MODULE 2 Flashcards
It is an interconnected set of autonomous computers.
Computer Network
Computer networks have emerged as a result of the convergence of two technologies of this century
Computer and Communication
The exchange of data between two nodes (e.g., computer) via some form of transmission media (e.g., cable).
Data Communication
3 types of data flow
✓ Simplex
✓ Half Duplex
✓ Full Duplex
In this case data flows in only one direction on the data communication line (medium).
Simplex
Data flows in both directions but not at the same time. If one device is sending, the other can only receive (vice versa).
Half Duplex
Data flows in both directions simultaneously. Device can send and receive at the same time.
Full Duplex
It is a set of rules that govern data communication.
Protocol
Protocol used in network communications also define:
✓ Message Encoding
✓ Message Formatting and encapsulation
✓ Message timing
✓ Message size
✓ Message delivery options
Illustration of message encoding:
Message source – Encoder (Signal) – Transmitter – Transmitter Medium – Receiver - Decoder (Signal) - Message Destination
Both sender and receiver must agree upon a format.
Message Formatting
The process in which some extra information is added to the data item to identify the sender and receiver.
Data Encapsulation
Long messages must be broken into smaller pieces to travel across a network so that the transmission medium can handle it.
Message Size
3 Types of Message Delivery Options
✓ Unicast
✓ Multicast
✓ Broadcast
2 Types of Transmission Network
✓ Broadcast Network
✓ Point-to-point Network
It has a single communication channel that is shared by all the machines on the network.
Broadcast Networks
This system generally also
allows possibility of addressing
the packet to all destinations (all nodes on the network). When
such a packet is transmitted
and received by all the
machines on the network, this mode of operation is known as ___ .
Broadcast Mode
Some Broadcast systems also supports transmission to a sub-set of machines, something
known as ___ .
Multicasting
The end devices that wish to communicate are called stations.The switching devices are called nodes. Some nodes connect to other nodes and some attached stations. There may exist multiple paths between a source-destination pair for better network reliability. The switching nodes are not concerned with the contents of data.
Point-to-point Networks
As a general rule (although there are many exceptions),smaller, geographically localized networks tend to use ___, whereas larger networks normally use are ___ .
✓ Broadcasting
✓ Point-to-point Communication
3 Types of Network under Scale:
✓ Local Area Network (LAN)
✓ Metropolitan Area Network (MAN)
✓ Wide Area Network (WAN)
It is usually privately owned and links the devices in a single office, building or campus of up to few kilometers in size.
Local Area Network (LAN)
It is designed to extend over the entire city. It may be a single network as a cable TV network or it may be means of connecting a number of LANs into a larger network so that resources may be shared.
Metropolitan Area Network (MAN)
This provides long distance transmission of data, voice, image, and information over large geographical areas that may comprise a country, continent, or even the whole world.
Wide Area Network (WAN)
In computer networking, ___ refers to the layout of connected devices. It is the physical connection of wires that connect nodes of the network.
Topology
Types of Network Topology
✓ Linear Bus Topology
✓ Star Topology
✓ Ring Topology
✓ Hybrid Topology
A single cable, the backbone functions as a shared communication medium that devices attach or tap into with an interface connector. A device wanting to communicate with another device on the network sends a broadcast message onto the wire that all other devices see, but only the intended recipient actually accepts and processes the message.
Bus Topology
In this type of network topology, the server(s), nodes and other hardware devices are connected to a central hub. All messages and data from the source node must first pass through the central hub before it can reach the target node. The hub is responsible for preventing data collision.
Star Topology
In this type of network topology, the server(s), the nodes and other hardware devices are connected in a circular chain where each node is connected to the next. The last node to be connected is connected to the first node which forms a ring. So, every device has exactly two neighbors for communication purposes. All messages travel through a ring in the same direction (either clockwise or counterclockwise) until it reaches a target node.
Ring Topology
In this type of network topology, the other types of topologies are combined to form a combination or hybrid network topology. Hybrid topologies are usually used to connect different floors or rooms of a building.
Hybrid Topology
Defined as the physical path between transmitter and receiver in a data transmission system.
Transmission Media
2 Types of Transmission Media
✓ Guided
✓ Unguided
Transmission capacity depends critically on the medium, the length, and whether the medium is point-to-point or multipoint (e.g. LAN).
Guided
This provides a means for transmitting electro-magnetic signals but do not guide them.
Unguided
In ___ technology, two copper wires are strung between two points. The two wires are typically twisted together in a helix to reduce interference between the two conductors. Twisting decreases the cross-talk interference between adjacent pairs in a cable. Typically, a number of pairs are bundled together into a cable by wrapping them in a tough protective sheath.
Twisted Pair
2 Types of Twisted Pair
✓ Unshielded Twisted-Pair (UTB) cables
✓ Shielded Twisted-Pair (STB) cables
Typically wrapped inside a plastic cover (for mechanical protection).
Unshielded Twisted-Pair (UTP)
These cables are similar to UTP cables, except there is a metal foil or braided-metal-mesh cover that encases each pair of insulated wire.
Shielded Twisted-Pair (STP)
In this type of guided transmission media, the medium consists of a copper core surrounded by insulating material and a braided outer conductor.
Coaxial
2 Types of Coaxial Cable
✓ Base Band
✓ Broadband
This refers to digital transmission.
Base band
This refers to analog transmission.
Broadband
In this type of guided transmission media, the medium consists of a hair-width strand of silicon or glass, and the signal consists of pulses of light. For instance, a pulse of light means 1, lack of pulse means 0. It has a cylindrical shape and consists of three concentric sections: the core, the cladding, and the jacket.
Fiber Optics
This is used when running a physical cable (either fiber or copper) between two endpoints is not possible.
Unguided Transmission
___ are typically used for short distances (across the street or within the same room), and microwave signals are commonly used for longer distances (tens of km). The sender and receiver use some sort of dish antenna.
Infrared Signals
This is based on ideas similar to those used for line-of-sight. It is essentially a big microwave repeater or relay station in the sky. Microwave signals from a ground station is picked up by a transponder, it then amplifies the signal and rebroadcasts it in another frequency, which can be received by ground stations at long distances.
Satellite Communication
