2. A network is a collection of systems and devices exchanging data over some form of media.
A host is defined as any device that holds a logical address on your network.
Hosts can be workstations, servers, printers, connection devices, or routers.
3. Modern networks are charged with delivering our phone calls and, soon, our television and
entertainment options. Data—no matter what its form—is transmitted in the form of bits.
A single bit is a 1 or a 0 (based on the binary number system of two digits versus the typically
used decimal numbering system based on the digits 0–9).
4. A protocol is simply an agreed upon set of rules for a particular network function.
Bandwidth is generally considered to be the total amount of data (in bits) you can theoretically
transmit within a given time period (typically one second).
Bandwidth is expressed in bits or bytes per second in digital networking.
5. Network Topologies
The topology can refer to how the network actually looks
Physical Topologies:
The physical topology of the network refers to how the network actually looks from a
bird’s-eye view—the physical cabling layout of the network itself.
6. A bus topology consists of all devices connecting to a single wire—a coaxial cable.
A physical bus looks like a straight line—a stick—with connections to hosts coming off
in a “T” shape.
In a ring topology, all devices are connected to each other in the shape of a circle—the first
device feeds into the second device, which in turn feeds into the third, and so on and so on until
the loop plugs back into the first device
7. Star topologies can also include extended star, where the central device extends links to other
hubs and switches.
A token passing, or ring, topology works in a more organized, almost friendly format. In a
token passing logical topology, systems can only transmit information when they hold a special
data packet, known as a token. The token is passed from one device to the next, in a prescribed,
circular path. Each device receives the token and examines it. If it holds a message for the
device, it will open and process it.
8. Network Categories
Networks are typically of two types: LANs and WANs.
LANs :
A LAN (local area network) can be defined as a network that serves users within a small
geographic footprint.
WANs:
A WAN(wide area network ) is nothing more than the network connecting a collection of LANs
across a wide geographic area—perhaps a state, nation, or even the whole world! Aside from
the distance variable, another defining characteristic of WANs is the concept of a leased line.
9. The OSI Reference Model 11 CERTIFICATION OBJECTIVE 1.02 The OSI Reference
Model
One word bandied about quite a bit in regards to the OSI model is encapsulation.
Encapsulation is the process of adding a header and a trailer to a piece of data. While each stage
of communication (layer of the model) adds a header to the data, only one layer always adds a
trailer. Some texts define encapsulation as occurring in all layers of the model; however, it
technically only occurs at one—the Data Link layer.
10. The Layers
The OSI Reference Model splits the communications process into seven distinct modular layers,
with each layer accomplishing a specific function independently of all other layers. The layers do
rely on layers above and below to provide something to work with, but they don’t necessarily
care what they receive to work with.
11. The OSI REFERENCE MODEL SERIES
PRESENTATION LAYER(6)
SESSION LAYER(5)
TRANSPORT LAYER(4)
NETWORK LAYER(3)
DATALINK LAYER(2)
PHYSICAL LAYER(1)
APPLICATION LAYER(7)
