JPH0461448A - Packet transfer system - Google Patents

Abstract

PURPOSE:To prevent each packet form terminal equipment from being poorly served by transferring a long packet whose frame length is in excess of n-octet while it is divided in the unit of n-octets. CONSTITUTION:This packet exchange system consists of packet form terminal equipments PT1-PTn, a packet multiplexer 1 and a packet switchboard 2, and the packet multiplexer 1 and the packet switchboard 2 are interconnected by a packet multiplex channel l. In the case of a long packet in excess of n-octet, since the packet is transferred while being divided in the unit of n-octet, only packets whose length is n-octet or below similar to that of short packets are transferred on the packet multiplex channel l. Thus, it is prevented that each packet form terminal equipment is poorly served.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a packet transfer system between a packet multiplexing device and a packet switching device.

[Prior Art] FIG. 5 is a configuration model of a packet switching system for explaining a conventional packet transfer system, and the direction of packet transfer is from the packet type terminals PT, ~PTn to the packet switching device M4. do. Packet multiplexer 3
is composed of terminal-side link level control units a, -an, a transmission queue j, and a system-side link level control unit d. The packet switching device 4 includes a system-side link level control section g and a packet switching processing section i, and is connected to the packet multiplexing device 3 via a packet multiplexing channel 2.

Packet transfer in the above configuration is performed as follows.

When the terminal-side link level control units a1 to a, n receive packets from packet-format terminals PT, to PT, they perform link-level processing with the terminals, and queue packet-level packet data in a transmission waiting queue j on a first-come, first-served basis. ing. If there is no packet data currently being processed, the system side link level control unit d transfers data from the transmission waiting queue j to the FIFO
The packet data is extracted according to the format, and link level processing with the packet switching device 4, including multiplexing processing to identify the source packet format terminal, is performed, and a packet multiplexing channel is created! The packet is transmitted to the packet switching device 4 via the .

When the system side link level control section g in the packet switching device 4 receives the packet from the packet multiplexing device 3, it performs link level processing and transfers the packet level packet data to the packet switching processing section i. The packet exchange processing unit i performs exchange processing at a higher level than the packet level on the transferred packet data on a first-come, first-served basis.

[Problems to be Solved by the Invention] As described above, in conventional packet transfer systems, processing is generally performed in each device on a first-come, first-served basis, and data is transferred in the order in which the processing is completed. At this time, since the frame length of the packet is not taken into account, the communication path between the packet multiplexer 3 and the packet switching device 4 is data packets of tens to hundreds of octets transmitted from short packet packet format terminals. This results in a mixture of data packets of several thousand octets transmitted from long packet format terminals.

Problems occurring in such a conventional configuration will be further explained using FIG. 6.

FIG. 6 is a time chart of the packet multiplexer 3 manufactured based on the model of FIG. 5. In FIG. 6, the packet multiplexer 3 has three packet type terminals PT.
, ~PT, are connected, and the packet form terminal P
T, and PT2 are packet format terminals for short packets, PT3 is a packet format terminal for long packets, and packet numbers 11 and 1 are obtained from the packet format terminal PT.
A short packet with packet number 21 is sent from the packet type terminal PT2, a long packet with packet number 31 is sent from the packet type terminal PT3, and each of the short packets with packet numbers 11, 12, and 21 are all sent. The frame length shall be the same. Furthermore, the packet sending interval is a specific model. The total delay time of each packet within the packet multiplexer 3 is:
It is expressed as the sum of the processing time in the terminal-side link level control units a to a3, the processing time in the system-side link level control unit d, and the waiting time in the transmission queue j. Note that the processing time at the system side link level control section d includes the time for transmitting the packet onto the packet multiplexing channel c.

From FIG. 6, although it is a specific model, among the short packets sent by short packet packet type terminals PT, PT2, the packet with packet number 12.21 is a long packet sent by long packet type terminal PT3. It is clear that the waiting time in the transmission queue j increases due to the influence of the packet, resulting in a large delay. Therefore, in the conventional configuration, the short packets transmitted by the packet type terminals PT, PT2 for short packets are delayed due to the influence of the long packets transmitted by the other long packet type terminals PTs due to multiplexing. The time increases, which causes deterioration of service to short packet type terminals. In particular, if the transmission speed of the communication path is not sufficiently high, the above possibility becomes high and becomes a problem.

