JP3033658B2 - Cell pointer indication method - Google Patents

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.

[0002] Here, the cell pointer is information included in an area allocated on a payload in a cell and indicating a head position of a frame of user information.

[0003]

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

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

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

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

Here, a cell in which a cell pointer area is allocated to the payload 33 is referred to as a cell pointer insertable cell, and a cell in which a cell pointer area is not allocated to the payload 33 is referred to as a cell pointer non-insertable cell.

FIG. 4 is a diagram showing a range in which the head of a frame can be designated by a conventional cell pointer.

In FIG. 4, reference numeral 41 denotes a header, reference numeral 42 denotes a cell pointer, reference numerals 43A and 43B denote cells into which a cell pointer can be inserted, reference numeral 44 denotes a cell into which a cell pointer cannot be inserted, and reference numeral 45 denotes a frame indicating a cell pointer value of 0. The start position 46 indicates the frame start position indicated by the cell pointer value 92.

Referring to FIG. 4, CCITT Recommendation I. 3
In 63, the cell pointer insertable cells are inserted only every other cell, and the cell pointer value is the payload range of the own cell pointer insertable cell 43A (shown by hatching) and the subsequent payload range of the cell pointer non-insertable cell 44. (Shown by oblique lines), that is, a range of cell pointer values 0 to 92.

[0011] The cell pointer insertion unit on the transmitting side stores the user information using the cell pointer insertable cell 43A when the data length up to the head of the frame of the user information is less than 93 bytes when the user information is stored in the cell. I do.

The data length up to the head of the frame is 94
When the number of bytes is equal to or more than the byte, the cell pointer non-insertable cell 44 is used to store user information.

[0013]

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

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

Conventionally, when the data length of the user information up to the head of the frame is 94 bytes, as shown in FIG. 5A, if the user information is stored in the cell pointer non-insertable cell 54, the user information is contained in the payload. There is a problem that, despite the existence of the information frame start position 55 (shown by hatching), the cell pointer 52 cannot indicate the frame start.

At this time, when the user information is to be stored in the cell pointer insertable cell, as shown in FIG. 5B, the user information frame start position 55 (shaded line) is added to the payload of the next cell pointer insertable cell 53B. Shown in
There will be present, there is a problem that can not be instructed to frame head by the cell pointer 5 2.

In FIGS. 5A and 5B, reference numeral 51 denotes a header.

An object of the present invention is to provide an A
In the TM transmission system, a cell pointer that allows the frame pointer position to be indicated by the cell pointer even when the frame head of the user information moves to an area to be pointed to by the next cell pointer when the cell pointer is to be inserted. To provide an instruction method.

According to the present invention, in an ATM transmission system in which user information is converted into cells and transmitted, a cell pointer insertion unit on the transmitting side for inserting a cell pointer indicating the head of a frame of the user information is provided. The first payload range of the cell pointer insertable cell, the second payload range of the cell pointer non-insertable cell following the first payload range, and the second payload range of the cell pointer insertable cell. , A cell pointer designating method in which the head of the cell into which the cell pointer can be inserted subsequent to the cell pointer can be designated.

Further, the transmission-side cell pointer insertion unit has a data length of up to 9 bytes up to the head of the frame of the user information.
When the length is less than 4 bytes, the cell pointer insertable cell contains the user information, thereby obtaining a cell pointer instruction method.

Further, the transmission-side cell pointer insertion section has a data length of up to 9 bytes up to the head of the frame of the user information.
When the length is equal to or more than 5 bytes, the cell pointer indication method is characterized in that the user information is stored in the cell into which the cell pointer cannot be inserted.

Furthermore, when the data length of the user information up to the head of the frame is 94 bytes, the head of the frame is indicated by both the cell pointer having the pointer value 93 and the cell pointer having the pointer value 0. Is obtained.

[0022]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a range in which a cell pointer can be designated according to an embodiment of the cell pointer designation system of the present invention, and FIG. 2 is a diagram showing an example in which the head of a frame is designated by the cell pointer designation system of the present invention.

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

When the user information is stored in the cell, the cell pointer insertion unit on the transmission side stores the user information in the cell pointer insertable cell 13A when the data length up to the head of the frame of the user information is less than 94 bytes. I do.

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

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

In FIGS. 1 and 2, reference numeral 11 denotes a header.

[0029]

As described above, the cell pointer designating method according to the present invention can be used even when the head of the user information frame is moved to the area to be designated by the next cell pointer when trying to insert the cell pointer. This has the effect that the beginning of the frame can be indicated by the cell pointer.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cell pointer pointing range in one embodiment of a cell pointer pointing method according to the present invention.

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

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

FIG. 4 is a diagram showing a range in which a head of a frame can be designated by a conventional cell pointer.

FIGS. 5A and 5B are diagrams showing first and second examples in which the head of a frame is designated by a conventional cell pointer designation 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 non-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

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hitoshi Uematsu 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Hiromi Ueda 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Japan Inside Telegraph and Telephone Corporation (56) References “ITU-T White Book Recommendation I Series (B-ISDN), Foundation Japan New Japan ITU Association, published October 28, 1993, pp. 144-145 ( 58) Field surveyed (Int.Cl. ⁷ , DB name) H04L 12/28 H04L 12/56

Claims (1)

(57) [Claims] 1. ATM for transmitting user information in cells
In the transmission method, the head of the frame of the user information is designated.
Insert the cell pointer to be inserted
The entry is a payload range that can be indicated by the cell pointer.
To the first payload area of the cell into which the cell pointer can be inserted.
And insertion of cell pointer following this first payload area
The second payload range of the impossible cell as well as the second
Start of cell where cell pointer can be inserted following payload range
Can indicateAnd The transmission-side cell pointer insertion unit is configured to transmit the user information
If the data length up to the beginning of the frame is less than 94 bytes
The user information is stored in the cell pointer insertable cell.
And the data up to the top of the frame of the user information
When the length is 95 bytes or more, the cell pointer insertion is performed.
The user information is stored in a non-accessible cell, and the user information is stored.
If the data length up to the beginning of the report frame is 94 bytes
The user information is stored in the cell pointer insertable cell.
And the top of the frame is a cell having a pointer value of 93.
Both the pointer and the cell pointer with pointer value 0
Including means for instructing Cell pointer finger characterized by the following:
Indication method.