Network Working Group J. Ash
Request for Comments: 3214 AT&T
Category: Standards Track Y. Lee
Ceterus Networks
P. Ashwood-Smith
B. Jamoussi
D. Fedyk
D. Skalecki
Nortel Networks
L. Li
SS8 Networks
January 2002
Network Working Group J. Ash
Request for Comments: 3214 AT&T
Category: Standards Track Y. Lee
Ceterus Networks
P. Ashwood-Smith
B. Jamoussi
D. Fedyk
D. Skalecki
Nortel Networks
L. Li
SS8 Networks
January 2002
LSP Modification Using CR-LDP
CR-LDP对LSP的改性
Status of this Memo
本备忘录的状况
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
本文件规定了互联网社区的互联网标准跟踪协议，并要求进行讨论和提出改进建议。有关本协议的标准化状态和状态，请参考当前版本的“互联网官方协议标准”（STD 1）。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (C) The Internet Society (2002). All Rights Reserved.
版权所有（C）互联网协会（2002年）。版权所有。
Abstract
摘要
This document presents an approach to modify the bandwidth and possibly other parameters of an established CR-LSP (Constraint-based Routed Label Switched Paths) using CR-LDP (Constraint-based Routed Label Distribution Protocol) without service interruption. After a CR-LSP is set up, its bandwidth reservation may need to be changed by the network operator, due to the new requirements for the traffic carried on that CR-LSP. The LSP modification feature can be supported by CR-LDP by use of the _modify_value for the _action indicator flag_ in the LSPID TLV. This feature has application in dynamic network resources management where traffic of different priorities and service classes is involved.
本文档介绍了一种使用CR-LDP（基于约束的路由标签分发协议）在不中断服务的情况下修改已建立CR-LSP（基于约束的路由标签交换路径）的带宽和可能的其他参数的方法。在建立CR-LSP之后，由于对该CR-LSP上承载的业务的新要求，网络运营商可能需要更改其带宽预留。CR-LDP可以通过使用LSPID TLV中的_actionindicator flag_的_modify_值来支持LSP修改功能。此功能在涉及不同优先级和服务类别的流量的动态网络资源管理中有应用。
Table of Contents
目录
1. Conventions Used in This Document ............................ 2
2. Introduction ................................................. 2
3. LSP Modification Using CR-LDP ................................ 3
3.1 Basic Procedure for Resource Modification .................. 3
3.2 Rerouting LSPs ............................................. 5
3.3 Priority Handling .......................................... 6
3.4 Modification Failure Case Handling ......................... 6
4. Application of LSP Bandwidth Modification in Dynamic Resource
Management ................................................... 7
5. Acknowledgments .............................................. 8
6. Intellectual Property Considerations ......................... 8
7. Security Considerations ...................................... 8
8. References ................................................... 8
9. Authors' Addresses ........................................... 9
10. Full Copyright Statement ..................................... 11
1. Conventions Used in This Document ............................ 2
2. Introduction ................................................. 2
3. LSP Modification Using CR-LDP ................................ 3
3.1 Basic Procedure for Resource Modification .................. 3
3.2 Rerouting LSPs ............................................. 5
3.3 Priority Handling .......................................... 6
3.4 Modification Failure Case Handling ......................... 6
4. Application of LSP Bandwidth Modification in Dynamic Resource
Management ................................................... 7
5. Acknowledgments .............................................. 8
6. Intellectual Property Considerations ......................... 8
7. Security Considerations ...................................... 8
8. References ................................................... 8
9. Authors' Addresses ........................................... 9
10. Full Copyright Statement ..................................... 11
L: LSP (Label Switched Path) L-id: LSPID (LSP Identifier) T: Traffic Parameters R: LSR (Label Switching Router) FEC: Forwarding Equivalence Class NHLFE: Next Hop Label Forwarding Entry FTN: FEC To NHLFE TLV: Type Length Value
L:LSP（标签交换路径）L-id:LSPID（LSP标识符）T:流量参数R:LSR（标签交换路由器）FEC:转发等价类NHLFE:下一跳标签转发条目FTN:FEC到NHLFE TLV:类型长度值
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 RFC 2119 [4].
