CCAMP and PCE Working Group X. Lin Internet-Draft G. Xie Intended status: Standards Track G. Xiang Expires: April 22, 2010 X. Fu ZTE Corporation October 19, 2009 A Path Computation Element (PCE) Solution for multilayer lsp draft-lin-pce-ccamp-multilayer-lsp-00 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. 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. This Internet-Draft will expire on April 22, 2010. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract This document mainly describes the extensions of single PCE inter- Lin, et al. Expires April 22, 2010 [Page 1] Internet-Draft PCE Ext for multilayer-lsp October 2009 layer path computation for multiple FA-LSP. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Description of Question . . . . . . . . . . . . . . . . . . . 4 3. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Explicit Control of FA-LSP . . . . . . . . . . . . . . . . 5 3.2. Process of multiple FA-LSPs in multiple layers . . . . . . 6 3.3. Process of multiple FA-LSPs in the same layer . . . . . . 7 4. Updated Message Formats . . . . . . . . . . . . . . . . . . . 8 4.1. Updated PCEP Message Formats . . . . . . . . . . . . . . . 9 4.2. Updated RSVP Message Formats . . . . . . . . . . . . . . . 10 5. Security Considerations . . . . . . . . . . . . . . . . . . . 10 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 6.1. SERO Object-Class in PCEP . . . . . . . . . . . . . . . . 10 6.2. SERO Object-Type in RSVP . . . . . . . . . . . . . . . . . 10 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10 8. Normative References . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Lin, et al. Expires April 22, 2010 [Page 2] Internet-Draft PCE Ext for multilayer-lsp October 2009 1. Introduction Generalized MPLS (GMPLS) extends MPLS to handle multiple switching technologies. For example: packet switching(PSC), Layer-2 switching (L2SC), Time-Division Multiplexing switching(TDM) , wavelength switching(LSC), and fiber switching(FSC) (see [RFC3945]). GMPLS is not designed for a particular layer network design, so it can be unified management of the network with multiple switching capability. A MRN/MLN is defined as a TE domain supporting at least two different switching types (e.g.,TDM and LSC), and under the control of a single GMPLS control plane instance.In MRN TE links are consolidated into a single Traffic Engineering Database (TED). Since this TED contains the information relative to all the different regions and layers existing in the network, a path across multiple regions or layers can be computed using this TED. Thus, optimization of network resources can be achieved across the whole MLN/MRN. Path computation in large, multi-domain networks is complex and may require special computational components and cooperation between the elements in different domains. IETF PCE group specifies the architecture for a Path Computation Element PCE)-based model to address this problem space. A Path Computation Element (PCE) is an entity that is capable of computing a network path or route based on a network graph, and of applying computational constraints during the computation. In [draft-ietf-pce-inter-layer-frwk-10] two models are defined to perform PCE-based inter-layer path computation, mainly including: o Single PCE Inter-Layer Path Computation In this model inter-layer path computation is performed by a single PCE that has topology visibility to all layers. o Multiple PCE Inter-Layer Path Computation In this model there is at least one PCE per layer, and each PCE has topology visibility restricted to its own layer A set of one or more lower-layer LSPs provides information for efficient path handling in higher layer(s) of the MLN, in other words, provides a virtual network topology (VNT) to the higher layers.A VNT Manager (VNTM) is defined as a functional element that manages and controls the VNT. PCE and VNT Manager are distinct functional elements that may or may not be co-located.There are three Inter-Layer Path Control Models: Lin, et al. Expires April 22, 2010 [Page 3] Internet-Draft PCE Ext for multilayer-lsp October 2009 o PCE-VNTM Cooperation Model o Higher-Layer Signaling Trigger Model o NMS-VNTM Cooperation Model A MRN/MLN is a traffic engineering domain, so TE topology for all layer networks is visible within this routing domain.