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Data communications networks (Reference Model OSI (Physical (Transmission…
Data communications networks
Protocol switching
These protocols offer the same functionality but are optimized for different environments or applications.
Reference Model OSI
Physical
Transmission of the bits Define: Transmission medium Electrical characteristics Voltage levels Ex: 10BaseT and 100BaseT
Data link
Transmission between adjacent nodes: Without errors Flow control Retransmissions Eg: Ethernet protocol
Network
Route data packets from source to destination
Determine the most appropriate route
Network congestion Package not for him it is forwarded to another node
Ex: Internet protocol (IP)
Transport
Route data packets from source to destination
Determine the most appropriate route
Network congestion
Package not for him it is forwarded to another node
Ex: Internet protocol (IP)...
Session
Maintain sessions between nodes
Create
Keep
End up
Resume
Presentation
Presentation of the information
Coding
Compression
Encryption
Application
Emulation of terminals
Transmission of files
Email
Ex: FTP protocol, SMTP, HTTP
Communication protocols:
Data communication in the OSI model The data goes through all the layers In each layer:
Origin:
process the received data add the header (control) go to the lower layer.
Destination:
process the received data remove the header go to the top layer
Types of Data Networks
Ethernet Local Area Network Original: coaxial cable to which the devices are connected (medium - bus, devices - PC) Signaling Structure: CSMA / CD Messages: Packages or Frames It is the most used: easy to understand and install
Network Interconnection
Devices Switches (switches) Interconnect network nodes the entire bandwidth Join many nodes without reducing performance Routers (routers) Interconnect networks Ensure that the information reaches its destination Tables with routing information
Communication techniques
Point to point links Rental of line / s to telephone operator (2 Mbps) Circuit switching Establishment of physical circuit (ISDN - 2Mbps) Packet switching Packet switching network to transmit data Ex: Frame Relay - 2 Mbps, ATM - 2.5 Gbps
Control and Protection of Data
Objective: the data arrives at the destination without being modified
Control functions
Flow control
Problem: the sender sends at a higher speed than the receiver can process
Solution: exchange of messages.
Error Control
Causes: Interferences, Breakdowns, ..
They state: data different from the expected
How to detect them: add redundant information
It is not very effective