本文件中的关键词“必须”、“不得”、“要求”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照RFC 2119[4]中所述进行解释。
Consider an LSP L1 that has been established with its set of traffic parameters T0. A certain amount of bandwidth is reserved along the path of L1. Consider then that some changes are required on L1. For example, the bandwidth of L1 needs to be increased to accommodate the increased traffic on L1. Or the SLA associated with L1 needs to be modified because a different service class is desired. The network operator, in these cases, would like to modify the characteristics of L1, for example, to change its traffic parameter set from T0 to T1, without releasing the LSP L1 to interrupt the service. In some other cases, network operators may want to reroute a CR-LSP to a different path for either improved performance or better network resource utilization. In all these cases, LSP modification is required. In section 3 below, a method to modify an active LSP using CR-LDP is
考虑已经建立了一组流量参数T0的LSP L1。沿L1的路径保留一定数量的带宽。请考虑在L1上需要进行一些更改。例如，需要增加L1的带宽以适应L1上增加的业务量。或者需要修改与L1相关联的SLA，因为需要不同的服务类别。在这些情况下，网络运营商希望修改L1的特性，例如，将其业务参数设置从T0更改为T1，而不释放LSP L1以中断服务。在其他一些情况下，网络运营商可能希望将CR-LSP重新路由到不同的路径，以提高性能或更好地利用网络资源。在所有这些情况下，都需要修改LSP。在下面的第3节中，描述了使用CR-LDP修改有源LSP的方法
presented. The concept of LSPID in CR-LDP is used to achieve the LSP modification, without releasing the LSP and interrupting the service and, without double booking the bandwidth. In Section 4, an example is described to demonstrate an application of the presented method in dynamically managing network bandwidth requirements without interrupting service. In CR-LDP, an action indicator flag of _modify_ is used in order to explicitly specify the behavior, and allow the existing LSPID to support other networking capabilities in the future. Reference [3], RFC XXXX, specifies the action indicator flag of _modify_ for CR-LDP.
提出了。CR-LDP中的LSPID概念用于实现LSP修改，无需释放LSP和中断服务，无需双重预订带宽。在第4节中，描述了一个示例以演示所提出的方法在不中断服务的情况下动态管理网络带宽需求的应用。在CR-LDP中，使用_modify u的动作指示符标志来明确指定行为，并允许现有LSPID将来支持其他联网功能。参考文献[3]，RFC XXXX，规定了CR-LDP的_modify_uu_u的动作指示器标志。
LSP modification can only be allowed when the LSP is already set up and active. That is, modification is not defined nor allowed during the LSP establishment or label release/withdraw phases. Only modification requested by the ingress LSR of the LSP is considered in this document for CR-LSP. The Ingress LSR cannot modify an LSP before a previous modification procedure is completed.
仅当LSP已设置并处于活动状态时，才允许修改LSP。也就是说，在LSP建立或标签发布/撤销阶段，不定义也不允许修改。对于CR-LSP，本文件仅考虑LSP入口LSR要求的修改。在完成之前的修改程序之前，入口LSR无法修改LSP。
Assume that CR-LSP L1 is set up with LSPID L-id1, which is unique in the MPLS network. The ingress LSR R1 of L1 has in its FTN (FEC To NHLFE) table FEC1 -> Label A mapping where A is the outgoing label for LSP L1. To modify the characteristics of L1, R1 sends a Label Request Message. In the message, the TLVs will have the new requested values, and the LSPID TLV is included which indicates the value of L-id1. The Traffic Parameters TLV, the ER-TLV, the Resource Class (color) TLV and the Preemption TLV can have values different from those in the original Label Request Message, which has been used to set up L1 earlier. Thus, L1 can be changed in its bandwidth request (traffic parameter TLV), its traffic service class (traffic parameter TLV), the route it traverses (ER TLV) and its setup and holding (Preemption TLV) priorities. The ingress LSR R1 now still has the entry in its FTN as FEC1 -> Label A. R1 is waiting to establish another entry for FEC1.
