| IP option 21, Selective Directed Broadcast Mode |
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Description | Glossary | RFCs | Publications | Obsolete RFCs |
| Protocol suite: | TCP/IP. |
| Protocol type: | Connectionless network layer protocol. |
| Option length: | 6 to 38 bytes. |
| Host implementation: | |
| Router implementation: | |
| Links: | IANA: IP option numbers. |
The IP Selective Directed Broadcast Mode option provides unreliable UDP delivery to a set of IP addresses included in the option field of an IPv4 datagram.
| MAC header | IP header | IP option 21 | Data |
IP option 21:
| 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Type | Length | ||||||||||||||
| IP Address [] ::: | |||||||||||||||
Type. 8 bits. Set to 149.
| 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 |
|---|---|---|---|---|---|---|---|
| C | Class | Option | |||||
C, Copy flag. 1 bit. Set to 1.
This option is to be copied into all fragments.
Class. 2 bits. Set to 0.
The option is a control option.Option. 5 bits. Set to 21.
The IP option number.
Length.
8 bits.
6 to 38 bytes.
Total lenth of the option in bytes.
IP Address [].
16 bits.
Contains a list of IP addresses.
RFCs:
[RFC 1770] IPv4 Option for Sender Directed Multi-Destination Delivery.
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Description | Glossary | RFCs | Publications | Obsolete RFCs |