JPH0271646A - Virtual call setting control system - Google Patents

Abstract

PURPOSE:To improve the reliability of the system by revising the window size when a sum of maximum buffer quantities of a virtual call (PC) set already and usable by a PC set newly exceeds a buffer quantity to a terminal line. CONSTITUTION:When a setting request 1CR of a PC with a window size of WSt=2 is outputted from a terminal equipment 11, the call is sent to a terminal equipment 21 via packet exchanges 1, 2 with a network window size WSn=4 as 1CN(WSt=2). The terminal equipment 21 sends a PC setting acceptance 1CA(WBt=2) and the terminal equipment 11 receives a set acceptance 1CC(WSt=2) via exchanges 1, 2 to set a PC with WB1=2, WSn=4 in a logic channel (CH) 1. If the sum of the quantities of maximum buffer used by a preset CH1 and a PC of a CH2 requested newly exceeds the buffer quantity assigned to the terminal equipment 11, the packet is sent to the exchange while its size WBt is decremented from two to one.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a virtual call setup control system in a packet switch.

[Conventional technology]

FIG. 3 is a block diagram showing the general configuration of a communication system that establishes communication links (virtual calls) between terminals via a packet switch and performs 9 communications.
1) to (3) are a packet switch, an-(2
), (To), 01 to 01 are the above packet switches! 1), +2), (3)K each terminal line a4
~ tilt, (to) ~ (2), terminals connected by C14 ~ aa, (4) ~ (6) are each of the above exchanges (1), (2), (3
) is a line that connects between

How to set up a virtual call between terminals in such a communication system is described in 9, for example, p. 51 of ``Telecommunication Research Institute Research Conference Proceedings No. 42 J (February 11186, published by Nippon Telegraph and Telephone Co., Ltd. Telegraph Communication Research Institute). The sequence shown in Figure 4 is shown in Figure 4.

The setting of a virtual call will be explained based on FIG.

For example, when setting up a virtual call from terminal αυ connected to packet switch (1) to terminal r29 connected to packet switch (2), first the sequence +
411, the terminal window size W1 is determined from the terminal αD.
3i is 2's virtual call setup request tan (wsl.

-2) is issued, and upon receiving this, the packet switch (1) sends the virtual call setup request to the packet switch (2) with the network window size WSn as 4.
SaraK This virtual call setup request is 1a1wst-
2) is sent to the terminal Qυ. Here, the terminal window size wst indicates the number of data packets that can be sent at one time from the terminal to the packet switch, or vice versa, without confirmation of packet delivery from the receiving side. The network window size W8n indicates the number of data packets that one packet switch can send at one time without confirmation of packet delivery from the other packet switch. This is determined between packet switches. Terminal 12υ that has accepted the above virtual call setting request 1 ON (wst-2) receives virtual call setting request 10 (WSt-2).
-2), which is transmitted via packet switch (2) and packet switch (1) to 10G! (WB2.-2) is delivered to the terminal (+11) (sequence (43).

At this point, the terminal window size WS1 is -2 and the network window size is 1 day between the terminal (11) and the terminal c29.

-4 virtual call is now set up on logical channel 1. From this point, data packets are exchanged, and first, since the terminal window size wst is 2, 1, for example, 2 data packets I n'r1 from the terminal αυ.
(o), I DTl (1) is a packet switch (1)
(sequence Cj). Packet switch (1)
teeth.

This I I)T1 (0), I I)TI (1)
When received, it sends it to the packet switch (2) and returns a local delivery confirmation response RR1 (2>) to the terminal αυ (sequence (44)).

Also, at this time, the packet switch (1) may retransmit the data packet until the delivery confirmation is returned from the packet switch (21).
I) Tl (0)
.

