Govt Exams
The Physical Layer (Layer 1) handles the conversion of data into electrical signals, light pulses, or radio waves for transmission over physical media.
Real-time applications like video conferencing use UDP (Layer 4) instead of TCP because UDP has lower latency despite no guaranteed delivery, which is acceptable for video streams.
TCP establishes a connection before data transfer (handshake), while UDP sends data without pre-established connection. Both are Layer 4 protocols.
If intra-switch communication works but inter-switch fails, Layer 2 is functional. The issue is at Layer 3 (routing/IP configuration) for cross-network communication.
Each OSI layer adds its own header (and trailer) to data, creating PDUs with different names: Segment (L4), Packet (L3), Frame (L2), Bits (L1).
VPN encryption primarily occurs at Layer 6 (Presentation Layer) for data encryption, though some VPN protocols like IPSec operate at Layer 3.
QoS mechanisms like traffic prioritization, bandwidth allocation, and packet classification operate at Layers 3 and 4 using IP and TCP/UDP information.
Since ping (Layer 3) works, Layers 1-3 are functional. HTTP failure indicates an issue at Layer 7 (Application) or Layer 6 (Presentation).
HTTPS (web browsing) is an Application Layer protocol. A, C, and D belong to Presentation, Network, and Physical layers respectively.
The Data Link Layer (Layer 2) uses CRC (Cyclic Redundancy Check) to detect frame errors and corruption in the frame header.