Network Working Group J. Ash
Request for Comments: 4126 AT&T
Category: Experimental June 2005
Network Working Group J. Ash
Request for Comments: 4126 AT&T
Category: Experimental June 2005
Max Allocation with Reservation Bandwidth Constraints Model for Diffserv-aware MPLS Traffic Engineering & Performance Comparisons
区分服务MPLS流量工程中带预留带宽约束的最大分配模型及性能比较
Status of This Memo
关于下段备忘
This memo defines an Experimental Protocol for the Internet community. It does not specify an Internet standard of any kind. Discussion and suggestions for improvement are requested. Distribution of this memo is unlimited.
这份备忘录为互联网社区定义了一个实验性协议。它没有规定任何类型的互联网标准。要求进行讨论并提出改进建议。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (C) The Internet Society (2005).
版权所有（C）互联网协会（2005年）。
Abstract
摘要
This document complements the Diffserv-aware MPLS Traffic Engineering (DS-TE) requirements document by giving a functional specification for the Maximum Allocation with Reservation (MAR) Bandwidth Constraints Model. Assumptions, applicability, and examples of the operation of the MAR Bandwidth Constraints Model are presented. MAR performance is analyzed relative to the criteria for selecting a Bandwidth Constraints Model, in order to provide guidance to user implementation of the model in their networks.
本文档通过提供带保留的最大分配（MAR）带宽约束模型的功能规范，补充了区分服务感知MPLS流量工程（DS-TE）需求文档。介绍了MAR带宽约束模型的假设、适用性和操作示例。根据选择带宽约束模型的标准分析MAR性能，以便为用户在其网络中实现该模型提供指导。
Table of Contents
目录
1. Introduction ....................................................2
1.1. Specification of Requirements ..............................3
2. Definitions .....................................................3
3. Assumptions & Applicability .....................................5
4. Functional Specification of the MAR Bandwidth
Constraints Model ...............................................6
5. Setting Bandwidth Constraints ...................................7
6. Example of MAR Operation ........................................8
7. Summary .........................................................9
8. Security Considerations ........................................10
9. IANA Considerations ............................................10
10. Acknowledgements ..............................................10
A. MAR Operation & Performance Analysis ..........................11
B. Bandwidth Prediction for Path Computation ......................19
Normative References ..............................................20
Informative References ............................................20
1. Introduction ....................................................2
1.1. Specification of Requirements ..............................3
2. Definitions .....................................................3
3. Assumptions & Applicability .....................................5
4. Functional Specification of the MAR Bandwidth
Constraints Model ...............................................6
5. Setting Bandwidth Constraints ...................................7
6. Example of MAR Operation ........................................8
7. Summary .........................................................9
8. Security Considerations ........................................10
9. IANA Considerations ............................................10
10. Acknowledgements ..............................................10
A. MAR Operation & Performance Analysis ..........................11
B. Bandwidth Prediction for Path Computation ......................19
Normative References ..............................................20
Informative References ............................................20
Diffserv-aware MPLS traffic engineering (DS-TE) requirements and protocol extensions are specified in [DSTE-REQ, DSTE-PROTO]. A requirement for DS-TE implementation is the specification of Bandwidth Constraints Models for use with DS-TE. The Bandwidth Constraints Model provides the 'rules' to support the allocation of bandwidth to individual class types (CTs). CTs are groupings of service classes in the DS-TE model, which are provided separate bandwidth allocations, priorities, and QoS objectives. Several CTs can share a common bandwidth pool on an integrated, multiservice MPLS/Diffserv network.
[DSTE-REQ，DSTE-PROTO]中规定了区分服务感知MPLS流量工程（DS-TE）要求和协议扩展。DS-TE实现的一个要求是规范用于DS-TE的带宽约束模型。带宽约束模型提供了支持将带宽分配给单个类类型（CT）的“规则”。CT是DS-TE模型中服务类的分组，提供单独的带宽分配、优先级和QoS目标。多个CT可以在集成的多服务MPLS/Diffserv网络上共享一个公共带宽池。
This document is intended to complement the DS-TE requirements document [DSTE-REQ] by giving a functional specification for the Maximum Allocation with Reservation (MAR) Bandwidth Constraints Model. Examples of the operation of the MAR Bandwidth Constraints Model are presented. MAR performance is analyzed relative to the criteria for selecting a Bandwidth Constraints Model, in order to provide guidance to user implementation of the model in their networks.
本文件旨在通过提供带保留的最大分配（MAR）带宽约束模型的功能规范来补充DS-TE需求文件[DSTE-REQ]。给出了MAR带宽约束模型的操作示例。根据选择带宽约束模型的标准分析MAR性能，以便为用户在其网络中实现该模型提供指导。
Two other Bandwidth Constraints Models are being specified for use in DS-TE:
DS-TE中使用的另外两个带宽约束模型正在指定中：
1. Maximum Allocation Model (MAM) [MAM] - the maximum allowable bandwidth usage of each CT is explicitly specified.
1. 最大分配模型（MAM）[MAM]-明确规定了每个CT的最大允许带宽使用。
2. Russian Doll Model (RDM) [RDM] - the maximum allowable bandwidth usage is done cumulatively by grouping successive CTs according to priority classes.
2. 俄罗斯玩偶模型（RDM）[RDM]-最大允许带宽使用量是通过根据优先级等级对连续CT进行分组累积完成的。
MAR is similar to MAM in that a maximum bandwidth allocation is given to each CT. However, through the use of bandwidth reservation and protection mechanisms, CTs are allowed to exceed their bandwidth allocations under conditions of no congestion but revert to their allocated bandwidths when overload and congestion occurs.
MAR类似于MAM，因为每个CT都有一个最大带宽分配。然而，通过使用带宽保留和保护机制，允许CT在无拥塞的情况下超过其带宽分配，但在发生过载和拥塞时恢复其分配的带宽。
All Bandwidth Constraints Models should meet these objectives:
所有带宽限制模型应满足以下目标：
1. applies equally when preemption is either enabled or disabled (when preemption is disabled, the model still works 'reasonably' well),
1. 在启用或禁用抢占时同样适用（禁用抢占时，模型仍然“合理”运行良好），
2. bandwidth efficiency, i.e., good bandwidth sharing among CTs under both normal and overload conditions,
2. 带宽效率，即正常和过载条件下CT之间的良好带宽共享，
3. bandwidth isolation, i.e., a CT cannot hog the bandwidth of another CT under overload conditions,
3. 带宽隔离，即一台CT在过载条件下不能占用另一台CT的带宽，
4. protection against QoS degradation, at least of the high-priority CTs (e.g., high-priority voice, high-priority data, etc.), and
4. 针对QoS降级的保护，至少针对高优先级CT（例如，高优先级语音、高优先级数据等），以及
5. reasonably simple, i.e., does not require additional IGP extensions and minimizes signaling load processing requirements.
5. 相当简单，即不需要额外的IGP扩展，并将信令负载处理要求降至最低。
In Appendix A, modeling analysis is presented that shows the MAR Model meets all of these objectives and provides good network performance, relative to MAM and full-sharing models, under normal and abnormal operating conditions. It is demonstrated that MAR simultaneously achieves bandwidth efficiency, bandwidth isolation, and protection against QoS degradation without preemption.
附录A中的建模分析表明，MAR模型满足所有这些目标，并且在正常和异常运行条件下，相对于MAM和完全共享模型，提供了良好的网络性能。结果表明，MAR在不抢占的情况下同时实现了带宽效率、带宽隔离和防止QoS下降。
In Section 3 we give the assumptions and applicability; in Section 4 a functional specification of the MAR Bandwidth Constraints Model; and in Section 5 we give examples of its operation. In Appendix A, MAR performance is analyzed relative to the criteria for selecting a Bandwidth Constraints Model, in order to provide guidance to user implementation of the model in their networks. In Appendix B, bandwidth prediction for path computation is discussed.
在第3节中，我们给出了假设和适用性；在第4节中，MAR带宽约束模型的功能规范；在第5节中，我们给出了它的操作示例。在附录A中，根据选择带宽约束模型的标准分析了MAR性能，以便为用户在其网络中实施该模型提供指导。在附录B中，讨论了用于路径计算的带宽预测。
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
本文件中的关键词“必须”、“不得”、“必需”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照[RFC2119]中所述进行解释。
For readability a number of definitions from [DSTE-REQ, DSTE-PROTO] are repeated here:
为便于阅读，此处重复[DSTE-REQ，DSTE-PROTO]中的许多定义：
Traffic Trunk: an aggregation of traffic flows of the same class (i.e., treated equivalently from the DS-TE perspective), which is placed inside a Label Switched Path (LSP).
交通干线：位于标签交换路径（LSP）内的同一类交通流的集合（即，从DS-TE角度等效处理）。
Class-Type (CT): the set of Traffic Trunks crossing a link that is governed by a specific set of bandwidth constraints. CT is used for the purposes of link bandwidth allocation, constraint-based routing, and admission control. A given Traffic Trunk belongs to the same CT on all links.