假设CR-LSP L1使用LSPID L-id1设置，这在MPLS网络中是唯一的。L1的入口LSR R1在其FTN（FEC到NHLFE）表FEC1->标签中有一个映射，其中A是LSP L1的输出标签。为了修改L1的特性，R1发送标签请求消息。在消息中，TLV将具有新请求的值，并且包含指示L-id1值的LSPID TLV。流量参数TLV、ER-TLV、资源类（颜色）TLV和抢占TLV可以具有不同于原始标签请求消息中的值，原始标签请求消息已用于设置L1。因此，可以改变L1的带宽请求（业务参数TLV）、业务服务类别（业务参数TLV）、所经过的路由（ER-TLV）及其设置和保持（抢占TLV）优先级。入口LSR R1现在在其FTN中仍然有一个条目，即FEC1->标签A。R1正在等待为FEC1建立另一个条目。
When an LSR Ri along the path of L1 receives the Label Request message, its behavior is the same as that of receiving any Label request message. The only extension is that Ri examines the LSPID carried in the Label Request Message, L-id1, and identifies if it already has L-id1. If Ri does not have L-id1, Ri behaves the same as receiving a new Label Request message. If Ri already has L-id1, Ri takes the newly received Traffic Parameter TLV and computes the new bandwidth required and derives the new service class. Compared with the already reserved bandwidth for L-id1, Ri now reserves only the difference of the bandwidth requirements. This prevents Ri from doing
当沿着L1路径的LSR Ri接收标签请求消息时，其行为与接收任何标签请求消息的行为相同。唯一的扩展是Ri检查标签请求消息L-id1中携带的LSPID，并确定它是否已经有L-id1。如果Ri没有L-id1，则Ri的行为与接收新标签请求消息的行为相同。如果Ri已经具有L-id1，则Ri获取新接收的流量参数TLV，并计算所需的新带宽，并导出新的服务类。与L-id1已经保留的带宽相比，Ri现在只保留带宽要求的差异。这就阻止了Ri这样做
bandwidth double booking. If a new service class is requested, Ri also prepares to receive the traffic on L1 in just the same way as handling it for a Label Request Message, perhaps using a different type of queue. Ri assigns a new label for the Label Request Message.
带宽双倍预订。如果请求了一个新的服务类，Ri还准备在L1上接收通信量，方法与处理标签请求消息相同，可能使用不同类型的队列。Ri为标签请求消息分配新标签。
When the Label Mapping message is received, two sets of labels exist for the same LSPID. Then the ingress LSR R1 will have two outgoing labels, A and B, associated with the same FEC, where B is the new outgoing label received for LSP L1. The ingress LSR R1 can now activate the new entry in its FTN, FEC1 - > Label B. This means that R1 swaps traffic on L1 to the new label _B_ (_new_ path) for L1. The packets can now be sent with the new label B, with the new set of traffic parameters if any, on a new path, that is, if a new path is requested in the Label Request Message for the modification. All the other LSRs along the path will start to receive the incoming packets with the new label. For the incoming new label, the LSR has already established its mapping to the new outgoing label. Thus, the packets will be sent out with the new outgoing label. The LSRs do not have to implement new procedures to track the new and old characteristics of the LSP.
收到标签映射消息时，同一LSPID存在两组标签。然后，入口LSR R1将具有与相同FEC相关联的两个出站标签A和B，其中B是为LSP L1接收的新出站标签。入口LSR R1现在可以激活其FTN中的新条目，FEC1->标签B。这意味着R1将L1上的流量交换到L1的新标签B（新路径）。现在，如果在标签请求消息中请求了用于修改的新路径，则可以在新路径上使用新标签B和新的流量参数集（如果有）发送分组。路径上的所有其他LSR将开始接收带有新标签的传入数据包。对于传入的新标签，LSR已经建立了到新传出标签的映射。因此，数据包将与新的传出标签一起发送。LSR无需实施新程序来跟踪LSP的新特性和旧特性。
The ingress LSR R1 then starts to release the original label A for LSP L1. The Label Release Message is sent by R1 towards the down stream LSRs. The Release message carries the LSPID of L-id1 and the Label TLV to indicate which label is to be released. The Release Message is propagated to the egress LSR to release the original labels previously used for L1. Upon receiving the Label Release Message, LSR Ri examines the LSPID, L-id1, and finds out that the L-id1 has still another set of labels (incoming/outgoing) under it. Thus, the old label is released without releasing the resource in use. That is, if the bandwidth has been decreased for L1, the delta bandwidth is released. Otherwise, no bandwidth is released. This modification procedure can not only be applied to modify the traffic parameters and/or service class of an active LSP, but also to reroute an existing LSP (as described in Section 3.2 below), and/or change its setup/holding priority if desired. After the release procedure, the modification of the LSP is completed.
