| TCP option 4, SACK permitted |
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Description | Glossary | RFCs | Publications | Obsolete RFCs |
| Protocol suite: | TCP/IP. |
| Protocol type: | Transport layer protocol. |
| Option length: | 2 bytes. |
| Host implementation: | |
| Router implementation: | |
| Links: | IANA: TCP option numbers. |
The TCP SACK permitted option may be sent in a SYN by a TCP that has been extended to receive the SACK option once the connection has opened. It MUST NOT be sent on non-SYN segments.
| MAC header | IP header | TCP header | TCP option 4 | Data |
TCP Option 4:
| 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Kind | Length | ||||||||||||||
Kind. 8 bits. Set to 4.
Length. 8 bits. Set to 2.
RFCs:
[RFC 2018] TCP Selective Acknowledgment Options.
[RFC 1072] TCP Extensions for Long-Delay Paths.
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Description | Glossary | RFCs | Publications | Obsolete RFCs |