类别类型（CT）：由一组特定的带宽限制控制的穿越链路的一组交通干线。CT用于链路带宽分配、基于约束的路由和准入控制。给定的交通干线在所有链路上属于同一个CT。
Up to 8 CTs (MaxCT = 8) are supported. They are referred to as CTc, 0 <= c <= MaxCT-1 = 7. Each CT is assigned either a Bandwidth Constraint, or a set of Bandwidth Constraints. Up to 8 Bandwidth Constraints (MaxBC = 8) are supported and they are referred to as BCc, 0 <= c <= MaxBC-1 = 7.
最多支持8个电流互感器（最大电流互感器=8）。它们被称为CTc，0<=c<=MaxCT-1=7。每个CT分配一个带宽约束或一组带宽约束。最多支持8个带宽限制（MaxBC=8），它们被称为BCc，0<=c<=MaxBC-1=7。
TE-Class: A pair of: a) a CT, and b) a preemption priority allowed for that CT. This means that an LSP, transporting a Traffic Trunk from that CT, can use that preemption priority as the set-up priority, the holding priority, or both.
TE类：一对：A）CT，和b）该CT允许的抢占优先级。这意味着，从该CT传输业务中继线的LSP可以使用该抢占优先级作为设置优先级、保持优先级或两者。
MAX_RESERVABLE_BWk: maximum reservable bandwidth on link k specifies the maximum bandwidth that may be reserved; this may be greater than the maximum link bandwidth, in which case the link may be oversubscribed [OSPF-TE].
MAX_RESERVABLE_BWk：链路k上的最大可保留带宽指定可以保留的最大带宽；这可能大于最大链路带宽，在这种情况下，链路可能被超额订阅[OSPF-TE]。
BCck: bandwidth constraint for CTc on link k = allocated (minimum guaranteed) bandwidth for CTc on link k (see Section 4).
BCck：链路k上CTc的带宽限制=链路k上CTc的分配（最低保证）带宽（见第4节）。
RBW_THRESk: reservation bandwidth threshold for link k (see Section 4).
RBW_THRESk：链路k的预留带宽阈值（参见第4节）。
RESERVED_BWck: reserved bandwidth-in-progress on CTc on link k (0 <= c <= MaxCT-1), RESERVED_BWck = total amount of the bandwidth reserved by all the established LSPs that belong to CTc.
RESERVED_BWck：链路k（0<=c<=MaxCT-1）上CTc上正在进行的保留带宽，RESERVED_BWck=属于CTc的所有已建立LSP保留的带宽总量。
UNRESERVED_BWk: unreserved link bandwidth on link k specifies the amount of bandwidth not yet reserved for any CT, UNRESERVED_BWk = MAX_RESERVABLE_BWk - sum [RESERVED_BWck (0 <= c <= MaxCT-1)].
UNRESERVED_BWk：链路k上的UNRESERVED link bandwidth指定尚未为任何CT保留的带宽量，UNRESERVED_BWk=MAX_RESERVABLE_BWk-sum[保留的_BWck（0<=c<=MaxCT-1）]。
UNRESERVED_BWck: unreserved link bandwidth on CTc on link k specifies the amount of bandwidth not yet reserved for CTc, UNRESERVED_BWck = UNRESERVED_BWk - delta0/1(CTck) * RBW-THRESk where
UNRESERVED_BWck：链路k上CTc上的UNRESERVED link bandwidth指定尚未为CTc保留的带宽量，UNRESERVED_BWck=UNRESERVED_BWk-delta0/1（CTck）*RBW THRESk，其中
delta0/1(CTck) = 0 if RESERVED_BWck < BCck
delta0/1(CTck) = 1 if RESERVED_BWck >= BCck
delta0/1(CTck) = 0 if RESERVED_BWck < BCck
delta0/1(CTck) = 1 if RESERVED_BWck >= BCck
A number of recovery mechanisms under investigation in the IETF take advantage of the concept of bandwidth sharing across particular sets of LSPs. "Shared Mesh Restoration" in [GMPLS-RECOV] and "Facility-based Computation Model" in [MPLS-BACKUP] are example mechanisms that increase bandwidth efficiency by sharing bandwidth across backup LSPs protecting against independent failures. To ensure that the notion of RESERVED_BWck introduced in [DSTE-REQ] is compatible with such a concept of bandwidth sharing across multiple LSPs, the wording of the definition provided in [DSTE-REQ] is generalized. With this generalization, the definition is compatible with Shared Mesh Restoration defined in [GMPLS-RECOV], so that DS-TE and Shared Mesh Protection can operate simultaneously, under the assumption that Shared Mesh Restoration operates independently within each DS-TE Class-Type and does not operate across Class-Types. For example, backup LSPs protecting primary LSPs of CTc also need to belong to CTc; excess traffic LSPs that share bandwidth with backup LSPs of CTc also need to belong to CTc.
IETF中正在研究的许多恢复机制利用了跨特定LSP组共享带宽的概念。[GMPLS-RECOV]中的“共享网格恢复”和[MPLS-BACKUP]中的“基于设施的计算模型”是通过在备份LSP之间共享带宽以防止独立故障而提高带宽效率的示例机制。为了确保[DSTE-REQ]中引入的保留BWck概念与跨多个LSP共享带宽的概念兼容，对[DSTE-REQ]中提供的定义的措辞进行了概括。通过这种推广，该定义与[GMPLS-RECOV]中定义的共享网格恢复兼容，因此DS-TE和共享网格保护可以同时运行，前提是共享网格恢复在每个DS-TE类类型内独立运行，并且不跨类类型运行。例如，保护CTc主LSP的备份LSP也需要属于CTc；与CTc的备份LSP共享带宽的多余流量LSP也需要属于CTc。
In general, DS-TE is a bandwidth allocation mechanism for different classes of traffic allocated to various CTs (e.g., voice, normal data, best-effort data). Network operation functions such as capacity design, bandwidth allocation, routing design, and network planning are normally based on traffic-measured load and forecast [ASH1].
通常，DS-TE是一种带宽分配机制，用于分配给各种CT的不同类别的流量（例如，语音、正常数据、尽力而为数据）。网络运营功能，如容量设计、带宽分配、路由设计和网络规划，通常基于流量测量负载和预测[ASH1]。
As such, the following assumptions are made according to the operation of MAR:
因此，根据MAR的运作情况，做出以下假设：
1. Connection admission control (CAC) allocates bandwidth for network flows/LSPs according to the traffic load assigned to each CT, based on traffic measurement and forecast.
1. 连接允许控制（CAC）根据分配给每个CT的流量负载，基于流量测量和预测，为网络流/LSP分配带宽。
2. CAC could allocate bandwidth per flow, per LSP, per traffic trunk, or otherwise. That is, no specific assumption is made about a specific CAC method, except that CT bandwidth allocation is related to the measured/forecasted traffic load, as per assumption #1.
2. CAC可以为每个流、每个LSP、每个流量中继或其他方式分配带宽。也就是说，根据假设#1，除了CT带宽分配与测量/预测的流量负载相关外，未对特定的CAC方法作出具体假设。
3. CT bandwidth allocation is adjusted up or down according to measured/forecast traffic load. No specific time period is assumed for this adjustment, it could be short term (seconds, minutes, hours), daily, weekly, monthly, or otherwise.
3. CT带宽分配根据测量/预测的流量负载向上或向下调整。本次调整不设具体时间段，可以是短期（秒、分钟、小时）、每日、每周、每月或其他时间段。
4. Capacity management and CT bandwidth allocation thresholds (e.g., BCc) are designed according to traffic load, and are based on traffic measurement and forecast. Again, no specific time period is assumed for this adjustment, it could be short term (hours), daily, weekly, monthly, or otherwise.
4. 容量管理和CT带宽分配阈值（如BCc）根据流量负载设计，并基于流量测量和预测。同样，本次调整未假设具体时间段，可以是短期（小时）、每日、每周、每月或其他时间段。
5. No assumption is made on the order in which traffic is allocated to various CTs; again traffic allocation is assumed to be based only on traffic load as it is measured and/or forecast.
5. 未对各CT的流量分配顺序进行假设；同样，假设交通分配仅基于测量和/或预测的交通负荷。
6. If link bandwidth is exhausted on a given path for a flow/LSP/traffic trunk, alternate paths may be attempted to satisfy CT bandwidth allocation.
6. 如果流/LSP/业务中继的给定路径上的链路带宽耗尽，则可尝试备用路径以满足CT带宽分配。
Note that the above assumptions are not unique to MAR, but are generic, common assumptions for all BC Models.
请注意，上述假设并非MAR独有，而是所有BC模型的通用通用假设。
A DS-TE Label Switching Router (LSR) that implements MAR MUST support enforcement of bandwidth constraints, in compliance with the specifications in this section.
