JP2002529005A - Adjustable connection admission control method and apparatus for packet-based switches - Google Patents

Abstract

(57) [Summary] An adjustable connection admission control method and apparatus for a packet-based switch allocates an equivalent bandwidth to a variable rate connection. The equivalent bandwidth of the variable rate connection is increased or decreased using a scaling factor to achieve the allocated bandwidth. The method and apparatus of the present invention provides for a new variable rate connection based on whether the sum of the equivalent bandwidth of the existing variable rate connection and the equivalent bandwidth of the new variable rate connection exceeds the bandwidth available for the variable rate connection. Should be allowed or denied. The connection admission control method and apparatus of the present invention determines whether a new fixed-rate connection and a new unspecified connection should be allowed or rejected. In the case of a fixed-rate connection, the sum of the bandwidth of the existing fixed-rate connection and the new fixed-rate connection is obtained. When the sum of the bandwidth of the existing fixed-rate connection and the new fixed-rate connection exceeds the maximum factor, the bandwidth available for the fixed-rate connection is reduced using the fixed-rate traffic factor. At least a portion of the unspecified connection does not include a sustained cell rate. The sustained cell rate is determined by multiplying the peak cell rate by a sustained cell rate (SCR) factor. The equivalent bandwidth is assigned to the unspecified connection, and the equivalent bandwidth of the unspecified connection is increased or decreased by a scaling factor to realize the assigned bandwidth. The new unspecified connection is allowed or denied based on whether the sum of the bandwidth of the existing unspecified connection and the new unspecified connection exceeds the bandwidth available for the unspecified connection. The scaling factor, traffic factor, maximum factor, fixed speed traffic factor, and SCR factor are adjustable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[Cross Reference to Related Application] This application is based on US Provisional Patent Application No. 60/105, filed Oct. 26, 1998.
Claim priority under 836.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates generally to techniques for controlling the approval of a new connection to a packet-based switch. The present invention particularly relates to an adjustable connection admission control system for packet-based switching.

[0003] 2. Description of Related Art FIG. 1 is a schematic diagram of a conventional packet-based switching system. In FIG. 1, traffic flows from left to right. The interfaces IF1 to IF4 are
It is shown on both the left and right sides of the switching matrix. The left interface shows traffic entering the switching matrix and the right interface shows traffic exiting the switching matrix. The user supplies traffic to the left interface and gets traffic from the right interface (of the same name). The user contracts for the type of connection required. For example, a user contracts for a constant bit rate (CBR) connection, a variable bit rate (VBR) connection, or an unspecified bit rate (UBR) connection. Users may provide traffic information such as sustained cell rates, peak cell rates, and maximum burst sizes. This traffic information provides the switch with information regarding the maximum limit on the user's traffic. However, typically not all users work at their maximum. The traffic rate is considered bursty and somewhat difficult to predict, and the switch can accommodate all traffic that matches the maximum limit defined by the traffic information. This causes a problem in resource allocation. That is, when the traffic rate of each connection is variable, it is difficult to determine the number of connections that can be processed by the exchange.

One way to address the resource allocation problem is for the switch to assign a nominal bit rate to each requested connection. The number of allowable connections is determined from the nominal bit rate using a connection admission control (CAC) system. Connection admission control is performed for each possible point of congestion. In FIG. 1, black circles represent points where congestion can occur, at which point connection admission control is used. Generally, connection admission control is
This is done at each exit point. For example, when all users connected to the interface IF1 transmit at their respective maximum allowable rates, congestion occurs on the link that propagates traffic from the interface IF1 to the switching matrix. Conventional connection admission control is disclosed in U.S. Patent Nos. 5,949,757, 5
No. 5,936,958, 5,751,691, 5,696,764, 5,583,857, 5,555,265 and 5,341,366.

[0005] Connection admission control is based on traffic descriptors such as peak cell rate, sustained cell rate, maximum burst size, cell delay variation tolerance, and the like. The connection admission control mechanism allocates the minimum required switching resources to meet the required connection requirements. If not enough resources are available, connection admission control does not complete the connection. Connection admission control is performed in different ways for different traffic classes (hereinafter also referred to as different connection types). That is, the connections of the fixed bit rate, the variable bit rate, and the unspecified bit rate are processed separately. For non-fixed bit rate services, connection admission control performs statistical multiplexing.
The bandwidth for the variable bit rate connection is allocated by determining an equivalent bandwidth (EBW) based on the peak cell rate, sustained cell rate and maximum burst size. The equivalent bandwidth is determined based on the link between the switching components of interest. For the link, parameters such as link speed, buffer size, buffer read rate, buffer structure (shared or dedicated) are considered.

