Page 24 - CITS - Computer Software Application -TT

COMPUTER SOFTWARE APPLICATION - CITS

• Remote Offices: If the company has remote offices or branches, consider connecting them to the core network
through secure VPN connections. This can create a hub-and-spoke topology, with the core network being the
hub and remote offices as spokes.

• Internet Connectivity: Connect the entire network to the internet through a dedicated firewall and router. This
connection can be implemented in a bus or star topology, depending on your specific needs for scalability and
redundancy.

By using a hybrid topology in this way, you can create a network that is cost-effective, easily scalable, and
provides redundancy where needed. It allows you to tailor the network design to the specific requirements of
different parts of the organization while ensuring reliable and efficient data flow across the entire infrastructure.

Link & Medium Access protocols, IEEE 802 standards,

Performance issues

A link protocol, also known as a data link protocol or link layer protocol, operates on the data link layer (Layer 2)
of the OSI model.

Its primary functions include framing, error detection and correction, flow control and addressing.
Link protocols are responsible for packaging higher-level data into frames that can be transmitted over a physical
medium.
They also handle acknowledgements, retransmissions, and other mechanisms to ensure reliable data transfers
between directly connected nodes.
Common examples of link protocols include
Ethernet - A widely used wired link protocol that uses MAC addresses to identify devices on a network and
employs CSMA/CD (Carrier Sense Multiple Access with Collision Detection) for medium access control.
HDLC (High-Level Data Link Control) - A synchronous link protocol used primarily in point-to-point and multipoint
communication networks.
PPP (Point-to-Point Protocol) - A protocol used for establishing a direct connection between two nodes over
various physical medium.

Medium Access Control (MAC) Protocol
MAC protocols are a subset of link protocols.
They deal specifically with the access to and control of a shared communication medium, such as a wired or
wireless channel.
MAC protocols determine how devices on a network compete for the right to transmit data in order to minimize
collisions and ensure fair and efficient access to the medium.
CSMA / CD (Carrier Sense Multiple Access with Collision Detection) - Used in Ethernet networks, devices
listen for carrier signals before transmitting. If a collision is detected, the devices back off and try again after a
random time.

CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) - Used in wireless networks to avoid
collisions. Devices sense the channel and wait for it to be cleared before transmitting to prevent simultaneous
transmissions.
Token passing - In networks using token passing protocols like Token Ring, a special token is passed between
devices, granting the holder the right to transmit. This ensures an orderly access to the medium.

TDMA (Time Division Multiple Access) - The available transmission time is divided into time slots, and each
device is assigned a specific time slot for transmission.
FDMA (Frequency Division Multiple Access) - Different devices are assigned different frequency bands within
a shared medium.
CDMA (Code Division Multiple Access) - Each device uses a unique code to transmit data simultaneously over
the same frequency band, and receivers use the corresponding code to distinguish between signals.

11

CITS : IT&ITES - Computer Software Application - Lesson 01-17