入口LSR R1然后开始释放LSP L1的原始标签A。标签释放消息由R1向下游LSR发送。释放消息携带L-id1的LSPID和标签TLV，以指示要释放的标签。释放消息被传播到出口LSR以释放先前用于L1的原始标签。收到标签释放消息后，LSR Ri检查LSPID L-id1，发现L-id1下还有另一组标签（传入/传出）。因此，释放旧标签时不会释放正在使用的资源。也就是说，如果L1的带宽已减少，则释放增量带宽。否则，不会释放带宽。此修改程序不仅可用于修改活动LSP的流量参数和/或服务等级，还可用于重新路由现有LSP（如下文第3.2节所述），和/或根据需要更改其设置/保持优先级。发布程序后，LSP的修改完成。
The method described above follows the normal behavior of Label Request / Mapping / Notification / Release / Withdraw procedure of a CR-LDP operated LSR with a specific action taken on an LSPID. If a Label Withdraw Message is used to withdraw a label associated with an LSPID, the Label TLV should be included to specify which label to withdraw. Since the LSPID can also be used for other feature support, an action indication flag of _modify_ assigned to the LSPID would explicitly explain the action/semantics that should be associated with the messaging procedure. The details of this flag are addressed in the CR-LDP document, Reference [3].
上述方法遵循CR-LDP操作的LSR的标签请求/映射/通知/释放/撤回过程的正常行为，并对LSPID采取特定动作。如果标签撤销消息用于撤销与LSPID关联的标签，则应包括标签TLV，以指定要撤销的标签。由于LSPID还可用于其他功能支持，因此分配给LSPID的_modify u的动作指示标志将明确解释应与消息传递过程关联的动作/语义。CR-LDP文件（参考文献[3]）中阐述了该标志的详细信息。
LSP modification can also be used to reroute an existing LSP. Only modification requested by the ingress LSR of the LSP is considered in this document for CR-LSP. The Ingress LSR cannot modify an LSP before a previous modification procedure is completed.
LSP修改也可用于重新路由现有LSP。对于CR-LSP，本文件仅考虑LSP入口LSR要求的修改。在完成之前的修改程序之前，入口LSR无法修改LSP。
As in the previous section, consider a CR-LSP L1 with LSPID L-id1. To modify the route of the LSP, the ingress LSR R1 sends a Label Request Message. In the message, the LSPID TLV indicates L-id1 and the Explicit Route TLV is specified with some different hops from the explicit route specified in the original Label Request Message. The action indication flag has the value _modify_.
与前一部分一样，考虑一个带有LSPID L ID1的CR-LSP L1。为了修改LSP的路由，入口LSR R1发送标签请求消息。在消息中，LSPID TLV指示L-id1，显式路由TLV使用与原始标签请求消息中指定的显式路由不同的跳数指定。动作指示标志的值为“修改”。
At this point, the ingress LSR R1 still has an entry in FTN as FEC1 -> Label A. R1 is waiting to establish another entry for FEC1.
此时，入口LSR R1在FTN中仍有一个条目，即FEC1->标签A。R1正在等待为FEC1建立另一个条目。
When an LSR Ri along the path of L1 receives the Label Request message, its behavior is the same as that of receiving a Label Request Message that modifies some other parameters of the LSP. Ri assigns a new label for the Label Request Message and forwards the message along the explicit route. It does not allocate any more resources except as described in section 3.1.
当沿着L1路径的LSR Ri接收到标签请求消息时，其行为与接收修改LSP的一些其他参数的标签请求消息的行为相同。Ri为标签请求消息分配新标签，并沿显式路由转发消息。除第3.1节所述外，它不分配任何其他资源。
At another LSR Rj further along the path, the explicit route diverges from the previous route. Rj acts as Ri, but forwards the Label Request message along the new route. From this point onwards the Label Request Message is treated as setting up a new LSP by each LSR until the paths converge at later LSR Rk. The _modify_ value of the action indication flag is ignored.
