Short
Note on Computer Networking
A set of devices (nodes) connected by
communication links.
A node can be a
·
Computer
·
Printer
·
Or any other
device
Capable
of sending and/or receiving data generated by other nodes on the network.
Ø Components needed
in communication
·
Two or more
parties
·
A communication
medium
·
Compatible
standards(language, protocols)
Ø Telecommunication means communication at a distance.
Ø Data communication means the exchange of data between two devices using transmission
medium.
Ø Types of communication (Based on data flow)/Transmission
Modes
o Simplex
o Half-Duplex
o Full-Duplex
Ø Use of Networks
o
Resource
sharing(HW/SW)
o
Information
sharing(Files)
o
Communication(Emails)
o
Remote
computing
o
Distributed
computing(GRID)
o
Social
networking
o
E-commerce
Ø Network Topologies
o
Mesh
o
Star
o
Bus
o
Ring
o
Tree
o
Hybrid
Ø Mesh Topology
o
Connects
all devices to each other (redundant).
o
Use
in WAN to interconnect LAN.
o
Use
in mission critical networks.
o
Implantation
is expensive.
Ø Star Topology
o
Commonly
use in Ethernet LANs.
Ø Tree Topology
o
Extended
star topology.
o
Reduce
traffic on wires (sending packets only to the wires of the destination).
Ø Bus Topology
o
Referred
as linear bus.
o
Use
single cable.
Ø Ring Topology
o
Frames
travel around the rings.
o
Node
adds data and destination address to the frame.
OSI Model
|
|
Application
(Telnet
,ftp ,NFS,NIS)
|
Allow
access to network resources
|
Presentation
|
Translate encrypt
and compress data
|
Session
|
Establish,
Manage & terminate sessions
|
Transport
(TCP,UDP)
|
Provide process to
process reliable message delivery and error recovery
|
Network
(IP,ICMP)
|
Move
packet from source to destination
|
Data
Link
(Ethernet)
|
Organize bits into
frames. Hop to hop communication
|
Physical
|
Transmit
bit over medium & provide mechanical & electrical specification
|
Ø IP Packet/IP Datagram refers to a message send by protocols
operating at the network layer of the OSI model.
Ø PDU (Protocol Data Unit) Formal term use in OSI model to
describe protocol messages.
Ø Segment refer to TCP PDU.
Ø Network Protocol
o Set of rules & actions.
o Define format & order of the message exchange.
o
Routing
Protocols defines the path
from source to destination.
o HW implemented protocols in NIC control the flow of bits in wire.
o Congestion – control protocol in end systems control the rate of packet transmission.
Network Components
Ø Transmission medias
Ø Interconnecting devices
Ø End devices
Ø Network Software
Ø Applications
Ø Interconnecting Devices
o Repeaters
§ Operating at the physical layer
§ Connect separate segments
§ Do not understand frames packets or
headers
§ Functionality
·
Take
incoming frames
·
Regenerate
or amplify the signal
o Hubs
§ Operate at the physical layer.
§ Similar to repeaters.
§ Coppices incoming frames.
§ Collision can occur.
§ Not amplify the signal.
o Bridges
§ Operate at data link layer.
§ Connect 2 or more LANs.
§ Inspect incoming frame headers and
forward it into relevant LAN.
o Switches
§ Operate at data link layer.
§ Similar to bridge.
§ Learn addresses dynamically.
§ No collision.
o Routers
§ Operate at the network layer.
§ Make forwarding decisions based on
Network Layer.
§ When multiple paths available router
decide which path to use
§ Provide methods to
·
Filter
traffic based on addresses
·
Route
redundancy
·
Load
balancing
·
Hierarchical
addressing
Ø Network Applications
o
Email
o
E-Commerce
o
Video
conferencing
Ø Classification of networks(Classification Mainly based on scale
and ownership)
o
PAN(USB,
Firewall, Bluetooth)
o
HAN(wireless
access point, residential LAN)
o
LAN(Privately
owned network, broadcast)
o CAN(Covering limited geographical area)
o MAN(Metro-Ethernet)
o
WAN(Large
geographical area)
