JPH0355065B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to communication technology in computer networks.

PRIOR ART The use of computer network systems to process and transmit data is well known in the art. A typical computer network system includes at least one host computer running under some type of operating system, a communication controller, a communication medium,
It consists of multiple end users (terminals, printers, displays, etc.). The host computer is connected to a communication controller or end user terminal via a communication medium. The communication controller interfaces with other communication controllers or end user terminals via a communication medium. The communication medium may be a telephone line, channel, satellite, or the like. A user can extract data from a host computer by placing a request at a user terminal. Similarly, a user can enter information from a terminal and send it to a host computer for processing or to other terminals on the network.

Beyond physical structure, conventional computer systems are controlled by a system architecture that provides an organized flow of information throughout the system. There are several types of architectures. For example, see the paper “Computer Network” by S. Wecker
Computer Architecture, September 1979, provides an overview of the architectures used in computer networks.
(System Network Architecture) is included in the paper “An
Introduction to Network Architectures and
Protocols”, IBM System Journal, Volume 18, No. 2, 1979. These papers include:
Various computer networks, such as SNA, DMA, and ARPANET, are built on layers of a hierarchical architecture, with the lowest layer concerned with the physical communication lines interconnecting the various user nodes of the network, and the highest layer concerned with the physical communication lines interconnecting the various user nodes of the network. (which pertains to the interaction itself between the various end users of the work).

In an effort to standardize network architecture, the International Organization for Standardization (ISO)
IEEE Transactions on Communications, 1980
“OSI” by Herbert Zimmerman, April 2016
Reference Model−the ISO Model of
Architecture for Open Systems
The architecture of this model consists of seven layers: physical layer, data link layer,
These are the network layer, transport layer, session layer, presentation layer, and application layer. The present invention primarily relates to the presentation service layer of SNA.
This layer is concerned with "information units" used to transmit information between two end users.

The prior art utilizes "units of information" having various types of formats to convey messages over networks. Nevertheless, prior art information units suffer from common problems. That is, the problem is how to identify the length of a message, and how to distinguish between control information and user data. User data is for the end user, while control information is for use at the presentation layer.

One solution is to use delimiters to group messages. A start delimiter is used to indicate the beginning of a message, and a stop delimiter is used to indicate the end of a message. In addition to delimiters, identification markers are used in messages to distinguish between "user data" and "control data."

[Problems to be Solved by the Invention] Although these information units and their methods work well for their purpose, they are not efficient. This is because such methods necessarily require parsing the message at the receiving node to determine the type of information. This analysis takes time and results in a decrease in the overall performance of the system. Moreover, the traditional information unit,
It is not easy to adapt control data and/or user data to be transported in a common data stream. Ultimately, there will be applications where predefined delimiters cannot be used to indicate the start and end points of user data.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an information unit that can efficiently convey information within a communication network.

[Means for solving the problems] The present invention provides a method for solving problems in a computer network.
a data field for sending user data or system control information; a length field for sending a first value when sending user data in the data field and a second value when sending system control information in the data field; It is characterized by transmitting information by the included information units.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a general delivery means for communicating data and control information throughout a computer network system. Although the present invention is applicable to any type of computer network, it works well with an IBM SNA network that uses the SNA architecture and SNA protocol, and this example describes such an environment.

Typical SNA networks are described in the IBM manual “Advanced Communication Functions for
Virtual Telecommunications Access
Method”, GC-27-0463-2, February 1981. SNA networks use SNA entities called logical units (LUs) to connect terminals, application programs, and other logical SNA allows quality sources to communicate with each other.
Use.

Figures 1A-1C illustrate the format of communication transport units according to the present invention. The transport unit is a delivery means for transporting information across a network (which will be explained later). The information that is transported is user data and/or control data. The format shown in the figure is a link header (LH) 70, a transmission header (TH) 72, a request response header (RH) 74, a request response unit (RU) 76,
and a link footnote (LT) 78. The request-response header 74 and the request-response unit 76 constitute a basic information unit (BIU). The basic information unit and the transmission header 72 constitute a path information unit (PIU).

Finally, link heading 70 is created for each path information unit.
and link postscript 78 are combined to form a basic link unit (BIU). A basic link unit can also include one or more path information units. Note that as the elementary information units move through the various levels of the SNA, additional units are added. A basic unit of information is a unit that moves from one end user to another within a network. The basic information unit is modified in accordance with the present invention to provide a more effective means of delivery.
This will be explained later. Transmission header 72 contains information that guides the elementary information unit through the network. The transmission heading 72 has address information for transmission control and other necessary information. By adding a link header 70 and a link footnote 78 to a path information unit, transmission of the path information unit via the link is controlled.