在路径的另一个LSR Rj处，显式路由与前一个路由不同。Rj充当Ri，但沿新路由转发标签请求消息。从这一点开始，标签请求消息被视为每个LSR建立一个新的LSP，直到路径在稍后的LSR Rk收敛。忽略动作指示标志的_modify_值。
At Rk and subsequent LSRs, the Label Request Message is handled as at Ri.
在Rk和后续LSR中，标签请求消息的处理方式与在Ri中相同。
On the return path, when the Label Mapping message is received, two sets of labels for the LSPID exist where the new route coincide with the old. Only one set of labels will exist at LSRs where the routes diverge.
在返回路径上，当收到标签映射消息时，存在两组LSPID标签，其中新路由与旧路由重合。在路线分叉的LSR处，仅存在一组标签。
When the Label Mapping message is received at the ingress LSR R1 it has two outgoing labels, A and B, associated with the same FEC, where B is the new outgoing label received for LSP L1. R1 can now activate the new entry in the FTN, FEC1 - > Label B and de-activate the old entry FEC1 - > Label A. This means that R1 swaps traffic on L1 to the new label B. The packets are now sent with the new label B, on the new path.
当在入口LSR R1处接收到标签映射消息时，它具有与同一FEC相关联的两个传出标签A和B，其中B是为LSP L1接收的新传出标签。R1现在可以激活FTN中的新条目，即FEC1->标签B，并取消激活旧条目FEC1->标签A。这意味着R1将L1上的流量交换到新标签B。数据包现在与新标签B一起在新路径上发送。
The ingress LSR R1 then starts to release the original label A for LSP L1. The Label Release Message is sent by R1 towards the down stream LSRs following the original route. The Release message carries the LSPID of L-id1 and the Label TLV to indicate which label is to be released. At each LSR the old label is released - no further action is required to change the path of the data packets which are already following the new route programmed by the Label Mapping message.
入口LSR R1然后开始释放LSP L1的原始标签A。标签释放消息由R1按照原始路由向下游LSR发送。释放消息携带L-id1的LSPID和标签TLV，以指示要释放的标签。在每个LSR处，旧标签被释放-无需采取进一步措施来更改数据包的路径，这些数据包已经遵循标签映射消息编程的新路由。
At some LSRs, where the routes diverged, there is only one label for the LSPID. For example, between Rj and Rk, the Label Release Message will follow the old route. At LSRs between Rj and Rk only the labels from the original route will exist for LSPID L-id1. At these LSRs the LSPID TLV does not need to be examined to release the correct label, but it must still be updated and passed on to the next LSR as the Label Release message is propagated. In this way, at Rk where the routes converge, the downstream LSR will know which label to release and can continue to forward the Label Release Message along the old route.
在某些LSR（路线分叉）处，LSPID只有一个标签。例如，在Rj和Rk之间，标签释放消息将遵循旧路线。在Rj和Rk之间的LSR处，LSPID L-id1仅存在原始路线的标签。在这些LSR中，无需检查LSPID TLV以释放正确的标签，但在传播标签释放消息时，它仍必须更新并传递给下一个LSR。这样，在路由汇聚的Rk处，下游LSR将知道要释放哪个标签，并且可以继续沿着旧路由转发标签释放消息。
When sending a Label Request Message for an active LSP L1 to request changes, the setup priority used in the label Request Message can be different from the one used in the previous Label Request Message, effectively indicating the priority of this _modification_ request. Network operators can use this feature to decide what priority is to be assigned to a modification request, based on their policies/algorithms and other traffic situations in the network. For example, the priority for modification can be determined by the priority of the customer/LSP. If a customer has exceeded the reserved bandwidth of its VPN LSP tunnel by too much, the modification request's priority may be given as a higher value. The Label Request message for the modification of an active LSP can also be sent with a holding priority different from its previous one. This effectively changes the holding priority of the LSP. Upon receiving a Label Request Message that requests a new holding priority, the LSR assigns the new holding priority to the bandwidth. That is, the new holding priority is assigned to both the existing incoming / outgoing labels and the new labels to be established for the LSPID in question. In this way self-bumping is prevented.