IDTl(1) is memorized and held. In addition, in this example, the average buffer size per terminal line connected to each packet switch (1) to (3) is assumed to be 11, and one packet is stored in one buffer. shall be taken as a thing. Therefore I DTl
(0), I DTl (1), the amount of free buffers among the buffers allocated to the terminal line αφ in the packet switch (1) is 9. Furthermore, the ID is sent from the packet switch (2) to the terminal QI).
Tt (0) + ' ”1 (1) is sent. Next, the above sequence ■ is used to send a local delivery confirmation response RR1 (2
) has been returned, it is possible for terminal U to send two data packets again, and in sequence (c) another two data packets I D'h (2), I
DTl (3) is sent. In the packet switch (1), the previously sent 1 p'r1 (o), 11)T
Although the delivery confirmation for I (1) has not been returned from the packet switch (2), since the network window size WSn is 4, the above data packet I DTl
(2), I DTl (3) also uses a packet switch (
2), and these I)TI (2), I
DTl (3) and the above-mentioned I DT
l (0), I I)'r1 As in the case of (1), a hold is made for retransmission. Therefore, the packet switch (1
)'s empty buffer for terminal line a4 is further reduced by two to γ. Also, at this point, there is no more space in the network window, so the packet switch (1) switches to the terminal (
Even if further data packets are sent from 11), they cannot be sent to the packet switch (2), so the local delivery confirmation to terminal αO is not sent so that no packets are sent from terminal α9.

In addition, the packet switch (2) has an I DTI (2)
, I DTI (a) from the terminal (I D T 1 (0) + I D T 1 (1
), and there is no free space in the terminal window.
) in that buffer. Therefore, the amount of empty buffers among the buffers allocated to the terminal line @ in the packet switch (2) is 9. Further sequence (to)
Then, conversely, when two data packets I DT2 (0) and I DT2 (1) are sent from the terminal Qυ, the data packets I DT2 (0) and I DT2 (1) are sent out at the packet switch (2) in the same way as when the data packet was sent from the terminal αυ. These I
Sends DT2(0) and I DT2(1) to packet switch +11 and holds them for retransmission,
In addition, a local delivery confirmation response RR2 (21) is sent to the terminal Q (sequence value η). At this point, the packet switch (21) is sent to the terminal Q (sequence value η).
) The empty buffer amount of the terminal line @atashi is further decreased by two to 7. 11) T2(') + ' DT2 (
1) The packet switch (!) that received them transfers them to terminal t1
Send to υ. The above local delivery confirmation response RR2 (21
Since there was a sequence, two data packets I DT2 (2), I DT2 were sent from the terminal QD.
(3) is sent out, and since there are two vacant spaces in the network window from packet switch (2) to packet switch ft), these are sent to packet switch (1), and in case of retransmission, the packet switch The message is held until there is a delivery confirmation in the buffer in (2). Therefore,
At this point, the number of empty buffers per terminal line (2) in the packet switch (2) decreases by two to five. - On the other hand, the packet switch 111 that received these IDT2 (2) * IDT2 (3) received confirmation of delivery of the IDT2 (0) *IDT2 (1) sent to the terminal aD previously. Since there is no space in the terminal window for terminal αυ, IDT2(2), II)T2(3) is held in the buffer. Therefore, among the buffers allocated to the terminal line (141 Kmllll) in the packet switch (1) at this point, the number of empty buffers decreases by two to five.

As described above, when one virtual call is set up with the terminal window size W81; -2 and the network window size W8n'-4, each packet switch (1
), +21 requires 4+2-6 buffers considering the largest case. On the other hand, setting up multiple virtual calls by changing the logical channel from one terminal can normally be done, for example, as shown in sequence [41] in FIG.

Furthermore, another virtual call is made from terminal (11) on logical channel 2 to terminal (window size W81. −2, if the network window size WEIn” is set to 4.

As with logical channel 1, up to 6 buffers are provided for this logical channel 2 in each packet switch (1), (
2) Required within. However, each packet switch (1
), or in (2), the amount of buffer that should be allocated to terminal line a4 or terminal line @ is 11, and the empty buffer amount when logical channel 2 is set is 5, so logical channel If you set up virtual call 2,
The amount of allocated buffer for terminal line I will be exceeded. In such a case, buffers that should be allocated to other lines will be used within each packet switch.

