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    Network Terminology
    Brett Lee
    =============================================================================
    
    Terminology (incomplete, incorrect, really a draft...)
    
    Relay - any network connector
    
    Level 1 - Physical Layer
    
    Repeater - simply repeats bits - can connect thick/thin coax
    Amplifier - amplifies the signal (and probably the noise) works on coax and UTP
    Level 2 - Data Link Layer
    Bridge - connects different protocols/ devices - uses hardware and software
    - reads ethernet and token ring frames, forwards to the appropriate port when required
    - can be simple (NIC card) or more elaborate (converting MAC frames)
    - primarily used to segment network or to provide high speed WAN link
    
    Level 3 - Network Layer
    Router - connect same protocols (as long as they have a network level protocol)
    - used to create a firewall (no broadcast traffic) to protect sensitive areas
    - can be a multiprotocol router (2 routers - no protocol conversion)
    - can be a B/Router - sometimes bridging, sometimes routing, depending upon subnet
    Gateway - generic term - one type is a protocol converter (transport / network layers)
    Hub - device that centralize connections (ethernet hub or token ring hub)
    Switching Hub - either port switching (VLAN) or segment switching
    
    X.25 - Layer 3 Switching
    NOT Connection Oriented
    Network = PLP (Virtual Circuits)
    Data Link = LAPB (Framing and Error Detection)
    Physical = X.21 (DTE/DCE Interface)
    
    ISDN - Basic = 2B+D, Primary = D plus some number of B.s
    	NOT Connection Oriented
    Network = PLP
    Data Link = LAPD & LAPB
    Physical = I.430 & 431
    NOT Connection Oriented
    
    B-ISDN - Broadband
      Connection Oriented
    Does not run on X.25
    Uses Cell Relay / ATM Cell
    ATM Layers
    1. 	Physical Layer
    a. 	PM - Physical Medium - sends cells over any medium
    b. 	TC - Transmission Convergence - cells <==> bits
    2. 	ATM Layer
    a. 	VC Level - Virtual Channel
    b. 	VP Level - Virtual Path
    3. 	ATM Adaptation Layers - provides services to the higher layers
    
    Frame Relay 
    	Connection Oriented
    	Must access using a FRAD
    	Frames are created and broken at every hop
    	Uses Asynchronus Trahsport Mechanisms
    	Errors only detected - if exist are discarded
    	Smaller LLC than LAPD - is a subset of
    	Faster than X.25 - layer 2 only
    	FRAD to UNI to NNI
    	Services offer CCI Rate but may burst above
    	No sequencing, acknowledgement, information, or error correction
    
    Cell Relay - ATM
    	Connection Oriented
    	Synchronus transfer of cells
    	Asynchronus transfer of bits / data
    	53 byte cell, contains 48 bytes of data
    	No multiplexing, just loading and unloading of bits
    
    MAN 802.6, DQDB, SMDS
    	Connectionless Protocol
    	Level 2 device
    	DQDB - FDDI w. reserved status - dual bus
    	- meant to replace FDDI on Sonet
    	- sends data when cell is empty and not reserved
    	- uses slots - ATM cells with a different header
    	- uses LLC layer interface
    	SMDS - uses cell-relay, but is technically a frame switch
    		- this is because it uses LLC
    		- 
    

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  • This site contains many of my notes from research into different aspects of the Linux kernel as well as some of the software provided by GNU and others. Thouugh these notes are not fully comprehensive or even completetly accurate, they are part of my on-going attempt to better understand this complex field. And, they are your to use.

    Should you wish to report any errors or suggestions, please let me know.

    Should you wish to make a donation for anything you may have learned here, please direct that donation to the ASPCA, with my sincere thanks.

    Brett Lee
    Everything Penguin

    The code for this site, which is just a few CGI scripts, may be found on GitHub (https://github.com/userbrett/cgindex).

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    "We left all that stuff out. If there's an error, we have this routine called 'panic', and when its called, the machine crashes, and you holler down the hall, 'Hey, reboot it.'"

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