicate ACKs can signal packet loss (used in TCP fast retransmit)
Piggybacked ACKs may be delayed if no data to send (timer limits delay)

arp

2026-04-30T00:00:00.000Z

The Problem

Devices know the destination IP address but need the MAC (hardware) address to send frames on the local network. A mechanism is needed to map IP addresses to MAC addresses.

Core Idea

A protocol that resolves IP addresses to MAC addresses within a local network by broadcasting a request and receiving a unicast reply from the owner of the IP.

How It Works

Device wants to send to IP address on same LAN
Device checks ARP cache for existing IP-to-MAC mapping
If not cached, device broadcasts ARP request: “Who has IP 192.168.1.1?”
Target device with that IP sends unicast ARP reply: “I have it, my MAC is AA:BB:CC:DD:EE:FF”
Sender caches the mapping and sends the frame

Visual Explanation

Key Properties

Resolves IP to MAC addresses on local network
Uses broadcast for requests, unicast for replies
Maintains ARP cache to avoid repeated lookups
Works at the link layer (between network and link layers)

Semantic Network

Connections

Built from: IP Protocol — resolves IP addresses
Built from: MAC Address — what ARP discovers
Related: LAN — operates within single network
Related: ARP Cache — stores recent resolutions

Edge Cases & Gotchas

ARP spoofing/poisoning: attacker can send fake ARP replies to intercept traffic
ARP cache timeout: entries expire and must be re-resolved
Doesn’t work across routers (routers don’t forward broadcasts)

best-effort-delivery

2026-04-30T00:00:00.000Z

The Problem

Network layers want to forward packets as fast as possible without the overhead of guaranteeing delivery. Some services (like IP) prioritize speed and simplicity over reliability.

Core Idea

A delivery model where the network makes its “best effort” to deliver packets but provides no guarantees — packets can be lost, duplicated, or arrive out of order.

How It Works

Network layer receives packet from transport layer
Attempts to route and forward packet toward destination
If link is congested or error occurs: packet may be dropped
No acknowledgments, retransmissions, or error recovery at this layer
Higher layers (e.g., TCP) must handle reliability if needed

Visual Explanation

Key Properties

No delivery guarantees
No order guarantees
No error recovery (just detection via checksums)
Minimal overhead — fast and simple

Semantic Network

Connections

Built from: IP Protocol — uses best-effort delivery
Built from: Connectionless Service — inherently best-effort
Contrasts with: Reliable Data Transfer — guarantees vs no guarantees
Related: UDP — transport layer best-effort protocol

Edge Cases & Gotchas

Higher layers must implement reliability if needed (TCP does this on top of IP)
Packet loss is expected and must be handled by applications or transport layer
“Best effort” doesn’t mean “no effort” — routers still try their best to forward

binary-exponential-backoff

2026-04-30T00:00:00.000Z

The Problem

After a collision, if all devices retry immediately, they’ll collide again. A randomized waiting mechanism is needed to reduce the probability of repeated collisions.

Core Idea

An algorithm where the maximum random wait time doubles after each successive collision, reducing retry attempts when the network is congested.

How It Works

First collision: wait random time between 0 and 1 slot time
Second collision: wait random time between 0 and 2 slot times
Third collision: wait random time between 0 and 4 slot times
Nth collision: wait random time between 0 and 2^N slot times (capped at 1024)
After successful transmission, the backoff counter resets

Visual Explanation

Key Properties

Reduces collision probability under high load
Wait time grows exponentially with repeated collisions
Capped at maximum backoff (e.g., 1024 slots in Ethernet)
Used in CSMA/CD and some wireless protocols

Semantic Network

Connections

Built from: CD — uses this backoff algorithm
Related: Collision — triggers backoff
Related: Jam Signal — sent before backoff
Related: Random Access — broader category of protocols using backoff

Edge Cases & Gotchas

Maximum backoff limit prevents excessive wait times
Many collisions can still cause long delays (exponential growth)
Not used in modern full-duplex Ethernet (no collisions to back off from)

congestion-control

2026-04-30T00:00:00.000Z

The Problem

When too many senders transmit too fast, network routers become overloaded, leading to packet loss and reduced throughput for everyone. Individual flow control can’t prevent this because the bottleneck is the network, not the receiver.