当为活动LSP L1发送标签请求消息以请求更改时，标签请求消息中使用的设置优先级可能不同于先前标签请求消息中使用的设置优先级，从而有效地指示此修改请求的优先级。网络运营商可以根据其策略/算法和网络中的其他流量情况，使用此功能来决定为修改请求分配的优先级。例如，修改的优先级可以由客户/LSP的优先级确定。如果客户超出了其VPN LSP隧道的保留带宽太多，修改请求的优先级可能会被赋予更高的值。用于修改活动LSP的标签请求消息也可以以不同于其先前的保持优先级发送。这有效地改变了LSP的保持优先级。在接收到请求新保持优先级的标签请求消息时，LSR将新保持优先级分配给带宽。也就是说，新的保持优先级被分配给现有的传入/传出标签和要为所讨论的LSPID建立的新标签。这样可以防止自碰撞。
A modification attempt may fail due to insufficient resource or other situations. A Notification message is sent back to the ingress LSR R1 to indicate the failure of Label Request Message that intended to modify the LSP. A retry may be attempted if desired by the network
由于资源不足或其他情况，修改尝试可能会失败。通知消息被发送回入口LSR R1，以指示用于修改LSP的标签请求消息的失败。如果网络需要，可以尝试重试
operator. If the LSP on the original path failed when a modification attempt is in progress, the attempt should be aborted by using the Label Abort Request message as specified in the LDP document [5].
操作人员如果在进行修改尝试时原始路径上的LSP失败，则应使用LDP文档[5]中指定的标签中止请求消息中止尝试。
In the event of a modification failure, all modifications to the LSP including the holding priority must be restored to their original values.
在修改失败的情况下，必须将LSP的所有修改（包括保留优先级）恢复到其原始值。
4. Application of LSP Bandwidth Modification in Dynamic Resource Management
4. LSP带宽修改在动态资源管理中的应用
In this section, we gave an example of dynamic network resource management using the LSP bandwidth modification capability. The details of this example can be found in a previous internet-draft [2]. Assume that customers or services are assigned with given CR-LSPs. These customers/services are assigned with one of three priorities: key, normal or best effort. The network operator does not want to bump any LSPs during an LSP setup, so after these CR-LSPs are set up, their holding priorities are all assigned as the highest value.
在本节中，我们给出了一个使用LSP带宽修改功能的动态网络资源管理示例。此示例的详细信息可在以前的互联网草案[2]中找到。假设为客户或服务分配了给定的CR LSP。为这些客户/服务分配三个优先级之一：关键、正常或尽力而为。网络运营商不希望在LSP设置期间碰撞任何LSP，因此在设置这些CR LSP之后，它们的保持优先级都被分配为最高值。
The network operator wants to control the resource on the links of the LSRs, so each LSR keeps the usage status of its links. Based on the usage history, each link is assigned a current threshold priority Pi, which means that the link has no bandwidth available for a Label Request with a setup priority lower than Pi. When an LSP's bandwidth needs to be modified, the operator uses a policy-based algorithm to assign a priority for its modification request, say Mp for LSP L2. The ingress LSR then sends a Label Request message with Setup Priority = Mp. If there is sufficient bandwidth on the link for the modification, and the Setup priority in the Label Request Message is higher in priority (Mp numerically smaller) than the Pi threshold of the link, the Label Request Message will be accepted by the LSR. Otherwise, the Label Request message will be rejected with a Notification message which indicates that there are insufficient resources. It should also be noted that when OSPF (or IS-IS) floods the available-link-bandwidth information, the available bandwidth associated with a priority lower than Pi (numerical value bigger) should be interpreted as _0_.
