Encapsulating MPLS in UDP
Author(s): Nischal Sheth, Fan Yongbing, Carlos Pignataro, Lucy Yong, KuiKe Building
Existing technologies to encapsulate Multi-Protocol Label Switching (MPLS) over IP are not adequate for efficient load balancing of MPLS application traffic, such as MPLS-based Layer2 Virtual Private Network (L2VPN) or Layer3 Virtual Private Network (L3VPN) traffic across IP...
Network working group X. Xu Internet Draft Huawei Category: Standard Track N. Sheth Contrail Systems L. Yong Huawei C Pignataro Cisco Y. Fan China Telecom Expires: May 2013 December 10, 2012 Encapsulating MPLS in UDP draft-xu-mpls-in-udp-06 Abstract Existing technologies to encapsulate Multi-Protocol Label Switching (MPLS) over IP are not adequate for efficient load balancing of MPLS application traffic, such as MPLS-based Layer2 Virtual Private Network (L2VPN) or Layer3 Virtual Private Network (L3VPN) traffic across IP networks. This document specifies additional IP-based encapsulation technology, referred to as MPLS-in-User Datagram Protocol (UDP), which can facilitate the load balancing of MPLS application traffic across IP networks. 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. Xu, et al. Expires May 10, 2013 [Page 1] Internet-Draft Encapsulating MPLS in UDP December 2012 The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on May 10, 2013. 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. 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 RFC2119 [RFC2119]. Table of Contents 1. Introduction ................................................ 3 1.1. Existing Technologies .................................. 3 1.2. Motivations for MPLS-in-UDP Encapsulation .............. 4 2. Terminology ................................................. 4 3. Encapsulation in UDP......................................... 4 4. Processing Procedures ....................................... 5 5. Applicability ............................................... 6 6. Security Considerations ..................................... 6 7. IANA Considerations ......................................... 6 8. Acknowledgements ............................................ 6 9. References .................................................. 7 9.1. Normative References ................................... 7 9.2. Informative References ................................. 7 Authors' Addresses ............................................. 8 Xu, et al. Expires May 10, 2013 [Page 2] Internet-Draft Encapsulating MPLS in UDP December 2012 1. Introduction To fully utilize the bandwidth available in IP networks and/or facilitate recovery from a link or node failure, load balancing of traffic over Equal Cost Multi-Path (ECMP) and/or Link Aggregation Group (LAG) across IP networks is widely used. In effect, most existing core routers in IP networks are already capable of distributing IP traffic flows over ECMP paths and/or LAG based on the hash of the five-tuple of User Datagram Protocol (UDP)[RFC 0768] and Transmission Control Protocol (TCP) packets (i.e., source IP address, destination IP address, source port, destination port, and protocol). In practice, there are some scenarios for Multi-Protocol Label Switching (MPLS) applications (e.g., MPLS-based Layer2 Virtual Private Network (L2VPN) or Layer3 Virtual Private Network (L3VPN)) where the MPLS application traffic needs to be transported through IP-based tunnels, rather than MPLS tunnels. For example, MPLS-based L2VPN or L3VPN technologies may be used for interconnecting geographically dispersed enterprise data centers or branch offices across IP Wide Area Networks (WAN) where enterprise own router devices are deployed as L2VPN or L3VPN Provider Edge (PE) routers. In this case, efficient load balancing of the MPLS application traffic across IP networks is much desirable. 1.1. Existing Technologies With existing IP-based encapsulation methods for MPLS applications, such as MPLS-in-IP and MPLS-in-Generic Routing Encapsulation (GRE) [RFC4023] or even MPLS-in-Layer Two Tunneling Protocol - Version 3 (L2TPv3)[RFC4817], distinct customer traffic flows between a given PE router pair would be encapsulated with the same IP-based tunnel headers prior to traversing the core of the IP WAN. Since the encapsulated traffic is neither TCP nor UDP traffic, for many existing core routers which could only perform hash calculation on fields in the IP headers of those tunnels (i.e., source IP address, destination IP address), it would be hard to achieve a fine-grained load balancing of these traffic flows across the network core due to the lack of adequate entropy information. [RFC5640] describes a method for improving the load balancing efficiency in a network carrying Softwire Mesh service over L2TPv3 and GRE encapsulation. However, this method requires core routers to be capable of performing hash calculation on the "load-balancing" field contained in the tunnel encapsulation headers (i.e., the Session ID field in the L2TPv3 header or the Key field in the GRE Xu, et al. Expires May 10, 2013 [Page 3] Internet-Draft Encapsulating MPLS in UDP December 2012 header), which means a non-trivial change to the date plane of many existing core routers. 