[draft-ietf-pce-inter-layer-frwk-10] suggest that the single PCE inter-layer path computation model may be adopted because a PCE is able to collect all layers' TE topologies by participating in only one routing domain. However, in the above scenario, if Higher-Layer Signaling Trigger Model is used to establish FA-LSP there are some flaws. 2. Description of Question In Single PCE Inter-Layer Path Computation model, the PCE know the TE information of all the layers, so PCE can calculate a complete path,which include the higher path and the lower path. In [RFC4606], the information carried in the Interface Switching Capabilities is used to construct LSP regions and to determine regions' boundaries as follows: o Define an ordering among interface switching capabilities as follows: PSC-1 < PSC-2 < PSC-3 < PSC-4 < TDM < LSC < FSC. Given two interfaces if-1 and if-2 with interface switching capabilities isc-1 and isc-2 respectively, say that if-1 < if-2 iff isc-1 < isc-2 or isc-1 == isc-2, and if-1's max LSP bandwidth is less than if-2's max LSP bandwidth. For a LSP, if two adjacent interfaces if-(i-1) < if-i, then we say the LSP has crossed a region boundary at the node where if-(i-1) locate.This node is the source node of lower FA-LSP. If two adjacent interfaces if-(k-1)> if-k, then the node where if-k locate is the destination node of the lower FA-LSP. In Section 6.2 further shows that when RSVP-TE is as a signaling protocol, how to establish the FA-LSP automatically, briefly described as follows: o when a region boundary node receives a Path message, the node determines whether or not it is at the edge of an LSP region with respect to the ERO carried in the message. If the node is at the edge of a region, it must then determine the other edge of the region with respect to the ERO,using the IGP database. The node Lin, et al. Expires April 22, 2010 [Page 4] Internet-Draft PCE Ext for multilayer-lsp October 2009 then extracts from the ERO the sub-sequence of hops from itself to the other end of the region. o Then the LSR establish a new FA-LSP, and this FA-LSP is as a higher FA. However, in Single PCE Inter-Layer Path Computation model, the above method has some defects: o Because TED is centralized management, each node may not have the IGP database, it PCE needs to determine the region boundary. o When there are multi-nested FA-LSP exists, PCE already know the region boundary nodes ,so it is not necessary to use IGP database to determine the region boundary. In a word, in Single PCE Inter-Layer Path Computation model, using signaling explicitly specify the FA-LSP can simplify the process of FA-LSP esstablishment. 3. Solution When PCE computes the route,it can determine the regions' boundaries and the initiator and the terminator of the FA-LSP via the description in [RFC4206] section 5.1. 3.1. Explicit Control of FA-LSP In[RFC4873],the Secondary Explicit Route objects( SEROs) is used to indicate the protected path of the LSP!_s segment recovery. When service path includes one layer or multilayer FA-LSP, FA-LSP!_s Explicit routes are specified via the Secondary Explicit Route objects. When the Higher-Layer node creates a service,it sends a route request to PCE,in the response message of the route request from PCE, the whole LSP!_s routes are specified.The Higher-Layer path's Explicit routes are specified via the ERO.The FA-LSP!