In order to allocate bandwidth for significantly different types of traffic, connection admission control requires complex mathematical operations on the data. To achieve excellent service, it is desirable to allocate resources conservatively. On the other hand, in order to accept a larger number of users, it is desirable to actively allocate resources. The switching operators include those who desire active resource allocation and those who do not actively allocate resources. However, the connection admission control is predetermined by the switch manufacturer. Due to the complexity associated with connection admission control, it is difficult for individual exchange operators to change connection admission control.

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to enable an individual switch operator to customize a switch to allocate resources proactively or conservatively.

The above and other objects are achieved by providing an adjustable connection admission control method and apparatus for a packet-based switch that allocates an equivalent bandwidth to a variable rate connection. Equivalent bandwidth is allocated to variable rate connections. The equivalent bandwidth of the variable rate connection is increased or decreased using a scaling factor to achieve the allocated bandwidth. The scaling factor is adjustable to change the allocated bandwidth. The method and apparatus of the present invention is based on whether the sum of the bandwidth allocated to an existing variable rate connection and the bandwidth allocated to a new variable rate connection exceeds the bandwidth available on the variable rate connection. Decide whether to allow or reject the variable rate connection. The bandwidth available for a variable rate connection is increased or decreased using a variable rate traffic factor. The variable speed traffic factor is adjustable.

The connection admission control method and apparatus of the present invention determines whether a new fixed-rate connection should be allowed or rejected. Thus, the total bandwidth of the existing fixed-rate connection and the new fixed-rate connection is obtained.
When the sum of the bandwidth of the existing fixed-rate connection and the new fixed-rate connection exceeds the maximum factor, the bandwidth available for the fixed-rate connection is reduced using the fixed-rate traffic factor. The maximum factor and the fixed speed traffic factor are adjustable.

[0010] The connection admission control method and apparatus determine whether to permit or reject a new unspecified connection. At least part of the unspecified connection does not include the sustained cell rate. The sustained cell rate is the peak cell rate SC
It is determined by multiplying by the R coefficient. This SCR coefficient is adjustable. The equivalent bandwidth is assigned to the unspecified connection. The equivalent bandwidth of the unspecified connection is increased or decreased by a scaling factor to achieve the allocated bandwidth. New unassigned connections are allowed or denied based on whether the sum of the bandwidth allocated to the existing unassigned connection and the new unassigned connection exceeds the bandwidth available for the unassigned connection.

[0011] The old scaling factor is maintained for all existing variable rate connections.
The new scaling factor is used to allocate bandwidth for all new variable rate connections. When an existing variable rate connection terminates, the amount of allocated bandwidth released upon termination is determined based on the old scaling factor.
However, the available resources are reallocated based on the new scaling factor.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood by reference to the following preferred embodiments, given by way of example, with reference to the accompanying drawings, in which: In the accompanying drawings, the same reference numerals denote the same components.

FIG. 2 shows a schematic diagram of an adjustable connection admission control device according to the present invention. The device schematically shown in FIG. 2 is used at each point of possible congestion where connection admission control should be performed. That is, the device schematically illustrated in FIG. 2 is used at the exit point indicated by the solid circle in FIG. In FIG. 2, a plurality of connections are multiplexed on one link using a multiplexer 8. In the description of the present invention, the terms "bandwidth" and "bit rate" are used interchangeably, and may both be expressed in units of bits per second.

In the device shown in FIG. 2, different types of connections are treated separately. That is, the total bandwidth available at the egress point, the physical capacity of the link where congestion can occur, is allocated by the bandwidth allocator 10 to different types of connections. New connections of a given type (CBR, UBR
Or VBR) is rejected if the additional connection results in a bandwidth exceeding the bandwidth allocated to the connection type. Bandwidth allocator 10
Can reallocate the available bandwidth at the egress point. For example, if 1 Gbps (1 gigabit per second) of bandwidth is available at the egress point, 300 Mbps (300 megabits per second) can be allocated to the CBR connection, 300 Mbps can be allocated to the UBR connection, and 400 Mbps can be allocated to the VBR connection. Can be assigned to connections. When the amount of CBR traffic is high and the amount of VBR traffic is low, the bandwidth allocator 1
A value of 0 can change the assignment so that 500 Mbps is assigned to the CBR connection and 200 Mbps is assigned to the VBR connection. The assignment allows connection admission control to be performed separately for each connection type. Reassignment minimizes the number of rejected connections.

