Connected: An Internet Encyclopedia
Parameter Problem Message

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### Parameter Problem Message

Parameter Problem Message

```    0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     Type      |     Code      |          Checksum             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|    Pointer    |                   unused                      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Internet Header + 64 bits of Original Data Datagram      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

IP Fields:

The source network and address from the original datagram's data.

ICMP Fields:

Type

12

Code

0 = pointer indicates the error.

Checksum

The checksum is the 16-bit ones's complement of the one's
complement sum of the ICMP message starting with the ICMP Type.
For computing the checksum , the checksum field should be zero.
This checksum may be replaced in the future.

Pointer

If code = 0, identifies the octet where an error was detected.

Internet Header + 64 bits of Data Datagram

The internet header plus the first 64 bits of the original
datagram's data.  This data is used by the host to match the
message to the appropriate process.  If a higher level protocol
uses port numbers, they are assumed to be in the first 64 data
bits of the original datagram's data.

Description

If the gateway or host processing a datagram finds a problem with
the header parameters such that it cannot complete processing the
datagram it must discard the datagram.  One potential source of
such a problem is with incorrect arguments in an option.  The
gateway or host may also notify the source host via the parameter
problem message.  This message is only sent if the error caused
the datagram to be discarded.

The pointer identifies the octet of the original datagram's header
where the error was detected (it may be in the middle of an
option).  For example, 1 indicates something is wrong with the
Type of Service, and (if there are options present) 20 indicates
something is wrong with the type code of the first option.

Code 0 may be received from a gateway or a host.
```

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Connected: An Internet Encyclopedia
Parameter Problem Message