JPH07162432A - Cell pointer point-out system - Google Patents

Abstract

PURPOSE:To point out by a cell pointer even when a head of a frame of user information is moved to an area to be pointed out by a pointer of a succeeding cell in the case of inserting a cell pointer in the ATM transfer system using the cell pointer. CONSTITUTION:A cell pointer 12 points out a range 16 from a pay load range of its own cell pointer insertion enable cell 13A to a head of a succeeding cell pointer insertion enable cell 13B. A cell pointer insert section of a sender side accommodates user information to the cell pointer insertion enable cell 13A when the user information is accommodated in a cell and a data length up to a frame head of the user information is within 94 bytes and accommodates the user information to a cell pointer insertion disable cell 14 when the data length up to the frame head of the user information is 95 bytes or over.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cell pointer indicating system in an ATM transmission system.

Here, the cell pointer is information contained in an area allocated on the payload in the cell and indicating the head position of the frame of user information.

[0003]

2. Description of the Related Art When user information having a frame structure is stored in a cell, it is necessary to transmit the frame position of the user information to the opposite device so that the opposite device can reproduce the user information. This is, for example, CCITT Recommendation I. It can be realized by the means described in 363.

FIG. 3 is a diagram showing an example of a cell format. In 363, the cell format as shown in FIG. 3 is used.

In FIG. 3, the cell length is 53 bytes,
The cell header 31 is 5 bytes, and the SAR-PDU header (S
enforcement And Reassembl
ysublayer-Protocol Data U
In nit Header, hereinafter simply referred to as header) 32
Is 1 byte and the SAR-PDU payload (hereinafter simply referred to as payload) 33 is 47 bytes.

The header 32 has a payload 33 depending on its value.
The cell pointer 34 indicates whether the cell pointer area is allocated or not, and the cell pointer 34 indicates the frame start position of the user information.

Here, a cell to which the cell pointer area is assigned to the payload 33 is referred to as a cell pointer insertable cell, and a cell to which the cell pointer area is not assigned to the payload 33 is referred to as a cell pointer uninsertable cell.

FIG. 4 is a diagram showing a range in which a conventional cell pointer can indicate the beginning of a frame.

In FIG. 4, 41 is a header, 42 is a cell pointer, 43A and 43B are cell pointer insertable cells, 44 is a cell pointer insertable cell, and 45 is a cell pointer value 0. The head position 46 indicates a frame head position designated by the cell pointer value 92.

Referring to FIG. 4, CCITT Recommendation I.S. Three
In 63, a cell pointer insertable cell can be inserted only every other cell, and the cell pointer value is the payload range of its own cell pointer insertable cell 43A (shown by diagonal lines) and the payload range of the cell pointer insertable cell 44 that follows it. (Indicated by diagonal lines), that is, the cell pointer value ranges from 0 to 92.

The cell pointer insertion section on the transmission side stores the user information by using the cell pointer insertable cell 43A when the user information is stored in the cell and the data length up to the head of the frame of the user information is less than 93 bytes. To do.

The data length up to the beginning of the frame is 94.
When the number of bytes is equal to or larger than the byte, the cell 44 in which the cell pointer cannot be inserted is used to store user information.

[0013]

In this conventional cell pointer designating method, the size of user information that can be accommodated in the payload changes depending on the presence or absence of the cell pointer area in the payload.

FIGS. 5A and 5B are diagrams showing first and second examples in which the frame head is designated by the conventional cell pointer designating method.

Conventionally, when the data length of the user information up to the beginning of the frame is 94 bytes, as shown in FIG. 5A, if the user information is accommodated in the cell pointer non-insertable cell 54, the user information is contained in the payload. There is a problem that the cell head 52 cannot be designated by the cell pointer 52 even though the information frame head position 55 (shown by diagonal lines) is present.

At this time, if the user information is to be accommodated in the cell pointer insertable cell, as shown in FIG. 5B, the frame start position 55 (hatched line) of the user information is added to the payload of the next cell pointer insertable cell 53B. (Illustrated by)
Therefore, there is a problem that the cell pointer 55 cannot indicate the head of the frame.

In FIG. 5A and FIG. 5B, 51 is a header.

An object of the present invention is to use A using a cell pointer.
In the TM transmission method, even when the frame head of the user information moves to the area to be pointed to by the next cell pointer when trying to insert the cell pointer, the cell pointer that enables pointing of the frame head position by the cell pointer It is to provide an instruction method.