网络运营商希望控制LSR链路上的资源，因此每个LSR保持其链路的使用状态。根据使用历史，每个链路都分配了当前阈值优先级Pi，这意味着该链路没有带宽可用于设置优先级低于Pi的标签请求。当LSP的带宽需要修改时，运营商使用基于策略的算法为其修改请求分配优先级，例如Mp for LSP L2。然后，入口LSR发送设置优先级为Mp的标签请求消息。如果链路上有足够的带宽用于修改，且标签请求消息中的设置优先级高于链路的Pi阈值（Mp数值小于），则LSR将接受标签请求消息。否则，标签请求消息将被拒绝，并显示一条通知消息，表明资源不足。还应注意，当OSPF（或IS-IS）淹没可用链路带宽信息时，与低于Pi（数值更大）的优先级相关联的可用带宽应解释为0。
This example based on a priority threshold Pi is implementation specific, and illustrates the flexibility of the modification procedure to prioritize and control network resources. The calculation of Mp can be network and service dependent, and is based on the operator's routing policy. For example, the operator may assign a higher priority (lower Mp value) to L2 bandwidth modification if L2 belongs to a customer or service with _Key_ priority. The operator may also collect the actual usage of each LSP
这个基于优先级阈值Pi的示例是特定于实现的，并说明了修改过程的灵活性，以对网络资源进行优先级排序和控制。Mp的计算可以依赖于网络和服务，并且基于运营商的路由策略。例如，如果L2属于具有_Key _优先级的客户或服务，则运营商可以为L2带宽修改分配更高的优先级（较低的Mp值）。操作员还可以收集每个LSP的实际使用情况
and assign a lower priority (higher Mp) to L2 bandwidth-increase modification if, for example, in the past week L2 has exceeded its reserved bandwidth by 2 times on the average. In addition, an operator may try to increase the bandwidth of L2 on its existing path unsuccessfully if there is insufficient bandwidth available on L2. In that case, the operator is willing to increase the bandwidth of another LSP, L3, with the same ingress/egress LSRs as L2, in order to increase the overall ingress/egress bandwidth allocation. However, in this case the L3 bandwidth modification is performed with a lower priority (higher Mp value) since L3 is routed on a secondary path, which results in the higher bandwidth allocation priority being given to the LSPs that are on their primary paths [2].
并为L2带宽增加修改分配较低优先级（较高Mp），例如，在过去一周内，L2平均超过其保留带宽的2倍。此外，如果L2上的可用带宽不足，运营商可能会尝试在其现有路径上增加L2的带宽，但没有成功。在这种情况下，运营商愿意增加具有与L2相同的入口/出口lsr的另一LSP L3的带宽，以便增加总体入口/出口带宽分配。然而，在这种情况下，L3带宽修改以较低的优先级（较高的Mp值）执行，因为L3路由在次要路径上，这导致将较高的带宽分配优先级给予其主要路径上的LSP[2]。
The authors would like to acknowledge the careful review and comments of Adrian Farrel.
作者希望感谢阿德里安·法雷尔的仔细审查和评论。
The IETF has been notified of intellectual property rights claimed in regard to some or all of the specification contained in this document. For more information consult the online list of claimed rights.
IETF已收到关于本文件所含部分或全部规范的知识产权声明。有关更多信息，请查阅在线权利主张列表。
Protection against modification to LSPs by malign agents has to be controlled by the MPLS domain.
防止恶意代理修改LSP的保护必须由MPLS域控制。
[1] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996.
[1] Bradner，S.，“互联网标准过程——第3版”，BCP 9，RFC 2026，1996年10月。
[2] Ash, J., "Traffic Engineering & QoS Methods for IP-, ATM-, & TDM-Based Multiservice Networks", Work in Progress.
[2] Ash，J.“基于IP、ATM和TDM的多服务网络的流量工程和QoS方法”，正在进行中。
[3] Jamoussi, B., Editor, Andersson, L., Callon, R., Dantu, R., Wu, L., Doolan, P., Worster, T., Feldman, N., Fredette, A., Girish, M., Gray, E., Heinanen, J., Kilty, T. and A. Malis, "Constraint-based LSP Setup Using LDP", RFC 3212, January 2002.
[3] 《使用LDP的基于约束的LSP设置》，RFC 3212，2002年1月。
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[4] Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[5] Andersson, L., Doolan, P., Feldman, N., Fredette, A. and B. Thomas, "LDP Specification", RFC 3036, January 2001.
[5] Andersson，L.，Doolan，P.，Feldman，N.，Fredette，A.和B.Thomas，“LDP规范”，RFC 3036，2001年1月。
[6] Rosen, E., Viswanathan, A. and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, January 2001.
[6] Rosen，E.，Viswanathan，A.和R.Callon，“多协议标签交换体系结构”，RFC 30312001年1月。
[7] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M. and J. McManus, "Requirements for Traffic Engineering Over MPLS", RFC 2702, September 1999.
