JPH0340620A - Slot access system - Google Patents

Abstract

PURPOSE:To attain throughput whose value is '1' or over without causing impartial provision of access right by adopting a system that a reception node releases a slot, supervising the occurrence of an impartial access, and employing the system that a transmission node releases the slot when the access is judged as impartial. CONSTITUTION:A transmission node (S1)41 acquires a slot access right by setting information to a received idle slot (((B bit), (R bit))=(0,0)) to revise a header content into (1, 0). A reception node (D) 42 copies the content of the said slot, and sets the content to (0, 0) to release the slot access right. A transmission node (S2) 43 can acquire the released slot access right. An acquisition request node (R)44 unable to acquire the access right for a long time having information to be sent applies acquisition request of the access right to the transmission node (S1)41 by revising the content to (1, 1).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a slot access method, and more specifically, a method in which a plurality of nodes are connected in a ring shape through a transmission path, and a frame consisting of a plurality of slots is placed on the transmission path. make it go around,
The node relates to a slot access method in a data communication system that uses unused slots to transmit data.

[Conventional technology]

In a data transmission system, a plurality of nodes are connected on a ring by a transmission path, a frame consisting of a plurality of slots is circulated on the transmission path, and the nodes transmit data using empty slots in the frame, If a slot access method is adopted in which each node occupies an access right once acquired for a long period of time, an unfair situation arises in that some nodes cannot acquire an empty slot for a long period of time.

To solve this problem, conventionally, for example, I.E.E., Journal on Selected Areas
In communication, varnish, knee, sea, 3,1
985. Pages 815 to 824 (IHt<H, Jou
rnal on 5 selected Area inC
communications, 5AC3, 1986, p.
, 815 to 824), each node that has acquired the access right has the slot tb used by its own node.
An access method is known in which \ is always released in the next round.

[Problem to be solved by the invention]

However, in the access method described above.

First, under low traffic conditions, when transferring data whose length is longer than the information transfer area length of a slot on the ring, the transfer efficiency deteriorates.
5 μsec, the ring circuit delay is equivalent to one frame, and the slot length is 69 bytes (internal information transfer area is 64 bytes), the transmission speed is 35 Mbps, and 8
The reason is that there are 2 slots. At this time, assuming that a data transfer of 1000 bytes occurs on a certain node, in the conventional method, it is necessary to obtain access rights at least three times before the data transfer is completed, and the access waiting time is also shortened to three cycles. This will require time to go around the ring. 3
One of the laps is spent circling the empty slot.

Furthermore, as shown in FIG. 2, even under high traffic conditions, with this method, the number of times the slot can reach II!
! The problem is that only 1 access opportunities are given, that is, the throughput cannot exceed 1.

W! , 1, as described in Japanese Patent Application No. 62-220123, for example,
There is also a method that allows the sending node to continuously access slots that are already in use, but this does not solve the second problem.

As a method to solve the second problem, there is a method in which slots are released at the receiving node, but in this method, on average, a throughput of 1 or more can be coupled, but on the other hand, there are nodes that cannot acquire empty slots. “Hog” that is said to occur
It is known that unfairness in granting access rights, called ``ging'', occurs.

An object of the present invention is to provide an access method that can achieve one or more throughputs without causing unfairness in granting access rights.

[Means to solve the problem]

In the above-mentioned method of releasing slots at the receiving node, the probability that unfairness in granting access rights will occur is relatively low. This can be achieved by monitoring the occurrence of this problem and, if it is determined to be unfair, controlling the sending node to release the slot, which is a fair access method.

[Effect]

In the method of the present invention, a slot for which an access right release request is requested is released by the sending node, and since this can only be used by the node that issued the request, there is a conventional A fair access method is adopted. Furthermore, if a fair access method is adopted, the maximum access waiting time is given by the product of the ring circulation delay and the number of connected nodes, so by monitoring this time, it is possible to know when to change the method.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows the overall configuration of a data transmission system to which the present invention is applied, in which multiple nodes 200, 202, 203, 2
04 and 205 are connected in a ring by the transmission circuit 201, and on the ring, (ring circulation delay) / (152μ
sec ) number of frames F circulate. Each node communicates by placing transfer information on this frame. In this embodiment, the node 200 functions as a master node, and the other nodes function as slave nodes. 242,2
43 is a host computer; 1 communication processing device 222;
223, 224, 225, 234, and 235 are communication terminals connected via branch LANs 214 and 215, respectively, and communicate with each other by a burst exchange method.

