MPLS WG J. Ash Internet Draft Y. Lee Document: draft-ash-crlsp-modify-00.txt AT&T P. Ashwood-Smith B. Jamoussi L. Li D. Fedyk D. Skaleki Nortel Networks July 1999 LSP Modification Using CR-LDP Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [1]. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. 1. Abstract 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 [2]. This contribution presents an approach to modify the bandwidth and possibly other parameters of an established CR-LSP using CR-LDP [3] without service interruption. The LSP modification feature can be supported by CR-LDP with a minor extension of an _action indicator flag_. This feature has application in dynamic network resources management where traffic of different priorities and service classes is involved. 2. Conventions used in this document L: LSP (Label Switched Path) Lid: LSPID (LSP Identifier) T: Traffic Parameters Ash, et. al 1 LSP Modification Using CR-LDP July, 1999 R: LSR (Label Switching Router) FTN: FEC To NHLFE FEC: Forwarding Equivalence Class NHLFE: Next Hop Label Forwarding Entity TLV: Type Length Value 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]. 3. Introduction 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 4 below, a method to modify an active LSP using CR-LDP is 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. Only a minimum extension on CR-LDP, an action indication flag of _modify_ is needed in order to explicitly specify the behavior, and allow the existing LSPID to support other networking capabilities in the future. Section 5 specifies the action indication flag of _modify_ for CR-LDP. In the appendix, an example is described to demonstrate an application of the presented method in dynamically managing network bandwidth requirements without interrupting service. 4. LSP Modification Using CR-LDP 4.1 Basic Procedure 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 draft for CR-LSP. Ingress LSR cannot modify an LSP before a previous modification procedure is completed. 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 Ash, et. Al. February 2000 2 LSP Modification Using CR-LDP July, 1999 Request Message. In the messages, 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 FTN as FEC1 -> Label A. R1 is waiting to establish another entry for FEC1. 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 bandwidth double booking. If a new service class is requested, Ri also prepares to receive the traffic on L1 in, perhaps a different type of queue, just the same as handling it for a Label Request Message. Ri assigns a new label for the Label Request Message. 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 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. 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 R1 examines the LSPID, L-id1 and finds out that the L- id1 has still another set of label (incoming/outgoing) under it. Ash, et. Al. February 2000 3 LSP Modification Using CR-LDP July, 1999 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, and/or change its setup/holding priority if desired. After the release procedure, the modification of the LSP is completed. 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 LSPID. If 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 Section 3 below. 4.2 Priority Handling 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 higher. 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. 4.3 Modification Failure Case Handling 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. Retry may be attempted if desired by the network operator. Ash, et. Al. February 2000 4 LSP Modification Using CR-LDP July, 1999 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 LDP draft [5]. 5. Proposed Extensions to CR-LDP for CR-LSP Modification 5.1 _Action indicator Flag_ in LSPID TLV As LSPID can be used for other purpose as well, for example, for LSP merge or stacking, etc. which are not intended to be covered here, an _action indicator flag_ is proposed to be carried in the LSPID TLV. This _action indicator flag_ shows explicitly the action that should be taken if the LSP already exists on the LSR receiving the message. The indicator flag can take 4 bits (right most 4 bits) out of the two reserved bytes in the LSPID TLV. A set of indicator code points is proposed as follows: 0001: modify The procedure for code point _modify_ is defined as in the above section 2.1. The procedures for others are for future work. 5.2 New Status Code Status code Type Modify request not supported 0x04000008 This error code can be used to indicate that for some reason, the modification attempt on the given LSPID is not allowed by the LSR. For example, this can be an attempt that is sent out too soon after last modification, before the LSR has completed the procedures in the last modification attempt. 