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Translation time: 2001-4-2
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Network Working Group Steve CROCKER
Request for Comments: 1 UCLA
7 April 1969
RFC 1 - Host Software
(RFC 1 host software)
table of Contents
Introduction 1
I. IMP Software Summary 2
Message 2
Chain 2
IMP transmission and error check 3
IMP software discussion problem 3
II. Host - Host Software Supply 3
Simple application 3
Advanced application 3
Error check 3
III. Host Software 4
Connection establishment 4
Big data volume transfer 4
Basic Operation Summary 4
Error check 5
Focus interaction 5
Discussion: 7
IV. Preliminary Experiment 8
Experiment one 8
Experiment 2 8
Introduction
The software of the ARPA (Advanced Research Project) network is partially present in the IMP (Interface Messaging Machine) and a stand-alone host. BB & N pointed out the software on the IMP and indicates that the host group is responsible for the software's software.
In 1968, the representatives of the four initial sites met several times to discuss the initial experiment of host software and network. After the followers of autumn and winter, a three-person working group headed by Steve Carr, Sri's Jeff Rulifson and Ucla of Utah. The last week of the subsequent meeting is UTAH at the last week of March. At the same time, there is also RSI Bill Duvall, he later started working with Jeff Rulifson.
In complete independent case, UCLA's Gerard Deloche started the work of the host-interface message handling machine (Host-IMP) interface.
Here, I will listen to some consensus and problems. Of course, it is not certain, I hope to get a feedback.
I. IMP software summary
Message
A harbor information passed between the host-host is a message. A message is a stream including its head in length and no more than 8080 bits. Head has 16 bits, including the following information:
5 digits of destination address
Link 8 digits
Tracing 1 bit
Idle bit 2
The destination address is a digital encoding, used to indicate the host to arrive. Tracking the status information of the location signal notifies the IMP record message and returns the information to NMC (Network Calculation Center, Network Measurement Center, I.E., UCLA) idle bit is not used.
Link
The link field is a special policy used by IMP to limit some obstruction. The role is as follows: There are 32 logical full-duplex connections between each pair of hosts to bidirect delivery messages. IMP has restrictions on these links, that is, before the destination IMP returns a special message, the message is called RFNM (next message request, Request for next message), no host can send it on the same link Two continuous messages. This arrangement limits the occurrence of problems that occur if the sender host attempts to send too many messages on the same link can cause the problem of the other end block. Note: Since the destination IMP does not have sufficient ability to process all 32 links, this link is implemented only in the case where the two or two links are overloaded. Therefore, both parties must cooperate with each other. These links have the following basic characteristics: they always work and always have 32. "Always play" means that IMP is always ready to send another message. There is no concept of start and end in the IMP software. In this case, we cannot query an IMP to get the status of the link (although IMP may query IMP to get a link recent history - the difference is far).
Another basic feature of the link is: no matter whether they are used or not, there are always 32. This means that each IMP must maintain 18 tables, 32 per table, independent of the actual communication.
Although some people have objection to the structure of the link, it is easy to implement in IMP internal programming, and because of its simple, it is a better and feasible approach to form a more complex structure.
IMP transmission and error check
After the IMP receives a message from the host, it is divided into one or more packages. The package is the unit of IMP and IMP data transmission, and the length does not exceed 1010 bits. The transmission device calculates a 24-bit cyclic check code and adds it to the package to be sent. The acceptance device calculates the generated check code and compared with the original check code. The IMP in the destination will reorganize the package into a message.
IMP software discussion problem
1. The link specification is a 8-bit field, but why only provide 32 links?
2. The host can send a message to its IMP, how is it implemented?
3. Do Imp's host controls RFNM?
4. Is Imp for code conversion? How to control?
II. Host - host software necessary conditions
Simple application
Like any new tool, the group's users take a period of time to perform deep network experiments and gradually dependent on. One of our goals is to make it easier to master for most users. For this goal, it is clear that the ability to use the remote host is needed, just like a TTY (telegraph switch, teletype) terminal dialing. In addition, we want to have such a capability that is transmitted in the form different from the simulated TTY.
Advanced application
An intrinsic issue of the network must receive a response from the remote host every half second, regardless of how it is simple. For TTY applications, half-duplexing, local responses, but this will destroy some of the validity of the network. For example, a 940 system will have special echoes. The problem will become particularly serious when considering a graphic workstation or other complex terminal controlled by a remote host. Therefore, you need to find a reasonable solution to use a more complex device that is directly connected to the remote computer.
Error check
SRI's Jeff Rulifson pointed out that the error check for the mainstream software interface is a good thing. He pointed out some of the experience of SRI to solve many wasteful arms and energy. Because of this, we hope to see the error check between the host-host. In addition to checking the interface of the software, you need to check the host-interface message processor (Host-IMP) device (BB & N claim host - interface message processing machine device is just trustworthy as registers inside the host. We believe this, but still hope Error check).
Iii. Host software
Connection establishment
The easiest connection that you can think of is that the local host is similar to a TTY and has been dial-up to the remote host. Considering the issues of initialization and interrupt connections, link 0 retains communication between host operating systems, and the remaining 31 links are used as dial-up lines. Each host operating system must provide a basic operation to its user-level program to establish a connection with the remote host and a basic operation to abort the connection. When these operations are called, the operating system selects an empty link. At the same time, send a message on the link 0 to remote host requests to connect on the selected link. The operating system of the remote host allows and to send a message from the link 0. In the entire event, the two hosts select the same link to initialize a connection, and send a request message almost simultaneously, then use a simple priority policy: low priority hosts to high priority hosts, yourself Select another free link. A viable priority scheme is based on the identity number of the host to determine the high level of the priority. Note that both hosts know that the request is at the same time, but the high-priority host ignores the request and the low priority host has sent a request message in addition to sending an acceptance message.