In this case, the information is the nodes 202, 203, 204, 2
The packets are multiplexed on the transmission path 201 via 05.

232.233 is a private branch exchange (PBX).

Accommodates a telephone or low-speed data terminal. Voice information from the telephone is communicated using a single circuit switching system. In this case, the information is transmitted via transmission line 2 through nodes 202, 203 &
01, time division multiplexing is performed.

3rd [1i! Figure 1 shows the frame format and slot structure used in the transmission system of the present invention.
SONET (Synchronous Op.
ticalNetwork) format,
Although the details are omitted, in the present invention, the path overhead section of 1 byte x 9 lines in the S ON E 'r format is also transferred to the information transfer section 3.
The difference is that it is included in 0. The information transfer department has
A slot 31 having a length of 69 bytes is placed, and the remaining area 32 is an invalid area.

Slot 31 is a 5-byte slot with ladders 32 and 64.
It consists of a byte information section 33, and a slot header 3.
2 contains 1 byte of AcF (Accsts Conto
rl? '1eld) 34 and a 4-byte address area 35 are included.

The S bit 341 of the most significant bit of A CF34 indicates whether the slot is used/unused (B=1 and in use), and the S bit 342 is information written in the slot that requests time division multiplexing. 5co, i> indicates information for controlling between nodes, and (1, O) indicates information requesting packet multiplexing.

The M bit 343 is a monitor bit for monitoring abnormal ring rotation of the slot in use.

The master node sets the bit to 1 for the slot with B=1, the transmitting node sets it to 0, and the master node monitors the slot with B=1 and M=1.

The R bit 344 is a release request bit (requested when R=1), and since this is information that implements the present invention, the details will be described later.

The address area 35 includes a destination address (DA) 351, a source address (SA) 352, and error detection information (HO2).
) consists of 353.

In the system of this embodiment, information requesting the above-mentioned packet multiplexing and time division multiplexing coexists. The master node secures a transfer band especially for information requiring time division multiplexing by setting in advance the S bit 342 of each slot 31 shown in FIG.

FIG. 4 shows an outline of the procedure for acquiring and releasing access rights to slots allocated for packet multiplexing.
In Figure a, the host computer 242 in Figure 2 is communicating with the host computer 243, and the node 204
The case is shown in which the node 205 has a transmission request to the node 205. Therefore, the sending node (Sl) 41 corresponds to the node 202, the receiving node (D) 42 corresponds to the node 203, and the sending node (S2) 43 corresponds to the node 204.

The sending node (Sl) 41 receives the empty slot (((B
bit), (R bit)) = (0, 0)) to acquire slot access rights and change the header contents to (
1,0). The receiving node (L3) 42 copies the contents of the slot and sets it to (0, O), thereby releasing the slot access right. Sending node C82
) 4:3, the host computer 243 of FIG. 2 acquires access rights to the released slot.
While communicating with host computer 242, node 204 has a request to send to node 205, but node 204 loses access because node 203 continues to use the slot released by node 202. This shows the procedure to be followed in case it becomes impossible to obtain.

Therefore, in this case, the sending node (51) 41 is the node 203
In other words, the receiving node (1) 42 corresponds to the node 202, and the release requesting node (R) 44 corresponds to the node 204.

The sending node (81) 41 receives the empty slot (((B
bit), (R bit)) = (0, 0)) to acquire slot access rights and change the header contents to (
1,0). Acquisition requesting node (R) that has information to be sent but cannot obtain access rights for a long time
44 becomes the sending node (Si) by changing it to (1, 1)
The slot set to R=1 that requests the acquisition of access rights to the receiving node (L) is changed to (0, 1) by the transmitting node (Sl:) 41 instead of the receiving node (L). be released against. This (0, 1) slot can be used only by the node that issued the acquisition request, and when used, the release request is canceled by setting R=O.

The release request is for the number of sentences ((
1, 0) at a timing of (waiting time)>(ring circulation delay)×(number of connected nodes).

Release the slot in use (1, 1) with a release request,
Although it is possible to perform this at the receiving node (L) 42, it is preferable to release at the transmitting node (81) 41 in consideration of impartially granting the right to request release.

Figure 1 shows the slot state transitions. Unused condition 1
The slot located at 0 is called an empty slot.

When the transmitting node acquires this slot, the slot transitions to the in-use state 11, and when the slot is released by the receiving node, it transitions to the unused state. This situation corresponds to Figure 4a.