6. Intellectual Property Consideration Nortel Networks may seek patent or other intellectual property protection for some or all of the technologies disclosed in this document. If any standards arising from this document are or become protected by one or more patents assigned to Nortel Networks, Nortel Networks is prepared to make a license available to any qualified applicant upon reasonable and non-discriminatory terms and conditions. Any such licenses will be subject to negotiations outside of the IETF. 7. Security Considerations No security issues are addressed in this draft. 8. References Ash, et. Al. February 2000 5 LSP Modification Using CR-LDP July, 1999 1 Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. 2 Ash, J., et. al., QoS Resource Management in MPLS-Based Networks, draft-ash-qos-routing-00.txt, (work in progress). 3 Jamoussi, B., et. al., Constraint-Based LSP Setup using LDP, draft-ietf-mpls-cr-ldp-01.txt, February 1999,(work in progress). 4 Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 5 Andersson, L., et. al., LDP Specification, draft-ietf-mpls-ldp- 05.txt (work in progress) 9. Author's Addresses Gerald R. Ash Young Lee AT&T AT&T Room MT E3-3C37 Room MT E3-3A04 200 Laurel Avenue 200 Laurel Avenue Middletown, NJ 07748 Middletown, NJ 07748 USA USA Phone: 732-420-4578 Phone: 732-420-4477 Fax: 732-440-6687 Fax: 732-440-6697 Email: gash@att.com Email: younglee@att.com Bilel Jamoussi Nortel Networks Corp. 3 Federal Street Billerica, MA 01821 USA phone: 978-288-4506 Email: jamoussi@NortelNetworks.com Peter Ashwood-Smith Li Li Nortel Networks Corp. Nortel Networks Corp. P O Box 3511 Station C P O Box 3511 Station C Ottawa, ON K1Y 4H7 Ottawa, ON K1Y 4H7 Canada Canada Phone: +1 613 763-4534 phone: +1 613 765 3088 Email: petera@NortelNetworks.com lili@nortelnetworks.com Darek Skalecki Don Fedyk Nortel Networks Corp. Nortel Networks Corp. P O Box 3511 Station C P O Box 3511 Station C Ottawa, ON K1Y 4H7 Ottawa, ON K1Y 4H7 Canada Canada phone: +1 613 765-2252 phone: +1 613 763 3268 Email: skalecki@NortelNetworks.com fedyk@nortelnetworks.com Ash, et. Al. February 2000 6 LSP Modification Using CR-LDP July, 1999 Appendix Application of LSP Bandwidth Modification in Dynamic Resource Management 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 presented in the last meeting. Assume that customers are assigned with their CR-LSPs. These customers' are assigned with one of the priorities as key, normal or best effort. The network operator doesn't want to bump any LSPs during an LSP setup, so after these CR-LSPs are set up, their holding priority are all assigned as the highest. The network operator wants to control the resource on the links of LSRs, so all LSRs keep the usage status of its links and based on the usage history, each link is assigned a current threshold priority Pi. Which means that the link has no bandwidth available for Label Request with a setup priority lower than Pi. When a LSP's bandwidth needs to be modified, the operator uses policy based algorithm to assign a priority for its modification request, say Mp for LSP L2. Then the ingress LSR sends Label Request message with (Setup Priority = Mp). The rule is then only if there is enough bandwidth on the link and, the Setup priority in the Label Request Message is higher in priority (Mp numerically smaller) than Pi 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 indicates that there isn't enough resources. It should also be note that when OSPF (or IS-IS) floods the link available bandwidth information, the available bandwidth associated with priority lower than Pi (numerical value bigger) should be indicated as _0_. This procedure based on a priority threshold Pi is implementation specific and value added. It offers networks flexibility to prioritize and control its resources. The calculation of Mp is network dependent, based on operator's own algorithm. For example, the operator may assign a higher Mp to L2 if L2 belongs to a customer with _Key_ priority. The operator may also collect the actual usage of each LSP and assign a high Mp to L2 if in the past week, L2 has exceeding its reserved bandwidth by 2 times on the average, and the customer of L2 agrees to increase its bandwidth for a better guaranteed service. Some operator may try to increase the bandwidth of L2 on its existing path unsuccessfully as there isn't enough bandwidth there. Then the operator is willing to change the path of L2 in order to increase its bandwidth, but with a lower priority Mp this time as L2 now is routed on its secondary path, which should yield priority to the LSPs that are on its primary paths here. Ash, et. Al. February 2000 7 LSP Modification Using CR-LDP July, 1999 Full Copyright Statement "Copyright (C) The Internet Society (date). All Rights Reserved. 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 implmentation 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 Ash, et. Al. February 2000 8