1.2. Motivations for MPLS-in-UDP Encapsulation On basis of the fact that most existing core routers (i.e., P routers in the context of MPLS-based L2VPN or L3VPN) are already capable of balancing IP traffic flows over the IP networks based on the hash of the five-tuple of UDP packets, it would be advantageous to use MPLS-in-UDP encapsulation instead of MPLS-in-GRE or MPLS-in- L2TPv3 in the environments where the load balancing of MPLS application traffic across IP networks is much desired but the load balancing mechanisms defined in [RFC5640] have not yet been widely supported by most existing core routers. In this way, the default load balancing capability of most existing core routers as mentioned above can be utilized directly without requiring any change to them. 2. Terminology This memo makes use of the terms defined in [RFC 4364] and [RFC4664]. 3. Encapsulation in UDP MPLS-in-UDP encapsulation format is shown as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Port = entropy | Dest Port = MPLS | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | UDP Length | UDP Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ MPLS Label Stack ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ Message Body ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Source Port of UDP This field contains an entropy value that is generated by the ingress PE router. For example, the entropy value can be generated by performing hash calculation on Xu, et al. Expires May 10, 2013 [Page 4] Internet-Draft Encapsulating MPLS in UDP December 2012 certain fields in the customer packets (e.g., the five tuple of UDP/TCP packets). Destination Port of UDP This field is set to a value (TBD) indicating the MPLS packet encapsulated in the UDP header is a MPLS one or a MPLS one with upstream-assigned label. UDP Length The usage of this field is in accordance with the current UDP specification. UDP Checksum The usage of this field is in accordance with the current UDP specification. To simplify the operation on egress PE routers, this field is recommended to be set to zero. MPLS Label Stack This field contains an MPLS Label Stack as defined in [RFC3032]. Message Body This field contains one MPLS message body. 4. Processing Procedures This MPLS-in-UDP encapsulation causes MPLS packets to be forwarded through "UDP tunnels". When performing MPLS-in-UDP encapsulation by an ingress PE router, the entropy value would be generated by the ingress PE router and then be filled in the Source Port field of the UDP header. P routers, upon receiving these UDP encapsulated packets, could balance these packets based on the hash of the five-tuple of UDP packets. Upon receiving these UDP encapsulated packets, egress PE routers would decapsulate them by removing the UDP headers and then process them accordingly. Xu, et al. Expires May 10, 2013 [Page 5] Internet-Draft Encapsulating MPLS in UDP December 2012 As for other common processing procedures associated with tunneling encapsulation technologies including but not limited to Maximum Transmission Unit (MTU) and preventing fragmentation and reassembly, Time to Live (TTL) and differentiated services, the corresponding procedures defined in [RFC4023] which are applicable for MPLS-in-IP and MPLS-in-GRE encapsulation formats SHOULD be followed. 5. Applicability Besides the MPLS-based L3VPN [RFC 4364] and L2VPN [RFC4761, RFC4762] [E-VPN] applications, MPLS-in-UDP encapsulation could apply to other MPLS applications including but not limited to 6PE [RFC4798] and PWE3 services. 