Core Idea

A set of algorithms that detect network congestion and reduce sending rate to prevent overwhelming the network, then increase rate when congestion clears.

How It Works

Sender maintains a congestion window (cwnd) limiting unacknowledged data
Effective window = min(receive window, congestion window)
Slow start: exponentially increase cwnd until packet loss detected
Congestion avoidance: linearly increase cwnd after slow start threshold
Fast retransmit: retransmit on duplicate ACKs without waiting for timeout
Fast recovery: halve cwnd and continue after fast retransmit

Visual Explanation

Key Properties

Network-driven: responds to network congestion signals (loss, delay)
Uses congestion window separate from flow control window
Multiple algorithms: slow start, congestion avoidance, fast retransmit, fast recovery
Essential for internet stability

Semantic Network

Connections

Built from: Sliding Window Protocol — window-based mechanism
Built from: Packet Loss — primary congestion signal
Builds into: TCP — implements congestion control
Related: Flow Control — receiver-based vs network-based
Contrasts with: Flow Control — different control objective

Edge Cases & Gotchas

Bufferbloat: large router buffers hide congestion, causing high latency
TCP fairness: different TCP variants compete differently for bandwidth
Congestion control vs congestion avoidance: detection vs prevention strategies

connection-oriented-service

2026-04-30T00:00:00.000Z

The Problem

Network communication needs reliable, ordered delivery for applications like web browsing and file transfers. Without a connection-oriented approach, data might arrive out of order, get lost, or overwhelm receivers.

Core Idea

A service that establishes a dedicated logical connection between sender and receiver before exchanging data, guaranteeing reliable, ordered delivery with flow and congestion control.

How It Works

A connection establishment phase occurs using a handshake (e.g., TCP three-way handshake: SYN, SYN-ACK, ACK)
Both endpoints maintain state information including sequence numbers, acknowledgments, and buffer sizes
Data is delivered reliably with guaranteed ordering, error checking, and retransmission of lost packets
Flow control prevents fast senders from overwhelming slow receivers
Congestion control manages network traffic to prevent bottlenecks
A teardown phase releases the connection when communication ends

Visual Explanation

Key Properties

Guaranteed delivery through retransmission of lost packets
Ordered delivery preserving send sequence
Stateful: both endpoints maintain connection state
Higher overhead due to setup, maintenance, and reliability mechanisms
Uses a logical path (virtual circuit) for the connection duration

Semantic Network

Connections

Built from: Three-Way Handshake — connection establishment mechanism
Built from: Reliable Data Transfer — core guarantee provided
Builds into: TCP — primary protocol implementing this service
Contrasts with: Connectionless Service — no setup or reliability guarantees
Related: Flow Control — prevents receiver overload
Related: Congestion Control — manages network bottlenecks

Edge Cases & Gotchas

Higher latency due to connection setup overhead
State maintenance consumes memory on both endpoints
Connection state can be lost during network failures requiring re-establishment
Not suitable for bursty, small messages where setup cost dominates

connectionless-service

2026-04-30T00:00:00.000Z

The Problem

Some applications need fast, low-latency communication where occasional packet loss is acceptable. Setting up connections for every small message wastes bandwidth and adds delay.

Core Idea

A service where packets are sent independently without connection setup, offering best-effort delivery with no guarantees of order, reliability, or flow control.