根据本节中的规范，实现MAR的DS-TE标签交换路由器（LSR）必须支持带宽约束的实施。
In the MAR Bandwidth Constraints Model, the bandwidth allocation control for each CT is based on estimated bandwidth needs, bandwidth use, and status of links. The Label Edge Router (LER) makes needed bandwidth allocation changes, and uses [RSVP-TE], for example, to determine if link bandwidth can be allocated to a CT. Bandwidth allocated to individual CTs is protected as needed, but otherwise it is shared. Under normal, non-congested network conditions, all CTs/services fully share all available bandwidth. When congestion occurs for a particular CTc, bandwidth reservation prohibits traffic from other CTs from seizing the allocated capacity for CTc.
在MAR带宽约束模型中，每个CT的带宽分配控制基于估计的带宽需求、带宽使用和链路状态。标签边缘路由器（LER）进行所需的带宽分配更改，并使用[RSVP-TE]来确定链路带宽是否可以分配给CT。分配给各个CT的带宽会根据需要受到保护，但在其他情况下是共享的。在正常、非拥塞的网络条件下，所有CT/服务完全共享所有可用带宽。当某个特定CTc发生拥塞时，带宽预留禁止来自其他CTc的流量占用分配给CTc的容量。
On a given link k, a small amount of bandwidth RBW_THRESk (the reservation bandwidth threshold for link k) is reserved and governs the admission control on link k. Also associated with each CTc on link k are the allocated bandwidth constraints BCck to govern bandwidth allocation and protection. The reservation bandwidth on a link (RBW_THRESk) can be accessed when a given CTc has bandwidth-in-use (RESERVED_BWck) below its allocated bandwidth constraint (BCck). However, if RESERVED_BWck exceeds its allocated bandwidth constraint (BCck), then the reservation bandwidth (RBW_THRESk) cannot be accessed. In this way, bandwidth can be fully shared among CTs if available, but is otherwise protected by bandwidth reservation methods.
在给定链路k上，保留少量带宽RBW_THRESk（链路k的保留带宽阈值），并控制链路k上的接纳控制。链路k上的每个CTc还与分配的带宽约束BCck相关，以控制带宽分配和保护。当给定CTc的使用带宽（保留带宽）低于其分配带宽约束（BCck）时，可以访问链路上的保留带宽（RBW_THRESk）。但是，如果保留带宽超过其分配带宽限制（BCck），则无法访问保留带宽（RBW\U THRESk）。通过这种方式，带宽可以在CT之间完全共享（如果可用），但通过带宽保留方法进行保护。
Bandwidth can be accessed for a bandwidth request = DBW for CTc on a given link k based on the following rules:
根据以下规则，可以访问给定链路k上CTc的带宽请求=DBW的带宽：
Table 1: Rules for Admitting LSP Bandwidth Request = DBW on Link k
表1：允许链路k上LSP带宽请求=DBW的规则
For LSP on a high priority or normal priority CTc:
对于高优先级或正常优先级CTc上的LSP：
If RESERVED_BWck <= BCck: admit if DBW <= UNRESERVED_BWk
If RESERVED_BWck > BCck: admit if DBW <= UNRESERVED_BWk - RBW_THRESk;
If RESERVED_BWck <= BCck: admit if DBW <= UNRESERVED_BWk
If RESERVED_BWck > BCck: admit if DBW <= UNRESERVED_BWk - RBW_THRESk;
or, equivalently:
或者，相当于：
If DBW <= UNRESERVED_BWck, admit the LSP.
如果DBW<=无保留检查，则接受LSP。
For LSP on a best-effort priority CTc: allocated bandwidth BCck = 0; Diffserv queuing admits BE packets only if there is available link bandwidth.
对于最大努力优先级CTc上的LSP：分配的带宽BCck=0；只有当存在可用链路带宽时，Diffserv队列才允许数据包。
The normal semantics of setup and holding priority are applied in the MAR Bandwidth Constraints Model, and cross-CT preemption is permitted when preemption is enabled.
MAR带宽约束模型中应用了设置和保持优先级的正常语义，启用抢占时允许交叉CT抢占。
The bandwidth allocation rules defined in Table 1 are illustrated with an example in Section 6 and simulation analysis in Appendix A.
表1中定义的带宽分配规则以第6节中的示例和附录A中的模拟分析为例进行了说明。
For a normal priority CTc, the bandwidth constraints BCck on link k are set by allocating the maximum reservable bandwidth (MAX_RESERVABLE_BWk) in proportion to the forecast or measured traffic load bandwidth (TRAF_LOAD_BWck) for CTc on link k. That is:
对于正常优先级的CTc，链路k上的带宽约束BCck是通过按照链路k上CTc的预测或测量的业务负载带宽（TRAF_load_BWck）的比例分配最大可保留带宽（MAX_reservable_BWk）来设置的。即:
PROPORTIONAL_BWck = TRAF_LOAD_BWck/[sum {TRAF_LOAD_BWck, c=0, MaxCT-1}]
X MAX_RESERVABLE_BWk
PROPORTIONAL_BWck = TRAF_LOAD_BWck/[sum {TRAF_LOAD_BWck, c=0, MaxCT-1}]
X MAX_RESERVABLE_BWk
For normal priority CTc: BCck = PROPORTIONAL_BWck
对于正常优先级CTc:BCck=比例
For a high priority CT, the bandwidth constraint BCck is set to a multiple of the proportional bandwidth. That is:
对于高优先级CT，带宽约束BCck设置为比例带宽的倍数。即:
For high priority CTc: BCck = FACTOR X PROPORTIONAL_BWck
对于高优先级CTc：BCck=系数X比例
where FACTOR is set to a multiple of the proportional bandwidth (e.g., FACTOR = 2 or 3 is typical). This results in some 'over-allocation' of the maximum reservable bandwidth, and gives priority
其中，系数设置为成比例带宽的倍数（例如，典型情况下，系数=2或3）。这会导致最大可保留带宽的“过度分配”，并给予优先权
to the high priority CTs. Normally the bandwidth allocated to high priority CTs should be a relatively small fraction of the total link bandwidth, with a maximum of 10-15 percent being a reasonable guideline.
高优先级CTs。通常，分配给高优先级CT的带宽应该是总链路带宽的一个相对较小的部分，最大10-15%是一个合理的准则。
As stated in Section 4, the bandwidth allocated to a best-effort priority CTc should be set to zero. That is:
如第4节所述，分配给尽力而为优先级CTc的带宽应设置为零。即:
For best-effort priority CTc: BCck = 0
对于最大努力优先级CTc:BCck=0
In the example, assume there are three class-types: CT0, CT1, CT2. We consider a particular link with
在本例中，假设有三种类类型：CT0、CT1、CT2。我们考虑一个特定的链接。
MAX-RESERVABLE_BW = 100
MAX-RESERVABLE_BW = 100
And with the allocated bandwidth constraints set as follows:
并且分配的带宽限制设置如下：
BC0 = 30 BC1 = 20 BC2 = 20
BC0=30 BC1=20 BC2=20
These bandwidth constraints are based on the normal traffic loads, as discussed in Section 5. With MAR, any of the CTs is allowed to exceed its bandwidth constraint (BCc) as long a there are at least RBW_THRES (reservation bandwidth threshold on the link) units of spare bandwidth remaining. Let's assume
如第5节所述，这些带宽限制基于正常流量负载。对于MAR，只要剩余至少RBW_THRES（链路上的保留带宽阈值）单位的备用带宽，则允许任何CT超过其带宽约束（BCc）。让我们假设
RBW_THRES = 10
RBW_THRES = 10
So under overload, if
所以在过载的情况下，如果
RESERVED_BW0 = 50 RESERVED_BW1 = 30 RESERVED_BW2 = 10
保留的\u BW0=50保留的\u BW1=30保留的\u BW2=10
Therefore, for this loading
因此，对于此加载
UNRESERVED_BW = 100 - 50 - 30 - 10 = 10
UNRESERVED_BW = 100 - 50 - 30 - 10 = 10
CT0 and CT1 can no longer increase their bandwidth on the link, because they are above their BC values and there is only RBW_THRES=10 units of spare bandwidth left on the link. But CT2 can take the additional bandwidth (up to 10 units) if the demand arrives, because it is below its BC value.
CT0和CT1无法再增加链路上的带宽，因为它们高于其BC值，并且链路上只剩下10个单位的空闲带宽。但如果需求到达，CT2可以占用额外的带宽（最多10个单位），因为它低于其BC值。
As also discussed in Section 4, if best effort traffic is present, it can always seize whatever spare bandwidth is available on the link at the moment, but is subject to being lost at the queues in favor of the higher priority traffic.
