| TCP
| UDP
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| Transport layer (4)
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| 16-bit source & destination ports
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Multiplex and segment outgoing stream of data from apps (ie. ports) to IP.
Demultiplex incoming packets from IP to apps via ports.
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| Transmission Control Protocol
| User Datagram Protocol
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| PDU: segment
| PDU: datagram
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| IP protocol field: 6
| IP protocol field: 17
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| reliable
| unreliable
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| guaranteed delivery
| not guaranteed delivery
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| Corrects: missing, out-of-order, duplicated, and corrupted segments
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| connection-oriented
| connectionless
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| high overhead. heavyweight value-added to IP
| low overhead. lightweight port wrapper on top of IP
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| 20 byte header
| 8 byte header
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| bidirectional connection Establishment (3-way handshake) & teardown
| unidirectional
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| Acknowledgments: sequence & ack numbers. timeouts & retransmission
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| flow & congestion control: sliding window
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| checksum
| optional (unused?) checksum
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| "file transfer" stuff
| real-time streaming & short request/response stuff
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| accuracy
| speed
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| web, email, remote login, ftp, buffered stream
| DNS query, SNMP, DHCP. Real-time audio & video
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