_s Explicit routes are specified via the SEROs. Consider the following topology: PCE H1---H2 H5---H6 \ / Lin, et al. Expires April 22, 2010 [Page 5] Internet-Draft PCE Ext for multilayer-lsp October 2009 L3---L4 In this topology, H1,H2,H5,H6 are the network nodes of Higher-Layer, while H2,L3,L4,H5 are the network nodes of low layer. And, H2 and H5 are the region boundaries. The process of creating a LSP from H1 to H6 is as the following: o H1 sends a route request to PCE,which responses a message with the Higher-Layer path's explicit route specified via the ERO and the FA-LSP's explicit routes specified via the subsequent SEROs.Explicit routes are encoded as follows:ERO = {H1,H2, H5, H6}, SERO = {H2,L3,L4,H5}. o H1 Sends Path message to the downstream node H2 with ERO = {H2,H5,H6} and SERO = {H2,L3,L4,H5}. o After H2 receivs the Path message from H1,H2 confirm that it is the initiator of FA-LSP via the SERO,and extracts the complete route of the FA-LSP. o Then H2 starts the creation of FA-LSP , the route is H2,L3,L4,H5. o After the creation of the FA-LSPGBP[not]the Higher-Layer LSP!_s creation is to be continued. And the SERO in the Path message is deleted.. 3.2. Process of multiple FA-LSPs in multiple layers Consider the following topology: PCE H1---H2 H7---H8 \ / M3 M6 \ / L4---L5 In this topology, from top to down, the network is divided into three layers. Then H1,H2,H7,H8 belong to the first layer. H2,M3,M6,H7 are the nodes of the second layer, while M3,L4,L5,M6 belong to the third layer. And, H2 and H7 are regions boundaries between the first layer Lin, et al. Expires April 22, 2010 [Page 6] Internet-Draft PCE Ext for multilayer-lsp October 2009 and the second layer. M3 and M6 are region boundaries between the second layer and the third layer. The process of creating a LSP from H1 to H8 is as the following : o H1 sends a route request to PCE, in the response message of route request from PCE, the first-layer path's Explicit routes are specified via the ERO. The first FA-LSP!_s Explicit routes are specified via the first SERO. The second FA-LSP!_s Explicit routes are specified via the SERO. Encoded as follows:ERO = {H1,H2,H7,H8},SERO = {H2,M3,M6,H7},SERO={M3,L4,L5,M6}. o H1 sends Path message to the downstream node H2,with ERO = {H2,H7, H8}, SERO = {H2,M3,M6,H7},SERO={M3,L4,L5,M6}. o After H2 receives the Path message from H1,H2 confirms that it is the initiator of the second layer!_s FA-LSP via the first SERO,and extracts the route of the second layer!_s FA-LSP. Then H2 starts the creation of the first FA-LSP, the route is H2,M3,M6,H7. H2 sends a new Path message to M3 with ERO = {M3,M6,H7},SERO={M3,L4,L5,M6}. o After M3 receives the Path message from H2,M3 confirms that it is the initiator of the third layer!_s FA-LSP via the second SERO.and extracts the complete route of the third layer!_s FA-LSP. Then M3 starts the creation of the second FA-LSP, the route is M3,L4,L5,M6.M3 sends another new Path message to L4 with ERO={L4,L5,M6}. o After the creation of the third layer!_s FA-LSP,the second layer FA-LSP!_s creation is to be continued.And the second SERO in the second Path message is deleted. o After the creation of the second layer!_s FA-LSP,the first layer LSP!_s creation is to be continued.And the first SERO in the first Path message is deleted. 3.3. Process of multiple FA-LSPs in the same layer Consider the following topology: Consider the following topology: PCE H1---H2 H5---H6 H9---H10 \ / \ / L3---L4 L7---- L8 Lin, et al. Expires April 22, 2010 [Page 7] Internet-Draft PCE Ext for multilayer-lsp October 2009 In this topology, the network is divided into two layers.H1,H2,H5,H6,H9,H10 are the nodes of the first layer.H2,L3,L4,H5,H6,L7,L8,H9 belong to the second layer,and H2,H5,H6 and H9 are regions' boundaries. Creat a LSP from H1 to H10,the process is as the following: o H1 sends a route request to PCE,in the response message of route request from PCE, the first layer path Explicit routes are specified via the ERO. The first FA-LSP!_s Explicit routes are specified via the first SERO. The second FA-LSP!