正如第4节中所讨论的，如果存在尽力而为的流量，它始终可以占用链路上当前可用的任何空闲带宽，但会在队列中丢失，以支持更高优先级的流量。
Let's say an LSP arrives for CT0 needing 5 units of bandwidth (i.e., DBW = 5). We need to decide, based on Table 1, whether to admit this LSP or not. Since for CT0
假设一个LSP到达需要5个带宽单位（即DBW=5）的CT0。我们需要根据表1决定是否接受这一LSP。从CT0开始
RESERVED_BW0 > BC0 (50 > 30), and
DBW > UNRESERVED_BW - RBW_THRES (i.e., 5 > 10 - 10)
RESERVED_BW0 > BC0 (50 > 30), and
DBW > UNRESERVED_BW - RBW_THRES (i.e., 5 > 10 - 10)
Table 1 says the LSP is rejected/blocked.
表1显示LSP被拒绝/阻止。
Now let's say an LSP arrives for CT2 needing 5 units of bandwidth (i.e., DBW = 5). We need to decide based on Table 1 whether to admit this LSP or not. Since for CT2
现在让我们假设一个LSP到达需要5个带宽单位（即DBW=5）的CT2。我们需要根据表1决定是否接受该LSP。二号货柜码头
RESERVED_BW2 < BC2 (10 < 20), and
DBW < UNRESERVED_BW (i.e., 5 < 10)
RESERVED_BW2 < BC2 (10 < 20), and
DBW < UNRESERVED_BW (i.e., 5 < 10)
Table 1 says to admit the LSP.
表1显示接受LSP。
Hence, in the above example, in the current state of the link and in the current CT loading, CT0 and CT1 can no longer increase their bandwidth on the link, because they are above their BCc values and there is only RBW_THRES=10 units of spare bandwidth left on the link. But CT2 can take the additional bandwidth (up to 10 units) if the demand arrives, because it is below its BCc value.
因此，在上述示例中，在链路的当前状态和当前CT加载中，CT0和CT1不能再增加其在链路上的带宽，因为它们高于其BCc值，并且链路上只剩下RBW_THRES=10个单位的备用带宽。但是，如果需求到达，CT2可以占用额外的带宽（最多10个单位），因为它低于其BCc值。
The proposed MAR Bandwidth Constraints Model includes the following:
拟议的MAR带宽约束模型包括以下内容：
1. allocation of bandwidth to individual CTs,
1. 将带宽分配给各个CT，
2. protection of allocated bandwidth by bandwidth reservation methods, as needed, but otherwise full sharing of bandwidth,
2. 根据需要，通过带宽保留方法保护分配的带宽，但在其他方面完全共享带宽，
3. differentiation between high-priority, normal-priority, and best-effort priority services, and
3. 区分高优先级、正常优先级和尽力而为优先级服务，以及
4. provision of admission control to reject connection requests, when needed, in order to meet performance objectives.
4. 提供准入控制，在需要时拒绝连接请求，以达到性能目标。
The modeling results presented in Appendix A show that MAR bandwidth allocation achieves a) greater efficiency in bandwidth sharing while still providing bandwidth isolation and protection against QoS
附录A中给出的建模结果表明，MAR带宽分配在提供带宽隔离和QoS保护的同时，实现了更高的带宽共享效率
degradation, and b) service differentiation for high-priority, normal-priority, and best-effort priority services.
降级和b）高优先级、正常优先级和尽力而为优先级服务的服务差异。
Security considerations related to the use of DS-TE are discussed in [DSTE-PROTO]. They apply independently of the Bandwidth Constraints Model, including the MAR specified in this document.
[DSTE-PROTO]中讨论了与使用DS-TE相关的安全注意事项。它们独立于带宽约束模型应用，包括本文档中指定的MAR。
[DSTE-PROTO] defines a new name space for "Bandwidth Constraints Model Id". The guidelines for allocation of values in that name space are detailed in Section 13.1 of [DSTE-PROTO]. In accordance with these guidelines, the IANA has assigned a Bandwidth Constraints Model Id for MAR from the range 0-239 (which is to be managed as per the "Specification Required" policy defined in [IANA-CONS]).
[DSTE-PROTO]为“带宽约束模型Id”定义了一个新的名称空间。[DSTE-PROTO]第13.1节详细介绍了该名称空间中的值分配指南。根据这些指南，IANA为MAR分配了一个范围为0-239的带宽约束模型Id（将根据[IANA-CONS]中定义的“所需规范”策略进行管理）。
Bandwidth Constraints Model Id 2 was allocated by IANA to MAR.
带宽限制模型Id 2由IANA分配给MAR。
DS-TE and Bandwidth Constraints Models have been an active area of discussion in the TEWG. I would like to thank Wai Sum Lai for his support and review of this document. I also appreciate helpful discussions with Francois Le Faucheur.
DS-TE和带宽约束模型一直是TEWG讨论的一个活跃领域。我要感谢魏森礼对这份文件的支持和审阅。我还感谢与弗朗索瓦·勒·福彻进行的有益讨论。
Appendix A. MAR Operation & Performance Analysis
附录A.MAR运行和性能分析
In the MAR Bandwidth Constraints Model, the bandwidth allocation control for each CT is based on estimated bandwidth needs, bandwidth use, and status of links. The LER makes needed bandwidth allocation changes, and uses [RSVP-TE], for example, to determine if link bandwidth can be allocated to a CT. Bandwidth allocated to individual CTs is protected as needed, but otherwise it is shared. Under normal, non-congested network conditions, all CTs/services fully share all available bandwidth. When congestion occurs for a particular CTc, bandwidth reservation acts to prohibit traffic from other CTs from seizing the allocated capacity for CTc. Associated with each CT is the allocated bandwidth constraint (BCc) which governs bandwidth allocation and protection; these parameters are illustrated with examples in this Appendix.
在MAR带宽约束模型中，每个CT的带宽分配控制基于估计的带宽需求、带宽使用和链路状态。LER进行所需的带宽分配更改，并使用[RSVP-TE]，例如，确定链路带宽是否可以分配给CT。分配给各个CT的带宽会根据需要受到保护，但在其他情况下是共享的。在正常、非拥塞的网络条件下，所有CT/服务完全共享所有可用带宽。当某个特定CTc发生拥塞时，带宽预留将禁止来自其他CTc的流量占用分配给CTc的容量。与每个CT相关联的是分配带宽约束（BCc），它控制带宽分配和保护；本附录举例说明了这些参数。
In performing MAR bandwidth allocation for a given flow/LSP, the LER first determines the egress LSR address, service-identity, and CT. The connection request is allocated an equivalent bandwidth to be routed on a particular CT. The LER then accesses the CT priority, QoS/traffic parameters, and routing table between the LER and egress LSR, and sets up the connection request using the MAR bandwidth allocation rules. The LER selects a first-choice path and determines if bandwidth can be allocated on the path based on the MAR bandwidth allocation rules given in Section 4. If the first choice path has insufficient bandwidth, the LER may then try alternate paths, and again applies the MAR bandwidth allocation rules now described.
在对给定流/LSP执行MAR带宽分配时，LER首先确定出口LSR地址、服务标识和CT。为连接请求分配一个等效带宽，以便在特定CT上路由。然后，LER访问LER和出口LSR之间的CT优先级、QoS/流量参数和路由表，并使用MAR带宽分配规则设置连接请求。LER选择第一选择路径，并根据第4节中给出的MAR带宽分配规则确定是否可以在该路径上分配带宽。如果第一选择路径的带宽不足，则LER可以尝试备用路径，并再次应用现在描述的MAR带宽分配规则。
MAR bandwidth allocation is done on a per-CT basis, in which aggregated CT bandwidth is managed to meet the overall bandwidth requirements of CT service needs. Individual flows/LSPs are allocated bandwidth in the corresponding CT according to CT bandwidth availability. A fundamental principle applied in MAR bandwidth allocation methods is the use of bandwidth reservation techniques.
MAR带宽分配是在每个CT的基础上进行的，在这种基础上，对聚合CT带宽进行管理，以满足CT服务需求的总体带宽要求。单个流/LSP根据CT带宽可用性在相应CT中分配带宽。MAR带宽分配方法中应用的一个基本原则是使用带宽预留技术。
Bandwidth reservation gives preference to the preferred traffic by allowing it to seize idle bandwidth on a link more easily than the non-preferred traffic. Burke [BUR] first analyzed bandwidth reservation behavior from the solution of the birth-death equations for the bandwidth reservation model. Burke's model showed the relative lost-traffic level for preferred traffic, which is not subject to bandwidth reservation restrictions, as compared to non-preferred traffic, which is subject to the restrictions. Bandwidth reservation protection is robust to traffic variations and provides
带宽预留通过允许首选流量比非首选流量更容易地占用链路上的空闲带宽，从而优先考虑首选流量。Burke[BUR]首先从带宽保留模型的生灭方程的解分析了带宽保留行为。Burke的模型显示了首选流量（不受带宽保留限制）与非首选流量（受限制）的相对丢失流量水平。带宽保留保护对流量变化具有鲁棒性，并提供
significant dynamic protection of particular streams of traffic. It is widely used in large-scale network applications [ASH1, MUM, AKI, KRU, NAK].