[7] Awduche，D.，Malcolm，J.，Agogbua，J.，O'Dell，M.和J.McManus，“MPLS上的流量工程要求”，RFC 2702，1999年9月。
[8] Ash, J., Girish, M., Gray, E., Jamoussi,B. and G. Wright, "Applicability Statement for CR-LDP", RFC 3213, January 2002.
[8] Ash，J.，Girish，M.，Gray，E.，Jamoussi，B.和G.Wright，“CR-LDP的适用性声明”，RFC 3213，2002年1月。
Gerald R. Ash AT&T Room MT D5-2A01 200 Laurel Avenue Middletown, NJ 07748 USA Phone: 732-420-4578 EMail: gash@att.com
Gerald R.Ash AT&T室MT D5-2A01美国新泽西州劳雷尔大道中城200号07748电话：732-420-4578电子邮件：gash@att.com
Bilel Jamoussi Nortel Networks Corp. 600 Tech Park Billerica, MA 01821 USA Phone: 978-288-4506 EMail: jamoussi@NortelNetworks.com
Billel Jamoussi Nortel Networks Corp.600美国马萨诸塞州比尔里卡科技园01821电话：978-288-4506电子邮件：jamoussi@NortelNetworks.com
Peter Ashwood-Smith Nortel Networks Corp. P O Box 3511 Station C Ottawa, ON K1Y 4H7 Canada Phone: +1 613 763-4534 EMail: petera@NortelNetworks.com
Peter Ashwood Smith Nortel Networks Corp.加拿大渥太华C站3511号邮政信箱K1Y 4H7电话：+1 613 763-4534电子邮件：petera@NortelNetworks.com
Darek Skalecki Nortel Networks Corp. P O Box 3511 Station C Ottawa, ON K1Y 4H7 Canada Phone: +1 613 765-2252 EMail: dareks@nortelnetworks.com
Darek Skalecki Nortel Networks Corp.加拿大渥太华C站3511号邮政信箱K1Y 4H7电话：+1 613 765-2252电子邮件：dareks@nortelnetworks.com
Young Lee Ceterus Networks EMail: ylee@ceterusnetworks.com
Young Lee Ceterus Networks电子邮件：ylee@ceterusnetworks.com
Li Li SS8 Networks 495 March Rd., 5th Floor Kanata, Ontario K2K 3G1 Canada Phone: +1 613 592-2100 ext. 3228 EMail: lili@ss8networks.com
Li Li SS8 Networks加拿大安大略省卡纳塔市3月路495号5楼K2K 3G1电话：+1 613 592-2100分机3228电子邮件：lili@ss8networks.com
Don Fedyk Nortel Networks Corp. 600 Tech Park Billerica, MA 01821 USA Phone: 978-288-3041 EMail: dwfedyk@nortelnetworks.com
Don Fedyk Nortel Networks Corp.600美国马萨诸塞州比尔里卡科技园01821电话：978-288-3041电子邮件：dwfedyk@nortelnetworks.com
Copyright (C) The Internet Society (2002). All Rights Reserved.
版权所有（C）互联网协会（2002年）。版权所有。
This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.
本文件及其译本可复制并提供给他人，对其进行评论或解释或协助其实施的衍生作品可全部或部分编制、复制、出版和分发，不受任何限制，前提是上述版权声明和本段包含在所有此类副本和衍生作品中。但是，不得以任何方式修改本文件本身，例如删除版权通知或对互联网协会或其他互联网组织的引用，除非出于制定互联网标准的需要，在这种情况下，必须遵循互联网标准过程中定义的版权程序，或根据需要将其翻译成英语以外的其他语言。
The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.
上述授予的有限许可是永久性的，互联网协会或其继承人或受让人不会撤销。
This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
本文件和其中包含的信息是按“原样”提供的，互联网协会和互联网工程任务组否认所有明示或暗示的保证，包括但不限于任何保证，即使用本文中的信息不会侵犯任何权利，或对适销性或特定用途适用性的任何默示保证。
Acknowledgement
确认
Funding for the RFC Editor function is currently provided by the Internet Society.
RFC编辑功能的资金目前由互联网协会提供。