_s Explicit routes are specified via the SERO. Encoded as follows: ERO = {H1,H2,H5,H6,H9,H10}, SERO ={H2,L3,L4,H5},SERO={H6,L7,L8,H9}. o H1 Sends Path message to the downstream node H2,with ERO = {H2, H5, H6,H9,H10}, SERO = {H2,L3,L4,H5},SERO={H6,L7,L8,H9} o After H2 receives the Path message from H1,H2 confirms that it is the initiator of the second layer!_s first FA-LSP via the first SERO,and extracts the route of the second layer!_s first FA-LSP. Then H2 starts the creation of the first FA-LSP, the route is H2,L3,L4,H5. H2 sends a new Path message to L3 with ERO = {L3,L4,H5}. o After the creation of the second layer!_s first FA-LSP,the first- layer LSP!_s creation is to be continued.And the first SERO in the Path message is deleted. o After H6 receive the Path Message from H5,H6 confirm it is the initiator of the second layer!_s second FA-LSP via the second SERO and extracts the complete route of the second layer!_s second FA- LSP. Then H6 starts the creation of the second FA-LSP, the route is H6,L7,L8,H9. o After the creation of the second FA-LSP,the first-layer LSP!_s creation is to be continued.And the second SERO in the Path message is deleted. 4. Updated Message Formats Lin, et al. Expires April 22, 2010 [Page 8] Internet-Draft PCE Ext for multilayer-lsp October 2009 4.1. Updated PCEP Message Formats The format of a PCRep message is as follows: ::= The format of the response-list is: ::=[] ::= [] [] [] ::=[] ::= [] The format of the sero-list is: ::= [] ::= [] [] [] [] [] [] [] [] ::=[] ::=[] Lin, et al. Expires April 22, 2010 [Page 9] Internet-Draft PCE Ext for multilayer-lsp October 2009 4.2. Updated RSVP Message Formats The format of a Path message is as follows: ::= [ ] [ [ | ] ... ] [ ] [ ] [ ] [ ... ] [ ] [ ] [ ] [] [ ... ] ::= [] 5. Security Considerations This document has no requirement for a change to the security models within PCEP and associated protocols. 6. IANA Considerations 6.1. SERO Object-Class in PCEP SERO Object-Class is 25 (suggested value) SERO Object-Type is 2 (suggested value). 6.2. SERO Object-Type in RSVP SERO Object-Type is 3 (suggested value). 7. Acknowledgments The RFC text was produced using Marshall Rose's xml2rfc tool. Lin, et al. Expires April 22, 2010 [Page 10] Internet-Draft PCE Ext for multilayer-lsp October 2009 8. Normative References [ITUT-G709] ITU-T, "Interface for the Optical Transport Network (OTN)", G.709 Recommendation (and Amendment 1) , October 2001. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, September 2003. [RFC4203] Kompella, K. and Y. Rekhter, "OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4203, October 2005. [RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP) Hierarchy with Generalized Multi-Protocol Label Switching (GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005. [RFC4328] Papadimitriou, D., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Extensions for G.709 Optical Transport Networks Control", RFC 4328, January 2006. [RFC5150] Ayyangar, A., Kompella, K., Vasseur, JP., and A. Farrel, "Label Switched Path Stitching with Generalized Multiprotocol Label Switching Traffic Engineering (GMPLS TE)", RFC 5150, February 2008. Authors' Addresses Xuefeng Lin ZTE Corporation 12F,ZTE Plaza,No.19,Huayuan East Road,Haidian District Beijing 100191 P.R.China Phone: +8615901011821 Email: lin.xuefeng@zte.com.cn URI: http://www.zte.com.cn/ Lin, et al. Expires April 22, 2010 [Page 11] Internet-Draft PCE Ext for multilayer-lsp October 2009 Gang Xie ZTE Corporation 12F,ZTE Plaza,No.19,Huayuan East Road,Haidian District Beijing 100191 P.R.China Phone: +8613691280432 Email: xie.gang@zte.com.cn Xiaoshan Xiang ZTE Corporation 12F,ZTE Plaza,No.19,Huayuan East Road,Haidian District Beijing 100191 P.R.China Phone: +8613718525451 Email: xiang.xiaoshan@zte.com.cn Xihua Fu ZTE Corporation West District,ZTE Plaza,No.10,Tangyan South Road,Gaoxin District Xi An 710065 P.R.China Phone: +8613798412242 Email: fu.xihua@zte.com.cn URI: http://wwwen.zte.com.cn/ Lin, et al. Expires April 22, 2010 [Page 12]