An object of the present invention is to provide a packet transfer method that relatively easily solves the above problems.

[Means for Solving the Problems] A packet transfer system according to the present invention is configured to divide a long packet whose frame length exceeds n octets into units of n octets and transfer them.

[For use] In the present invention, in the case of a long packet exceeding n octets, the packet is divided into n octets and transferred. Therefore, in a packet multiplexed call, only packets of n octets or less, similar to short packets, are transmitted.

[Embodiment] FIG. 1 shows an embodiment of a packet switching system using the packet transfer system of the present invention, and this packet switching system includes two packet type terminals 1 to PTn, a packet multiplexer 1, and a bucket switching device. Consists of 2. The packet multiplexing device 1 and the packet switching device 2
are connected to each other by a packet multiplex communication path.

Here, a case is shown in which packets are transferred from packet type terminals PT, to PT, in the direction of the packet switching device 2.

Next, the operation will be explained.

When the terminal-side link level control units a1 to an receive packets transmitted from the packet-format terminals PT+ to PTn, they process the link level with the terminal, and send the packet level to the long packet division processing units a1 to bn. packet data is transferred. Long packet division processing unit b1~
If the transferred packet data is a long packet, it is divided into n octets or less, and the divided long packet data and short packet data are queued in FIFO format selection queues e1 to en.

The selection circuit C selects one of the selected queues e, -en in which packet data is queued, and sequentially queues the packet data in the transmission queue f. At this time, if the divided long packet data and short packet data are queued at the head of separate queues at the same time, the short packet data is selected with priority.

If there is no packet data currently being processed, the system side link level control unit d sequentially extracts the packet data from the transmission waiting queue f in FIFO format, and performs the above-mentioned multiplexing process for identifying the source packet type terminal. It performs link level processing with the packet switching device 2, and transmits packets to the packet switching device 2 via the packet multiplexing channel.

When the system-side link level control unit g in the packet switching device 2 receives the packet from the packet multiplexing device 1, it performs link-level processing and transfers the packet-level packet data to the long packet assembly processing unit. . If the transferred packet data is divided long packet data, the long packet assembly processing section assembles it and then transfers it to the packet switching processing section i. The packet exchange processing unit i performs exchange processing at a higher level than the packet level on the transferred packet data on a first-come, first-served basis.

Through the above operations, the packet form terminal PT, ~
Packets are transferred from PTn to the packet switching device 2. Note that when a packet is transferred in the opposite direction (from the packet switching device 2 to the packet type terminals PT to PTn), the long packet division processing units b1 to bn in the packet multiplexing device 1 and the packet The configuration is such that the functions of the long packet assembly processing unit in the switching device 2 are replaced, and the operation can be easily imagined (therefore, the explanation thereof will be omitted).

Next, the effects of using the packet transfer system of the present invention will be clearly shown below using FIG.

FIG. 2 is a time chart for the packet multiplexing device 1 created based on the embodiment shown in FIG. There is.

In FIG. 2, like the conventional example, the packet multiplexer 1
Assume that three packet type terminals PT and PT3 are connected to , the packet type terminals PT and PT2 are the packet type terminals for short packets, the PT3 is the packet type terminal for long packets, and the packet type terminal P is connected to the packet type terminal P.
T, to packet number 11. ．． 12 short packets are sent from the packet type terminal PT2, a short packet with the packet number 21 is sent from the packet type terminal PT3, and a long packet with the packet number 31 is sent from the packet type terminal PT3, and the frame length and sending interval of each packet are the same as the conventional example in FIG. is the same as Note that the long packet with packet number 31 is divided into packets with packet numbers 3a to 3a in the packet division processing unit b3.
It is assumed that the packet is divided into 3f packets, and each divided packet has the same frame length as the short packet.