In FIG. 2, three types of fixed bit rate connections CBR _{1 to} CBR ₃ are received by the first controller 12. The bandwidth allocated for a constant bit rate connection must at least match the nominal bandwidth (bit rate) of the CBR connection. If the number of CBR connections is less than the maximum number m, the first controller 12 signals the CBR traffic controller 14A to operate at 100% efficiency. The value of m is adjustable by the switch operator when the switch is online (uninterrupted connection) or offline. With 100% efficiency, the entire bandwidth allocated to the CBR connection can be used. That is, a new CBR connection is established when the following equation is satisfied.

ΣCBR ≦ TBW _CBR · ρ _CBR (1) where ΣCBR is the sum of the nominal bit rates for all existing CBR connections and new connections. TBW _CBR is the bandwidth allocated to the CBR connection by the bandwidth allocator 10. ρ _CBR is a CBR traffic parameter, which is equal to “1” for 100% efficiency.

When the number of CBR connections exceeds the maximum number m, the first controller 12
Communicates with the CBR traffic controller 14A to reduce the available bandwidth available on the CBR connection. ρ _CBR is set to 1 for maximum efficiency, but is reduced to a number between 0 and 1 when the number of CBR connections exceeds the maximum number m. By reducing the value of ρ _CBR , the switch takes into account a decrease in efficiency.
When the switch is online (the connection is not interrupted) or offline, the value of ρ _CBR can be adjusted by the switch operator.

It is important to note that when the value of ρ _CBR decreases while the switch is online, the available bandwidth available on all CBR connections decreases immediately. This problem translates numerically into an oversubscription problem. However, there is no need to release the connections since the actual number of connections has not changed. The general formula for determining whether a new CBR connection is allowed is:

CBR ₁ / ρ _{CBR, 1} + CBR ₂ / ρ _{CBR, 2} + CBR ₃ / ρ _{CBR, 3} +. . . +. . . CBR _n / ρ _{CBR, n} ≦ TBW _CBR (2)
Where CBR ₁ through CBR _n are the nominal bit rates for n CBR connections and ρ _{CBR, 1} through ρ _{CBR, n} are the C bit rates for n CBR connections.
It is a BR traffic parameter. The above equation (2) shows that the different connections are ρ _CBR
Consider being established using different values for As described above, the value of ρ _{CBR at} the peak efficiency (usually 1) is different from the value of ρ _CBR when the number of CBR connections exceeds the maximum number m. In addition, the switch operator can manipulate the value of ρ _CBR while the switch is online. In general, the switch operator does not change the peak efficiency value of ρ _CBR from the default value of one. However, there is a very high possibility that the exchange operator changes the lowered value of ρ _CBR (greater than the number m of CBR connections) while the exchange is online.

For unspecified bit rate UBR connections, the user may or may not specify a sustained cell rate. If the user does not specify a sustained cell rate, U
The BR connection is sent to the second controller 16. UBR ₁ is sent to the second controller 16. In the second controller 16, the sustained cell rate is calculated based on the peak cell rate. The sustained cell rate is calculated by multiplying the peak cell rate by the SCR parameter α. The SCR parameter α is adjustable by the switch operator, and in one embodiment, the range of α is 0.
The particle size is 001, and 0 ≦ α ≦ 2.

If the UBR connection has an associated sustained cell rate, there is no need to supply the connection to the second controller 16. Referring to FIG. 2, UBR ₂ has a specified sustained cell rate and is not transmitted via the second controller 16. UBR ₁ and UBR ₂ are ultimately transmitted to an equivalent bandwidth (EBW) device 18 where the equivalent bandwidth (EBW) is determined in a manner similar to that described with respect to the related art. That is, the equivalent bandwidth is determined based on parameters such as the sustained cell rate, peak cell rate, maximum burst size, exit location, buffer read rate, and the like. After the equivalent bandwidth is determined, the equivalent bandwidth is increased or decreased in the third controller 20 by a scaling factor β. The scaling factor β indicates that the exchange is online (no interruption of connection)
Or it can be adjusted by the switch operator when it is offline. New UBR connections are allowed if the following formula is satisfied:

EBW ₁ · β ₁ + EBW ₂ · β ₂ + EBW ₃ · β ₃ +. . . + EBW _n · β _n ≦ TBW _UBR (3) In the expression, EBW _{1 to} EBW _n are equivalent bandwidths for n UBR connections. β is a scaling factor. By using β _{1 to} β _n , the equation (3)
) Takes into account that different values for β were used to establish different UBR connections. TBW _UBR is the bandwidth allocated to the UBR connection by the bandwidth allocator 10.

