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3. protocols/tcp
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79 ../../protocols/tcp.rst:250
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `acknowledgment number`. TCP uses cumulative positive acknowledgments. Each TCP segment contains the `sequence number` of the next byte that the sender of the acknowledgment expects to receive from the remote host. In theory, the `acknowledgment number` is only valid if the `ACK` flag of the TCP header is set. In practice, almost all [#fackflag]_ TCP segments have their `ACK` flag set. 388/10000 · 388
80 ../../protocols/tcp.rst:251
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `window`. a TCP receiver uses this 16 bits field to indicate the current size of its receive window expressed in bytes. 119/10000 · 119
81 ../../protocols/tcp.rst:255
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — The Transmission Control Block 30/10000 · 30
82 ../../protocols/tcp.rst:257
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — For each established TCP connection, a TCP implementation must maintain a Transmission Control Block (:term:`TCB`). A TCB contains all the information required to send and receive segments on this connection :rfc:`793`. This includes [#ftcpurgent]_ : 250/10000 · 250
83 ../../protocols/tcp.rst:259
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — the local IP address 20/10000 · 20
84 ../../protocols/tcp.rst:260
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — the remote IP address 21/10000 · 21
85 ../../protocols/tcp.rst:261
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — the local TCP port number 25/10000 · 25
86 ../../protocols/tcp.rst:262
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — the remote TCP port number 26/10000 · 26
87 ../../protocols/tcp.rst:263
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — the current state of the TCP FSM 32/10000 · 32
88 ../../protocols/tcp.rst:264
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — the `maximum segment size` (MSS) 32/10000 · 32
89 ../../protocols/tcp.rst:265
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `snd.nxt` : the sequence number of the next byte in the byte stream (the first byte of a new data segment that you send uses this sequence number) 146/10000 · 146
90 ../../protocols/tcp.rst:266
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `snd.una` : the earliest sequence number that has been sent but has not yet been acknowledged 93/10000 · 93
91 ../../protocols/tcp.rst:267
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `snd.wnd` : the current size of the sending window (in bytes) 61/10000 · 61
92 ../../protocols/tcp.rst:268
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `rcv.nxt` : the sequence number of the next byte that is expected to be received from the remote host 101/10000 · 101
93 ../../protocols/tcp.rst:269
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `rcv.wnd` : the current size of the receive window advertised by the remote host 80/10000 · 80
94 ../../protocols/tcp.rst:270
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `sending buffer` : a buffer used to store all unacknowledged data 65/10000 · 65
95 ../../protocols/tcp.rst:271
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — `receiving buffer` : a buffer to store all data received from the remote host that has not yet been delivered to the user. Data may be stored in the `receiving buffer` because either it was not received in sequence or because the user is too slow to process it 260/10000 · 260
96 ../../protocols/tcp.rst:274
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — The original TCP specification can be summarized as a transport protocol that provides a byte stream service and uses `go-back-n` with a `selective-repeat` reception strategy. 175/10000 · 175
97 ../../protocols/tcp.rst:276
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — To send new data on an established connection, a TCP entity performs the following operations on the corresponding TCB. It first checks that the `sending buffer` does not contain more data than the receive window advertised by the remote host (`rcv.wnd`). If the window is not full, up to `MSS` bytes of data are placed in the payload of a TCP segment. The `sequence number` of this segment is the sequence number of the first byte of the payload. It is set to the first available sequence number : `snd.nxt` and `snd.nxt` is incremented by the length of the payload of the TCP segment. The `acknowledgment number` of this segment is set to the current value of `rcv.nxt` and the `window` field of the TCP segment is computed based on the current occupancy of the `receiving buffer`. The data is kept in the `sending buffer` in case it needs to be retransmitted later. 868/10000 · 868
98 ../../protocols/tcp.rst:278
	English ↹ ↵ NBS … “ ” ‘ ’ ﹙-﹚ ‐ – — When a TCP segment with the `ACK` flag set is received, the following operations are performed. `rcv.wnd` is set to the value of the `window` field of the received segment. The `acknowledgment number` is compared to `snd.una`. The newly acknowledged data is removed from the `sending buffer` and `snd.una` is updated. If the TCP segment contained data, the `sequence number` is compared to `rcv.nxt`. If they are equal, the segment was received in sequence and the data can be delivered to the user and `rcv.nxt` is updated. The contents of the `receiving buffer` is checked to see whether other data already present in this buffer can be delivered in sequence to the user. If so, `rcv.nxt` is updated again. Otherwise, the segment's payload is placed in the `receiving buffer`. 778/10000 · 778