How It Works

No handshake or connection establishment before sending data
Each packet (datagram) is treated independently with full addressing information
Packets may take different network paths and arrive out of order or not at all
No retransmission mechanism at this service layer
No flow control or congestion control — sender transmits at will
Stateless: neither endpoint maintains communication state

Visual Explanation

Key Properties

No connection setup, teardown, or state maintenance
Best-effort delivery with no guarantees
Lower overhead and faster than connection-oriented
Each packet routed independently
Stateless operation at the service layer

Semantic Network

Connections

Built from: IP Protocol — network layer connectionless foundation
Builds into: UDP — primary transport layer implementation
Contrasts with: Connection-Oriented Service — reliable vs best-effort
Related: Datagram — independent packet unit used
Related: Best Effort Delivery — no delivery guarantees

Edge Cases & Gotchas

Applications must handle reliability at higher layers if needed
Packet loss goes undetected unless application implements checking
No backpressure mechanism — can overwhelm receiver or network
Out-of-order delivery requires application-level reordering

csma-cd

2026-04-30T00:00:00.000Z

The Problem

CSMA reduces collisions but doesn’t handle them when they occur. Once a collision happens, devices keep transmitting garbage, wasting bandwidth until the packet finishes.

Core Idea

An extension of CSMA that detects collisions during transmission and immediately stops, then uses a backoff algorithm before retrying, minimizing wasted bandwidth.

How It Works

Device listens before transmitting (carrier sense)
If idle, start transmitting AND continuously monitor for collision
If collision detected (signal strength changes): stop transmitting immediately
Send a jam signal to notify all devices of the collision
Wait a random time (binary exponential backoff) before retrying

Visual Explanation

Key Properties

Listens before AND during transmission
Detects collisions quickly and stops transmission
Uses binary exponential backoff to reduce retry collisions
Standard for traditional wired Ethernet (10/100 Mbps)

Semantic Network

Connections

Built from: CSMA — adds collision detection to basic CSMA
Built from: Jam Signal — notifies others of collision
Built from: Binary Exponential Backoff — retry algorithm
Related: Collision Detection — the key addition over CSMA
Contrasts with: CA — detection vs avoidance

Edge Cases & Gotchas

Only works on wired networks (can’t detect collision in wireless due to hidden terminal)
Not used in modern full-duplex Ethernet (switches eliminate collisions)
Maximum network diameter limited by collision detection time (slot time)

csma

2026-04-30T00:00:00.000Z

The Problem

Multiple devices share a single communication channel (like Ethernet). If two devices transmit simultaneously, their signals collide and data is lost. A mechanism is needed to minimize collisions.

Core Idea

A protocol where devices listen to the channel (carrier sense) before transmitting, and wait if the channel is busy, reducing but not eliminating collisions.

How It Works

Device wants to transmit: first listens to the channel (carrier sense)
If channel is idle: transmit the data
If channel is busy: wait for a random time, then check again
If channel becomes idle: transmit
Collision can still occur if two devices sense idle at the same time and both start transmitting

Visual Explanation

Key Properties

“Listen before talk” approach
Reduces collisions compared to pure ALOHA
Does not eliminate collisions completely
Used in wireless and wired shared media

Semantic Network

Connections

Built from: Carrier Sense — the listening mechanism
Builds into: CD — adds collision detection
Contrasts with: CA — collision avoidance vs detection
Related: Multiple Access — broader category of protocols
Related: Collision — what CSMA tries to avoid

Edge Cases & Gotchas

Propagation delay causes collisions: device may sense idle while a transmission is in progress but hasn’t arrived yet
“Hidden terminal” problem in wireless (not solved by CSMA alone)
Efficiency depends on propagation delay vs packet transmission time

cumulative-acknowledgment

2026-04-30T00:00:00.000Z

The Problem

Sending an ACK for every received packet creates overhead. A more efficient approach is needed to acknowledge multiple packets with a single ACK.

Core Idea

An acknowledgment that confirms receipt of all packets up to and including a specific sequence number, not just the single packet being acknowledged.

