The router operates in which layer of OSI reference model?
(A). Session Layer
(B). Network Layer
(C). Presentation Layer
(D). Transport Layer
Correct Answer: Transport Layer
which of the following OSI layer is  Layers of the OSI Model
Layer Responsibility
7. Application Layer
Allows users to send data, access data, and use networks.
End User layer
Protocols:
File Transfer Protocol (FTP)
Simple Mail Transfer Protocol (SMTP)
Domain Name System (DNS)
IRC, HTTP
SSH, DNS
6. Presentation Layer
Presenting the data to the application layer Syntax layer
MPEG, IMAP, SSL, SSH, FTP, JPEG,
Data conversion
Character code translation
Data compression
Encryption and decryption
5. Session Layer
Responsible for opening sessions, ensuring they remain open and functional while data is being transferred, and closing them when communication ends.
Synch & send to port
WinSock, API’s, Sockets
Protocols:
Remote procedure call protocol (RPC)
Point-to-Point Tunneling Protocol (PPTP)
Session Control Protocol (SCP)
Session Description Protocol (SDP)
4. Transport Layer
Controls the reliability of a given link through flow control, segmentation and desegmentation, and error control.
End-to-end connections
Protocols: TCP, UDPerror control
flow control
congestion control
3. Network Layer
routing the data via the best physical path
Packets
Protocols: IPSec, ICMP, IGMP, IP, IPv4, IPv6.Best available path
traffic controls
 congestion of data packets
 encapsulation and fragmentation
2. Data Link Layer
Responsible for multiplexing data streams, data frame detection, medium access, and error control.
Frames
Switch, PPP, Bridge, Ethernet
Media Access Control (MAC) Layer
1. Physical Layer
Responsible for the communication of the unstructured raw data streams over a physical medium
Hardware: Coaxial cable, Fiber optic cable, Repeaters, Wireless, Hubs
Topologies: Bus, Ring, Star, and Mesh topology
Communication modes: Simplex, Half Duplex, Full Duplex, etc
Data transmission performance: Bit Rate and Bit Synchronization