For a VBR connection, the equivalent bandwidth is determined by the EBW device 18 as described for the UBR connection. Next, the equivalent bandwidth is increased or decreased by the scaling factor β and the third controller 20. Subsequently, the VBR connection is transmitted to the VBR traffic controller 14B. The amount of bandwidth available on the VBR connection is reduced from the amount allocated by the bandwidth allocator 10. The amount of available bandwidth is reduced by the VBR traffic parameter ρ _VBR as in the case of CBR connections. A new VBR connection is allowed if the following formula is satisfied:

EBW ₁ · β ₁ / ρ _{VBR, 1} + EBW ₂ · β ₂ / ρ _{VBR, 2} + EBW ₃ · β ₃ / ρ _{VBR, 3}
+. . . + EBW _n · β _n / ρ _{VBR, n} ≦ TBW _VBR (4)
Where EBW ₁ through EBW _n are the equivalent bandwidths for n VBR connections. TBW _VBR is allocated by bandwidth allocator 10 for VBR connections. The above equation takes into account different values of β, and ρ was used for different VBR connections. ρ _VBR is set independently of ρ _CBR . Alternatively, the same value may be used for both ρ _VBR and ρ _{C BR} . For every requested connection, the admission controller 22 establishes or rejects a new connection. For this purpose, the authorization controller 22 sends a CBR for the CBR connection.
It is connected to a traffic controller 14A, a third controller 20 for UBR connection, and a VBR traffic controller 14B for VBR connection.

To add flexibility to the switch, each parameter m, ρ _CBR , α, β and ρ _VBR can be changed separately by the switch operator. When the switch operator wants to be a little more aggressive than the switch manufacturer, the switch operator can use the parameters m, ρ _CBR , α
, Β and ρ _VBR can be increased or decreased. However, the parameters m, ρ _CBR , α,
The effect on the switch by changing one or more of the parameters in β and ρ _VBR is not easily discernable to the switch operator. Switch operators need a trial and error process to fully understand how to achieve their goals. But,
The bandwidth of an existing connection cannot be reallocated until the existing connection is terminated. Termination of the connection is not allowed due to quality of service and reliability issues. Therefore, it is necessary to enable the switching operator to change the connection admission control system while using the switching equipment. Thus, the present invention allows the switch operator to change the parameters m, ρ _CBR , α, β and ρ _VBR only for new connections without disturbing existing connections. When the existing connection terminates, the bandwidth is set to a new parameter m, ρ _CBR ,
_Reallocated based on α, β and ρ _VBR .

When an existing connection terminates, the bandwidth released for the new connection is equal to the bandwidth originally allocated to the terminated connection. Otherwise, the bandwidth may be lost forever or overcrowded. Authorization controller 22 is connected to memory 24 for storing the allocated bandwidth. When a new connection is established, memory 24 stores the nominal bandwidth allocated for that connection. When the connection is terminated, the memory 24 is used to determine the amount of bandwidth released by the termination.

There are two basic cases to consider when changing the connection admission control parameters during the operation of the exchange. First, the allocated bandwidth of existing connections is reduced due to changes. Connection admission control recalculates the bandwidth requirements for the class of service performed on each link (congestion point) in the switch. This process is performed step by step for each link to complete the recalculation. There is no need to reroute existing connections, and there is no strong temporal dependency between the reallocation of the first and last congestion points. Thus, it is possible to continue processing connections even when bandwidth is being reallocated.

Second, changing one or more connection control parameters during the operation of the switch increases the allocated bandwidth. This results in a temporary oversubscription of capacity. For example, consider a case where the scaling parameter β increases from 1 to 2. The bandwidth (TBW · ρ) available for allocation is 622 Mbps and 500
If Mbps is already allocated to an existing VBR connection, the bandwidth allocated for the existing VBR connection is efficiently 10,000 Mbps
Reach Even if the allocated bandwidth exceeds the capacity, the actual traffic does not change. Therefore, there is no need to stop the connection because the connection is accommodated in the 622 Mbps link. However, new connections are allowed over this link so that excess capacity is not utilized. Eventually, the existing connection is terminated and the bandwidth is available. This mechanism provides an excellent way for switch operators to adjust their systems without disrupting service. The same method is used for any connection admission control parameter m, ρ _CBR
, Α, β and ρ function when changing _VBR .

The present invention has been described with the device shown in FIG. However, in practice, the present invention
It is implemented using one or more application specific integrated circuits (ASICs), or more often using software.

Although the present invention has been described in terms of a preferred embodiment, it will be apparent to those skilled in the art that various modifications can be made without departing from the principles of the invention as outlined. For example, CB
The allocation for the R connection is not reduced by the scaling parameter β in the above description, but it is according to the current standard for CBR connections. However, since the bit rate of the CBR connection does not change, the reduced bandwidth may be allocated to a connection similar to the CBR connection. The present invention is not intended to be limited to the preferred embodiment, but is intended to cover such various modifications.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a conventional packet-based switching system.