The established connection is a connection to a TTY form in advance. This means that the remote host operating system will use the link as a TTY that just implements dial-up login. The remote host issues the same response, looking forward to the same login order, find the same interrupt character.
Big data transmission
Considering that the TTY acts as two specialized defects when the terminal will act as a large file. First, some characters are special interrupt characters. Second, these techniques are only suitable for low-speed characters transfer from timing due to special buffering techniques. Therefore, another class connection is defined to transmit a file or a relatively large amount of data. In order to initialize this type of link, the user-level program of the two ends of the established TTY form is required to implement the created file form connection to the TTY form link parallel. Therefore, the priority strategy is used: High priority hosts send messages through link 0, low priority hosts waiting for messages. User-level programs are not concerned about it. The selection of the idle link has a high priority host. The file form link is that there is no need to search interrupt characters and use buffer techniques suitable for high data ratios.
Basic operation summary
Each host operating system provides at least the following basic operations. This list is not required but not sufficient.
a) Host X initialize TTY form connection
b) interrupt connection
c) Connect transmission / receive characters in the form of TTY
d) Connection to the form of the file is connected in parallel with TTY
e) Interrupt file form connection
e) Connect transmission / reception via file form
Error check
Suppose each message has a message number, a number, and a check code, which is transparent for IMP. The end of the 16-bit carry is calculated according to the 1152 bits, and one bit is moved to the right. Check for every 1152-bit loop and is an error used to discover the error in the message.
Similar interaction
The basic operations described above help users master how to use remote devices. They are confused based on the intricate application of the network. Clearly, we pay attention to this fact: some sites have been a lot of work to make the computer respond quickly to the complex console. At least UCSB's Culler and SRI console are two examples. IT IS CLEAR THAT DELAYS OF A HALF-Second OR SO for Trivial Echo-like responses degrade the intection to the point
OF MAKING The Sophistication of The Console Irrelevant.)
Most console interactions can be divided into two parts, part of it is local, immediate and unimportant, and the other is remote, longer, more important. For a simple example, a user operates a keyboard and refreshes the display screen. Users typing a string of characters and a carriage return, and the console starts processing characters. They are displayed on the screen when typing characters. When you type the delete character, it deletes the previous non-deleted character. Users typing HE E L O <- <- p
The DEL specification is still in discussion. The following graph shows the entire sequence process.
A.
/ /
| --------- ----------- |
| | | | | | |
| | | | | | |
| | Terminal | | Terminal | |
| | | | | | |
| | | | | | |
| ----- ----- ---- ----- |
| | | | | |
| | | | | |
| | | | | |
| ----- ----- ---------- |
| | | | Request connection | | | | | |
UCLA {| | -> Via Link 25 | |} SRI
| | - | | | |
| | | OS | --- - = | i | ---------- | I | = - --- | OS | | || | - - | - | --- | |
| | | | | | |
| | | | | | |
| --------- ----------- |
| Host: UCLA host: SRI |
/ /
b. After establishing a link and login
/ /
| --------- ----------- |
| | | | | | |
| | | | | | |
| | Terminal | | Terminal | |
| | | | | | |
| | | | | | |
| ----- ----- ---- ----- |
| | | | | |
| | | | | |
| | | | | |
| --- ----- "Send Head" ----------- |
| | | | | End Control | | | | |
UCLA {| | | -> | | |} SRI ___
| | - | | - - | | / |
| | | Os | --- - = | i | ---------- | I | = - - | OS | NLS | ---- --- | |
| | - | - | ------ | | | ___ /
| | | DEL Program | | | | | |
| | | | <- | | | | ____ || ---------- --------- |
| Host: UCLA host: SRI |
/ /
c. After receiving and cheaper Del program
/ /
| --------- ----------- |
| | | | | | |
| | | | | | |
| | Terminal | | Terminal | |
| | | | | | |
| | | | | | |
| ----- ----- ---- ----- |
| | TRIVIAL | |
| | Responses | |
| | | | | |
| ---- ------ ----------- |
| | | | | | | | |
UCLA {| | | Main response | | |} SRI ___
| | - | | - - | | / |
| | | | DEL | --- - = | i | ---------- | I | = - - | OS | NLS | - --- | |
| | | | Head | | | ---- | | | ___ /
| | | | Tail | | | | | | |
| | | | Program. | | | | | | ____ |
| | ----- | | | | | |
| | | | OS | | | | | |
| | ----- | | | || | | | | | |
| ---------- ----------- |
| Host: UCLA host: SRI |
/ /
discuss a problem:
1. If IMP is transformed, the check code will be incorrect.
2. The process requesting the DEL start and ending is not described in detail.
IV. Preliminary Experiment
experiment one
SRI is currently modifying their online patches to operate by model 35tty, which will become the main software components of the Network Documentation Center. TTY's control is written in DEL. All sites will be written in the DEL compiler and use NLS in the DEL program.
Experiment 2
SRI will write a DEL start and end for complete NLS, including graphics. UCLA and UTAH use a graphic NLS.
[This RFC WAS PUT INTO MACHINE READABLE FORM for Entry]
[INTO THE online RFC Archives By Celeste Anderson 3/97]
RFC 1 - Host Software RFC 1 Host Software
1
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