Figure 1B shows the extended request-response unit (hereinafter extended
RU). The extended RU includes a length field 80. Length field 80 is combined with data field 82. Data field 82 can be used to transport user data and control data. data field 8
2 has user data or control data, it is necessary to examine the contents of length field 80, which will be explained later. The primary function of length field 80 is to identify the number of bytes of user data contained within data field 82.

The maximum length of a request-response unit depends on session creation time and is typically shorter than the length of the user data stream. Therefore, multiple request response units may be required to transport a particular user data stream. Two or more user data streams (each consisting of a length field and user data)
, the later data stream is actually 1
It does not have to start at the boundary of one request-response unit.

The condition placed on length field 80 is that the value transmitted by it is equal to the number of bytes in the user data field plus the number of bytes in the length field itself. So, for example, the data field is N bytes and the length field is M.
If bytes, the length field must be set to M+N when the data is generated. When the data is received at the destination LU, the LU knows that it needs to process N bytes of user data. The remaining value ((M+N)-N) indicates the number of bytes in the length field. The number of bytes in the length field may be determined by system definition or session setup time.

Since the length field has a finite length, the user data may be too long to be represented by the length field. To accommodate such a large amount of user data, an indicator is provided in the length field and used as a "continue" indicator. That is, if the user data is too long to encode it in the number of bytes allocated to the length field, then some arbitrary amount of user data is encoded and the continuation indicator is set to the first state. (turn on), and the remainder of the user data is sent to the subsequent logical message (with an appropriately coded length field).
placed in When the remaining portion of the user data is placed in the subsequent logical message, the continuation indicator is set to the second state (turned off).

In the preferred embodiment, the continuation indicator is the leftmost bit of the length field. A continuation marker is designated by reference number 84 in FIG. 1C. Other bits of the length field may be modified without departing from the scope of the invention.
Note that it can be used to indicate the arrival of additional data or the end of data.

Next, referring to FIG. 1C, the transfer of user data and control information will be described. Since the value of the length field is the sum of the number of bytes in the length field and the user data, there are some values that would be illegal to use in the length field (for example, the number of bytes in the length field may be too small). ). These illegal values are then placed in the control information identification field 86 (which is also a length field) to identify the control information. Therefore, as can be seen in Figure 1C, by placing a continuation indicator at the beginning of the length field, by placing this length field at the beginning of the user data, and by placing the control information identification field at the beginning of the control information. , the communication transport unit according to the present invention is capable of transporting variable length user data and system control information together in the same data stream.

Note that user data and system control information are distinguished from each other based on the value of the length field. An invalid value in the length field indicates the presence of system control information, while a valid value in the length field indicates the presence of user data. This allows user data to become a transparent bitstream. Additionally, the length field itself can be used for overall system control, or system control information can follow the length field as a formatted data stream.

An example will be used to explain the operation of the communication transport unit described above. Suppose that 50,000 bytes of user data are sent. Furthermore, suppose there is a system limitation that the amount that can be sent at one time is less than 32,767 bytes. Then, for example, the length field of the first logical message
27002 (consisting of 27000 bytes of user data and a 2 byte length field) and the continuation indicator is set to the first state (turn on).
In the second logical message, the continuation indicator is set to a second state (turned off). The length field of the second logical message is set to 23002. After removing the bytes allocated to the length field by checking that quantity, the user data totals 50,000 bytes. It does not matter how many consecutive logical messages there are as long as each logical message has fewer bytes than the system allows.

Length field values 0000, 0001, 8000, and
8001 (all hexadecimal) means that all logical messages are 2
This is an illegal value because it must have a length value greater than or equal to the length value. These illegal values are “extended characters” that indicate non-end user logical messages.
It can be used as As previously discussed and referring to FIG. 1C, such illegal values can be placed in the control information identification field at the beginning of the control information.

FIG. 5 is a diagram illustrating an algorithm for generating a data stream that is compatible with the communication transport unit protocol described above. step
88 is the entry step. Step 88 marks the entry into the algorithm of the processor (described later). The program then proceeds to decision step 90.
Decision step 90 tests whether the data to be migrated is user data. If so, proceed to step 92 where the value of the length field is set equal to the size of the user data plus the size of the length field. The program then exits via step 94. If the data is not user data at decision step 90, the process proceeds to step 96. step
96 sets the length field to the value of "extended characters". The program then exits via step 94.

