Networking Working Group A. Jiang Internet Draft X. Song Intended status: Informational Y. Qu Expires: September, 2010 S. Wu ZTE March 23, 2010 VPLS Ring draft-jiang-l2vpn-vpls-ring-01.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 September 2010. Abstract This document describes ring based VPLS architecture. This architecture is an alternative to existing VPLS architecture. It can simplify full mesh connections and provide a standard based protection mechanism, especially when underlying infrastructure is ring based. It can also reduce unnecessary customer multicast traffic compared with existing full mesh based VPLS. Jiang Expires September, 2010 [Page 1] Internet-Draft VPLS RING March 2010 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...................................................8 8.1. Normative References....................................8 8.2. Informative References..................................8 9. Acknowledgments..............................................8 1. Introduction VPLS uses MPLS to deliver Ethernet service over WAN. Currently, VPLS architecture is based on VPLS framework [RFC 4664]. And full mesh +split horizon is the most widely deployed mode. In this mode, VSIs belonging to the same VPLS VPN connect with each other via full mesh PWs, and use split horizon forwarding scheme to avoid loop. Full mesh imposes burden on forwarding, control & management plane, and is 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, if underlying infrastructure is ring, which is common for many service providers, there is another option - ring based VPSL. Mapping full mesh or hierarchical connections to ring is not efficient. It will also cause unnecessary copies of customer multicast traffic. Ring based Ethernet forwarding and protection scheme can be used to construct a more efficient VPLS solution. Jiang Expires September 2010 [Page 2] Internet-Draft VPLS RING March 2010 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, and is inherently different from MPLS-TP. 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 September 2010 [Page 3] Internet-Draft VPLS RING March 2010 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 (X) - 6 2 ----- 1 ----- 6 | Ring | <----> | Ring | 3 ----- 4 ----- 5 3 ----- 4 -(X)- 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 failure and inform the control node via OAM. Or control node detects failure via OAM. 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 (X) - N | Sub-ring | N ----- N ----- 2 ----- 1 (X) - 6 ----- N ----- N (X) Sub-ring | Ring | Sub-ring (X) N ----- N ----- 3 ----- 4 ----- 5 ----- N ----- N | Sub-ring | N (X) - 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 September 2010 [Page 4] Internet-Draft VPLS RING March 2010 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. L3VPN's native form 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 format. If we apply the same rule to Ethernet ring, we expect its native form to be deployed and accepted before its MPLS encapsulated version to be success. 4.3. CE-PE Ring (CE) ----- CE1 ------ PE1 (x) (x) | (CE) ---- (CE2) ----- PE2 : : | (CE)...... (CE)..... (PE) As stated in [draft-song-l2vpn-vpls-ring-access], ring is formed among CE and PE. It can be ring with 1 CE & 2 PEs, ring with 2 CEs & 2PEs, ring with n CEs & n PEs. 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 Jiang Expires September 2010 [Page 5] Internet-Draft VPLS RING March 2010 scalable and flexible VPLS access network. It is also the convenient way to build CE-PE multi-homing. 4.4. PE-PE Ring PE ---- PE(x)--- PE | Sub-ring | PE----- PE-----PE ---- PE(x)--- PE----- PE -----PE ----- CE (x) Sub-ring | Ring | Sub-ring (x) | PE----- PE-----PE ---- PE ----- PE----- PE -----PE ----- CE | Sub-ring | PE(x) - PE ----- PE Ring can be formed among PEs. It can be single ring or interconnected rings. This design is simple & neat for service providers with ring fiber/cable infrastructure. PE ring can also interconnect with CE-PE ring. Its forwarding process is different from that of full mesh VPLS. 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. There is only 1 bi-directional PW (virtual link) between each pair of PEs. For VPLS with N nodes, there are only N PWs in ring based VPLS as compared with N*(N-1)/2 PWs in full mesh VPLS. VPLS ring is Ethernet ring using PW as virtual link between PE nodes. MPLS protection mechanism is used to protect the PW locally. Ethernet ring protection mechanism is used to protect the VPLS service. Ring can also support PE redundancy. Other benefit is reduction of unnecessary customer multicast traffic, which will be discussed later. 4.5. Inter-VPLS Ring (VPLS 1 Border PE) ----- (VPLS 2 Border PE)(x)--- (VPLS 2 Border PE) | | (VPLS 1 Border PE) ----- (VPLS 3 Border PE) ----- (VPLS 3 Border PE) Jiang Expires September 2010 [Page 6] Internet-Draft VPLS RING March 2010 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. 4.6. Customer Multicast Traffic CE1 -->--PE1 ==>== PE2 -->-- CE2 | | V v CE3 --<--PE3 ---- PE4 -->-- CE4 In full mesh VPLS, there will be multiple copies of customer multicast traffic in inter-PE PW. For example, multicast traffic from CE1 to CE2~CE4 will be sent in PW from PE1 to PE2~PE4. 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 (around N/2~1) of traffic along the root to leaf path. 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 compared with full mesh design. It can also eliminate the unnecessary copies of customer multicast traffic in full mesh design. Ring can also provide a convenient way for node and link protection. Jiang Expires September 2010 [Page 7] Internet-Draft VPLS RING March 2010 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. [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 September 2010 [Page 8] Internet-Draft VPLS RING March 2010 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 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Jiang Expires September 2010 [Page 9]