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72 lines
1.9 KiB
Markdown
72 lines
1.9 KiB
Markdown
---
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title: "18-transport-layer"
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aliases:
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tags:
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- cosc203
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- lecture
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---
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chapter 3
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# service provided by transport layer
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services
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- process to process communication
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- logical communication between application processes
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- multi and demulti plexing
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- communication for multiple applications of the same host
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- flow control
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- ensure production reate <= consuption rate
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- congestion control
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- too many sender, sending too fast
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protocols
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- TCP transmission control protocol
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- UDP user datagram protocol
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## actions and sender
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- is passed an app layer lessage
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- determines segment header fields values
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- creates segment
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- passes segement to IP
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## actions at reciever
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- recieves segment from IP
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- checks header values
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- extract app layer message
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- de multiplexes message up to application via socket
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# multiplexing and demultiplexing
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sender: handle data from multiple sockets, add transport header
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reciever: user header info to deliver segments to correct socket
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## how it works
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port number
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- 16 bit integer (0, 66635)
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- segment has a source and a port number
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- host uses IP and port to direct segment to appropriate socket
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IANA (internet assign number authority) has divded port number into three ranges
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- 0-1023 well known
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- 1024-49151 registered
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- 49152-65535 dynamic
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## principle of reliable data transfer
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- compexity of reliable data transfer protocol depends on character istics of unreliable channel
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- sender and reciever do not know the 'state' of each other. they need to communicate via a message - ACKknowledgement
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# TCP
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- point to point communicate
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- one sender, one reciever
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- reliable, in-order byte stream
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- no message boundaries
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- each byte has a position in the stream
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- full duplex data
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- bi directional data flow in the same connection
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- MSS: maximum segment size
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- cumulative ACKs
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- connection-oriented
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- handshaking (exchange of control messages) initializes se
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# UDP |