110 lines
3.9 KiB
Markdown
110 lines
3.9 KiB
Markdown
# __Network +__
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# __OSI Model__
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## __Layer 1__ Bites
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* Physical Layer
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* It is the connects like Cat 6 RJ45 and fiber.
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* Its the on and off on the cables.
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---
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## __Layer 2__ - Frames
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* ### Data Link Layer.
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* Packagers data int frames and transmits those frames on the network.
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* Layer 2 devices view networks __logically__.
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* ### MAC Address
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* Media Access Control
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* Physical addressing system of a device which operates on the logical topology.
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* Uses a 48-bit address assigned to a network interface card.
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* __EX:__ `D2:51:F1:3A:34:65`
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* `D2:51:F1` is the vendor code
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* ### Logical Link Control
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* Provides connection services and allows acknowledgment of receipt of message.
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* Is the basic form of flow control.
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* Provides basic error control functions.
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* Uses a check sum.
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* ### How communication synchronized.
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* Isochronous
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* Network devices use a common reference a common reference clock source and create time slots for transmission.
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* Synchronous
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* Network devices agree on clocking method to indicate beginning and end of frames and can use control characters.
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* Asynchronous
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* Network devices reference their own internal clocks and use start and stop bits
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* ### What Devices are layer 2
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* network cards
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* Bridges
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* Switch
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* MAC Address
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---
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## __Layer 3__ Packets
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* ### Network Layer
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* Forwards traffic (routing) with logical address.
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* __IP address__ IPv4 IPv6
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* Logical addressing
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* Ip Addressing IPv4 and IPv6
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* Switching (Routing)
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* Route discovery and selection
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* Connection Services
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* Bandwidth usage
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* Multiplexing
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* ### How should data be __forward__ or __routed__
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* Packet Switching (Most common)
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* Data is divided into packets and then forwarded to is IP address.
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* Circuit Switching
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* Dedicated communication link is established between two devices.
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* It uses one path when the connect established and the whole time the connect is there.
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* Message Switching
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* Data is divided into messages which may be stored and then forwarded.
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* ### Route Discovery and Selection
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* Manually configured as a static route or dynamically through.
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* ### Connection Services
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* Augment Layer 2 connection services to improve reliability
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* Flow Control
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* Packet reordering
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* ### Internet Control Message Protocol
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* Sends error messages and operational information to an IP destination.
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* `Ping`
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* Trace Route `tracert`
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* ### Devices
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* __Routers__
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* Multilayer switches
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* ### Protocol
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* __IPv4__
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* __IPv6__
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* ICMP
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---
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## __Layer 4__ - Segments
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* ### Transport Layer
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* TCP Transmission Control Protocol
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* Connection-oriented protocol that is a reliable way to transport segments across the network
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* Will ask for an acknowledgement.
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* 
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* This is a Three-way handshake.
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* UDP User Datagram Protocol
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* Connectionless protocol that is an unreliable way to transport segments across the network
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* If it dropped, Sender is unaware
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* TCP vs UDP
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* 
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* Windowing
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* Allows the clients to adjust the amount opf data in eash segment.
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* Allows you to send more or fewer for eash segment.
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* Buffering
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* Occurs When devices allocate memory to store segments if bandwidth isn't readily avaiable
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---
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## __Layer 5__ - Session
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* Session Layer
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* Keeps conversations separate to prevent intermingling of data
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* Setup
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* Checking of user credentaials and assigning numbers to sessions to help identify them.
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* Some random number that would be assigned.
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* Maintain
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* Transfer Data (back and forth)
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* Reestablish connedtion
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* Acknowlegde receipt
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* Tear down
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* Ending of a session after the transfer is done or when the other party disconnects.
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