FIG. 2 is a schematic diagram of an adjustable connection admission control device according to a preferred embodiment of the present invention;

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, TZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP , KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, UZ, VN, YU, ZW (72) Inventor Rip, William United States, Connecticut 06511, New Haven, St. Lonan Street No. 317 (72) Inventor Deval, Geali 27609, Raleigh, North Carolina, United States, St. Albans Drive No. 1000, F-term in Fujitsu Network Communications Inc. 5K030 GA01 HA08 KX11 KX17 LC01 5K034 AA01 BB06 HH21 [Continued from summary] Does not include rates. The sustained cell rate is determined by multiplying the peak cell rate by the sustained cell rate (SCR) factor. Equivalent bandwidth is allocated to unspecified connections, and the equivalent bandwidth of unspecified connections is increased or decreased by a scaling factor to achieve the allocated bandwidth. A new unsolicited connection is allowed or denied based on whether the sum of the bandwidth of the existing unsolicited connection and the new unsolicited connection exceeds the bandwidth available on the unsolicited connection. The scaling factor, traffic factor, maximum factor, fixed speed traffic factor and SCR factor are adjustable.

Claims (12)

[Claims] 1. Assigning an equivalent bandwidth to a variable rate connection, increasing or decreasing the equivalent bandwidth of the variable rate connection by a scaling factor to obtain an assigned bandwidth, and adjusting the scaling factor to change the assigned bandwidth. Should the new variable-rate connection be allowed based on whether the sum of the allocated bandwidth for the existing variable-rate connection and the allocated bandwidth for the new variable-rate connection exceeds the bandwidth available for the variable-rate connection? Or a connection admission control method for a packet-based switching system that determines whether to reject. 2. The connection admission control method according to claim 1, wherein a bandwidth available for said variable rate connection is increased / decreased using a variable rate traffic coefficient, and said variable rate traffic coefficient is adjusted. 3. The scaling factor and the variable speed traffic factor are:
3. The connection admission control method according to claim 2, wherein the adjustment is performed while the packet-based switching system is online. 4. Summing the bandwidths of the existing fixed-rate connection and the new fixed-rate connection, and if the sum of the bandwidths of the existing fixed-rate connection and the new fixed-rate connection exceeds a maximum coefficient, 2. The connection admission control of claim 1, wherein the maximum coefficient is adjusted to determine whether a new fixed rate connection and a new variable rate connection should be allowed or rejected. Method. 5. A new fixed-rate connection should be allowed based on whether the sum of the bandwidth of the existing fixed-rate connection and the new fixed-rate connection exceeds the bandwidth available for the fixed-rate connection, or 5. The connection admission control method according to claim 4, wherein it is determined whether or not the connection should be rejected. 6. The bandwidth available for the fixed-rate connection is reduced by a fixed-rate traffic factor if the sum of the bandwidths of the existing fixed-rate connection and the new fixed-rate connection exceeds a maximum factor. 5. The connection admission control method according to claim 4, wherein said fixed speed traffic coefficient is adjusted. 7. The connection admission control method according to claim 6, wherein the scaling coefficient, the maximum coefficient, and the fixed rate traffic coefficient are adjusted while the packet-based switching system is online. 8. The method of claim 8, wherein at least a portion of the unspecified connections are not provided with a sustained cell rate, the sustained cell rate is determined based on a sustained cell rate factor, the sustained cell rate factor is adjusted, 2. The connection admission control method according to claim 1, wherein whether to permit or reject the connection is determined. 9. The sustained cell rate for the unspecified connection is determined by multiplying a peak cell rate by the sustained cell rate factor.
Described connection approval control method. 10. Assigning an equivalent bandwidth to an unspecified connection, increasing or decreasing the equivalent bandwidth of the unspecified connection by the scaling factor to obtain an assigned bandwidth, Determine whether a new unsolicited connection should be allowed or rejected based on whether the total allocated bandwidth for the unsolicited connection exceeds the bandwidth available on the unsolicited connection Item 8. The connection approval control method according to Item 8. 11. The scaling factor and the sustained cell rate factor are adjusted while the packet-based switching system is online.
The connection approval control method according to claim 10. 12. Save the original scaling factor for all existing variable rate connections, use the new scaling factor to allocate bandwidth for all new variable rate connections, and exit the existing variable rate connection. 2. The method of claim 1, wherein the allocated bandwidth determined by the original scaling factor is released and the released bandwidth is reallocated by the new scaling factor.