[Problem to be solved by the invention]

As described above, in the conventional virtual call setting control method, a virtual call is set up in response to a virtual call setting request without considering the amount of empty buffer within the packet switch.

In cases where confirmation of delivery of data packets is delayed, the amount of buffer used increases, and communication on one terminal line uses buffers that should be used for other terminal lines, resulting in a buffer shortage. There was a problem in that it caused congestion in the packet switching equipment and caused communication problems on each terminal line.

This invention was made in order to solve the above-mentioned problems, and it is a virtual call system that allows appropriate virtual call settings to be made without causing congestion due to a lack of buffers in the packet switch. The purpose is to obtain a call setup control method.

[Failure to solve the problem]

The virtual call setup control method according to the present invention, when a virtual call setup request is issued from a terminal connected to a packet switch via a terminal line, is used for a virtual call that has already been set up using that terminal line. The sum of the maximum usage of the buffer within the packet switch and the maximum usage of the buffer that can be used by the virtual call undergoing the setting request is the predetermined buffer allocated to the terminal line within the packet switch. If the amount is larger than the above amount, change the setting specifications so that the sum of the buffer usage amounts is less than or equal to the allocated buffer amount and perform the setting process of the virtual call that is requesting the above setting, or reject the setting of the virtual call. This is what I did.

[Effect]

In this invention, when a virtual call setup request is made from a terminal, the usage amount of the maximum packet switch internal buffer that can be used for the already set virtual call using the terminal line connected to the terminal and the virtual call being requested for setup If the sum of the maximum buffer usage that can be used in is greater than the predetermined buffer amount allocated to the terminal line, change the setting specifications so that the sum of the buffer usage is less than or equal to the allocated buffer amount. As a result, an unreasonable virtual call can be set up that causes the buffer usage to exceed the buffer amount allocated to each terminal line. Therefore, even if delivery confirmation for data packets is delayed, if a buffer shortage occurs in a virtual call that has already been set up, other terminal lines may be using buffers that should be used. This prevents the width end state from spreading to other lines.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1(a) is a sequence diagram showing an embodiment of the present invention, and shows a virtual call setting procedure in the communication system shown in FIG.

In this embodiment, the allocation of the amount of buffer that can be used for each of the plurality of terminal lines connected in each packet switch is determined, and each packet switch (
1) to (3) are the buffer amount determined for each terminal line minus the maximum buffer usage that can be used in a virtual call set using that terminal line, that is, the buffer amount at each point in time. In addition, each terminal line has an empty buffer information table indicating the amount of completely empty buffer that is allowed to be used.

FIG. 1(1)) is an explanatory diagram showing the stored contents of the empty buffer information table of the packet switch (11, (2+) at each point in the sequence of FIG. 1(a),
~(43 is an empty buffer information table in the packet switch (1).

(F) to (F) indicate the contents of the empty buffer information table in the packet switch (2) at each point in time.

Next, virtual call setup between terminal I and terminal 011 will be explained.

Here, the buffer amount allocated in the packet switch (1) to the terminal line α (to which terminal I is connected) is 1
1. It is also assumed that the amount of buffer allocated within the packet switch (2) to the terminal line (c) to which the terminal t2D is connected is 15. Therefore, each terminal line Q4) in a state where no virtual call is set up, 24
The empty buffer amount corresponding to is shown in the empty buffer information table (4
0, (11 and 15, respectively, as shown in 44) from terminal αυ in sequence (51).

When a virtual call setup request 1cR (wsl, -2) with terminal window size 1 day t set to 2 is issued.

As in the above conventional example, this setting request is sent to the terminal υ as 1cN (wst-2) with a network window size W8n-4 via the packet exchangers (1) and (2).

Terminal QD receiving this sends out virtual call setup reception 1aA (wst-2) in sequence (52), and terminal αυ receives setup reception 100 (wSloo) via packet switch +11 (2). Terminal window size W8t- between terminal aυ and terminal 121)
2. A virtual call with network window size WBn=”4 has been set up on logical channel 1.

