(a) Functions and Layers of Network Nodes:
i. Hubs:

Function: Hubs operate at the physical layer (Layer 1) of the OSI model. They are basic
networking devices that connect multiple devices in a LAN. Hubs broadcast data to all connected
devices, making them simple and effective for small networks.
ii. Switches:

Function: Switches operate at the data link layer (Layer 2) of the OSI model. They forward data
based on MAC addresses, enabling more efficient and targeted communication within a LAN.
Switches reduce network congestion compared to hubs.
iii. Routers:

Function: Routers operate at the network layer (Layer 3) of the OSI model. They connect
different networks and make decisions about the best path for data to travel between them.
Routers use IP addresses for packet forwarding and help in dividing large networks into smaller
subnets.
iv. Repeaters:

Function: Repeaters operate at the physical layer (Layer 1). Their primary function is to amplify
and regenerate signals to extend the reach of a network. Repeaters are used to overcome signal
degradation over long distances in a network.
v. Bridges:

Function: Bridges operate at the data link layer (Layer 2). They connect and filter traffic between
different segments of a network based on MAC addresses. Bridges help in reducing collision
domains and improving overall network performance.
vi. Gateways:

Function: Gateways operate at the higher layers of the OSI model (Layers 3 and above). They
provide translation between different network protocols and data formats, allowing
communication between different types of networks. Gateways can connect networks with
different architectures.
(b) Comparison of OSI and TCP/IP Models:

OSI Model:
1. Physical Layer (Layer 1): Concerned with physical connections and electrical
specifications.
2. Data Link Layer (Layer 2): Manages access to the physical medium, error detection, and
MAC addresses.
3. Network Layer (Layer 3): Deals with logical addressing, routing, and packet forwarding.
4. Transport Layer (Layer 4): Provides end-to-end communication, flow control, and error
recovery.
5. Session Layer (Layer 5): Manages sessions (connections) between applications.
6. Presentation Layer (Layer 6): Deals with data translation, encryption, and compression.
7. Application Layer (Layer 7): Provides network services directly to end-users and
applications.

TCP/IP Model:
1. Link Layer (equivalent to OSI Layers 1 and 2): Combines functionalities of OSI's Physical
and Data Link layers.
2. Internet Layer (equivalent to OSI Layer 3): Similar to the OSI Network layer, deals with
logical addressing and routing (IP).
3. Transport Layer (equivalent to OSI Layer 4): Ensures end-to-end communication and
reliability (TCP and UDP).
4. Application Layer (combines OSI Layers 5, 6, and 7): Provides network services directly
to applications.
Key Differences:

OSI has seven layers, while TCP/IP has four.

The naming and functionalities of the layers differ.
(c) Packet Forwarding vs. Packet Routing:

Packet Forwarding: Involves the process of passing data from one device to the next in a
network based on the device's MAC address (data link layer). It occurs within the same network
segment, usually handled by switches or bridges.

Packet Routing: Refers to the process of determining the optimal path for data to travel
between different networks based on the destination IP address (network layer). Routers are
responsible for packet routing, making decisions about the next hop on the route.
(d) Packet Losses in Computer Networks:
Packet losses can occur due to various reasons, including:

Congestion: Network congestion may lead to packet drops when routers and switches are
overwhelmed with traffic.

Collisions: In Ethernet networks, collisions may occur, leading to packet losses.

Faulty Hardware or Connections: Malfunctioning network devices, cables, or connectors can
result in packet loss.

Buffer Overflow: If network devices' buffers are full, incoming packets may be discarded.

Software Errors: Bugs or issues in network protocols or software can cause packet losses.
(e) Network Core vs. Network Edge:

Network Core: The core is the central part of the network where high-speed, long-distance
communication occurs. It typically involves high-capacity routers and switches. The core focuses
on fast and efficient packet forwarding.

Network Edge: The edge comprises the devices, such as end-user devices, servers, and entry
points to the network. Functions like data input, output, and user access occur at the network
edge. Security and access control are crucial at the network edge.
(f) Transmission Media in Networks:

Twisted Pair Cable: Commonly used for Ethernet networks. Examples include Cat5e and Cat6
cables.

Coaxial Cable: Used in cable television networks. Provides higher bandwidth than twisted pair
cables.

Fiber Optic Cable: Utilizes light signals for high-speed data transmission. Offers high bandwidth
and is immune to electromagnetic interference.

Wireless Transmission: Includes Wi-Fi, Bluetooth, and cellular networks. Enables mobility and
eliminates the need for physical cables.

Satellite Communication: Uses satellites to transmit data over long distances. Suitable for
remote areas.