Networking Working Group A. Jiang Internet Draft X. Song Intended status: Informational X. Qu Expires: March, 2010 S. Wu J. Luo ZTE October 16, 2009 VPLS Ring draft-jiang-l2vpn-vpls-ring-00.txt 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 2010. Abstract This document describes ring based VPLS architecture. This architecture is an alternative to existing VPLS architecture. It can simplify the full mesh connection overhead and provide a standard based protection mechanism, especially when the underlying cable or fiber infrastructure is ring based. It is also an optimal architecture for customer multicast traffic compared with existing VPLS. Jiang Expires April, 2010 [Page 1] Internet-Draft VPLS RING October 2009 Table of Contents 1. Introduction.................................................2 2. Conventions used in this document............................3 3. Analysis of related documents................................3 4. Ethernet Ring Based VPLS.....................................3 4.1. Native Ethernet Ring....................................3 4.2. MPLS Services & Their Native Form.......................5 4.3. CE-PE Ring..............................................5 4.4. PE-PE Ring..............................................6 4.5. Inter-VPLS Ring.........................................6 4.6. Customer Multicast Traffic..............................7 5. Security Considerations......................................7 6. IANA Considerations..........................................7 7. Conclusions..................................................7 8. References...................................................7 8.1. Normative References....................................7 8.2. Informative References..................................8 9. Acknowledgments..............................................8 1. Introduction VPLS is to use MPLS to deliver Ethernet service over WAN. Currently, VPLS architecture is based on VPLS framework [RFC 4664]. And full mesh +split horizon is one of the most widely deployed modes. In this mode, VSIs in the same service VPN connect with each other via full mesh PWs, and use split horizon forwarding scheme. This design is to prevent loop in the forwarding path. Full mesh imposes heavy load on forwarding, control & management plane, and not scalable. Hierarchical VPLS discussed in LDP VPLS [RFC 4762] (Hub-Spoke) and BGP VPLS [RFC 4761] (Route Reflector) are proposed to fix the problem. However, in certain scenario like ring network, it can be optimized. Ring is a common network topology for many service provider's cable or fiber infrastructure. Mapping basic full mesh or hierarchical connections to ring is not very elegant. It will also cause unnecessary customer multicast traffic copies, which will be explained in following section. There are some ring based Ethernet forwarding and protection designs that we can use to construct a more elegant and simple VPLS solution. Jiang Expires April 2010 [Page 2] Internet-Draft VPLS RING October 2009 2. Conventions used in this document 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]. 3. Analysis of related documents There are several works on ring based VPLS. 1) VPLS protection switching with ring access [draft-song-l2vpn-vpls- ring-access] In this document, ring based technology is deployed in the access part of VPLS, which includes CE and the connected PE. They can use ring for multi-homing access and protection. It covers single, dual and multiple CE multi-homing scenarios. 2) Pseudowire (PW) Redundancy Framework [draft-ietf-pwe3-redundancy] In this document, PW redundancy is used to provide multi-homing solution for VPLS. It has discussed the scenario of PW redundancy for dual-homing between PEs in ring topology, and has a very brief overview of the possible solutions. 3) BGP based VPLS Multi-homing [draft-kothari-henderickx-l2vpn-vpls- multihoming] This is to use BGP as provisioning mechanism for multi-homing VPLS. 4) There are also some ring solutions for MPLS-TP. But VPLS forwarding is closely related to Ethernet, these 2 are inherently different. 4. Ethernet Ring Based VPLS 4.1. Native Ethernet Ring There are some documents on this topic. In [ITU-T G.8032] Ethernet Ring Protection Switching, native Ethernet ring protection protocol and switching mechanism is defined. Jiang Expires April 2010 [Page 3] Internet-Draft VPLS RING October 2009 In [RFC 3619] Ethernet Automatic Protection Switching, a similar design is presented. The main idea is to define a control node adjacent to a protection link. As shown in figure below, Node 1 is the control node and the link between 1 and 6 is the protection link. 2 ----- 1 o---- 6 2 ----- 1 ----- 6 | Ring | <----> | Ring | 3 ----- 4 ----- 5 3 ----- 4 o---- 5 Node 1 will block its port in the protection link to prevent loop. When there is link or node failure, node adjacent to the failure will detect the failure and inform the control node via protection control protocol. Or control node itself can do the job via fault detection protocol. When control node is informed, it will unblock the previously blocked port. When fault is cleared, control node will block the port again to prevent loop. In this example, when link between node 4 and 5 is broken, control node 1 will detect the failure and will unblock port in the protection link. When the failure is cleared, node 1 will block the port in protection link again. N ----- N o---- N | Sub-ring | N ----- N ----- 2 ----- 1 o---- 6 ----- N ----- N o Sub-ring | Ring | Sub-ring o N ----- N ----- 3 ----- 4 ----- 5 ----- N ----- N | Sub-ring | N o---- N ----- N Interconnected rings are also supported, as shown above. This is a hierarchical structure of a ring and several sub-rings. Ring is viewed by sub-ring as a permanent link. Each sub-ring