The TCP Service Model
| Property |
Behavior |
| Stream of bytes |
Reliable byte delivery service |
| Reliable delivery |
1. Acknowledgements indicate correct delivery |
- Checksums detect corrupted data
- Sequence numbers detect missing data
- Flow-control prevents overrunning receiver |
| In-sequence | Data delivered to application in sequence transmitted |
| Congestion Control | Controls network congestion |
Connection
When two applications use TCP, they establish a two-way communication channel between the TCP peers at both ends.
We call the two way communication a “connection”. At both ends of the connection, TCP keeps a state machine to keep track of how the connection is doing.
3-way Handshake
The TCP connection is established using a 3-way handshake.
- 1. SYN
- 2. SYN + ACK
- 3. ACK
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📖 More details
- Active opener sends first packet
- Passive opener responds
- SYN with sequence number
- CKs active opener’s SYN packet
- Active opener responds
- ACKs passive openers SYN packet
- Also support “simultaneous open”
- Two SYNs pass each other
- Each side ACKs the other
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Stream of Byte