FIG. 6 shows an algorithm for setting continuation indicators. The program includes step 98. The program enters this algorithm via step 98. The program is a decision step.
At step 100, it is checked whether the length of the user data is less than or equal to a predetermined maximum length (the maximum amount of data that can be sent by the system). If so, the program proceeds to step 102. In step 102, the continuation indicator is turned off and the length field is set to the length of the user data. The program exits via step 104.

If the user data is longer than the predetermined maximum length, the program proceeds to step 106.
In step 106, the continuation indicator is turned off and the length field is set to the length of the user data actually sent plus the length of the length field, and the length of the user data actually sent is set to the length of the user data actually sent. is reduced. The program remains in a loop until all user data has been sent. The continuation indicator is then turned off,
The program exits via step 104.

FIG. 4 shows an algorithm for processing a data stream. This algorithm would be implemented in the processor of the node receiving the message. Step 108 is the entry point to this algorithm. The program proceeds to step 110 where it selects the first length field in the received data stream as the length field to be examined. Next, the program takes a decision step.
Proceed to 112. Decision step 112 tests to see if the length field has a valid value. If so, the program proceeds to step 114. In step 114, the received data is processed as user data. The program then proceeds to decision step 116. Decision step 116 tests to see if it is the end of the data stream. If so, proceed to step 118.

If it is determined at decision step 116 that this is not the end of the data stream, the process proceeds to step 120. In step 120, the next length field in the data stream is selected as the length field to be tested, and then decision step 112 is entered. As previously mentioned, decision step 112 tests to see if the length field has a valid value.
If not, proceed to step 122. In step 122, the data is processed as control information. In summary, by checking the length field of a received message, if it has a valid length value, the data is sent to the end user to be treated as user data, and the length field is If the field does not have a valid value, the data is sent to the LU's control unit so that it is processed as control information.

FIG. 7 shows an algorithm for processing continuation indicators at the receiving node. In summary, by checking the status of the continuation indicator, the algorithm treats the data as incomplete user data when the continuation indicator is on, and treats the data as complete user data when the continuation indicator is off. It is processed as user data.

FIG. 2 is a diagram showing the configuration of a basic SNA network. The communication transport unit described above can be used for transporting messages between LUs as shown in FIG. The system has a transport network 130. Transport network 130 includes a plurality of nodes and transmission links (not shown) for interconnecting them. SNA transport networks are well known technology and will not be described in further detail. Multiple LUs (LUa, LUb,
LUc) is connected to the transport network 130. Each LU comprises an application program P, an I/O device, and an associated database. For example, LUa may be an application subsystem having an application program p and a database. LUa is a formalized format for interfacing with programs for ease of use by users, and for interfacing with transport networks for efficiency of transmission within that network. It is composed as it is.

LUa is a high level language (it has its own program) that is easy for users to use.
It has the characteristic of being able to communicate in a user friendly language. As a result of the communication, a message is assembled and formatted in accordance with the present invention;
It is transmitted to LUa' (not shown). LUa′ has a similar configuration to LUa. The function of LUa' is to process messages from LUa and send them to a program (not shown) connected to LUa'. A user friendly language called “Verbs” is “Transaction
Programmer's Reference Manual for Logical
Unit 6.2” (GC30-3084-1). LUb is an intelligent office workstation, such as a display writer, with local office application programs, local document storage, keyboard/display, and printer. The LUc may be a regular display terminal with fixed functionality.Of course, other types of devices and LUs may be connected to the transport network 130.
It can also be connected to.

FIG. 3 is a diagram showing details of the case where the transport network 130 shown in FIG. 2 includes, for example, two domains A and B. Since the two domains are similar, only domain A is shown in detail. Transport network 130 includes host processor 1 at node A and host processor 9 at domain B. These host processors may be conventional host computers. In the preferred embodiment, the host computer is an IBM system/
It is 370. The host processor 1 includes an operating system 17, a plurality of application programs 13, and a virtual memory communication access method unit (hereinafter abbreviated as VTAM) 12. LUa is application program 13 and VTAM12
Connect with. The configuration of LUa is the same as the configuration of LUa explained in FIG. In summary, LUa is an application program 13
It accepts instructions and commands from node A to construct a message and transports the message from node A to node B. It goes without saying that the message is configured in the form of the communication transport unit described above.

VTCM12 is the system service control point (hereinafter referred to as
(abbreviated as SSCP) 14. SSOP 14 is a component of VTAM that manages the network domain. VTAM is IBM's well-known communication access method, so we will not discuss it further.
SSCP 14 utilizes the aforementioned algorithms for forming transportation units, reacts to network problems such as link failures or control unit failures, performs network activation and deactivation, and Performs various functions such as assisting in, establishing, and terminating communications between work addressable units. To perform these functions, the SSCP must be able to communicate with physical units (PUs) and logical units (LUs). Communication usually refers to communication within one's own domain.
VTAM/SSCP is specified in the IBM manual “General
Information for Virtual Telecommunications
Access Method” (GC27−2763 and GC27−
0462), but what is necessary for the embodiments will be explained as needed.