If there is a release request for a slot in use, the sending node shifts to the release waiting state 12, and when released, the requesting node shifts to the requesting node use waiting state 13, where only the release requesting node can use-iJ. When the release requesting node uses the slot that is waiting for the requesting node to use it, the slot becomes in use 11.
If it goes around the ring without being used, it is left unused by the sending node.

Note that the slot access methods shown up to FIG. 4a are commonly used in slotted ring LANs as described in the prior art, and furthermore, the processing added by the present invention can be easily realized as a logic circuit. Therefore, the detailed circuit structure will not be shown in detail.

According to this embodiment, when the own node re-receives a slot released in accordance with a release request in that state, the requesting node transitions from the waiting state for use to the unused state. Immediately after, if the transfer of the waiting information using an empty slot is completed, (0
, 1) can be prevented from going around the ring more than once.

〔Effect of the invention〕

The effects of the present invention 1 will be explained using the throughput-access waiting time characteristics shown in FIG.

Here, the throughput indicates the ratio of the amount of information to the speed of the sailing route, and the access waiting time is the time from when information becomes ready to be transmitted until it is actually sent onto the route. Characteristic 51 is a method of releasing slot access rights at the transmitting node, and is a characteristic of the method (method 1) in which the slot access right is required to be released regardless of whether there is information to be transmitted.

In method 1, the characteristic 52, which is usually used because it is possible to grant access rights fairly, releases the slot at the transmitting node as in method 1, but if there is information to be transmitted, the corresponding This is a characteristic of the method (method 2) that allows continuous use of slots. In both methods, the throughput does not exceed 1.

Furthermore, in method 1, the access latency is approximately twice as high as other methods due to low traffic at the cost of fair access.

Characteristic 53 is a method in which slots are released at the receiving node (
A characteristic of method 3) is that on average a throughput of 1 or more can be achieved, but on the other hand, it is known that unfairness in granting access rights called "Hogging" occurs.

If the method of the present invention is adopted, "'H" can be achieved under low traffic conditions.
The probability that ogg1ng ``'' will occur is extremely low.

In the relationship between the slot (0, 1) and the acquisition requesting node, method 1, which is a fair access method, is adopted, so even the worst performance under high traffic conditions can be guaranteed to be close to method 1. Considering that the characteristic is between characteristic 52 and characteristic 53, depending on the traffic characteristic.

As described above, according to the invention, a highly efficient access method can be realized with relatively simple control while ensuring fairness in granting access rights.

[Brief explanation of drawings]

FIG. 1 is a slot state transition diagram according to the access method of the present invention, FIG. 2 is a diagram showing the constituent countries of the data transmission system,
The figure shows the frame format used in the transmission system of the present invention,
FIG. 4 is a diagram of the structure of the slot, and is an outline of the procedure for acquiring and releasing access rights. FIG. 5 is a throughput-access latency characteristic diagram. 30... Information transfer section of transfer frame, 31... Slot, 32... Slot header, 33... Information section,
34...ACI-', 35...Address section, 344
...Release request bit. Whisper diagram 34 22t+ Flute 3 Figure 4d Figure 4F) Figure 4; 2; No. 1. /-'7°・puY・

Claims (1)

[Claims] 1. One master node and a plurality of snob nodes are connected in a ring shape by a transmission path, and the master node circulates a fixed-length slot consisting of a header section and an information section on the transmission path. In a slotted ring LAN access method, a node transfers information to a receiving node using a slot whose used/unused indication in the header section indicates that it is unused, and also changes the indication to use. If there is no request to acquire the transmission right from another node, the receiving node releases the slot by making the slot display unused, and if the other node has a request to acquire the transmission right, the receiving node releases the slot. A slot access method characterized in that a transmitting node releases a slot access right instead, and the released slot can be used only by a node that has issued a request to acquire the access right. 2. In claim 1, a new acquisition request indication is provided in the header section, and a node requesting acquisition of an access right can, for a slot that is in use and does not have an acquisition request indication,
By setting the acquisition request display for the number of slots corresponding to the bandwidth of the transmission waiting information, the transmitting node and receiving node of the slot are notified of the presence or absence of a transmission right acquisition request, and the unused slot with the acquisition request display is A slot access method characterized in that the node in use cancels the setting and acquisition request while the node is in use. 3. The slot access method according to claim 2, wherein the node with the transmission request issues an acquisition request when the transmission waiting time exceeds the product of the ring circulation delay and the number of connected nodes. .