NETWORK TECH QUIZ 2

Physical Layer (Layer 1)

Transmits raw bits over physical media as signals (electrical, light, or radio waves).

Physical Connections

Wired (cables) or wireless (radio waves).

NIC (Network Interface Card)

Connects a device to the network (wired or wireless).

Encoding

Converts data bits into predefined codes for transmission.

Signaling

Represents bits as electrical pulses, light, or RF.

Bandwidth

Capacity of a medium to carry data (measured in bits per second).

Throughput

Actual data transfer rate achieved.

Goodput

Throughput minus protocol overhead.

Latency

Delay for data to travel from source to destination.

Copper Cable

Uses electrical pulses; subject to attenuation, EMI, and crosstalk.

UTP (Unshielded Twisted Pair)

Most common, terminated with RJ-45.

STP (Shielded Twisted Pair)

Adds shielding for better noise protection.

Coaxial Cable

Used in older Ethernet and wireless antenna links.

Fiber Optic Cable

Uses light pulses, high bandwidth, immune to EMI/RFI.

Wireless Media

Uses radio or microwave; affected by interference, coverage, and security issues.

Data Link Layer (Layer 2)

Packages data into frames, handles addressing, and controls media access.

Sublayers: LLC (Logical Link Control)

Interfaces with network layer protocols (IPv4, IPv6).

Sublayers: MAC (Media Access Control)

MAC (Media Access Control)

Physical Topology

Actual physical layout of devices.

Logical Topology

Path that data signals follow, defined by protocols.

Duplex Modes: Half-duplex

Devices send or receive, but not both at once.

Duplex Modes: Full-duplex

Devices send and receive simultaneously.

Contention-based (CSMA/CD, CSMA/CA)

Devices compete for access; collisions occur in CSMA/CD.

Media Access Control Methods - Contention-based (CSMA/CD, CSMA/CA)

Devices compete for access; collisions occur in CSMA/CD.

Media Access Control Methods - Controlled access

Devices take turns accessing the medium (e.g., Token Ring).

Data Link Frame - Components

Header, Data (payload), Trailer.

Data Link Frame - Fields

Frame delimiters, addressing, type, control, error detection.

Data Link Frame - Layer 2 Addressing

NIC MAC addresses used for local delivery.

Data Link Frame - Protocols

Ethernet, Wi-Fi (802.11), PPP, HDLC, Frame Relay.

Ethernet

LAN technology operating at Layers 1 and 2; defined by IEEE 802.2/802.3.

Ethernet - Speeds

10 Mbps to 100 Gbps and beyond.

Sublayers - Logical Link Control (LLC)

Software-based, communicates with upper layers.

MAC (Media Access Control)

Hardware-based (in NIC), handles encapsulation and media access.

64 bytes (runt frames are discarded)

Ethernet Frame: Min size

1518 bytes (larger are “jumbo frames”)

Ethernet Frame: Max size

MAC Addresses

48-bit hardware addresses (burned-in on NICs), written in hexadecimal

Unicast

One device to one device.

Broadcast

One device to all devices (FF:FF:FF:FF:FF:FF).

Multicast

One device to a group of devices (starting with 01:00:5E).

OUI (Organizationally Unique Identifier)

First 3 bytes assigned by IEEE to vendors.

MAC Address Table (CAM Table)

Switch learns source MAC addresses and stores port mappings.

send only to specific port.

LAN Switching - If destination known →

flood to all ports.

LAN Switching - If unknown →

Receives entire frame, checks for errors before forwarding.

Switching Methods - Store-and-Forward

Forwards after reading destination MAC only (faster, no error check).

Switching Methods - Cut-Through

Forwards after first 64 bytes (compromise).

Switching Methods - Fragment-Free

Duplex mismatch

One side full-duplex, other half-duplex → performance problems.

Auto-MDIX

Allows switches/routers to detect cable type automatically (no need for crossover cables).

Address Resolution Protocol (ARP)

Maps IPv4 addresses to MAC addresses.

ARP Request

Broadcast asking "Who owns this IP?"

ARP Reply

Device with the IP responds with its MAC.

ARP Cache/Table

Stores IP-to-MAC mappings temporarily.

(attacker fakes MAC)

Security Threat - ARP Spoofing ___ . Mitigated by Dynamic ARP Inspection (DAI).

IPv4, IPv6.

Network Layer (Layer 3) - Protocols

Network Layer (Layer 3)

Addressing, encapsulation, routing, de-encapsulation.

No session setup.

Characteristics of IP - Connectionless

No delivery guarantee.

Characteristics of IP - Best Effort

Works on copper, fiber, or wireless.

Characteristics of IP - Media Independent

MTU (Maximum Transmission Unit)

Largest packet size supported on a link. IPv4 allows fragmentation; IPv6 does not.

Host Routing

Device decides if destination is local or remote.

Sent directly on LAN.

Host Routing - Local

Sent to default gateway.

Host Routing - Remote

Default Gateway

Router IP address that connects LAN to other networks.

Router Routing Table - Directly Connected Routes

Learned automatically when interface active.

Router Routing Table - Remote Routes

Learned via static config or dynamic protocols.

Router Routing Table - Default Route

Used when no specific route is known.

Static Routing

Manually configured; good for small networks.

Dynamic Routing

• Routers share updates automatically and choose best paths.