How It Works

Receiver gets packets 0, 1, 2, 3 in order
Receiver sends ACK for packet 3, meaning “I have received all packets up to 3”
Sender receives ACK 3 and knows packets 0, 1, 2, 3 were all received
If packet 1 is lost but 2, 3 arrive, receiver keeps ACKing 0 (last in-order packet)
Used by Go-Back-N and TCP

Visual Explanation

Key Properties

Reduces number of ACK packets needed
Confirms receipt through a sequence number
Used by Go-Back-N and TCP (with selective ACK option available)
If gap detected, ACK stays at last in-order packet

Semantic Network

Connections

Built from: Acknowledgment — cumulative is a type of ACK
Built from: Go-Back-N ARQ — uses cumulative ACKs
Built from: TCP — uses cumulative ACKs (default behavior)
Contrasts with: Selective Repeat — individual ACKs vs cumulative

Edge Cases & Gotchas

Doesn’t identify which specific packets are missing (just the last contiguous one)
TCP selective ACK (SACK) option extends cumulative ACK to identify gaps
Duplicate ACKs (same cumulative ACK repeated) can signal packet loss

datagram

2026-04-30T00:00:00.000Z

The Problem

Connectionless services need a unit of data that is self-contained with all necessary addressing, so it can be routed independently without connection state.

Core Idea

A self-contained, independent packet in a connectionless service that carries its own addressing and can take any path to the destination.

How It Works

Application data is encapsulated in a datagram with source and destination addresses/ports
Each datagram is treated independently by the network
Datagrams may take different paths and arrive out of order
No relationship between consecutive datagrams (no connection state)
UDP packets are datagrams; IP packets are also datagrams

Visual Explanation

Key Properties

Self-contained with full addressing
No connection state maintained
Can arrive out of order or not at all
Used by UDP and IP (connectionless protocols)

Semantic Network

Connections

Built from: Connectionless Service — datagrams are the unit of transfer
Built from: UDP — uses datagrams
Built from: IP Protocol — IP packets are datagrams
Contrasts with: Virtual Circuit — independent vs stateful path

Edge Cases & Gotchas

No delivery guarantees — applications must handle loss
Datagram size limits (UDP: 65,507 bytes minus IP header; practical limit often 1,500 bytes due to MTU)
Fragmentation at IP layer if datagram exceeds MTU

decapsulation

2026-04-30T00:00:00.000Z

The Problem

When a packet arrives at its destination, each layer needs to extract and process its own header, then pass the remaining data up to the next layer. Without decapsulation, the receiving application would get raw bits with no structure.

Core Idea

The process of removing layer-specific headers (and trailers) as data moves up the protocol stack from the physical layer to the application.

How It Works

Physical layer receives bits and passes to link layer
Link layer processes frame header and trailer, extracts IP packet, passes up
Network layer processes IP header, extracts transport segment, passes up
Transport layer processes TCP/UDP header, extracts application data, passes to application
Application receives the original data

Visual Explanation

Key Properties

Reverse of encapsulation
Each layer processes and removes its header
Passes payload to next higher layer
Errors detected at each layer (if error checking exists)

Semantic Network

Connections

Contrasts with: Encapsulation — unwrapping vs wrapping
Built from: Layered Model — decapsulation happens between layers
Related: Protocol Header — what gets removed
Related: Error Detection — often checked during decapsulation

Edge Cases & Gotchas

If a layer detects an error (bad checksum), it may discard the packet
Some layers may not have a header to remove (e.g., physical layer)
Tunneling requires recursive decapsulation (decapsulate inner packet)

dns

2026-04-30T00:00:00.000Z

The Problem

Humans remember domain names (google.com) but network protocols use IP addresses (142.250.191.78). Without a translation system, users would need to memorize numeric addresses for every website.

Core Idea

A distributed hierarchical system that translates human-readable domain names into IP addresses, acting as the internet’s phonebook.

How It Works

Application requests IP for a domain name (e.g., google.com)
DNS resolver checks cache, then queries root servers, TLD servers, and authoritative servers
Responses are cached to improve performance
Primarily uses UDP for queries (port 53) due to speed requirements
Falls back to TCP for large responses (zone transfers) or when UDP is blocked