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Networking Fundamentals    
Network Topologies
Domain Diagram
Networking Protocols
     The Open Systems Interconnection reference model (OSI/RM) was defined by the International Organization for Standardization (ISO) in 1983.  The OSI/RM has three practical functions:
  • It gives developers necessary, universal concepts so they can develop and perfect protocols.
  • It explains the framework used to connect heterogeneous systems.  In other words, it allows clients and servers to communicate even if they are using different applications and operating systems; all they need is a common protocol, such as TCP/IP or IPX/SPX.
  • It describes the process of packet creation.

OSI Model Layers
Application | Presentation | Session | Transport
Network | Data Link | Physical
Layer Function Protocols Network Components
Application
User Interface


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  • used for applications specifically written to run over the network
  • allows access to network services that support applications
  • directly represents the services that directly support user applications
  • handles network access, flow control and error recovery
  • Example apps are file transfer, e-mail, NetBIOS-based applications
 DNS; FTP; TFTP;

BOOTP; SNMP; RLOGIN;

SMTP; MIME; NFS;

FINGER; TELNET; NCP;

APPC; AFP; SMB

Gateway
Presentation
Translation


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  • Translates from application to network format and vice-versa
  • all different formats from all sources are made into a common uniform format that the rest of the OSI model can understand
  • responsible for protocol conversion, character conversion, data encryption/decryption, expanding graphics commands, data compression
  • sets standards for different systems to provide seamless communication from multiple protocol stacks
  • not always implemented in a network protocol
  

Gateway

Redirector
Session
"Syncs and Sessions"


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  • establishes, maintains and ends sessions across the network
  • responsible for name recognition (identification) so only the designated parties can participate in the session
  • provides synchronization services by planning check points in the data stream (if session fails, only data after the most recent checkpoint need be transmitted)
  • manages who can transmit data at a certain time and for how long
  • Examples are interactive login and file transfer connections:  the session would connect and re-connect if there was an interruption, recognize names in sessions, and register names in history


NetBIOS

Names Pipes

Mail Slots

RPC

Gateway
Transport
packets; flow control & error-handling


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  • additional connection below the session layer
  • manages the flow control of data between parties across the network
  • divides streams of data into chunks or packets; the transport layer of the receiving computer reassembles the message from packets
  • "train" is a good analogy:  the data is divided into identical units
  • provides error-checking to guarantee error-free data delivery with on losses or duplications
  • provides acknowledgment of successful transmissions; requests retransmission if some packets don't arrive error-free
  • provides flow control and error-handling


TCP, ARP, RARP

SPX

NWLink

NetBIOS / NetBEUI

ATP

Gateway

Advanced Cable Tester

Brouter
Network
addressing; routing


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  • translates logical network address and names to their physical address (e.g. computername ----> MAC address)
  • responsible for
    • addressing
    • determining routes for sending
    • managing network problems such as packet switching, data congestion and routing
  • if router can't send data frame as large as the source computer sends, the network layer compensates by breaking the data into smaller units; at the receiving end, the network layer reassembles the data
  • think of this layer stamping the addresses on each train car
IP; ARP, RARP; ICMP; RIP; OSFP;

IGMP;

IPX

NWLink

NetBEUI

OSI

DDP

DECnet

Brouter

Router

Frame Relay Device

ATM Switch

Advanced Cable Tester
Data Link
data frames to bits


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  • turns packets into raw bits (e.g. 100101) and at the receiving end turns bits into packets
  • handles data frames between the Network and Physical layers
  • the receiving end packages raw data from the Physical layer into data frames for delivery to the Network layer
  • responsible for error-free transfer of frames to other computer via the Physical Layer
  • this layer defines the methods used to transmit and receive data on the network; it consists of the wiring, the devices used to connect the NIC to the wiring, the signaling involved to transmit/receive data, and the ability to detect signaling errors on the network media
Logical Link Control
  • error correction and flow control
  • manages link control and defines SAPs
802.1 OSI Model

802.2 Logical Link Control

Bridge

Switch

ISDN Router

Intelligent Hub

NIC

Advanced Cable Tester
Media Access Control
  • communicates with the adapter card
  • controls the type of media being used:
802.3 CSMA/CD (Ethernet)

802.4 Token Bus (ARCnet)

802.5 Token Ring

802.12 Demand Priority
Physical
hardware; raw bit stream


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  • transmits raw bit stream over physical cable
  • defines cables, cards, and physical aspects
  • defines NIC attachments to hardware, how cable is attached to NIC
  • defines techniques to transfer bit stream to cable
IEEE 802

IEEE 802.2

ISO 2110

ISDN		 Repeater

Multiplexer

Hubs
  • Passive
  • Active

    TDR

    Oscilloscope

    Amplifier
    		•