Network 1.5 - 1.7

802.11a

5 GHz, 54 Mbps, less interference, shorter range.

802.11b

2.4 GHz, 11 Mbps, longer range, more interference.

802.11g

2.4 GHz, 54 Mbps, backward compatible with 802.11b.

802.11n (WiFi 4)

2.4/5 GHz, 600 Mbps, MIMO antennas, better speed/range.

802.11ac (WiFi 5)

5 GHz, up to 3.46 Gbps, wide channels, ideal for HD streaming.

802.11ac (WiFi 6)

2.4/5 GHz, up to 9.6 Gbps, OFDMA/BSS coloring, many

Single-mode

Long-distance, small core, low loss, telecom/cable TV.

Multimode

• Short-distance, multiple light modes, cheaper, LAN/campus.

Direct Attach Copper DAC

Short-range, low-cost, low-power connections.

Twinax

High-speed short-range, shielded, better noise immunity.

RG-6 Coaxial

Cable/satellite, shielded, low interference.

Plenum

Plenum: fire-resistant, low-smoke for air spaces; Non-plenum: cheaper, more toxic smoke.

Cable Speeds

Ethernet Cat 5–6a: 100 Mbps–10 Gbps; coax for broadband; fiber (single/multi) up to 100 Gbps. Speed depends on cable quality, installation, and interference.

Transceivers/Media Converters

Devices that send/receive data; media converters change signals between cable types (e.g., copper ↔ fiber).

Transceivers Protocol:

Must match network protocol (Ethernet, Fibre Channel) for reliable speed and performance.

Ethernet

LAN technology using twisted pair/fiber, speeds 10 Mbps–100 Gbps, CSMA/CD for access.

Fibre Channel

High-speed storage network tech, up to 16 Gbps+, reliable for SANs.

Small-Form-Factor Pluggable (SFP)

Small, hot-pluggable module, 1 Gbps, fiber or copper, easy upgrades.

Enhanced Form-Factor Pluggable (SFP+)

Enhanced SFP, 10 Gbps, used for high-speed connections over fiber/copper.

Quad Small Form-Factor Pluggable (QSFP)

Quad SFP, 4×10 Gbps = 40 Gbps, high-density data centers.

Enhanced Quad Small Form-Factor Pluggable (QSFP+)

Enhanced QSFP, 40 Gbps+, higher bandwidth and port density for cloud/data centers.

Subscriber Connector (SC)

Fiber optic, square push-pull, secure, common for single-mode telecom/CATV.

Local Connector (LC)

Small form-factor fiber, push-pull, high-density, low insertion loss, single/multi-mode.

Straight Tip (ST)

Fiber with bayonet lock, quick connection, durable, mainly multimode.

Multi-fiber Push On (MPO)

Multi-fiber connector, 12–24 fibers, high-density, fast deployment, data centers.

RJ11

Telephone connector, 6P4C, for 1–2 lines.

RJ45

Ethernet connector, 8P8C, LAN devices, high-speed network.

F-Type Connector

Coax connector for cable/satellite TV & broadband, screws onto RG-6/59.

Network Topologies

loayout or arranglement of elements of a computer netwr=ork

Spine and Leaf

Two-layer network topology; highly scalable, minimizes latency by keeping any leaf switch within two hops of another.

Three-tier Hierarchical Model

hierarchical model structured to network design that breaks the network into three layers

Distribution Layer

Acts as the intermediary between the core and access layers, managing, routing, filtering, and WAN access.

Access Layer

Is the network’s point of entry for devices and end users, connecting them to the network

Collapsed Core Architecture

core architecture merges the core and distribution layers into a single layer, simplifying

the network design & reducing hardware costs.

North-South Traffic

the flow of network traffic between the data center and the outside world, focusing on inbound and outbound traffic patterns

East-West Traffic

Traffic flow within the data center, in modern data centers with heavily virtualizaed envirnoments

APIPA

Windows auto-assigns 169.254.x.x if DHCP fails; allows local subnet communication only.

RFC1918

Private IP ranges (10.x.x.x, 172.16–31.x.x, 192.168.x.x) for internal networks, not routed publicly.

Loopback/Localhost

127.0.0.1 (IPv4) or ::1 (IPv6); used for testing network software locally.

VLSM (Classless Variable-Length Subnet Mask)

Allows flexible subnet sizes to reduce wasted IPs within the same network.

CIDR Classless Inter-Domain Routing Notation

IP/prefix (e.g., 192.168.1.0/24) replaces classful design for efficient address allocation.

Class A

1–126; huge networks; 16.7M hosts; default mask 255.0.0.0.

Class B

128–191; medium networks; 65,534 hosts; default mask 255.255.0.0.

Class C

192–223; small networks; 254 hosts; default mask 255.255.255.0.

Class D

224–239; multicast groups; no host/network division.

Class E

240–255; experimental/future use; no host/network division.