对特定流量的有效动态保护。它广泛应用于大规模网络应用[ASH1、MUM、AKI、KRU、NAK]。
Bandwidth reservation is used in MAR bandwidth allocation to control sharing of link bandwidth across different CTs. On a given link, a small amount of bandwidth (RBW_THRES) is reserved (perhaps 1% of the total link bandwidth), and the reservation bandwidth can be accessed when a given CT has reserved bandwidth-in-progress (RESERVED_BW) below its allocated bandwidth (BC). That is, if the available link bandwidth (unreserved idle link bandwidth UNRESERVED_BW) exceeds RBW_THRES, then any CT is free to access the available bandwidth on the link. However, if UNRESERVED_BW is less than RBW_THRES, then the CT can utilize the available bandwidth only if its current bandwidth usage is below the allocated amount (BC). In this way, bandwidth can be fully shared among CTs if available, but it is protected by bandwidth reservation if below the reservation level.
带宽预留用于MAR带宽分配，以控制不同CT之间的链路带宽共享。在给定链路上，保留少量带宽（RBW_THRES）（可能是总链路带宽的1%），并且当给定CT在其分配带宽（BC）以下保留了正在进行的带宽（保留的_BW）时，可以访问保留带宽。也就是说，如果可用链路带宽（无保留空闲链路带宽无保留带宽）超过RBW_THRES，则任何CT都可以自由访问链路上的可用带宽。然而，如果无保留带宽小于RBW THRES，则CT只有在其当前带宽使用低于分配量（BC）时才能利用可用带宽。通过这种方式，带宽可以在CT之间完全共享（如果可用），但如果低于保留级别，它将受到带宽保留的保护。
Through the bandwidth reservation mechanism, MAR bandwidth allocation also gives preference to high-priority CTs, in comparison to normal-priority and best-effort priority CTs.
通过带宽预留机制，与正常优先级和尽力而为优先级CT相比，MAR带宽分配还优先考虑高优先级CT。
Hence, bandwidth allocated to each CT is protected by bandwidth reservation methods, as needed, but otherwise shared. Each LER monitors CT bandwidth use on each CT, and determines if connection requests can be allocated to the CT bandwidth. For example, for a bandwidth request of DBW on a given flow/LSP, the LER determines the CT priority (high, normal, or best-effort), CT bandwidth-in-use, and CT bandwidth allocation thresholds, and uses these parameters to determine the allowed load state threshold to which capacity can be allocated. In allocating bandwidth DBW to a CT on given LSP (for example, A-B-E), each link in the path is checked for available bandwidth in comparison to the allowed load state. If bandwidth is unavailable on any link in path A-B-E, another LSP could be tried, such as A-C-D-E. Hence, determination of the link load state is necessary for MAR bandwidth allocation, and two link load states are distinguished: available (non-reserved) bandwidth (ABW_STATE), and reserved-bandwidth (RBW_STATE). Management of CT capacity uses the link state and the allowed load state threshold to determine if a bandwidth allocation request can be accepted on a given CT.
因此，根据需要，分配给每个CT的带宽由带宽保留方法保护，但在其他方面是共享的。每个LER监控每个CT上的CT带宽使用情况，并确定是否可以将连接请求分配给CT带宽。例如，对于给定流/LSP上DBW的带宽请求，LER确定CT优先级（高、正常或最大努力）、使用的CT带宽和CT带宽分配阈值，并使用这些参数确定可分配容量的允许负载状态阈值。在将带宽DBW分配给给定LSP（例如，a-B-E）上的CT时，将对照允许的负载状态检查路径中的每个链路的可用带宽。如果路径A-B-E中的任何链路上的带宽不可用，则可以尝试另一个LSP，例如A-C-D-E。因此，MAR带宽分配需要确定链路负载状态，并区分两种链路负载状态：可用（非保留）带宽（ABW_状态）和保留带宽（RBW_状态）。CT容量管理使用链路状态和允许的负载状态阈值来确定给定CT上是否可以接受带宽分配请求。
In this Appendix, modeling analysis is presented in which MAR bandwidth allocation is shown to provide good network performance, relative to full sharing models, under normal and abnormal operating conditions. A large-scale Diffserv-aware MPLS traffic engineering simulation model is used, in which several CTs with different
在本附录中，对模型进行了分析，结果表明，与完全共享模型相比，在正常和异常运行条件下，MAR带宽分配可提供良好的网络性能。采用了一种大规模区分服务感知的MPLS流量工程仿真模型，其中多个CT具有不同的性能
priority classes share the pool of bandwidth on a multiservice, integrated voice/data network. MAR methods have also been analyzed in practice for networks that use time division multiplexing (i.e., TDM-based networks) [ASH1], and in modeling studies for IP-based networks [ASH2, ASH3, E.360].
优先级类在多服务、集成语音/数据网络上共享带宽池。MAR方法也在使用时分复用的网络（即基于TDM的网络）[ASH1]的实践中进行了分析，并在基于IP的网络的建模研究[ASH2、ASH3、e.360]中进行了分析。
All Bandwidth Constraints Models should meet these objectives:
所有带宽限制模型应满足以下目标：
1. applies equally when preemption is either enabled or disabled (when preemption is disabled, the model still works 'reasonably' well),
1. 在启用或禁用抢占时同样适用（禁用抢占时，模型仍然“合理”运行良好），
2. bandwidth efficiency, i.e., good bandwidth sharing among CTs under both normal and overload conditions,
2. 带宽效率，即正常和过载条件下CT之间的良好带宽共享，
3. bandwidth isolation, i.e., a CT cannot hog the bandwidth of another CT under overload conditions,
3. 带宽隔离，即一台CT在过载条件下不能占用另一台CT的带宽，
4. protection against QoS degradation, at least of the high-priority CTs (e.g., high-priority voice, high-priority data, etc.), and
4. 针对QoS降级的保护，至少针对高优先级CT（例如，高优先级语音、高优先级数据等），以及
5. reasonably simple, i.e., does not require additional IGP extensions and minimizes signaling load processing requirements.
5. 相当简单，即不需要额外的IGP扩展，并将信令负载处理要求降至最低。
The use of any given Bandwidth Constraints Model has significant impacts on the performance of a network, as explained later. Therefore, the criteria used to select a model need to enable us to evaluate how a particular model delivers its performance, relative to other models. Lai [LAI, DSTE-PERF] has analyzed the MAM and RDM Models and provided valuable insights into the relative performance of these models under various network conditions.
如下文所述，任何给定带宽约束模型的使用都会对网络的性能产生重大影响。因此，用于选择模型的标准需要使我们能够评估特定模型相对于其他模型如何提供其性能。Lai[Lai，DSTE-PERF]分析了MAM和RDM模型，并对这些模型在各种网络条件下的相对性能提供了有价值的见解。
In environments where preemption is not used, MAM is attractive because a) it is good at achieving isolation, and b) it achieves reasonable bandwidth efficiency with some QoS degradation of lower classes. When preemption is used, RDM is attractive because it can achieve bandwidth efficiency under normal load. However, RDM cannot provide service isolation under high load or when preemption is not used.
在不使用抢占的环境中，MAM很有吸引力，因为a）它擅长实现隔离，b）它在较低级别的QoS降低的情况下实现了合理的带宽效率。当使用抢占时，RDM很有吸引力，因为它可以在正常负载下实现带宽效率。然而，在高负载或未使用抢占时，RDM无法提供服务隔离。
Our performance analysis of MAR bandwidth allocation methods is based on a full-scale, 135-node simulation model of a national network, combined with a multiservice traffic demand model to study various scenarios and tradeoffs [ASH3, E.360]. Three levels of traffic priority -- high, normal, and best effort -- are given across 5 CTs: normal priority voice, high priority voice, normal priority data, high priority data, and best effort data.
我们对MAR带宽分配方法的性能分析基于国家网络的全尺寸135节点仿真模型，并结合多服务流量需求模型来研究各种场景和权衡[ASH3，E.360]。在5个CT中给出了三个级别的流量优先级——高、正常和尽力而为：正常优先级语音、高优先级语音、正常优先级数据、高优先级数据和尽力而为数据。
The performance analyses for overloads and failures include a) the MAR Bandwidth Constraints Model, as specified in Section 4, b) the MAM Bandwidth Constraints Model, and c) the No-DSTE Bandwidth Constraints Model.
