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Network Working Group E.I. Ancona
Request for Comments: 42 m.i.t. lincoln laboratory
31 March 1970
RFC42 Message Data Type
(RFC42 Message Data Types)
Suggest:
We recommend that the first 8 digits of each normal message is reserved to indicate the type of message. The adoption of this agreement is not to agree to the actual type of use. It just suggests an agreement that the first 8 bits of each normal message cannot be used for user data.
discuss:
Socket Port
| | | | ____________
| V v / /
V / /
| = | / == | |
------- ( ) -> | Y | -> <|
| = | / == | |
| Process |
| | |
| = | / == | |
------- (-) -> | x | <- <|
| = | / == | |
/ /
/ ____________ /
It is very important to establish a convention for the content of the message early, so that there will be an information about every two programs running on the network.
With the development of the network, the language network language specified by the message syntax is developed. However, even before these conventions, there is already a simple manner of using a message type description message, the sender and the receiver can explain them.
Importantly, the currently running procedures still need to use this convention to continue to run. However, we recommend that the system programs at both ends can override, and the program begins to check the message type and delete the message type. We call these two programs X and Y. In general, x and y will conversion, such as converting alphabet sets and digital formats. As the network grows, X and Y may become a table driver, and the table is specified by the user.
Standard type and local type:
We recommend separating standards and local types of locations.
We cannot expect these two conversion programs to convert between each possible data representation and their data representations, and changes in data form should not involve procedures X and Y, so we recommend it throughout the network Only a fixed message type is meaningful. They are standard types.
There are two local types: MyLocal and YourLocal. A MYLOCAL N message indicates: This is the type N that sends host type set. A YourLocal N means: This is the type N that receives the host type. Convention:
One possible plan of the type of matrix and local type is to define standard type 0 as YourLocal, define standard type 1 as MyLocal. Thus, the second byte represents a local model.
Local Type 0 indicates that the user is specified, that is, the information content has not changed. Installation will define your own local model, which can be obtained from the network information center.
Thus, all messages that are initially sent to the current program should be type 0 or n, all the messages received from the current program should be type 1 or N, n is the alphabet type model number installed locally.
Possible standard types:
0. YourLocal
Mylocal
2. U.S. ASCII
3. EBCDIC
4. MOD 33 TTY ASCII
5. If the program x and y conversion is the table driver, the table drive the converter is loaded into the table #n, which specifies the table. Table number N is stored in the second byte of the message.
6. Use the table-drive converter table n
7. Network standard graphic message
Local type example:
1: Local alphabet set, for example: Lincoln Writer, DEC ASCII, etc.
2: Local graphics message, for example: TX-2 fixed point display execution call, GSAM
[This RFC WAS PUT INTO MACHINE READABLE FORM for Entry]
[INTO THE ONLINE RFC Archives by Robbie Bennet 11/98]
RFC42 Message Data Types RFC42 Message Data Type
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