Thereafter, data packets are exchanged (sequence (53)'), but at this point, as explained in the conventional example above, each packet switch (11, (2) In this case, the maximum buffer usage that can be used is 9 packet switches (1
), +21 both 2(WB2.)+4(W8n)-6
Adashi.

Therefore, at this time, terminal line α4. The amount of empty buffer for (Foundation) is the empty buffer information tape/I/target, Gt! As shown in 9, they are reduced by 6 to become 5 and 9, respectively. Here again, from the terminal aυ to the terminal window size we1. -2 to configure another logical channel 2 request 2cu(wsl, -2)
is issued (sequence (54)), the maximum buffer usage that can be used by this virtual call is 6, which is the same as for logical channel 1. At this time, the packet switch (
Referring to the empty buffer information table in step 1), the value corresponding to the terminal line a4 is 5.

One item is missing. In other words, the sum of the maximum buffer usage amount that can be used by the already configured logical channel 1 virtual call and the currently requested logical channel 2 virtual call exceeds the buffer amount allocated to terminal line a4. Therefore, if you just set up the virtual call for logical channel 2 requested this time, it would be a mistake.
This may result in a lack of access or the use of buffers from other terminal lines. Therefore, in the packet switch (1), the terminal window size WBt, which is a setting specification for virtual calls, is changed from 2 to 1 and the inter-office bucket) OR (WB2.-1
) is sent to the packet switch (2). That is, terminal window size W81; -1, network window size W8n! This is because if the virtual call is +4, the maximum amount of buffer usage in each packet switch 11> (2) is 5, and the empty buffer amount of packet switch (1) can correspond to this amount of usage. In addition.

In this example, the network window size WBn is 4.
It is assumed that it is fixed at . And 2ON (wsl,
-1) terminal c! 1) ;6! Receive and set up reception 2C! A
Sequence (SS) to return (W8 -1)>,
When the terminal aI receives 200 (WBt-1), a virtual call with the terminal size W day t-1 and the network window size W8n-4 is set up on the logical channel 2. At this point, each empty buffer information table −,
The values corresponding to the terminal lines α◆ and t24 of the Corporation are both reduced by 5 to 0 and 9. Thereafter, data packets are exchanged (sequence (56)).

Furthermore, when a request for setting up another logical channel 3 is issued (sequence (57)), the value corresponding to the terminal line I in the empty buffer information table (to) of the packet switch (1) is O, and the empty buffer information table (to) is O. Buffer number (-0) <Minimum terminal window size (-1) + Network window size (-4
), so the virtual call setup is rejected and the disconnection instruction bucket) 3 (:!I is sent to the terminal aυ to abort the setup (sequence (58)').

That is, the network window size WSn is a fixed value of 4, and the terminal window size WS1. Even if the value is set to the minimum value (-1), the empty buffer amount is insufficient, so the setting of a virtual call is rejected.

The above describes the case where the packet switch that receives the virtual call setup request adjusts or rejects the request. Below, the case where the virtual call setup receiving side adjusts or rejects the request is explained based on Figures 2 (a) and (b). Explain. However, at this time, the buffer amount allocated to the terminal line α is 18. The buffer amount allocated to the terminal line HK allocation is 1
1, and these values are the empty buffer information table (61) and (6
This is shown below.

First, in sequences (71) and (72), terminal window size W81. -2,
A virtual call with network window size W80m4 is set up on logical channel 1, and terminal line α4. The values corresponding to Q4 are reduced by 6 to 12 and 5. Then, in sequence (74), the terminal window size W81.
-2 setting request 2OR (WB2;-2) is terminal (El)
packet switch (1), the empty buffer amount (-12) ≧ vrst (-2) + ws, (-4)
Therefore, this setting request is sent directly to the packet switch (
2). In the packet switch (2), the empty buffer amount is 5, which is smaller than WI3t+wsn(-6), so the request terminal window size is changed from 2 to 1, and 1 incoming packet 2ON (W8i -1) is sent to the terminal + 21). Send to. Then, from terminal C◇, setting reception 20A (WBt
-1) is issued and the terminal window size W81. ””
1, a virtual call with network wind size W#nW 4 is set up (sequence (75))
. At this point, each empty buffer amount decreases by KS and becomes T and 0 as shown in the empty buffer information tables (63) and (66). Furthermore, if there is a request 30R (wst-2) for setting the terminal window size WS1;-2 from the terminal αD (sequence (77)).

