About this previous year paper
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
| Symmetric | Asymmetric |
|---|---|
| Single key | Public & private keys |
| Fast | Secure |
| Example: AES | Example: RSA |
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
| OSI | TCP/IP |
|---|---|
| 7 layers | 4 layers |
| Theoretical | Practical |
| ISO standard | DoD standard |