(SEM VI) THEORY EXAMINATION 2024-25 DATA COMMUNICATION NETWORKS

BEC062 – DATA COMMUNICATION NETWORKS

Time: 3 Hours | Max Marks: 70

SECTION A – Short Answer Questions

(2 × 7 = 14 marks | Attempt ALL)

Write definition + 2–3 key points

a. Internet Protocol (IP)

Internet Protocol is a network layer protocol responsible for logical addressing and packet routing across interconnected networks.                           It provides connectionless and best-effort delivery.

b. Design Issues in Network Layer                         Logical addressing

Routing and forwarding                                        Congestion control

Quality of Service (QoS)                                        Error handling

c. Guided vs Unguided Media

Guided Media (Wired):                                      Twisted pair, coaxial, optical fiber

High security, less interference

Unguided Media (Wireless):                              Radio waves, microwaves, infrared

Easy installation, more noise

d. Broadcast Mode in CSMA/CD                          In CSMA/CD, all stations share the same medium.
A station broadcasts frames to all nodes, detects collisions, and retransmits after a random back-off time.

e. Bit Stuffing in Data Link Layer

Bit stuffing inserts an extra 0 after five consecutive 1s in data to prevent accidental flag pattern generation.

f. Fast Ethernet

Fast Ethernet supports 100 Mbps data rate.        Standards include 100BASE-TX, 100BASE-FX, using CSMA/CD.

g. File Transfer Protocol (FTP)

FTP is an application layer protocol used for transferring files between client and server.
It uses TCP ports 20 (data) and 21 (control).

SECTION B – Medium Answer Questions

(7 × 3 = 21 marks | Attempt ANY THREE)

a. CSMA Persistence Methods & CSMA/CA

Persistence Methods:                                           1-persistent

Non-persistent                                                        p-persistent

CSMA/CA:

Uses Inter-Frame Space (IFS)                                  Contention window reduces collision probability
Used in wireless networks.

b. Framing in Data Link Layer                                 Framing divides data stream into manageable units.

Techniques:                                                           Character count

Byte stuffing                                                           Bit stuffing

(Draw framing diagram for full marks)

c. IEEE 802.11 Wireless LAN                                   Architecture:

Access Point (AP)                                                   Stations (STA)

Basic Service Set (BSS)

Working:                                                              Uses CSMA/CA

Supports infrastructure & ad-hoc modes

d. Intra-Domain & Inter-Domain Routing

Intra-domain: Routing within an autonomous system (RIP, OSPF)

Inter-domain: Routing between autonomous systems (BGP)

Link State Routing:                                             Each router builds complete network topology

Uses shortest path algorithm (Dijkstra)

e. Symmetric vs Asymmetric Cryptography

SECTION C – Attempt ANY ONE

(7 marks)

a. Role of Protocols & Protocol Layering

Roles:                                                                     Communication rules

Data formatting                                                      Error & flow control

Principles of Layering:                                         Each layer performs a specific function

Clear interfaces                                                      Independent implementation

b. TCP/IP vs OSI Model