Packet switch (1) has 7 empty buffers, so it is sent out without any problem, but in packet switch (2), empty buffer amount (-0) < minimum terminal window size (-1) + network window size (-4). , since it is unreasonable to set up the virtual call, in order to reject the setting, it discards the setting request inter-office bucket (CAR) and sends a disconnection request bucket OQ to the packet switch (13) (sequence (78)). Then, a disconnection instruction packet (30) is sent to terminal I, and no virtual call is set up.

Note that in the above embodiment, when there are few empty buffers.

We explained that the network window size W8n is fixed, the terminal window size W8t is changed to reduce the maximum buffer usage, and if the usage falls within the allowable range, a virtual call is set up. Even if the network window size W8n is changed to suppress the maximum amount of buffer usage and a virtual call is set, the same effect as in the above embodiment can be obtained.

In addition, in the above embodiment, each packet switch has its own empty buffer information table.9 For example, in a communication system having a host computer that controls traffic of each packet switch, A similar effect can be achieved by retaining information indicating the buffer status of each packet switch.

〔Effect of the invention〕

As described above, according to the present invention, when a virtual call setup request is made from a terminal, the usage amount of the maximum packet switch internal buffer that can be used in a preset virtual call using the terminal line connected to the terminal and the above settings are determined. If the sum of the maximum buffer usage that can be used by the requested virtual call is greater than the predetermined buffer amount allocated to the terminal line, the sum of the buffer usage is less than or equal to the allocated buffer amount. Since we changed the setting specifications to the following and performed the virtual call setting process or did not set the virtual call, the amount of buffer 7 used in each terminal line exceeds the amount of buffer 7 allocated to each terminal line. This prevents unreasonable virtual calls from being set up.

Even when acknowledgment of data packet delivery is delayed (because a buffer shortage has occurred in an already established virtual call), the buffers that should be used by other terminal lines are used to reduce congestion on other lines. This has the effect of preventing spillovers and increasing the reliability of the communication system.

[Brief explanation of the drawing]

FIG. 1(a) is a sequence diagram of a virtual call setting procedure according to an embodiment of the present invention, FIG. 1(b) is an explanatory diagram of an empty buffer information table showing the status of an empty buffer at each point in the sequence diagram, FIG. 2(a) is a sequence diagram of a virtual call setting procedure according to another embodiment of the present invention, FIG. 2(1)) is an explanatory diagram of an empty buffer information table at each point in this sequence diagram, and FIG. 4 is a block diagram of a communication system having a packet switch, and FIG. 4 is a sequence diagram showing a virtual call setting procedure using the conventional birch-'(/I/-x-call setting control method. In the figure, +1), ( 2), (3) are packet switches, aυ~(IS, (2+)~fi,
011~CI is the terminal, aJ-as, as~w
. (2) to (to) are terminal lines. Note that the same reference numerals in each figure indicate the same or corresponding parts. Figure 1

Claims (1)

[Claims] When a virtual call setup request is issued from a terminal connected to a packet switch via a terminal line, the maximum amount of usage of the packet switch internal buffer that can be used by a virtual call that has already been set up using that terminal line. If the sum of the maximum buffer usage amount that can be used by the virtual call undergoing the configuration request is greater than the predetermined buffer amount allocated to the terminal line in the packet switch, the sum of the buffer usage amount. The virtual call setting control method is characterized in that the virtual call setting process for the virtual call being requested is performed by changing the setting specifications such that the buffer size is less than or equal to the allocated buffer amount, or the setting of the virtual call is rejected.