过载和故障的性能分析包括a）第4节规定的MAR带宽约束模型、b）MAM带宽约束模型和c）无DSTE带宽约束模型。
The allocated bandwidth constraints for MAR are described in Section 5 as:
MAR的分配带宽限制在第5节中描述为：
Normal priority CTs: BCck = PROPORTIONAL_BWk,
High priority CTs: BCck = FACTOR X PROPORTIONAL_BWk
Best-effort priority CTs: BCck = 0
Normal priority CTs: BCck = PROPORTIONAL_BWk,
High priority CTs: BCck = FACTOR X PROPORTIONAL_BWk
Best-effort priority CTs: BCck = 0
In the MAM Bandwidth Constraints Model, the bandwidth constraints for each CT are set to a multiple of the proportional bandwidth allocation:
在MAM带宽约束模型中，每个CT的带宽约束设置为比例带宽分配的倍数：
Normal priority CTs: BCck = FACTOR1 X PROPORTIONAL_BWk,
High priority CTs: BCck = FACTOR2 X PROPORTIONAL_BWk
Best-effort priority CTs: BCck = 0
Normal priority CTs: BCck = FACTOR1 X PROPORTIONAL_BWk,
High priority CTs: BCck = FACTOR2 X PROPORTIONAL_BWk
Best-effort priority CTs: BCck = 0
Simulations show that for MAM, the sum (BCc) should exceed MAX_RESERVABLE_BWk for better efficiency, as follows:
模拟表明，对于MAM，总和（BCc）应超过最大可保留BWk，以获得更好的效率，如下所示：
1. The normal priority CTs and the BCc values need to be over-allocated to get reasonable performance. It was found that over-allocating by 100% (i.e., setting FACTOR1 = 2), gave reasonable performance.
1. 正常优先级CT和BCc值需要过度分配，以获得合理的性能。结果发现，100%的超额分配（即设置系数1=2）可以提供合理的性能。
2. The high priority CTs can be over-allocated by a larger multiple FACTOR2 in MAM and this gives better performance.
2. 在MAM中，高优先级CT可以通过更大的倍数2进行过度分配，从而提供更好的性能。
The rather large amount of over-allocation improves efficiency, but somewhat defeats the 'bandwidth protection/isolation' needed with a BC Model, because one CT can now invade the bandwidth allocated to another CT. Each CT is restricted to its allocated bandwidth constraint BCck, which is the maximum level of bandwidth allocated to each CT on each link, as in normal operation of MAM.
大量的过度分配提高了效率，但在某种程度上破坏了BC模型所需的“带宽保护/隔离”，因为一个CT现在可以侵入分配给另一个CT的带宽。每个CT被限制为其分配的带宽约束BCck，这是分配给每个链路上每个CT的最大带宽级别，与MAM的正常操作一样。
In the No-DSTE Bandwidth Constraints Model, no reservation or protection of CT bandwidth is applied, and bandwidth allocation requests are admitted if bandwidth is available. Furthermore, no queuing priority is applied to any of the CTs in the No-DSTE Bandwidth Constraints Model.
在无DSTE带宽约束模型中，不应用CT带宽的保留或保护，如果带宽可用，则允许带宽分配请求。此外，在无DSTE带宽约束模型中，不对任何CT应用排队优先级。
Table 2 gives performance results for a six-times overload on a single network node at Oakbrook, Illinois. The numbers given in the table are the total network percent lost (i.e., blocked) or delayed
表2给出了伊利诺伊州Oakbrook单个网络节点六倍过载的性能结果。表中给出的数字是网络丢失（即阻塞）或延迟的总百分比
traffic. Note that in the focused overload scenario studied here, the percentage of lost/delayed traffic on the Oakbrook node is much higher than the network-wide average values given.
交通请注意，在本文研究的重点过载场景中，Oakbrook节点上的丢失/延迟流量百分比远远高于给定的网络范围平均值。
Table 2 Performance Comparison for MAR, MAM, & No-DSTE Bandwidth Constraints (BC) Models 6X Focused Overload on Oakbrook (Total Network % Lost/Delayed Traffic)
表2：Oakbrook上的MAR、MAM和No DSTE带宽约束（BC）型号6X的性能比较（总网络丢失/延迟流量百分比）
Class Type MAR BC MAM BC No-DSTE BC Model Model Model NORMAL PRIORITY VOICE 0.00 1.97 10.30 HIGH PRIORITY VOICE 0.00 0.00 7.05 NORMAL PRIORITY DATA 0.00 6.63 13.30 HIGH PRIORITY DATA 0.00 0.00 7.05 BEST EFFORT PRIORITY DATA 12.33 11.92 9.65
类别类型MAR BC MAM BC No DSTE BC型号型号正常优先级语音0.00 1.97 10.30高优先级语音0.00 0.00 7.05正常优先级数据0.00 6.63 13.30高优先级数据0.00 0.00 7.05尽力而为优先级数据12.33 11.92 9.65
Clearly the performance is better with MAR bandwidth allocation, and the results show that performance improves when bandwidth reservation is used. The reason for the poor performance of the No-DSTE Model, without bandwidth reservation, is due to the lack of protection of allocated bandwidth. If we add the bandwidth reservation mechanism, then performance of the network is greatly improved.
显然，MAR带宽分配的性能更好，并且结果表明，当使用带宽预留时，性能会提高。没有带宽预留的无DSTE模型性能差的原因是由于缺少对分配带宽的保护。如果我们加入带宽预留机制，那么网络的性能将大大提高。
The simulations showed that the performance of MAM is quite sensitive to the over-allocation factors discussed above. For example, if the BCc values are proportionally allocated with FACTOR1 = 1, then the results are much worse, as shown in Table 3:
仿真结果表明，MAM的性能对上述过度分配因素非常敏感。例如，如果BCc值按比例分配系数1=1，则结果会更糟，如表3所示：
Table 3 Performance Comparison for MAM Bandwidth Constraints Model with Different Over-allocation Factors 6X Focused Overload on Oakbrook (Total Network % Lost/Delayed Traffic)
表3不同超分配系数的MAM带宽约束模型性能比较Oakbrook上的6X集中过载（总网络丢失/延迟流量百分比）
Class Type (FACTOR1 = 1) (FACTOR1 = 2) NORMAL PRIORITY VOICE 31.69 1.97 HIGH PRIORITY VOICE 0.00 0.00 NORMAL PRIORITY DATA 31.22 6.63 HIGH PRIORITY DATA 0.00 0.00 BEST EFFORT PRIORITY DATA 8.76 11.92
类别类型（FACTOR1=1）（FACTOR1=2）正常优先级语音31.69 1.97高优先级语音0.00 0.00正常优先级数据31.22 6.63高优先级数据0.00 0.00尽力而为优先级数据8.76 11.92
Table 4 illustrates the performance of the MAR, MAM, and No-DSTE Bandwidth Constraints Models for a high-day network load pattern with a 50% general overload. The numbers given in the table are the total network percent lost (i.e., blocked) or delayed traffic.
表4说明了MAR、MAM和无DSTE带宽约束模型在一般过载为50%的高日网络负载模式下的性能。表中给出的数字是网络丢失（即阻塞）或延迟流量的总百分比。
Table 4 Performance Comparison for MAR, MAM, & No-DSTE Bandwidth Constraints (BC) Models 50% General Overload (Total Network % Lost/Delayed Traffic)
表4 MAR、MAM和无DSTE带宽约束（BC）模型50%一般过载（总网络丢失/延迟流量百分比）的性能比较
Class Type MAR BC MAM BC No-DSTE BC Model Model Model NORMAL PRIORITY VOICE 0.02 0.13 7.98 HIGH PRIORITY VOICE 0.00 0.00 8.94 NORMAL PRIORITY DATA 0.00 0.26 6.93 HIGH PRIORITY DATA 0.00 0.00 8.94 BEST EFFORT PRIORITY DATA 10.41 10.39 8.40
类别类型MAR BC MAM BC No DSTE BC型号型号型号正常优先级语音0.02 0.13 7.98高优先级语音0.00 0.00 8.94正常优先级数据0.00 0.26 6.93高优先级数据0.00 0.00 8.94尽力而为优先级数据10.41 10.39 8.40
Again, we can see the performance is always better when MAR bandwidth allocation and reservation is used.
同样，我们可以看到，当使用MAR带宽分配和预留时，性能总是更好。
Table 5 illustrates the performance of the MAR, MAM, and No-DSTE Bandwidth Constraints Models for a single link failure scenario (3 OC-48). The numbers given in the table are the total network percent lost (blocked) or delayed traffic.
表5说明了单链路故障场景（3 OC-48）下MAR、MAM和无DSTE带宽约束模型的性能。表中给出的数字是网络丢失（阻塞）或延迟流量的总百分比。
Table 5 Performance Comparison for MAR, MAM, & No-DSTE Bandwidth Constraints (BC) Models Single Link Failure (2 OC-48) (Total Network % Lost/Delayed Traffic)
表5 MAR、MAM和无DSTE带宽约束（BC）模型单链路故障（2 OC-48）的性能比较（总网络丢失/延迟流量百分比）
Class Type MAR BC MAM BC No-DSTE BC Model Model Model NORMAL PRIORITY VOICE 0.00 0.62 0.63 HIGH PRIORITY VOICE 0.00 0.31 0.32 NORMAL PRIORITY DATA 0.00 0.48 0.50 HIGH PRIORITY DATA 0.00 0.31 0.32 BEST EFFORT PRIORITY DATA 0.12 0.72 0.63
类别类型MAR BC MAM BC No DSTE BC型号型号正常优先级语音0.00 0.62 0.63高优先级语音0.00 0.31 0.32正常优先级数据0.00 0.48 0.50高优先级数据0.00 0.31 0.32尽力而为优先级数据0.12 0.72 0.63
Again, we can see the performance is always better when MAR bandwidth allocation and reservation is used.