6. Security Considerations Just like MPLS-in-GRE and MPLS-in-IP encapsulation formats, the MPLS-in-UDP encapsulation format defined in this document by itself cannot ensure the integrity and privacy of data packets being transported through the MPLS-in-UDP tunnels and cannot enable the tunnel decapsulators to authenticate the tunnel encapsulator. In the case where any of the above security issues is concerned, the MPLS- in-UDP tunnels SHOULD be secured with IPsec in transport mode. In this way, the UDP header would not be seeable to P routers anymore. As a result, the meaning of adopting MPLS-in-UDP encapsulation format as an alternative to MPLS-in-GRE and MPLS-in-IP encapsulation formats is lost. Hence, MPLS-in-UDP encapsulation format SHOULD be used only in the scenarios where all the security issues as mentioned above are not significant concerns. For example, in a data center environment, the whole network including P routers and PE routers are under the control of a single administrative entity and therefore there is no need to worry about the above security issues. 7. IANA Considerations Two distinct UDP destination port numbers indicating MPLS and MPLS with upstream-assigned label respectively need to be assigned by IANA. 8. Acknowledgements Thanks to Shane Amante, Dino Farinacci, Keshava A K, Ivan Pepelnjak, Eric Rosen, Andrew G. Malis, Kireeti Kompella, Marshall Eubanks, Vivek Kumar, Weiguo Hao, Zhenxiao Liu and Xing Tong for their valuable comments on the idea of MPLS-in-UDP encapsulation. Thanks to Daniel King, Gregory Mirsky and Eric Osborne for their valuable reviews on this draft. Xu, et al. Expires May 10, 2013 [Page 6] Internet-Draft Encapsulating MPLS in UDP December 2012 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC2119, March 1997. 9.2. Informative References [RFC 4364] Rosen, E and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC 4364, February 2006. [RFC4664] Andersson, L. and Rosen, E. (Editors),"Framework for Layer 2 Virtual Private Networks (L2VPNs)", RFC4664, Sept 2006. [RFC4023] Worster, T., Rekhter, Y., and E. Rosen, "Encapsulating MPLS in IP or GRE", RFC4023, March 2005. [RFC5332] Eckert, T., Rosen, E., Aggarwal, R., and Y. Rekhter, "MPLS Multicast Encapsulations", RFC5332, August 2008. [RFC4817] M. Townsley, C. Pignataro, S. Wainner, T. Seely and J. Young, "Encapsulation of MPLS over Layer 2 Tunneling Protocol Version 3, March 2007. [RFC5640] Filsfils, C., Mohapatra, P., and C. Pignataro, "Load- Balancing for Mesh Softwires", RFC5640, August 2009. [RFC6391] Bryant, S., Filsfils, C., Drafz, U., Kompella, V., Regan, J., and S. Amante, "Flow Aware Transport of Pseudowires over an MPLS Packet Switched Network", RFC6391, November 2011 [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and L. Yong, "The Use of Entropy Labels in MPLS Forwarding", draft-ietf-mpls-entropy-label-01, work in progress, October, 2011. [RFC5512] Mohapatra, P. and E. Rosen, "The BGP Encapsulation Subsequent Address Family Identifier (SAFI) and the BGP Tunnel Encapsulation Attribute", RFC5512, April 2009. [RFC4798] J Declerq et al., "Connecting IPv6 Islands over IPv4 MPLS using IPv6 Provider Edge Routers (6PE)", RFC4798, February 2007. Xu, et al. Expires May 10, 2013 [Page 7] Internet-Draft Encapsulating MPLS in UDP December 2012 [RFC4761] Kompella, K. and Y. Rekhter, "Virtual Private LAN Service (VPLS) Using BGP for Auto-Discovery and Signaling", RFC 4761, January 2007. [RFC4762] Lasserre, M. and V. Kompella, "Virtual Private LAN Service (VPLS) Using Label Distribution Protocol (LDP) Signaling", RFC4762, January 2007. [E-VPN] Aggarwal et al., "BGP MPLS Based Ethernet VPN", draft-ietf- l2vpn-evpn-00.txt, work in progress, February, 2012. [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack Encoding", RFC3032, January 2001. [RFC 0768] Postel, J., "User Datagram Protocol", STD 6, RFC 0768, August 1980. [I-D.ietf-6man-udpchecksums] Eubanks, M., Chimento, P., and M. Westerlund, "UDP Checksums for Tunneled Packets", draft-ietf-6man-udpchecksums-04 (work in progress), September 2012. [I-D.ietf-6man-udpzero] Fairhurst, G. and M. Westerlund, "Applicability Statement for the use of IPv6 UDP Datagrams with Zero Checksums", draft-ietf-6man-udpzero-07 (work in progress), October 2012. Authors' Addresses Xiaohu Xu Huawei Technologies, Beijing, China Phone: +86-10-60610041 Email: email@example.com Nischal Sheth Contrail Systems Email: firstname.lastname@example.org Lucy Yong Huawei USA 5340 Legacy Dr. Plano TX75025 Phone: 469-277-5837 Email: Lucy.email@example.com Xu, et al. Expires May 10, 2013 [Page 8] Internet-Draft Encapsulating MPLS in UDP December 2012 Carlos Pignataro Cisco Systems 7200-12 Kit Creek Road Research Triangle Park, NC 27709 USA EMail: firstname.lastname@example.org Yongbing Fan China Telecom Guangzhou, China. Phone: +86 20 38639121 Email: email@example.com Zhenbin Li Huawei Technologies, Beijing, China Phone: +86-10-60613676 Email: firstname.lastname@example.org Xu, et al. Expires May 10, 2013 [Page 9]