The total delay time of each packet within the packet multiplexing device 1 is determined by the processing time in the terminal side link level control units a1 to a3, the processing time in the long packet division processing units bl to b3, and the system side link level control unit. Processing time in d, waiting time in selection queues e1 to e, and transmission queue f
It is expressed as the sum of the waiting times at

Comparing the time chart of FIG. 2 created using the above parameters with the conventional time chart of FIG. 6, it is found that the packet type terminal PT for short packets
In Figure 6, the short packet with packet number 12.21 sent by PT2 is significantly delayed due to the influence of the long packet with packet number 31, whereas in Figure 2, the long packet with packet number 31 Divide the
Packet number 12.21 between divided long packets
It can be seen that the delay of these short packets is improved by interrupting these short packets. That is, according to the present invention, the packet type terminal P for short packets as pointed out in the conventional example shown in FIGS.
It is possible to solve the problem that short packets transmitted by T, PT2 are affected by long packets and the waiting time increases.

However, in this invention, since the waiting time for long packets increases, the packet format terminal P for long packets
There is a concern that this may lead to service deterioration for T, but normally the required value for the service time of long packets is set to a much larger value than that of short packets.For example, in INS net, X25 optional user In the network relay delay selection display, which is a facility, the values reported by the network are fixed values of 600 m5 for short packets and 3000 ms for long packets for the time being. It is inevitable that the latency will be larger than for short packets, and it will not lead to service degradation.

Here, as an example of coding the packet frame format on the packet multiplexing channel ρ of the packet transfer system of the present invention, one based on CCI TT Recommendation V, 120 is shown in FIGS. 3 and 4. FIG. 3 shows an example of a frame format, and FIG. 4 shows an example of hella coding.

In Fig. 3, Fig. 3(a) is an example of a frame format, in which flag F, address A, control C (1 octet for modulo 8, 2 octets for modulo 128), information processing, frame check sequence F cs , flag F.

FIG. 3(b) shows the details of the area of information ■ in FIG. 3(a), including the header H and packet data PD (X'25
, layer 3). Header H is further
As shown in Figure (C), it consists of a terminal management header TH and an extension ladder EH.

FIG. 4 shows an example of the coding of the header H in FIG. 3(b), where FIG. 4(a) shows the header octets for terminal management, and FIG. 4(b) shows the extension header octets. .

The header octet for terminal management in FIG. 4(a) includes extension bit E (extended when E=1, no extension when E=O), 1 division start bit B, 5 division end bit F, and terminal management address TA. Consists of each area.

FIG. 4(b) shows an example when E=1 in FIG. 4(a), in which the terminal management address (lower 8 bits) is evaporated as an extension header octet.

[Effects of the Invention] As explained above, the packet transfer system of the present invention divides a long packet whose frame length exceeds n octets into units of n octets and transfers the packets, thereby eliminating the short-circuits that were pointed out in the conventional example. It is relatively possible to prevent short packets transmitted by packet type terminals from increasing the waiting time due to the transmission delay of long packets transmitted by long packet type terminals, and to prevent a decline in service performance for each packet type terminal. It's easy to do. Therefore, the packet transfer method of the present invention is particularly effective in a packet switching system where the communication path transmission rate is not sufficiently high, such as about 64 Kbps.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a packet switching system using the packet transfer method of the present invention, and FIG.
A time chart based on FIG. 1, FIG. 3 is a diagram showing an example of the frame format of the packet transfer method of the present invention,
4 is a diagram showing an example of coding in the header of FIG. 3, FIG. 5 is a block diagram showing an example of the configuration of a packet switching system using a conventional packet transfer method, and FIG. This is a time chart based on. In the figure, 1 is a packet multiplexing device, 2 is a packet switching device, PT, ~PT, are packet type terminals, a, ~an are terminal side link level control units, b1 to bn are long packet division processing units, C is a selection circuit, d is a system side link level control unit, e1 to en are selection waiting queues, f is a transmission waiting queue, g is a system side link level control unit, h is a long packet assembly processing unit, and i is a packet switching processing unit. , 2 is a packet multiplexing channel. Kuaki

Claims (1)

[Claims] A packet transfer system that transfers short packets of n octets or less and long packets of more than n octets between a packet multiplexing device and a packet switching device via a packet multiplexing channel, the long packets having a frame length of more than n octets. A packet transfer system characterized in that a packet is divided into n octets and transferred.