According to the present invention, in the ATM transmission system for converting user information into cells and transmitting the cells, a cell pointer inserting section on the transmitting side for inserting a cell pointer indicating a frame head of the user information is provided. A first payload range of the cell pointer insertable cell, a second payload range of the cell pointer non-insertable cell following the first payload range, and the second payload range A cell pointer designating method characterized in that the cell pointer can be inserted up to the beginning of the cell where the cell pointer can be inserted is obtained.

Further, the cell pointer insertion section on the transmission side has a data length up to the beginning of the frame of the user information of 9
When the length is less than 4 bytes, the cell pointer pointing method is obtained in which the user information is stored in the cell pointer insertable cell.

Further, in the cell pointer inserting section on the transmitting side, the data length up to the frame head of the user information is 9
When it is 5 bytes or more, the cell pointer designating method is obtained in which the user information is stored in the cell in which the cell pointer cannot be inserted.

Further, when the data length up to the frame head of the user information is 94 bytes, the frame head is designated by both the cell pointer having the pointer value 93 and the cell pointer having the pointer value 0. The cell pointer designating method can be obtained.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a cell pointer instructable range in one embodiment of the cell pointer instructing system of the present invention, and FIG. 2 is a diagram showing an example in which the frame head is instructed by the cell pointer instructing system of the present invention.

Referring to FIG. 1, the cell pointer 12 indicates a range from the payload range of its own cell pointer insertable cell 13A (shown by hatching) to the beginning 16 of the next cell pointer insertable cell 13B.

When accommodating the user information in the cell, the cell pointer insertion section on the transmission side accommodates the user information in the cell pointer insertable cell 13A when the data length of the user information up to the head of the frame is less than 94 bytes. To do.

If the data length of the user information up to the beginning of the frame is 95 bytes or more, the user information is stored in the cell 14 into which the cell pointer cannot be inserted.

In particular, when the data length of the user information up to the frame head is 94 bytes, the frame head position 25 of the user information is the cell pointer value 9 as shown in FIG.
3 is designated by both the cell pointer having the frame head position 26 designated by 3 and the cell pointer having the frame head position 27 designated by the cell pointer value 0. Further, in this case, the cell pointer having the cell pointer value 0 can be omitted.

In FIGS. 1 and 2, 11 is a header.

[0029]

As described above, according to the cell pointer designating method of the present invention, even when the head of the user information frame moves to the area designated by the next cell pointer when the cell pointer is inserted, The cell pointer has the effect of being able to indicate the beginning of the frame.

[Brief description of drawings]

FIG. 1 is a diagram showing a cell pointer instructable range in an embodiment of a cell pointer instructing system of the present invention.

FIG. 2 is a diagram showing an example in which a frame head is designated by the cell pointer designating method of the present invention.

FIG. 3 is a diagram showing an example of a cell format.

FIG. 4 is a diagram showing an instructable range of a frame head by a conventional cell pointer.

5A and 5B are diagrams showing first and second examples in which a frame head is instructed by a conventional cell pointer instructing method.

[Explanation of symbols]

11, 32, 41, 51 SAR-PDU header (header) 12, 34, 42, 52 Cell pointer 13A, 13B, 43A, 43B, 53A, 53B
Cell pointer insertable cell 14,44,54 Cell pointer not insertable cell 15,27,45 Frame start position indicated by cell pointer value 0 16,26 Frame start position indicated by cell pointer value 93 25,55 User information Frame start position 31 Cell header 33 SAR-PDU payload (payload) 46 Frame start position indicated by cell pointer value 92

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hitoshi Uematsu 1-1-6 Uchisaiwai-cho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Inventor Hiromi Ueda 1-1-6 Uchisaiwai-cho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (4)

[Claims] 1. An ATM for converting user information into cells and transmitting the cells.
In the transmission method, the cell pointer insertion unit on the transmission side, which inserts a cell pointer indicating the frame head of the user information, sets the payload range instructable by the cell pointer to the first payload range of the cell pointer insertable cell and this A cell pointer designating method, characterized in that it is possible to designate a second payload range of a cell pointer non-insertable cell following the first payload range and the beginning of a cell pointer insertable cell following the second payload range. . 2. The cell pointer insertion unit on the transmission side stores the user information in the cell pointer insertable cell when the data length of the user information up to the head of the frame is less than 94 bytes. The cell pointer pointing method according to claim 1. 3. The cell pointer insertion unit on the transmission side stores the user information in the cell pointer uninsertable cell when the data length of the user information up to the head of the frame is 95 bytes or more. Claim 1
Described cell pointer pointing method. 4. When the data length up to the frame head of the user information is 94 bytes, the frame head is designated by both a cell pointer having a pointer value 93 and a cell pointer having a pointer value 0. The cell pointer pointing method according to claim 1.