will run its own ring control protocol for loop prevention and protection. Jiang Expires April 2010 [Page 4] Internet-Draft VPLS RING October 2009 4.2. MPLS Services & Their Native Form MPLS provides a scalable encapsulation mechanism for multiple services. MPLS has been adapted by wide range of services including L3VPN, L2VPN (PW, VPLS), TE, FRR, multicast, QoS, BGP free core network, transport (MPLS-TP), etc. Some of these services are widely deployed and deemed a success, such as L3VPN, L2VPN (PW, VPLS), TE and FRR. Some are still under development, such as Transport and multicast. And some may have difficulty to take off, such as BGP free core. When we look at the winner, we can find that all successful MPLS services are successful in their native form, and vice versa. Native form of L3VPN is IP service, which is the foundation of Internet and broadband network. Native form of PW is legacy WAN services, which is dominant in traditional telecom world. Native form of VPLS is Ethernet, which is dominant in enterprise world. While multicast in its native form is not as widely deployed as unicast due to its inherent complexity. So does multicast in MPLS encapsulation. If we apply the same rule to Ethernet ring, we expect its native form to be deployed and accepted before its MPLS flavored version to be success. 4.3. CE-PE Ring (CE) ----- CE1 ------ PE1 o o | (CE) ---- (CE2) ----- PE2 : : | (CE)...... (CE)..... (PE) Ring is formed among CE and PE. It can be 1 CE & 2 PE ring, 2 CE & 2PE ring, n CE & n PE ring. It can be single ring or interconnected rings. PW between PE is treated by PE as virtual link. Ethernet ring control protocol is running in CE and PE for loop prevention and protection. We can use this mechanism to build scalable and flexible VPLS access network. It is also the convenient way to build CE-PE multi-homing. Jiang Expires April 2010 [Page 5] Internet-Draft VPLS RING October 2009 4.4. PE-PE Ring PE ---- PE o --- PE | Sub-ring | PE----- PE-----PE ---- PE o --- PE----- PE -----PE ----- CE O Sub-ring | Ring | Sub-ring o | PE----- PE-----PE ---- PE ----- PE----- PE -----PE ----- CE | Sub-ring | PE o - PE ----- PE Ring can be among PEs. It can be single ring or interconnected rings. This design is simple & neat for service provider with ring fiber/cable resources. PE ring can also interconnect with CE-PE ring. Its forwarding process is different from that of VPLS. There is only 1 bi-directional PW between each pair of PEs serving as virtual link. N PWs in this case compared with N*(N-1)/2 PWs in full mesh case for N nodes is one of the benefits, other benefits include customer multicast optimization, which will be explained in following section. There is also certain cost. In ring, each PE will turn on MAC learning. Ethernet packet will go through each PE in ring, and PE will forward Ethernet packet based on MAC forwarding table. The whole network is Ethernet ring using PW as virtual link between nodes. MPLS protection mechanism is used to protect the PW locally. Ethernet ring protection mechanism is used to protect the VPLS service. It is also the convenient way to build PE redundancy. 4.5. Inter-VPLS Ring (VPLS 1 Border PE) ----- (VPLS 2 Border PE) o --- (VPLS 2 Border PE) | | (VPLS 1 Border PE) ----- (VPLS 3 Border PE) ----- (VPLS 3 Border PE) Ring can also be used to provide inter-VPLS connection. Each VPLS can connect to other VPLS via border PE. inter-VPLS ring can also interconnect with PE ring or CE-PE ring. Protection mechanism is similar to PE ring. It also provides inter-VPLS PE redundancy. Jiang Expires April 2010 [Page 6] Internet-Draft VPLS RING October 2009 4.6. Customer Multicast Traffic CE1 -----PE1 ==>== PE2 -->-- CE2 | | V v CE3 -----PE3 ---- PE4 -->-- CE4 In full mesh VPLS, there will be multiple copy of customer multicast traffic in inter-PE PW and waste the bandwidth. For example, multicast traffic from CE1 to CE2-4 will be sent in PW from PE1 to PE2-4. There will be 2 copies of traffic in link between PE1 and PE2. If the number of multicast receiving node is N, there will be copies of traffic along the root to leaf path from around N/2 to 1. In ring VPLS, there will be only 1 copy of customer multicast traffic along the path from root to leaf. Its forwarding mechanism is similar to Ethernet multicast forwarding mechanism. 5. Security Considerations 6. IANA Considerations 7. Conclusions In this document, Ethernet ring based VPLS is presented. This architecture is most suitable to be deployed on infrastructure with fiber/cable ring. It can greatly reduce the number of inter-PE PWs in full mesh design. It can also eliminate the unnecessary copies of customer multicast traffic due to full mesh design. Ring can also provide a convenient way for node and link protection. 8. References 8.1. Normative References [RFC 2119] Bradner, S., Editor, "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC2119, March 1997. Jiang Expires April 2010 [Page 7] Internet-Draft VPLS RING October 2009 [RFC 4664] Andersson, L., Rosen, E., "Framework for Layer 2 Virtual Private Networks (L2VPNs)", RFC 4664, September 2006. 8.2. Informative References [VPLS RING ACCESS] Song, X., Wu, S., Shao, H., "VPLS protection switching with ring access", ID draft-song-l2vpn-vpls- ring-access-00, October 2008. 9. Acknowledgments This document was prepared using 2-Word-v2.0.template.dot. Jiang Expires April 2010 [Page 8] Internet-Draft VPLS RING October 2009 Authors' Addresses Albert Jiang ZTE Email: albert.john@zte.com.cn Xiaojuan Song ZTE Email: song.xiaojuan@zte.com.cn Yanfeng Qu ZTE Email: qu.yanfeng@zte.com.cn Shaoyong Wu ZTE Email: wu.shaoyong@zte.com.cn Jiang Luo ZTE Email: lu.jian@zte.com.cn Full Copyright Statement 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. Jiang Expires April 2010 [Page 9]