同样，我们可以看到，当使用MAR带宽分配和预留时，性能总是更好。
Table 6 illustrates the performance of the MAR, MAM, and No-DSTE Bandwidth Constraints Models for a multiple link failure scenario (3 links with 3 OC-48, 3 OC-3, 4 OC-3 capacity, respectively). The numbers given in the table are the total network percent lost (blocked) or delayed traffic.
表6说明了多链路故障场景（3条链路分别具有3 OC-48、3 OC-3、4 OC-3容量）下MAR、MAM和无DSTE带宽约束模型的性能。表中给出的数字是网络丢失（阻塞）或延迟流量的总百分比。
Table 6 Performance Comparison for MAR, MAM, & No-DSTE Bandwidth Constraints (BC) Models Multiple Link Failure (3 Links with 2 OC-48, 2 OC-12, 1 OC-12, Respectively) (Total Network % Lost/Delayed Traffic)
表6 MAR、MAM和No DSTE带宽约束（BC）模型多链路故障的性能比较（3个链路分别具有2 OC-48、2 OC-12和1 OC-12）（总网络丢失/延迟流量百分比）
Class Type MAR BC MAM BC No-DSTE BC Model Model Model NORMAL PRIORITY VOICE 0.00 0.91 0.92 HIGH PRIORITY VOICE 0.00 0.44 0.44 NORMAL PRIORITY DATA 0.00 0.70 0.72 HIGH PRIORITY DATA 0.00 0.44 0.44 BEST EFFORT PRIORITY DATA 0.14 1.03 1.04
类别类型MAR BC MAM BC No DSTE BC型号型号正常优先级语音0.00 0.91 0.92高优先级语音0.00 0.44 0.44正常优先级数据0.00 0.70 0.72高优先级数据0.00 0.44 0.44尽力而为优先级数据0.14 1.03 1.04
Again, we can see the performance is always better when MAR bandwidth allocation and reservation is used.
同样，我们可以看到，当使用MAR带宽分配和预留时，性能总是更好。
Lai's results [LAI, DSTE-PERF] show the trade-off between bandwidth sharing and service protection/isolation, using an analytic model of a single link. He shows that RDM has a higher degree of sharing than MAM. Furthermore, for a single link, the overall loss probability is the smallest under full sharing and largest under MAM, with RDM being intermediate. Hence, on a single link, Lai shows that the full sharing model yields the highest link efficiency, while MAM yields the lowest; and that full sharing has the poorest service protection capability.
Lai的结果[Lai，DSTE-PERF]使用单个链路的分析模型显示了带宽共享和服务保护/隔离之间的权衡。他表明RDM比MAM具有更高的共享度。此外，对于单个链路，完全共享情况下的总体丢失概率最小，MAM情况下的总体丢失概率最大，RDM处于中间状态。因此，在单个链路上，Lai表明完全共享模型产生的链路效率最高，而MAM产生的链路效率最低；而完全共享的服务保护能力最差。
The results of the present study show that, when considering a network context in which there are many links and multiple-link routing paths are used, full sharing does not necessarily lead to maximum, network-wide bandwidth efficiency. In fact, the results in Table 4 show that the No-DSTE Model not only degrades total network throughput, but also degrades the performance of every CT that should be protected. Allowing more bandwidth sharing may improve performance up to a point, but it can severely degrade performance if care is not taken to protect allocated bandwidth under congestion.
本研究的结果表明，当考虑存在多条链路且使用多条链路路由路径的网络环境时，完全共享不一定会导致最大的网络带宽效率。事实上，表4中的结果表明，无DSTE模型不仅降低了总网络吞吐量，而且还降低了应保护的每个CT的性能。允许更多的带宽共享可以在一定程度上提高性能，但如果不注意在拥塞情况下保护分配的带宽，则会严重降低性能。
Both Lai's study and this study show that increasing the degree of bandwidth sharing among the different CTs leads to a tighter coupling between CTs. Under normal loading conditions, there is adequate capacity for each CT, which minimizes the effect of such coupling.
Lai的研究和这项研究都表明，增加不同CT之间的带宽共享程度会导致CT之间更紧密的耦合。在正常负载条件下，每个CT都有足够的容量，从而将此类耦合的影响降至最低。
Under overload conditions, when there is a scarcity of capacity, such coupling can cause severe degradation of service, especially for the lower priority CTs.
在过载条件下，当容量不足时，这种耦合会导致服务严重退化，尤其是对于低优先级CT。
Thus, the objective of maximizing efficient bandwidth usage, as stated in Bandwidth Constraints Model objectives, needs to be exercised with care. Due consideration also needs to be given to achieving bandwidth isolation under overload, in order to minimize the effect of interactions among the different CTs. The proper tradeoff of bandwidth sharing and bandwidth isolation needs to be achieved in the selection of a Bandwidth Constraints Model. Bandwidth reservation supports greater efficiency in bandwidth sharing, while still providing bandwidth isolation and protection against QoS degradation.
因此，带宽约束模型目标中所述的最大化有效带宽利用率的目标需要谨慎执行。还需要适当考虑在过载情况下实现带宽隔离，以最小化不同CT之间交互的影响。在选择带宽约束模型时，需要实现带宽共享和带宽隔离的适当权衡。带宽保留支持更高的带宽共享效率，同时仍然提供带宽隔离和防止QoS下降的保护。
In summary, the proposed MAR Bandwidth Constraints Model includes the following: a) allocation of bandwidth to individual CTs, b) protection of allocated bandwidth by bandwidth reservation methods, as needed, but otherwise full sharing of bandwidth, c) differentiation between high-priority, normal-priority, and best-effort priority services, and d) provision of admission control to reject connection requests, when needed, in order to meet performance objectives.
总之，建议的MAR带宽约束模型包括以下内容：a）将带宽分配给各个CT，b）根据需要通过带宽保留方法保护分配的带宽，但在其他方面完全共享带宽，c）区分高优先级、正常优先级和尽力而为优先级服务，和d）提供准入控制，在需要时拒绝连接请求，以满足性能目标。
In the modeling results, the MAR Bandwidth Constraints Model compares favorably with methods that do not use bandwidth reservation. In particular, some of the conclusions from the modeling are as follows:
在建模结果中，与不使用带宽预留的方法相比，MAR带宽约束模型更具优势。具体而言，建模得出的一些结论如下：
o MAR bandwidth allocation is effective in improving performance over methods that lack bandwidth reservation; this allows more bandwidth sharing under congestion.
o MAR带宽分配可以有效地改善缺少带宽保留的方法的性能；这允许在拥塞情况下共享更多带宽。
o MAR achieves service differentiation for high-priority, normal-priority, and best-effort priority services.
o MAR实现了高优先级、正常优先级和尽力而为优先级服务的服务差异化。
o Bandwidth reservation supports greater efficiency in bandwidth sharing while still providing bandwidth isolation and protection against QoS degradation, and is critical to stable and efficient network performance.
o 带宽保留支持更高的带宽共享效率，同时仍然提供带宽隔离和防止QoS下降的保护，对于稳定高效的网络性能至关重要。
As discussed in [DSTE-PROTO], there are potential advantages for a Head-end when predicting the impact of an LSP on the unreserved bandwidth for computing the path of the LSP. One example would be to perform better load-distribution of multiple LSPs across multiple paths. Another example would be to avoid CAC rejection when the LSP no longer fits on a link after establishment.
如[DSTE-PROTO]中所述，当预测LSP对计算LSP路径的无保留带宽的影响时，前端具有潜在优势。一个示例是跨多条路径更好地分配多个LSP的负载。另一个例子是，当LSP在建立后不再适合链路时，避免CAC拒绝。
Where such predictions are used on Head-ends, the optional Bandwidth Constraints sub-TLV and the optional Maximum Reservable Bandwidth sub-TLV MAY be advertised in the IGP. This can be used by Head-ends to predict how an LSP affects unreserved bandwidth values. Such predictions can be made with MAR by using the unreserved bandwidth values advertised by the IGP, as discussed in Sections 2 and 4:
在头端上使用这种预测的情况下，可选带宽约束子TLV和可选最大可保留带宽子TLV可以在IGP中公布。这可以被前端用来预测LSP如何影响未保留的带宽值。如第2节和第4节所述，可通过使用IGP公布的无保留带宽值，使用MAR进行此类预测：
UNRESERVED_BWck = MAX_RESERVABLE_BWk - UNRESERVED_BWk -
delta0/1(CTck) * RBW-THRESk
UNRESERVED_BWck = MAX_RESERVABLE_BWk - UNRESERVED_BWk -
delta0/1(CTck) * RBW-THRESk
where
哪里
delta0/1(CTck) = 0 if RESERVED_BWck < BCck
delta0/1(CTck) = 1 if RESERVED_BWck >= BCck
delta0/1(CTck) = 0 if RESERVED_BWck < BCck
delta0/1(CTck) = 1 if RESERVED_BWck >= BCck
Furthermore, the following estimate can be made for RBW_THRESk:
此外，可对RBW_THRESk进行以下估算：
RBW_THRESk = RBW_% * MAX_RESERVABLE_BWk,
RBW_THRESk=RBW_%*最大可预订量，
where RBW_% is a locally configured variable, which could take on different values for different link speeds. This information could be used in conjunction with the BC sub-TLV, MAX_RESERVABLE_BW sub-TLV, and UNRESERVED_BW sub-TLV to make predictions of available bandwidth on each link for each CT. Because admission control algorithms are left for vendor differentiation, predictions can only be performed effectively when the Head-end LSR predictions are based on the same (or a very close) admission control algorithm used by other LSRs.