Communication control device 2 is connected to host processor 1 via channel 16, and collective control device 4 is connected to host processor 1 via channel 15. The communication control device 2 has an advanced communication function (ACF)/
This is a transmission control device equipped with a processing section controlled by a network control program (NCP).
ACF/NCP resides in the storage device of communication control device 2. The main purpose of the NCP is to send data received from the host processor 1 to a terminal, collective control mechanism, or other NCP;
or sending data received from other NCPs to the host processor 1. The NCP can process data in a variety of ways as it passes through the communication controller. When controlling the flow of data, the NCP always interacts with the hardware part of the communication controller. The NCP interacts on the line side with a communication scanning mechanism (not shown) and on the channel side with a channel adapter (not shown).

The communication control device 2 is connected to a remote collective control device 5 via a synchronous data link control (SDLC) link 21. Communication control device 2 is link 2
5 to a remote communication control device 6 and also to terminals 31 to 33 via links 22' to 24'. The inter-domain link 26' connects the communication control device 2 and the remote communication control device 11 of the domain B. Similarly, in domain B, the communication control device 10 is connected between the host processor 9 and the communication control device 11. Communication control device 11
And its control program is the same as that of the communication control device 2.

Each element of the network shown in FIG. 3 that can send or receive data is assigned a network address. Each element is therefore called a network addressable unit (NAU). A network address uniquely identifies an element.
This identification determines whether the element is a device such as a terminal or terminal controller, a program such as an application program, or a collective controller within a host processor (i.e., part of an access method such as VTAM). ), regardless of whether it is or not. A network address contains the necessary information to route data to its destination. Three types of network addressable units are defined in SNA. That is,
SSCP, PU, and LU.

In Figure 3, PU is represented by a circle. P.U.
is a part of a device that performs a control function for the device in which it resides (and possibly multiple devices connected to the device containing the PU), usually a program or circuit ( or both)
It is. If the device is under its control, its
The PU is active and inactive, during error recovery and restoration of synchronization, during testing, during statistical aggregation,
as well as take action during operation of the device. Each device in the network is associated with one PU.
The collective control device 4 has a PU 41, and the collective control device 5 has a PU 51. Similarly, the communication control device 2 and the communication control device 6 each have a PU.

An LU is a device or program. End users, terminal operators, and input/output facilities gain access to the network through the LU. An LU may consist of logic (or programs) associated with a terminal, a subsystem independent device, or an application program.
As far as the network is concerned, the LU is the access port to the network. LU may also be the starting resource. The content of the request
There is also a possibility that it was emitted from a device controlled by LU. Similarly, the network
Consider the LU as the destination of the requesting unit (RU). In Figure 3, LU is represented by a circle. In the host processor 1, each of the plurality of application programs 13 is an LU. There are two LUs 42' and 43 in the collective control device 4. LU4
2' and LU 43 control device 44' and device 45. The collective control device 5 has LUs 52 to 54. LUs 52-54 control loop devices 55-57. The terminals 31 to 33 are composed of PUs 34 to 36 and LUs 37 to 39, respectively.

[Effects of the Invention] As explained above, if the present invention is used, in a computer network, compared to the conventional
Efficient information transmission becomes possible.

[Brief explanation of drawings]

1A to 1C are diagrams showing the format of a communication transport unit according to the present invention, FIG. 2 is a block diagram showing a computer network that can use the communication transport unit, and FIG. A block diagram showing an example of a network configuration, FIG. 4 is a flowchart of a program for processing a data stream configured in the format of the communication transport unit, and FIG. Figure 6 is a flowchart of the program to generate a stream; Figure 6 is a flowchart of the program to set a continuation indicator;
The figure is a flow diagram of a program for processing a data stream containing continuation indicators.

Claims (1)

[Scope of Claims] 1. In a computer network having a plurality of nodes and including a plurality of host computers controlling resources associated with the nodes, a device connected to the nodes and addressable by the network. A system for generating messages of variable length for conveying user data or control information between (a) devices addressable by said network, consisting of M data bytes; 1st
and a remaining second field concatenated with the first field, the second field being within a predetermined range of data to identify the second field as user data. A data value equal to the sum of the number of bytes of the first and second fields is stored in the first field, and data outside the predetermined data is stored in the first field to identify the second field as control information. A communication system comprising: means for storing a value in the first field.