其中，RBW_%是一个本地配置的变量，对于不同的链路速度，它可能具有不同的值。该信息可与BC子TLV、MAX_可保留_BW子TLV和非保留_BW子TLV结合使用，以预测每个CT的每个链路上的可用带宽。由于准入控制算法留给供应商区分，因此只有当前端LSR预测基于其他LSR使用的相同（或非常接近）准入控制算法时，才能有效执行预测。
LSPs may occasionally be rejected when head-ends are establishing LSPs through a common link. As an example, consider some link L, and two head-ends H1 and H2. If only H1 or only H2 is establishing LSPs through L, then the prediction is accurate. But if both H1 and H2 are establishing LSPs through L at the same time, the prediction would not work perfectly. In other words, the CAC will occasionally run into a rejected LSP on a link with such 'race' conditions. Also, as mentioned in Appendix A, such a prediction is optional and outside the scope of the document.
当前端通过公共链路建立LSP时，有时可能会拒绝LSP。作为一个例子，考虑一些链路L和两个头端H1和H2。如果只有H1或H2通过L建立LSP，则预测是准确的。但如果H1和H2同时通过L建立LSP，则预测将无法完美工作。换句话说，CAC偶尔会在具有此类“竞争”条件的链路上遇到被拒绝的LSP。此外，如附录A所述，此类预测是可选的，不在本文件范围内。
Normative References
规范性引用文件
[DSTE-REQ] Le Faucheur, F. and W. Lai, "Requirements for Support of Differentiated Services-aware MPLS Traffic Engineering", RFC 3564, July 2003.
[DSTE-REQ]Le Faucheur，F.和W.Lai，“支持区分服务感知MPLS流量工程的要求”，RFC 3564，2003年7月。
[DSTE-PROTO] Le Faucheur, F., Ed., "Protocol Extensions for Support of Diffserv-aware MPLS Traffic Engineering," RFC 4124, June 2005.
[DSTE-PROTO]Le Faucheur，F.，编辑，“支持区分服务感知MPLS流量工程的协议扩展”，RFC 41242005年6月。
[RFC2119] Bradner, S., "Key words for Use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2119]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[IANA-CONS] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
[IANA-CONS]Narten，T.和H.Alvestrand，“在RFCs中编写IANA注意事项部分的指南”，BCP 26，RFC 2434，1998年10月。
Informative References
资料性引用
[AKI] Akinpelu, J. M., "The Overload Performance of Engineered Networks with Nonhierarchical & Hierarchical Routing," BSTJ, Vol. 63, 1984.
[AKI]Akinpelu，J.M.，“具有非分层和分层路由的工程网络的过载性能”，BSTJ，第63卷，1984年。
[ASH1] Ash, G. R., "Dynamic Routing in Telecommunications Networks," McGraw-Hill, 1998.
[ASH1]Ash，G.R.，“电信网络中的动态路由”，McGraw-Hill，1998年。
[ASH2] Ash, G. R., et al., "Routing Evolution in Multiservice Integrated Voice/Data Networks," Proceeding of ITC-16, Edinburgh, June 1999.
[ASH2]Ash，G.R.等人，“多业务综合语音/数据网络中的路由演进”，ITC-16会议论文集，爱丁堡，1999年6月。
[ASH3] Ash, G. R., "Performance Evaluation of QoS-Routing Methods for IP-Based Multiservice Networks," Computer Communications Magazine, May 2003.
[ASH3]Ash，G.R.，“基于IP的多服务网络QoS路由方法的性能评估”，计算机通信杂志，2003年5月。
[BUR] Burke, P. J., Blocking Probabilities Associated with Directional Reservation, unpublished memorandum, 1961.
[BUR]Burke，P.J.，与定向保留相关的阻塞概率，未出版备忘录，1961年。
[DSTE-PERF] Lai, W., "Bandwidth Constraints Models for Differentiated Services-aware MPLS Traffic Engineering: Performance Evaluation", RFC 4128, June 2005.
[DSTE-PERF]Lai，W.“区分服务感知MPLS流量工程的带宽约束模型：性能评估”，RFC 41282005年6月。
[E.360] ITU-T Recommendations E.360.1 - E.360.7, "QoS Routing & Related Traffic Engineering Methods for Multiservice TDM-, ATM-, & IP-Based Networks".
[E.360]ITU-T建议E.360.1-E.360.7，“基于TDM、ATM和IP的多服务网络的QoS路由和相关流量工程方法”。
[GMPLS-RECOV] Lang, J., et al., "Generalized MPLS Recovery Functional Specification", Work in Progress.
[GMPLS-RECOV]Lang，J.等人，“通用MPLS恢复功能规范”，正在进行的工作。
[KRU] Krupp, R. S., "Stabilization of Alternate Routing Networks", Proceedings of ICC, Philadelphia, 1982.
[KRU]Krupp，R.S.，“备用路由网络的稳定”，国际商会会议录，费城，1982年。
[LAI] Lai, W., "Traffic Engineering for MPLS, Internet Performance and Control of Network Systems III Conference", SPIE Proceedings Vol. 4865, pp. 256-267, Boston, Massachusetts, USA, 29 July-1 August 2002.
[LAI]LAI，W.“MPLS流量工程，网络系统的互联网性能和控制第三届会议”，SPIE会议录第4865卷，第256-267页，美国马萨诸塞州波士顿，2002年7月29日至8月1日。
[MAM] Le Faucheur, F., Lai, W., "Maximum Allocation Bandwidth Constraints Model for Diffserv-aware MPLS Traffic Engineering", RFC 4125, June 2005.
[MAM]Le Faucheur，F.，Lai，W.，“区分服务感知MPLS流量工程的最大分配带宽约束模型”，RFC 41252005年6月。
[MPLS-BACKUP] Vasseur, J. P., et al., "MPLS Traffic Engineering Fast Reroute: Bypass Tunnel Path Computation for Bandwidth Protection", Work in Progress.
[MPLS-BACKUP]Vasseur，J.P.等人，“MPLS流量工程快速重路由：用于带宽保护的旁路隧道路径计算”，正在进行的工作。
[MUM] Mummert, V. S., "Network Management and Its Implementation on the No. 4ESS, International Switching Symposium", Japan, 1976.
[MUM]Mummert，V.S.，“网络管理及其在第4ESS号国际交换研讨会上的实施”，日本，1976年。
[NAK] Nakagome, Y., Mori, H., Flexible Routing in the Global Communication Network, Proceedings of ITC-7, Stockholm, 1973.
[NAK]Nakagome，Y.，Mori，H.，全球通信网络中的灵活路由，ITC-7会议录，斯德哥尔摩，1973年。
[OSPF-TE] Katz, D., Kompella, K. and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, September 2003.
[OSPF-TE]Katz，D.，Kompella，K.和D.Yeung，“OSPF版本2的交通工程（TE）扩展”，RFC 3630，2003年9月。
[RDM] Le Faucheur, F., Ed., "Russian Dolls Bandwidth Constraints Model for Diffserv-aware MPLS Traffic Engineering", RFC 4127, June 2005.
[RDM]Le Faucheur，F.，Ed.“区分服务感知MPLS流量工程的俄罗斯玩偶带宽约束模型”，RFC 4127，2005年6月。
[RSVP-TE] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V. and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, December 2001.
[RSVP-TE]Awduche，D.，Berger，L.，Gan，D.，Li，T.，Srinivasan，V.和G.Swallow，“RSVP-TE：LSP隧道RSVP的扩展”，RFC 3209，2001年12月。
Author's Address
作者地址
Jerry Ash AT&T Room MT D5-2A01 200 Laurel Avenue Middletown, NJ 07748, USA
Jerry Ash AT&T室MT D5-2A01美国新泽西州劳雷尔大道中城200号，邮编07748
Phone: +1 732-420-4578
EMail: gash@att.com
Phone: +1 732-420-4578
EMail: gash@att.com
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